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Old 02-21-16, 04:58 PM   #11
pletby
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Quick question Stevehull: I like that method of finding the maximum BTU load of your heating system but I have a curveball. What if I have a newer natural gas furnace with throttling gas valves? It's no longer on or off, it can run at a reduced setting for quite some time. How would I go about running this test?

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Old 02-21-16, 07:28 PM   #12
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Many of those furnaces have a dip switch on the control board that disables the variable gas valve. It then operates in just the off or on mode.

For a +/- approximation, you can look at the plate to find out the BTUs when it runs 100%. A better way is to read the meter, do the test for 12 hours and then read the meter again. Most meters are in ccf with a subdivision to cf. Then you can look up the BTUs per ccf and multiply to get total BTUs and then apply the efficiency number 90-95% or so.

Look in the manual or get one on line.

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Old 03-03-16, 03:04 AM   #13
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Well I do have an air source heat pump, but it's neither effective (ductless, so only really warm in rooms with air handlers) nor efficient (runs up my electric bill to near $200 when it gets cold). On top of that, it's currently OOC. I was just planning on running the pellet stove all winter, then ditching the ductless system and installing something better over the summer. But from what you've said, it sounds like I might need to get in fixed so I can calculate the BTU load. Would that probably be better than trying to figure it out using the pellet stove?

Edit: I also have gaps in some of my doors that might be robbing me of heat, so I guess I need to make that more of a priority too. Would hanging heavy curtains on the windows make a significant difference?
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Old 03-03-16, 09:23 AM   #14
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Welcome, Sam!

I have made a number of posts that describe simpler, more effective ways to make the house more efficient and get what you need sustainably so you can fire your utilities. Instead of reiterating, check out my posts and the threads they are in. In particular, AC Hacker's DIY Hydronic Floor Heating, his Homemade Heat Pump Manifesto, and my Passive Annualized Heat Storage threads cover wide ranging topics that all interconnect to make an efficient house and have numerous worthy contributors.

Tons of useful info and helpful people in so many threads here!

Most important, it is easier to keep your energy in than it is to replace it efficently. Insulate properly and use your interior walls as your infiltration barrier. You can get about as good an envelope this way as you could with exterior house wrap.

Electrical boxes and gaps in HVAC equipment/ducts let an amazing amount of air in or out; seal them. $100 of weatherstripping, UL 181B rated duct tape like THIS KIND and fire retardant spray can foam (behind the electrical boxes) could save almost that much per month.

Air source heat pumps are great but only worthwhile if they are variable speed inverter drive. Conventional ones only have one compressor speed, making them inefficient and low output when you need their output the most. The inverter drive ones are amazing for their efficiency and output, plus they can modulate to match their output to the need.
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Old 03-04-16, 12:29 PM   #15
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Okay I'll definitely be taking a look at those when I get a chance! Luckily cooling isn't a huge concern due to the shape of the house (cracking open a few windows at ground level and up in the cupola is usually enough to keep me cool), so I should be able to wait until summer when school's out. I'll definitely make sealing up the doors and windows before next fall a priority though.

From what you said about heat pumps, it sounds like mine is the conventional type. As it got colder this winter, it actually started to sound worse and worse when it was running. Then when it got well below zero, it just quit on me. When I called tech support and gave them the error code it was displaying, they said it's a compressor issue and that their units aren't designed to operate below ~15F. Would the inverter drive type be able to keep up when it gets that cold? And would it still draw a lot of power in the cold months (compared to ground source, not to my current system)?
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Old 03-04-16, 02:44 PM   #16
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Yes, the inverter drive units keep up with cold temps. Most are rated to work down to 0F such as THIS Gree U-Match 24kbtu UNIT which replaced my girlfriend's 30 year old gas furnace (with a constant burn pilot light!) and air conditioner. We chose this one since it could be hooked up to ductwork as designed; she didn't want a more efficient unit hacked to mate with the ductwork. That would have worked ok in her case-no return ducts and the supply ducts are short and unrestrictive. ecomfort.com was great to buy from.

It works beautifully! Her 2BR condo is reasonably efficient, and this unit runs less than half the time unless it is extremely cold even though it can throttle down to 8kbtu. To put it through its paces, I set the thermostat to max on "Turbo" mode when it was 20F outside. I burned my hand on the vapor pipe at the indoor unit, the discharge air was toasty warm, and it made the whole place uncomfortably hot in less than half an hour. At sensible settings, it used less than $20 extra electricity during the coldest months.

Conventional ones don't pump much heat below 40F which is when you need it most. They rely on resistive heat or gas to make up the difference-expensive.

A ground source unit is very efficient because you are pulling heat from a 40F or better heat source, but you need a loop field, which needs to be large because your heating dominated climate will pull its temp lower and lower in a couple years. Good field design becomes evident after the 3rd year. Putting the field on more than one side of the house opens up the area you can draw heat from significantly. Check Energy Star rated units if you want a ready made one instead of rolling your own a la "Manifesto", or to get an idea of efficiency vs airsource. There are few site locations where I think an open loop GSHP makes sense. Their ratings don't include the energy required to "pump and dump" the water, which can be very high.

Of course, you could combine ground source and seasonal storage as I describe in my thread for "fire your energy companies" efficiency, but that is a multipart harmonized system.

Cheap heat with AC capability in multiple areas? An inverter multi-split (multiple indoor cassettes with one outdoor unit). Get one heavy on the HSPF rating and lowest temp capability. Some are optimized for cooling-dominated climates. My favorite vendors I might buy from are heatandcool.com and highseer.com.

Need a ducted system? One of the "concealed duct" models like our Gree.

There is some concern about ASHP efficiency in cold wet conditions because of the need to constantly defrost. I have never, ever seen my girlfriends unit have any frost on the fins, ever, even when it was 100% humidity in the low 30's, when in the 20's, or during the one instance we had snow. These observations were made while the unit was actively heating the condo. At low temps, there just isn't that much moisture available in the air to cause frost with.


After seeing many systems and installing a few, I would heartily recommend inverter drive heat pumps of any type, and would never recommend a conventional. You will need additional heat sources to keep up if temps are below 0F, but unless you need to rely on them frequently a wood stove or portable heaters would do it.


Warm floors are awesome if you feel like doing it. I will never go back to forced air heat if I can help it.
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Old 03-04-16, 11:03 PM   #17
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Sounds like GSHP might end up being the best route for me to go. Where I live, the temp regularly gets into the double-digits below zero. And frost is definitely a concern up here too. It's not uncommon for cars parked outside to be completely covered in a sheet of ice in the morning! My house sits on an acre that's at least half open space, so hopefully that will give me plenty of room for a sufficient loop field.

I was actually talking to a guy I go to school with just a few weeks ago about radiant floor heating (I assume that's what you meant by "warm floors"?). He said he's installed it before and that it's extremely effective. From a quick online search, it looks like it's not unheard of to combine GSHP and radiant heating. What's your opinion on combining the two?
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Old 03-05-16, 01:05 AM   #18
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The air source units frost up the most when temps are in the high 20's and low 30's. It all depends on the dewpoint outdoors. Below about 25, the majority of the moisture is frozen out of the air, so there is not as much available to frost up the outdoor heat exchanger.

The old school units defrost on a time vs temperature scheme: when it's below about 40, they defrost every 30, 60, 90,or 120 minutes and don't switch back to heating until the heat exchanger warms to above 50 or so. If there's not much frost on the coil, they might only defrost a minute or two. The colder it gets, the longer it takes for the coil to warm up, and the more heating capacity you lose every defrost cycle. The newer units use more sensors, both on the coil(s) and in the open air. They can sense if the outdoor unit needs defrosting and when. They vary so much more stuff (fan speeds, compressor speed, flow rate of refrigerant, etc.) to do their job than the old school units that it is difficult to compare them with each other in side by side tests.

The ground source systems take energy efficiency to a whole new level. When it is -10 outside, they straight up whoop an air source unit if the ground loop is designed correctly. Having a 40 degree heat source to pull from, they don't take a penalty in power or capacity. If the wind starts howling, they don't mind at all. The unit might run a little longer, but that's because the wind is robbing more heat from the house.

Combining a GSHP with a low-temperature radiant source can save you a whole lot of KWH to get the same BTU of heating capacity if the system is designed correctly. When combined with domestic hot water heating, the savings can be very substantial. A straight electric water heater has a performance level of 1. This translates to about 4 EER. An old school air source unit might have an EER of 10 or 12, a newer one maybe 20. An old school GSHP might start out at 20 EER, and the newer variable-speed "water furnaces" are pushing 40 EER. There have been measurements made by members of this forum where their GSHP systems averaged between 25 and 30 EER all season long (COP values of 4 to 5) and saved them the cost of their systems in electric bills in just a few years. Of course, a lot of them did a large portion of the labor involved on their own.
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Old 03-05-16, 05:06 AM   #19
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Sam,

Yes you can provide hot water for a radiant flooring with a geothermal heat pump. You can buy a unit that is a "water to water" type that uses ground heat/water to then heat water that is stored in an insulated tank. That stored hot water is then used in the radiant floor system for heat.

Here is one such water to water unit (I have no financial link to this or any GTHP retailer).

Buy Goodman Heat Pump | Geothermal Heat Pumps | Goodman Air Conditioner

The above is a 4 ton unit that will provide 48,000 BTU (40 kBTU) per hour. I don't know your total envelope insulation values, so I can't tell you if this will provide you enough heat when it is -15 F and windy.

Even though you can "reverse" the GTHP cycle and provide cold water to the floors, as in summer for cooling, your humid summer environment does not allow this. You regularly have dew points in the high 60 to mid 70s F. The reason is that you will literally have wet floors when the cold floor is below the dewpoint. To get much cooling, you need the floor about 45-50 F and that is WAY below the summer dewpoint.

Example. Put a glass of cold water on your kitchen table in the summer. That water is about 40 F or so. Note the condensation on the outside of the water glass? That is what your floors will be like. So radiant "cold" does not work for your location.

A small (compared to heating need) tonnage ac unit is called for. It could also be a GTHP.

WaterFurnace, a physically close to you manufacturer of GTHPs, makes a unit that not only provides chilled or hot air, but also radiant water for a loop. Problem: $$$$$ about $10k+

WaterFurnace Residential Product Line : Synergy3D

Personally, I would start with a water to air GTHP from Ingrams such as this:

4 Ton 2 Stage GeoCool Geothermal Heat Pump

The above is a 4 ton (48kBTU) unit that will certainly provide enough cool in summer and likely 60-80% (?) of your winter heating need.

Many people in your area use open loop systems where water from their domestic water well is used. The output water from the GTHP goes into a pond or such. Least expensive, and where lots of ground water is available and a high water table (such as you have), it is a very rational solution.

But again, we are just guessing at the tonnage size needed. You need a assessment (manual J or utility) or a load test for your home such as I described above. I can tell you with winters like you have at least 3 tons for heating and perhaps as much as double (triple?) that, depending on the above results. Your summer cooling load is low, so any system that provides sufficient heat at -15F winter will cool off a house when it is 95F summer.

No point is spending more for a heating/cooling system that you need.

Or read the manifesto and build your own . . . .


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Old 03-05-16, 08:00 AM   #20
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Default New home owner wanting to fire utilities

Samerikson

It sounds like your ready to embark on a great journey to net zero. If I'm understanding you want to tell the utilities to take a hike and still stay warm and in the light. Of course we will need more details but it sounds like your new digs are well insulated and just need the investment to take your new home to the next level.

My experience is I built a countryside contemporary home in Canada with solar hot water heated floors backed up with geo-thermal. The solar PV is my next step.

I believe your heading in the right direction. We fired the furnace oil delivery guy and are grinning ear to ear.

I would like to wet your appetite. For your homework have a look at what this smart guy Jerry accomplished
DIY Geothermal Heat Pump + PV System - No Heat Bills!

After you have a look at that drop back by

Randen

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