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Old 11-21-13, 09:42 AM   #341
AC_Hacker
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Originally Posted by michael View Post
Zip code 95460... We have a mild climate stabilized by the proximity of the Pacific Ocean and not hard on a heating system...
I went HERE and checked your Heating Degree Days. Not knowing any better, I chose the weather station at the Ukiah Municipal Airport. I used 68F as your base temp, that seems to be pretty commonly the case for most of the EcoRenovators.

Your HDD value came out to be 4886, which surprised me, as it is just a tad cooler than there in Portland... guess it must be an ocean current issue.

Anyway, as if you didn't already have enough data, here is how the average HDD from the last five years graphed out...


Also, your temperature data looks quite favorable...



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The house has energy compliance heat loss calculations to predict how it's supposed to perform. They were part of the permitting process, and they predict 17k BTU/hr loss in the worst case.
Wow, pretty impressive that your local government is so advanced in their thinking. I thought Portland was on an energy jihad, but now I see that we have work to do.

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The plans call for a geothermal heat pump to provide space heat, but that's another story.
Excellent!

I played around with the Carnot Efficiency equation, as it relates to heat pump COP curves, and I found out that heat pump efficiencies are more sensitive (in a favorable way) to small improvements in radiant floor efficiencies than fossil fueled systems may be.

> ...and they predict 17k BTU/hr loss in the worst case.

This is lovely.

I don't know what your typical solar exposure is, but this makes you a good candidate for solar.

It also opens up a good opportunity for ASHP-to-water providing heat for your slab. Your worst low air temperature is very ASHP-friendly.

It also puts you in the rare category of people (like me), who want to strangle every last efficiency possible out of their heating system and want to go GSHP. It may be good news or it may be bad news, but you are going to have trouble finding a commercial water-to-water GSHP that is small enough to heat your home most efficiently.

So don't forget where the Homemade Heat Pump Manifesto is.

On with the show...

Best,

-AC_Hacker

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Old 11-21-13, 11:53 PM   #342
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Thanks, AC, for taking the time to post the reply above. Using Ukiah is close, but we're really near the coast at less than a mile from the ocean four or five steps up what folks around here call the ecological staircase...a series of uplifts that pushed the ocean out and moved us up. The temps here are highly stabilized by the ocean's temp. In Ukiah it actually gets warm (and cold) with temps in the high 90s. We're about 45 miles west of Ukiah on the other side of a little coastal range. Our temperature here is mostly between 50 and 70 with a couple days in the high 70s, so when I entered a more local site, the one year heating degree day figure came up at just under 6000 (not enough data for five years which you must have discovered). The low temp on our heat loss calculation is 29 degrees. What I remember of Portland, having grown up there, it's lots hotter in summer and colder in winter than here.

Solar works pretty well here, and this property has good exposure with the trees on the north side. I'll be putting in a 2.5 kW PV array, and I will have a solar preheat for DHW. Everything in its time.

Anyway, thanks for the information. I'll check back in when there's some progress on the radiant floor or when there's something useful to say about the heat pump, and I won't forget about the Manifesto!

Last edited by michael; 11-22-13 at 12:20 AM..
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Old 12-03-13, 09:36 AM   #343
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Originally Posted by AC_Hacker View Post
I talked with a local hydronic guy who told me that around here, feed water temperatures are:
  • 80 to 85 degrees for tube in slab
  • 100 to 110 for on top of floor heating
  • 120 to 130 for below floor (AKA: staple up) heating

* * *

And just to get the thought process moving, here are some radiant floor links...
  • Here's a house heated with water from a solar shed, featuring DIY radiant floor heat. It utilized the large radiant area of the floor to compensate for the lower feed temperatures of the solar system. As a bonus, the solar collectors work more efficiently, too.
  • Guy Marsden does a 3" solar heated slab in Maine (w/propane backup).
  • (...the 'NEXT' tab at the bottom will take you to the other two pages...)
  • Here's a solar shed with a hot water heat storage feature. No radiant floor, yet.
  • Here's a link to a company that supports DIY. The web site is filled with grest photos & descriptions. They also have a free downloadable design manual available here. The manual pretty much duplicates the web site, photos not as good as the web version. There's good info here, but a fossil fueled boiler is assumed, so their 'rules-of-thumb' may not hold with the lower solar or hydronic feed temperatures.
  • Here's a page from Radiantec, also supportive of DIY, with free manuals too numerous to list. Raniantec also has a list of Solar heating articles, why not combine the two?
  • HouseNeeds hosts a Hydronic Heating University.
  • InFloor has a free Deluxo Design & Installation Guide.
Hey AC_Hacker,
Its really great idea. I will also work on it.
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Old 12-03-13, 06:02 PM   #344
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Originally Posted by AC_Hacker
"I talked with a local hydronic guy who told me that around here, feed water temperatures are:
80 to 85 degrees for tube in slab
100 to 110 for on top of floor heating
120 to 130 for below floor (AKA: staple up) heating"

First, a question: can someone explain what the terms "part load" vs. "full load" mean with regard to heat pump performance? I've been reading a PDF from roth-usa.com on their RWT Series Water-to-Water Heat Pumps, and in the performance data under the column titled "capacity," they list values for part and full load. Are they modulating heat pumps, or to what do the terms apply?

PEX tubing just arrived along with the manifolds, so things will be happening on the new house site very soon. Photos will follow.

A quote from quite a while back appeared and is re-quoted above, and the temperatures surprised me. In our current residence, the heating part of which has a 1.5" concrete slab and 1/2" ceramic tile with 1/2" polybutylene pipes at 6" centers, entering water is 110 degrees, and it returns to the heat exchanger at 85 degrees. I suppose entering temperatures (in the quote above at 80 to 85 degrees vs. our house at 110 degrees) depends a great deal on the pumping rate. I've been monitoring ours, and the water flows through the floor at the rate of 7 liters per minute (1.85 gpm). There are 2000 LF of tubing in the floor containing 23 gallons of water, so there's a complete change of water every 12 minutes or five times per hour, so 115 gallons of water could flow through the floor every hour if the pump ran continuously. At 115 gph and a 25 degree temperature drop, the set up could provide close to 24000 Btus per hour to the house. The house is 2000 SF; the central radiant portion is 1000 SF, and the rest is carpeted and unheated. In the weather we're having right now, the house is demanding 140K Btu per day, so the pump is running less than 6 hours per day. This is from data I've collected, not from heat loss calcs. The inside temperature is 70, and outside it is 65 during the day and 35 at night.

Heat loss calculations done in 1988 when we designed and built the house predicted a 32663 Btu per hour loss with an outside design temperature of 34 degrees. Just sayin'.
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Old 12-03-13, 07:30 PM   #345
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Quote:
Originally Posted by michael View Post
First, a question: can someone explain what the terms "part load" vs. "full load" mean with regard to heat pump performance? I've been reading a PDF from roth-usa.com on their RWT Series Water-to-Water Heat Pumps, and in the performance data under the column titled "capacity," they list values for part and full load. Are they modulating heat pumps, or to what do the terms apply?
OK, I looked through the PDF, thanks for the link.

I think there could be someone else on the forum who would be better to answer your question... and I don't know who.

Now, if you were building your own heat pump, I could help you out, but divining the intent the factory is just not my specialty.

Sorry,

-AC
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Old 12-03-13, 09:05 PM   #346
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http://www.roth-usa.com/PDF_Download...ies%20EDIM.pdf

Page 4, for example.

House insulation: R-19 floor and walls, R-40+ ceiling all fiber glass batt. Windows will be double pane U-0.580.

No comment necessary. I was just putting down information.
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Old 12-04-13, 10:53 AM   #347
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OK, I looked through the PDF, thanks for the link.

I think there could be someone else on the forum who would be better to answer your question... and I don't know who.

Now, if you were building your own heat pump, I could help you out, but divining the intent the factory is just not my specialty.

Sorry,

-AC
No problem. I sent an email off to the company in hopes of getting an explanation. Also, regarding an earlier reply, I understand the sinusoidal aspect of daily weather as well as the slower variation that's seasonal, but it's also worth noting that even with last nights low of 30 degrees, the heating system at 24k Btu/hr is keeping up with the heat loss. The house and floor were warm this morning at 5 when I got up, but to do that, the circulator ran 13 out of the last 24 hours.

I'm in awe of your ability to build heat pumps from scratch!

mm
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Old 12-04-13, 07:43 PM   #348
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...even with last nights low of 30 degrees, the heating system at 24k Btu/hr is keeping up with the heat loss. The house and floor were warm this morning at 5 when I got up, but to do that, the circulator ran 13 out of the last 24 hours.
Part of why it isn't easy to comment on your house and its heating, is that you have a 1000 sq. ft. radiant panel (your central heated floor) supplying heat to the whole 2000 sq. ft. of your house. I have been temperature monitoring my house, room by room, which is much smaller than yours, but only has a few central rooms directly heated. So I can see that the heat from the central room 'leaks' into the other rooms. All in all, it is working out fairly well, as the central room is where I spend my relaxed time. The other rooms are for activities and temporary activities... but none of them are ever at outdoor ambient temperature.

But requiring 24k Btu/hr for 1000 sq. ft. at 30F outdoor temp seems to me to be quite a bit of heat to balance 30F outdoor ambient.

And requiring 24k Btu/hr for 2000 sq. ft. at 30F outdoor temp sounds laudable, but still seems to not rise to the level of stellar energy conservation, either.

In my estimation, infiltration control and also robust insulation are under-rated and often misunderstood.

I'm not sure what California building code requirements are, but in my area, roof/vaulted ceiling insulation is R38, exterior walls is R20 and floors is R30,
windows R2.86.

I don't look at these specifications as achievement targets, but rather as starting points.

We all know that, in the long run, energy will become much more expensive.

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I'm in awe of your ability to build heat pumps from scratch!
Well, it's less like cooking from scratch than it is like cooking from prepared ingredients, since we start with a used air conditioner or de-humidifier, and the compressor and the cap tube or Temperature Control Valve (TXV) is already matched, so most of the tough engineering has already been done.

Best,

-AC
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Old 12-04-13, 08:28 PM   #349
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We all know that, in the long run, energy will become much more expensive.
If the efficiency and cost of heat pumps and photovoltaic cells continue to improve, it may turn out different than expected.
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Old 12-04-13, 08:53 PM   #350
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[QUOTE=AC_Hacker;33733] Well, it's less like cooking from scratch than it is like cooking from prepared ingredients, since we start with a used air conditioner or de-humidifier, and the compressor and the cap tube or Temperature Control Valve (TXV) is already matched, so most of the tough engineering has already been done.


Ah, well, seems to me that's rather like cooking from scratch for most folks. I may grow, harvest, thresh and grind my own wheat in our garden patch out back for the bread we eat, but I haven't taken to evaporating sea water for the salt or making my own yeast. "From scratch" is a pretty blurry concept, I think, so I'll continue to think of you as making heat pumps from scratch.

Except for three small rooms, our entire home is open all the time, so the heated zone is actually heating about 1700 SF and doing alright, but I hear what you're saying.

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