DIY hydronic heating installation
 

Hi all,

I've used this and other sites to get a lot of information before attempting my hydronic radiant (in-floor) installation, so I figured I'd give some back by making some information about the process, pitfalls, things that worked and didn't work, etc., available to others. I've started a blog on which I'll post about the process, including pictures, materials, etc.
What's currently on there is still very general, so bear with me as I dig through the hundreds of pictures taken during the installation, and post more. I should get around to providing a lot of info and tips over the next few days.

The Piesche family's home improvement adventures

Thanks,
Olaf

http://sphotos-a.xx.fbcdn.net/hphoto...46398123_n.jpg

Olaf,

Thanks for joining in the DIY party!

I'm about to do a small radiant project myself, starting real soon, so any info you offer will be extremely useful to me.

I'm about to start shopping for materials...

Best,

-AC_Hacker

Good to hear! If you have any questions, feel free to ask here or on the blog, I'll do my best to help. There are a couple of potential pitfalls (nothing too scary) with the tubing I hope to get to post about tonight.

A couple of things to know before buying the materials:

-If you're looking at doing it the same way we did, just make sure the OSB/Plywood is thick enough to support the tubing and plates - 19/32 worked for us for 1/2" PEX tubing, but it might depend on the transfer plates. I ordered the plates first, then measured the depth of the groove in the plate with a slide rule, then decided on the carrier OSB.

-It may be a good idea to make a rough plan for how many loops are going where (see the 'Materials Calculation' post on my blog) on paper or whiteboard, so you know the length of the individual loops - this will help in getting the right length rolls of tubing and to minimize waste in both tubing and OSB :)

Good luck with your project - it's a chunk of work, but definitely worth it once the floors are nice and toasty :)

I am still a number of years away from building my dream house, so I am still deciding what type of conditioning systems I want to use. With that being said, I really enjoy getting inspired from seeing these type of projects.

Glad to hear others are interested. As far as heating goes, there's not much that beats heated floors in terms of comfort and efficiency - I'm looking forward to mine in the winter! :)

I'm reading through your blog about your hydronic install...

How would you describe the length & severity of your heating season? Average information is important, but also the extremes that you have seen since you have lived in your house.

Does this average temperature chart seem to reflect your experience:


I also looked up your average Heating Degree Days for Rohnert Park, CA and the 5 year average, assuming that your base heating level is 65F, calculates out to 4172 heating degree days. This doesn't make any difference to you, but it might if someone was installing their own system, they could find out what the HDD was for their locale and compare it to your HDD and would have a rough idea if your design would work for them, too.

From what you have said so far, I assume that your house is built on a slab that has no insulation underneath, correct?

Regarding insulation, you said that your house was pretty well insulated...

• What exactly do you mean by that?
• Did you do the insulation yourself?
• What is the thickness of your outside walls?
• What kind of filling is in them?
• Do you have single pane/double pane/triple pane windows?
• Aluminum window sashes?
• Vinyl sashes?
• Wood sashes?
• Did you do any kind of a heat load analysis (similar to Manual-J)?
• Have you done a blower door test on your house?

In reading your blog, I saw that you didn't do any insulation UNDER your floor... and that you chose a thin foam underlayment to go OVER your floor, under your final flooring... Any thoughts on that?

I don't know if you looked at Vlad's hydronic install yet, but he built his own house (6" walls filled with mineral wool, 2x pane windows, highly effective infiltration prevention) and he did a similar install to yours, with just a few differences. His house is three stories tall, so it is somewhat more of a cube than your single level house (ranch I would assume). Since his 'cube-ish' would have lower surface area per unit volume, it would favor lower heat loss, too. Anyway his water feed temperatures are running about 95F to 100F, as I recall, which is astoundingly good, especially considering that he lives just outside Vancouver, Canada where his average HDD is about 5481 which is a fair bit higher than yours.

By the way, you haven't gone into any detail as to how you plan to get the heat into the water... and how you plan on regulating temperature/

I will be very interested to see how your system performs as winter comes to visit us. Please keep us posted!

Good work, Olaf... it's a big job that should last the rest of your life.

Best,

-AC_Hacker

All good questions! I'll need to collate some of the info and add it to my blog :)

Our house was built in 1984 on a crawlspace with posts in concrete. I'ts a two story with four betrooms and two baths upstairs. Underneath is packed dirt. When I said the house is pretty well insulated, I meant 6" exterior walls with fiberglass roll insulation. I didn't do it myself, but have opened some of the walls (to run new power outlets), and that's what I've found in two of the exterior walls. The windows are relatively new (late 90s or so), and are double pane vinyl. The attic is insulated with about 6" of loose fill fiberglass (something I plan to augment with additional batts in the future).

We didn't do a full heating load analysis - our estimate came from the fact that my parents' house sees temperatures at least 35 degrees below what we experience in winter. They've got double the density of heating loops, and similar insulation, and about the same water temperature (they have in-slab loops over a basement though). So we figured that half the density would work fine for us with the relatively mild temperatures we're seeing.
Your information about average temperatures seems roughly correct. There's a couple of weeks or so when the temps occasionally drop below 30 for a few hours (between 3 and 5am), but that's the worst we see.

We've never done a blower test, but the house seems reasonably infiltration proof from the fact that it's the front door doesn't easily slam if all windows are closed.

We haven't yet done any underfloor insulation, which is still on our list of things to do (I'll probably hire a few students from the nearby colleges to help because I don't fancy the idea of scooting around on my back in a 15" crawl space for several hours :P). It'll likely be fiberglass batts with tension wire to hold them in. The foam underlayment of course insulates a little, so I plan on insulating very well in the crawlspace to offset that.

As for the water (this is still upcoming, as I haven't actually hooked it up yet), I'm going back and forth between a dedicated 30 or 40gal natural gas water heater (the total water in the system is about 25 gallons for the 1/2" PEX) and an air source heat pump. The water heater is going to be much cheaper and should be pretty efficient, although not as efficient as a heat pump of course. I think it'll strike a pretty good balance between upfront and runtime costs.

Since I've got only 9 or 10mm of the bamboo flooring and the thin underlayment on between feet and heating, I figure 80 to 85 degree water temperature should be sufficient, but that and the flow rate is something I can play with and fine tune to the needs of the rooms. Regulating the temperature is likely going to be done just with the water heater itself - I'll set it so that the temp ends up about 85 degrees (a thermometer in the feed line to the manifold should do the trick) and the water will be pumped from there directly to the loops. That way I don't have to mess with a second cold water line and a mixing valve.

Edit: I haven't thought too much about the thermostat yet. I figure I'll regulate the system by outside temperature - if it drops below a certain level, it turns on the pump. It'll take some experimenting to find the right setting, but should work. Since I don't have the tubing in concrete or other large thermal mass, there should be relatively little delay between turning on the pump and the floors warming up.


Do you have any input on the above setup? I'd appreciate additional ideas! :)

Not too bad... but as we in this forum have found out, the R-ratings for various insulations are determined in lab conditions with NO INFILTRATION. This means that if you have a wall with holes for power wires and outlets, you will get infiltration and you will not get the full insulation that you have paid for. Some homes are now being built with a separate, inside, 2" utility partition, an all power and water intrusions and power outlet and switch installations take place there, leaving the insulated wall intact and air-tight to work to maximum effect.

...Just saying that things can be much better than they have been in the past... because in the future it may be very important.

I'm sure that your new system will work just fine... you will be warm and comfortable and rightly, proud of your new installation.

But some of us here are trying to go beyond that and are eagerly venturing into the realm of 'diminishing returns'. As you surly know, when you DIY, some projects that when hired out, might not 'pencil out' in a favorable fashion, and when done DIY, they actually become not only do-able but quite desirable. For instance, I assume that your parents in Germany are using pipe spacings at around 6", or whatever the metric equivalent is... it does make sense to widen the spacings to 12" inches in your locale because your weather is so much milder, and with natural gas dropping in price, tighter spacings would not pay off in your lifetime.

However, if you had used the same spacings as your parents, it would open up the possibility of using low intensity heating to it's best advantage. Low intensity heating could be something like solar heating, where feed water only occasionally gets up to the temperature level that you can rely on with natural gas.

Also, another low intensity method, heat pump systems greatly benefit from higher efficiency floors, as they don't need to raise the temperature as high to warm the home to a comfortable level, and thus don't have to do as much work. The benefit to you is much lower power bills.

This all sounds very good!

I have one of those crawl space insulation jobs coming up too, and I'm not looking forward to it.

But when you mentioned the foam underlayment, is it over or under your hydronic floor?

If you go with a larger size water heater (maybe even bigger than 40 gal), it will reduce the frequency of the 'heat-up' cycles. There is an efficiency curve that describes each firing of your water heater... the efficiency increases in the beginning of the firing, and levels off until the end of the cycle. By having fewer and longer firings, you will reduce the overall lower efficiency part of the cycle.

I'm very interested to see how it all works out. One thing we very badly need is a database of performance from DIY installs.

There are dual-sensor thermostats that are specially designed for hydronic heating, for applications exactly like yours. They cost maybe $200 or so. They even have an adjustable setting to find-tune for the thermal mass of your house, so that there is minimum over-shoot or under-shoot.

So, that's my take on it. I must confess that I have not put a hydronic system into my house yet, but I have been obsessively studying hydronic radiant floor systems for almost a decade. I am very interested in low intensity heat, as I am convinced that the future lies in that direction.

I'm hoping that Vlad will chime in here, as he has done a very good job in his house, and he has no shortage of opinions. He did not go the 'utility wall' approach when he built his house, but he did compensate with post-construction infiltration sealing that was phenomenally thorough... I've never seen anything like it.

Best,

-AC_Hacker

Interesting that you mention this. You're correct about the pipe spacing (it's almost exactly 6" for the room interior). One thought I've been playing with is, later on, installing solar water heating panels - water could go from the tubing returns into the panels (at an estimated 3F or so less than the feed temperature) to be preheated before being dumped back into the water heater. I'm a bit unclear as to how to control the temperature and prevent it from getting too high for the floors, short of using a mixing valve with cold water though.

What sort of temperatures can one expect from solar panels? If my estimates turn out to be good and 85 degree water is enough for our heating needs, is there a possibility to go only with solar heated water and turn the gas heater off altogether?


It's on top of the hydronic system, between it and the hardwood floor. It was primarily to keep the floor quiet and comfortable to walk on - it's only about 1mm thick, so its insulation value is relatively small. Good crawlspace insulation is still a must, of course :)

That's great information to have, thanks! I was wondering what size would be best and had a hunch that bigger would be better - sounds like basically, the smaller the heater, the more it'll be running, so I'll try to go with a larger option.


While it's still reasonably warm outside, I can take a no-heating run of measurements (maybe this weekend) during the day and at night. Days are currently between 78 and 82, nights between 52 and 65, so I could get a series of temperatures in, say, 2-hour intervals or so of interior and exterior temperature without heating.
Then, when the heating system is active, I could do the same, while correlating it with water feed and return temperatures. Is there any other data that would be useful?


Again, great info! These would be measuring both exterior and interior and decide turn on and off based on both measurements, I assume?


Thanks for the advice, it's much appreciated. It's good to be able to have a conversation about this sort of thing as I install and tune the system to avoid some of the inevitable pitfalls :)


Olaf

There are several approaches to the temperature control issue. In Europe where hydronic floors are usually high mass, the most used approach is to have the pumps circulating continuously, and the temperature of the water is continuously changed to maintain the desired set point. In this case, your heat stays on all the time, day and night and a night-time set back is not applicable due to the very large mass.

In the US, even with high mass floors, pumping is intermittent as is heating.

But low mass floors are not at all uncommon in the US, as you can attest. So, night time set back would be possible, due to lower thermal mass. With a low mass floor, your 'buffer tank' would be your thermal mass, and in your case, if you are using a water heater, it is your buffer tank, too.

Vlad had a very interesting, and complex controller that sensed outside temp and inside temp, and because he was using the same water heater for domestic hot water water and floor heating (the floor water was kept separate from the domestic hot water by using a heat exchanger), his controller would admit shots of hot water into the circulating floor water, as needed to maintain comfort.

You should go on over to Build It Solar and check around. Gary lives in Colorado, as I recall, and is using solar for heating with gas back up.. and he has radiant floors just like you built. He's pretty good about keeping records.


This is the kind of thing that you'd be best to find out locally. You might ask a local hydronics outfit, they probably won't be too insulted if you ask them for advice.


Well, one thing you could record is what temperature outside, with no heat and no cooling, makes your house a comfortable temperature (say about 68 to 72) inside? So lower comfortable would be the temperature you plan to heat it at in the winter, and higher comfortable would be the temp a little bit before you wish that the AC was running. So you're looking for the outside temps that produce the inside temps you like. This could be useful to you later.

Otherwise, just wait until the heating season gets rolling and record the temperature of the water that goes into your floors to provide heat and the temperature of the water coming back from the floors. at first the difference between these temps will be big, but then the difference will stabilize... this will give you an indication of the efficiency of your floors. Vlad ran some kind of design program for his floors and the program indicated that his water temp should be about 115 F, as I recall. He said that if he had kept the floors at 115 F he would have cooked his family. So he dialed it back to between 90 and 95, as I recall. He really did a very good job of insulating... curiously he said that his system keeps his house comfortably warm, but the floors don't feel warm. I take that to mean that he has really cut his heat loss way down.

Vlad, where are you, we need your input!

Best,

-AC

opiesche,

Be careful when you select your HWT. All HWT have their minimum temperature unless it is a condensing one. If you just get regular DHWT and try to run it @ 80F you will end up with condensation problem.

For this reason if you use regular DHWT (non condensing type) you have to keep it @ minimum allowed temperature an install mixing valve.

I used special mixing valve I050C2R-2 - Taco I050C2R-2 - 1/2", 2 Way Outdoor Reset I-Series Mixing Valve w/ Sensor which works as thermostat as well. It is pricey but worth every penny. Check eBay for better deal but make sure you get exactly this model.

Just a quick update on the temperatures. We're experiencing an unusually cool late summer - it's not even quite September yet, and outside temps are already at 55F around 10:00pm. Interior is 73F at that time, and between then and about 1am go down to roughly 72.5F, with the exterior at about 53.


So, in 3 hours with a dT of -2F exterior, I'm seeing an interior dT -0.5F with a total dT of 20F between exterior and interior.
So, that tells me that, roughly for every degree difference between interior and exterior, I'm seeing 0.015F of decrease of interior temperature per hour.

In the winter, if we're assuming 35F at night, the dT exterior-interior would be about 35F, and assuming a linear relationship (not sure if it is, more data will tell), I should expect a decrease of 0.53F per hour in the house, or the same as raising the temperature by 0.53F per hour to keep it at 70.

Now, that's only if the relationship between the exterior-interior dT and the heat loss is really a linear equation. Anyone know if that's actually the case?

Crawlspace insulation will of course change that equation again, and it'll also be interesting to see how effective it is once installed. I've got a few months of data logging ahead of me (there's something I could put my Raspberry Pi to good use for!), but 0.53F per hour sounds like a piece of cake for a 980sqft radiator ;)

opiesche,

I really like your approach here. I have wanted to do something like this in my house.

Keep up the good work and keep us posted.

Best,

-AC

Another quick update: After building a temperature logger with a Raspberry Pi, a couple of digital temperature sensors, a bit of wire and a few dozen lines of Python code, I now have proper temperature data to share!

This is currently all without heater, and it shows a few interesting things. First of all, down to about 50F exterior temperature at night, we can comfortably do without heating at all. We've got about a 4-5F interior drop over eight to nine hours at night, which I'd consider pretty decent.
It also shows that there's about a two hour lag between exterior temperature drop and the interior following suit. That means, that when I measure an exterior drop, I've got plenty of time to turn on the pump keep interior temperature at target. Of course, that time will shorten as exterior temperatures get lower, but it gives me a good indication that it'll be fairly easy to keep the interior comfortable.
Here's some graphs from my custom built logger:

http://opiesche.no-ip.org/2012-09-18.png
http://opiesche.no-ip.org/2012-09-19.png
http://opiesche.no-ip.org/2012-09-20.png

Exterior in green, interior in red. All temperatures are in degrees Celsius. Please ignore the downward spikes to 0, those are just failed readings from the sensor. In the current iteration, I'm sampling temperature every 5 minutes.

(I'm not sure how this forum handles the image links, so it's entirely possible that these immediately hit the webserver on my little Raspberry Pi. Please be gentle!)

Forgot to mention, the exterior sensor wire is going out a window, which is then shut as far as possible and the gap is padded with rolled up bubble wrap to create a reasonably airtight seal. The interior sensor is close to an outside wall, so the interior temps are probably half a degree or so lower than in the center of the room, but I'd say the difference is probably negligible.

Thanks for the info, Vlad! I've been thinking about a mixing valve, but then I'd have to worry about what to do with the additional water I'd introduce into the system. In the end, I think I might go with a tankless natural gas water heater. They usually have energy factors of around 0.8, so are pretty efficient - and since I'm only going to need <30F rise of water temperature, a small model should do the trick. I'm looking at this one:

Eccotemp-FVI12-NG Indoor Tankless Water Heater

Which allows for individual control of gas and water flow, so I should be able to adjust this very well for my target temperature. This heater turns on when the water flows, so my pump circuit would automatically also turn on the heater if the water temp is below target.

Has anyone here had experience with tankless heaters for hydronic floors? I'd be interested in hearing some experiences!

Using tankless HWT for low temperature application is going to be a real pain. It will short cycle on and off. With tank you just take as much water as you need and return water goes back to tank. Water mass in the tank will be like a buffer it will prevent short cycling. Short cycling is always bad because usually equipment efficiency is reached after some time not right away after starting.

Thanks, Vlad! A tank heater it is. I've found a few that list minimum temps of 80F, it's just a matter of picking the right one.

With the recent temperatue graphs, by the way, I can also calculate my total heat loss:

The temperatue graphs back up my previous estimate of 0.15 degrees of temperatur decrease interior for every degree difference between interior and exterior (in the graphs I'm seeing about 1C per hour for 10 degrees C difference).
So, let's be generous and assuming 0.2F per hour per degree F, or 2 degrees per 10 degree difference ext-int.
The total air in my house is roughly 2200 (sqft) * 9 (average ceiling height) = 19800 cubic feet.

The density of air at sea level is about 1.2 kg per cubic meter = 2.64lb / m^3. 1 m^3 = 35.31 cubic feet, so 0.07lbs per cubic foot, which means the weight of the total air in my house is 0.07*19800 = 1386 lb.

Specific heat of air is 0.24 BTU/lb/degree F. I'm losing 2 degrees F per hour at 10 degrees difference between exterior and interior, so

0.24 * 1386 * 2 = 664 BTUs per hour of heat loss, if the interior is at 68F and the exterior at 58F. Our coldest nights are about 30F and the interior should stay at 68. Assuming a linear relationship between heat loss and temperature difference, that would make the heat loss on our coldest nights about 0.24*1386*(0.2*(68-30)) = 2528 BTU/h.

Someone double check my math, please? I'm new to all this :)

Heat loss graphs
 

So, I couldn't help but tinker a little more. I've added another bit of code to my temperature logger based on the above calculations, so now I'm plotting heat loss against the exterior-interior temperature differential:

http://opiesche.no-ip.org/2012-09-23_heatloss.png

The blue curve is the temperature difference between exterior and interior (scaled by a factor of 100). Positive values mean it's warmer inside than outside. The red graph is the calculated heat loss in BTU/h. Negative values mean heat loss, positive are heat gain. I'm taking temperature differences within 5 minutes, calculate the BTU heat loss from them, and multiplying the result by 12 to get BTU/h.

This is today's data, so unless the forum caches the images, this plot should update live as long as my Raspberry Pi is online. The data is a little noisy despite smoothing, because sometimes between two 5 minute samples, the interior temperature doesn't change at all, which makes the heat loss graph spike towards 0 for that interval.

It shows one very interesting thing: The house gains heat much more easily than it loses it. Observe the temperature differential in the left half (about 10F) with a heat loss of about 1800 BTU/h on average. On the right, we're looking at a temperature differential of about -5F, but a also heat gain of roughly 1800BTU/h on average.
That tells me that I should probably invest in some attic insulation and radiant barrier foil to keep summer temperatures more comfortable :)

Going a little further with this: say we more than double the heat loss for our coldest nights, to 4000BTU/h.
I've got 980 ft^2 of heated floor surface, that means I'll have to put at the most 4 BTU/h/ft^2 into the floor.

Each square foot of flooring contains on average 13 inches or so of tubing, at 1/2". The volume of a cylinder is pi*r^2*h, so 3.14*0.25*13 = 10 cubic inches or 0.163l of water.
At 1kg/l, that's 0.163kg or 0.35lb of water per square foot.

Water has a specific heat of roughly 1 BTU/ lbdeg (1 BTU for each pound of water that is 1 degree warmer than ambient). So, to get 4BTU out of 0.35lb of water, it'll have to be 4/0.35 = 11 degrees warmer than the ambient temperature. If I'm considering 70 degree ambient temp, I'll need the water to be at least 81 degrees to satisfy the highest heating demand - take losses into account, and the 85 degrees I was originally considering don't sound too far off :)

Again, I'd appreciate if someone could double check my math here.

Also, what does that mean for my water heater? I'm seeing that most of them rated somewhere between 30,000 and 60,000 BTU/h - seeing how my need should be around 4000-5000BTU/h, and taking the energy factor of 0.6 of most gas water heaters into account, I shouldn't need more than 7000BTU/h in gas input during the coldest outside temperatures.
My guess is, to prevent short cycling as Vlad and AC_Hacker mentioned, that I should go with the lowest rated water heater in terms of energy input, that I can find. The 75,000 BTU tankless I mentioned would definitely not be a good choice - a 35k BTU tank water heater would probably do the trick nicely. Any thoughts?

Sounds like you also have a respectable project to share... and don't forget the photos and the Python code!

Best,

-AC

As requested :)

Adventures in home improvement: Temperature Logging

I'll update this with some more pictures and information, and finally code, this week. Just to show how simple it really was, here's the script that reads the sensors and outputs the values to a .csv file. I'll eventually make this prettier and more flexible as well (right now it's hardcoded for my particular sensors and setup).


I'll keep tinkering and adding to this. The source code and build instructions will likely end up on github when I'm done.
The cool thing about doing this with the Raspberry Pi is, that it's network accessible (I grab the plot images from a webserver running on it) and that I can program it remotely via SSH. It can sit in its current location running (at about 1W, by the way!), and I can tweak it, tune it, and grab the data and plots from it without ever touching the physical machine :)

This useful post will get lost very soon. You should start separate thread with name like "automated control system, code..." or whatever you think it should be . It is a really a big deal for most people to get sophisticated control system especially one that you can control from your computer....

I found many not expensive mini boards on eBay but they all require some sort of programming.

I think you put to much brain power to determine your heat demand. It doesn't really matter. If you have right controls you will only use just enough heat. Rest of heat will just be stored.

It is easy.

1. You should determine your highest temperature needed for your heating system. Let's assume you need 100F.

2. You have to check the lowest temperature your HWT can operate. Let's assume you will use regular DHWT (non condensing one) and set its thermostat @ 120F.

3. Thermostat will cycle on/off 120F-140F or 120F-130F or something close to this.

4. Now you have your heat source @ 120F-130F. If your HWT capacity 50000BTU or more or less and you only need 5000BTU your HWT will just seat and do nothing. If suddenly you need 40000BTU your HWT will start/stop more often.

I can't build my own control system so I used stock controls. I used taco 2 way mixing valve with outdoor sensor.
http://www.pexsupply.com/Taco-I050C2...Valve-w-Sensor
It allows to modulate floor loop temperature according to outside temperature. The colder outside the warmer loop water.

Also I added variable speed control for main circulating pump.
http://www.pexsupply.com/Tekmar-157-...peed-7955000-p
I put one temperature sensor on supply and one on return at manifold. I set 5F TD between supply-return.

Now mixing valve determines loop temperature according to outside temperature but often if you cook or outside cold but sunny day you don't need much heat. In this case TD will go down(if heat is not needed hot water can't loose it's temperature and return temperature goes up this lowers TD) and pump control will slow it down to keep TD @5F. If pump works at lowest set speed for set amount of time pump control will stop it for 5 min and restart it after.This is new cycle.

This 2 systems allow precisely control heat demand for house. It doesn't matter if my HWT is 40000BTU or 75000BTU my system allows to take just enough heat.

Vlad,

Thanks for posting your approach to heat sizing, your method is really appropriate and can only come from much experience... this is a very valuable insight.

But, at the same time, I think that opiesche is really on to something here... He is trying to determine the total thermal response characteristic of his house, which could be expressed in a simple mathematical expression... this could have utility far beyond just heating his house against the winter cold.

Best,

-AC

I have a similar project underway, for which I was planning to use an Arduino datalogger I got HERE.

On the plus side, it can store oodles of data and best yet, it works right out of the box. On the minus side, it doesn't talk to Ethernet... bummer.

I'm stringing 1-wire temp sensors in every room of the house. I don't heat the entire house, so I'm trying to get information on how the heat affects unheated areas as it passes on to its final destination... the great heat-sink in the sky.

I have five sensors functioning, but still have three sensors to hook up, which will include outdoor temp logging.

Right now, I'm using the CAI board that Xringer discovered, which has some interesting features (web server, email sender, alarms, some programmability, humidity reading ability) and it just may ultimately do the trick.

But I am closely following what you are doing here, with your logger.

What exactly are you using to plot your data? I've been using Excel... it's powerful, but requires a lot of intervention just to get simple plots. Life should be less difficult.

Best,

-AC

Good point! I'll start a new post for this as soon as I've got everything in a usable state :)

I see what you're saying - clearly, any system will only use as much heat as it needs based on turning on or off the circulator; what I'm getting at with the calculations is to figure out how much heat I'm going to need in the first place to properly size the heater. If I have a 75k BTU water heater with only 5k BTU of heating demand, the water heater is much more likely to switch on and off all the time (short cycle), as it inputs much more heat than is needed to reheat the water back to target temperature.
The most ideal setup would be a heater that uses exactly the amount of gas needed to heat the water to target temperature. Of course, all water heaters are either on or off in terms of firing, so the higher the rating of the water heater, the more likely it is to short cycle.

For example a 75k BTU water heater with 5k BTU/h of heat loss, will turn on and off so frequently that it'll only be on a little more than 6% or so of the time. This presents a problem because of the mentioned efficiency loss through short cycling, so choosing a water heater with a rating as little as possible over the demand should increase efficiency (and save money).
Am I making sense?

Yes, I'm hoping this will prove useful for other things - like I've already seen that I should install some radiant heat barrier in my attic to reduce summer heat gain ;)

As for the heat loss calculations I'm doing, these are primarily about

-sizing my heater properly to get the best efficiency I can

-find out what water temperatures I'll need to reduce experimentation

-find out what flow rates I'll need (I'm still working on that) with a given water temperature, so I can pick the right circulation pump

-make the system smart enough to turn on and off the pump at the right times, maximizing efficiency and keeping temperatures comfortable

The last point goes further than just setting parameters and forgetting - the controller should be able to adjust to changing exterior temperatures because it knows the relationship between heat loss and temperature difference (which follows a simple equation I'll be able to generate from the heat loss data once I've got a few days worth).
It can also learn the delay of the system when it turns on the pump, and make a decision based on that information to turn the pump on sooner or later - that timing will change with different i/e temperatures and current heat loss, and if it does it right, efficiency of the system can be further increased (the later I can start turning on the pump, the later the water heater will need to fire, further reducing short cycles of the heater).


Once I've got all the data and formulas right (I can verify them on my own system), I'm hoping to put everything into an SD card image for the Raspberry Pi for people to use and extend. Then anyone could solder a few wires together, leave a small box running for a couple of weeks, input a few values (floor area, heating loop density, air volume, etc) into a web site, and have the software spit out a range for flow rates and water temperatures to pick the right heaters and circulation pumps - all for less than 50 bucks in parts :)

Very interesting - I was thinking about using an Arduino, but the ease of setting up and programming the Pi (and the fact that it goes for $35) has completely sold me on it. I'm usually more of a C++ guy as far as programming goes (software engineer by trade), but being able to quickly whip something like this up in Python and take advantage of its facilities to easily wrangle data from text has some real perks.

For plotting, I use MatPlotLib (matplotlib: python plotting &mdash; Matplotlib 1.1.1 documentation), a really full featured Python library. With it and a couple other pieces of freely available code, I can read data from .csv files into arrays that can then be directly used to generate a plot and save it to an image file. The code for this is really simple, as you'll soon see. The images are saved directly to the web server directory, from where I can grab them from any web connected machine (the plot images in this thread are pulled live from the Pi's web server).

As for the data amount, it's really less than it seems. The .csv files for each day are only about 6kBytes in size, the .PNG images about 55k. With a cheap 4GByte SD card in the Pi, I could store 100 years of data and still have room to spare.

I'd like to put additional sensors on it as well (at least one upstairs, one downstairs, and one outside), and will have to experiment a little with the maximum wire length. I'm using the DS18B20 sensor (also Dallas 1-wire) - do you have any idea how long the wires can be before you start getting problems with signal degradation?

Web control of your heating or cooling system is super cool but most people have no idea how to set it up. Professional DDC systems are super expensive making them useless for DIYers. But we can share and benefit from each other knowledge. The problem with this thread is it is growing very fast and it is almost impossible to find what you found ones. I think it would be very useful to have separate thread about automation and web interface.

I do agree with you. This is probably the most sophisticated way to determine your heat demand. My heat loss calculations were done by "professionals" and they gave me 50000+ BTU number. My HWT which is the only heat source I used has 24000 BTU net output. We use it for heating hot water also. With 2 babies and 4 adults our hot water demand is very high. But we never ran out of hot water or heat even on coldest days. So just like always "thumb rules" rule the world. Heat demand has very wide range from 0 to maximum. For this reason I put "2 layers" of controlling (heat and flow).

This is a small story about professionals. Ones I was checking the boiler room in public library and noticed that boiler is short cycling. There were 2 boiler but only one was working. It was cycling at 30-40 SECONDS intervals. You only can imagine the efficiency of this boiler...... I brought this up but... But wait a sec this is a public place who cares about efficiency???? Tax payers don't get refund....:)

I'm using 4-strand bell wire that I had laying around just because I had it. I'm using a three-wire system because for me it's much easier to use an extra wire strand than to take all the precautions that a 2-wire setup require. I'm hearing that the 2-wire setup can be finicky.

Pure hear-say on this one, but the guy I got my Arduino data logger from said that he was able to deploy at least 70 sensors, and that runs of almost 100 feet are possible.

From the experiences of other, it seems that if you put branches in your system, you can risk the reliability of your data.


I am using some tiny printed circuit boards that were designed by a local guy to mount my sensors onto and to connect the leads to, also. There's nothing particularly worth noting about the boards, with the exception that there are pads for soldering a termination resistor onto for the last sensor (sensor most distant from the micro-processor board). The idea is that a signal pulse that travels down the wire, will 'echo back' if it hits a drastic change in impedance, like if it hits an open (zero impedance) at the end of the line. The board also has pads for tiny caps to go from V+ to ground, if required. No one around here has needed to use the caps.

My house is small, two-story with a basement, and I'm running my sensor string up along the chimney, which is pretty much in the center of the house.

So far on my system, I am doing everything wrong... I have two single-sensor branches (short ones) coming off the main line, and no termination resistors and no power line caps anywhere. I'm getting good, reliable data. My total length is about 30 feet, excluding the short branches. I figure I have another 25 feet, and three sensors to go.

I have read horror stories about people who have used CAT-6 cable, and have gotten horrible results, I have also read reports about the same setup and people who get great results.

I had one apparent problem with one mounted sensor, so I replaced it with another, problem solved. Closer inspection revealed that my bad mounted sensor had a bad solder joint. I re-soldered the joint and it is now reliably in use.

Aside from violating all the rules, I have been careful in the construction and deployment of my sensors... I check for good data, at each step. So far, I have not entered into the ZONE OF UNRELIABILITY. If things begin to get sporadic, I'll start with a termination resistor... If that doesn't do it, I'll go with the tiny caps... if that doesn't do it, I'll replace the branching topography with a linear one.

That's what I can tell you at this point, hope it is of some use to you.

Best,

-AC

Tiny little circuit boards, definitely very small cows :P

I didn't see this info anywhere but are you using O2 barriered tubing. If not, you will need a bronze pump, strainer, no steel fittings and the water heater should not be used for domestic water. I would look at the Vertex water heater as a heat source. It is condensing, reasonably priced and won't short cycle.

Oh, and we always use Beldon twisted pair wiring for sensors. It is the industrial standard.

Cheers

No, I'm not using O2 barrier tubing. It's a closed loop system and the water heater will be dedicated, and the manifold has an air eliminator at the end of the return side, so air that the tubing accumulates through expansion and subsequent contraction of the water should be removed by that to avoid corrosion. Do you figure I still need a non-ferrous pump and fittings?

I'll check out the Vertex water heater - the significantly higher efficiency would definitely make a condensing one more attractive, but they are usually so %$#^ expensive compared to regular ones :P

Thanks for the info!

Cool, that's great info to have! I'm getting some wire this week to rewire the controller and put the sensors and controller into a semi-final position. I'll post some more pictures of the setup when it's done.

BTW, I've also, as Vlad suggested, posted the controller piece into a separate thread:

Custom hydronic heating controller

As for the branching setup, electrically it should make no difference to a linear setup - the only difference is that you're attaching a bit of wire to the pins of each sensor - if you think of the sensor's legs themselves as short runs of wire, there's no practical difference between putting all the sensors onto one long wire run, or giving each sensor its own - you're only moving the place where all the signals start running in the same wire, but since two sensors aren't sampled at the exact same time, that shouldn't matter.

In a linear setup, you'll have more wire for each sensor, and hence more resistance and capacitance. Since it's DC, capacitance of the wires is irrelevant, and the resistance should only lead to a negligible voltage drop - at 50 feet with halfway decent wire, I would expect 1% at the very most (or 0.03 of 3.3V, which should be well within the tolerance of the sensors).

Absolutely, the pump and fittings need to be non-ferrous. While you may get the air out of the system, the O2 in the water will still attack ferrous components. I have removed many iron body pumps from jobs where the (usually plumber) has installed non barrier tubing and the rust has eaten out the non ferrous components. Another thing to remember is that some zone valves are designed for closed loop systems only because they do not have stainless steel components. I cannot tell you off hand which ones apply but typically ball valve type are fine.

Also, try to have the pump on a vertical pipe so that any sediment doesn't sit in the pump volute.

OK, thanks! Going for a different pump than I originally intended, then. The zone valves are built into the manifold, so I don't know what type they are - but it is a closed loop system. I'm still debating whether I want a mixing valve that I can control electronically so I can adjust the water temperature if necessary. I'd need something that I can switch via a relay - I've got a little research to do yet :)

Like this?

Danfoss Heating - North America

These 24vac motors will drive with any signal. I would think one of the guys could come up with an outdoor reset control that uses the PID control I saw on here. tekmar has one but it is more fun to make it.