The Homemade Heat Pump Manifesto

[pachai]

My GSHP project is inching along (just like
the rest of my home expansion project,
but that's outsourced :-).

Plumbing is in place for two Multi-Aqua Hydronic
air handlers. These seem to be a popular way
for GSHP installers to distribute air conditioning
(and heating) to the whole house.
I bought the two needed for the new space -
a 2 ton unit that will go above the basement stairs,
blowing into the new kitchen,
and a 3/4 ton for the Master Bedroom.
In the winter, these will be a backup for
the radiant heat....(I live in Northen NJ :-)

I have installed 1/2" pex and spreader plates
from Radiantec under all the floors that are
accessible, and done pressure testing to 50psi.

(hint - you don't need a Test Kit for each loop,
you just need a shutoff valve for each.
Charge it, close the valve, move to the next...
in the morning, come back, reconnect, open the valve).
The shutoff valve is NEEDED in any case, because
the test kit may (will) leak.


The local stores Home Desperate and Lowes
had the pex components I needed, including
a 6-port PEX manifold (no valves) 3/4 x 1/2",
the ratcheting cinch tool and I used the Harbor
Freight ratcheting PVC cutter to cut pipe.

(I even got Radiant tubes into one ceiling
that was only open for a few days. I have not
gotten back any complaints, and drywall is up
now, so only a real sleuth could find the pex :-)


My next issue is, I was THINKING of using
a redundant array of independent pumps
to control my heat. If I have 12 small pumps
for the 1/2" PEX x 300', and 12 thermostats,
then every room can be a different temperature.
And my hope is 12 small pumps won't cost
a LOT more than one or two big ones.
(I worry about cost in both up-front and recurring).

The alternative is one or two bigger pumps,
which would feed 3/4" pipe to each zone,
and then a manifold for each zone to split
the circulation across the pipes in that zone.
(But this will mean one thermostat to serve
both the Master BR and the kids rooms, for
example, and I don't like it so much.)


As for the ground loops, which are being discussed
in another sub-thread....my thought is to have
a separate pump for each loop.

My friend is calculating the estimated max load...
Last heating season, I was running his Steam Manager,
so he has a record of boiler run times for the whole
season.

I believe 3 tons of ground loops will cover me
to 70-80%. I won't remove the old boiler
until I have a lot of confidence. At the very
least, the old boiler can heat the loop fluid.

(Here's the math: To remove it COSTS money,
to keep it is Free....which one should I do ? :-)


I worked out an install plan for the ground loops,
have not gotten to talk to an excavator yet...
1. dig a 50' trench across back lot. 10' from
the carport, which is 20' wide, so it is far from house.
The trench will be 3.5-4' wide, 10' deep if possible.
2a. put pipes in first trench. One slinky, VERTICAL,
wrapping around the end of the trench. NO "RETURN."
2b. Put forms in the middle of the trench for
possible future digging. Material for the forms
to be worked out....6" PVC? Wood?
Then if/when I need a 4th ton, I just pull the
plugs out and resume digging from 10' down.
I don't even need to do them all at once.
2c. Backfill part of first hole with sand
3. dig 50' trench in driveway toward back of lot,
backfill first trench with the dirt from the second hole.
4. repeat for front half of lot.

I hope to include temperature sensors in each trench,
so not only do I monitor loop temperature, but also,
the temperature of the land around the pipe.

Again, if I have 3 separate pumps, though they will
cost more, I will have the ability to adjust the burden
placed on each loop.

I also plan on having some solar thermal collectors.

Lots to do, not so much time.
But last night I practiced my sweat soldering,
replaced a shutoff valve that was rusted out...
in preparation for moving the laundry hookup,
now that there is a doorway where the wall
used to be...

[AC_Hacker]

Originally Posted by pachai

My GSHP project is inching along...

Wow! You're making some real progress.

Do you have any photos you can intersperse? I know it would be great to actually see what you're up to.

Regards,

-AC_Hacker

[randen]

Just a quick note on our experience with multiple zone for hydronic floor heat. We have had the system running for 13 yrs. Its a concrete floor with eight zones. Didn't need so many zones. The kitchen didn't need a cooler temp than the living room. (open concept)During the depth of winter the individual therostats are all set to the same temp 28 deg C. I had installed programmable thermostats with the thermister unsoldered off the board and potted in the concrete with a 1/4" drilled hole 1/2" deep. As some of the programmable thermostats failed I replaced them with inexpensive ($12.00) ones they worked well, set and forget. There are zone controls and valves avalible that will operate a single pump and numerous zone valves fairly inexpensive (E-bay) The circulation pump runs almost continuously maintaining a 1 degree difference and the floor is a uniform temp. However if the loops are a distance away in seperate rooms that may require a different heat load (lots of windows or three outside walls)yes another zone.
The solar hot water collectors that we had installed are impressive the heat avalible from the sun, wow. Down side,the sun is not there all the time clouds/night. We have six flat plate panels and when the sun shines we collect enough heat that will carry us for near 24 hrs. One tip is to use a large brazed plate heat exchanger. One must harvest all the heat as quickly as the floor will take it as the suns heat is only there for 5-6 hrs. We placed the pannels vertically on the exterior wall facing south. That way in the summer the amount of heat collected is minimal (domestic hot water only)and in winter with the lower sun maximum.(domestic & space heating)

Randen

[pachai]

Originally Posted by randen

We placed the pannels vertically on the exterior wall facing south. That way in the summer the amount of heat collected is minimal (domestic hot water only)and in winter with the lower sun maximum.(domestic & space heating)
Randen

Randen,

That's really helpful. I don't have a lot of roof space left, but I do have the walls at 122 degrees and 212 degrees. (The 122 doesn't face the street, so I'll probably start with them)

Although, I was thinking of a passive collector for the walls - pull in cold air near floor, heat with sun, "exhaust" it into interior higher up on the wall.

That's later in project.

Does anyone know how to calculate the condensation point - i.e., if you can use radiant floors for a bit of summertime cooling - up until but below the point where condensation would occur?

[mrd]

Originally Posted by pachai

Does anyone know how to calculate the condensation point - i.e., if you can use radiant floors for a bit of summertime cooling - up until but below the point where condensation would occur?

Dewpoint depends on temperature and humidity, see Dew Point Calculator.

I've read that humidity sensors tend to be inaccurate, so if you were to utilize a combination of temperature & humidity sensors to determine dew point, you would probably need a good margin of error and make it adjustable as its tested in the real world. I'm not aware of a device that does this for you, but it may be out there.

Such a setup would ideally include a well-controlled indoor humidity - so a dehumidifier and good water vapor control in the envelope. This and/or a large amount of hygroscopic material such as cellulose insulation would stifle swings in humidity and make the environment more predictable.

[AC_Hacker]

Originally Posted by mrd

I've read that humidity sensors tend to be inaccurate...

I've come across reports of ceiling mounted radiant cooling panels being used in Germany... so it seems that it can be done.

Originally Posted by mrd

...a large amount of hygroscopic material such as cellulose insulation would stifle swings in humidity and make the environment more predictable.

Mud walls are also being used for this purpose.

-AC_Hacker

[randen]

Originally Posted by pachai
Does anyone know how to calculate the condensation point - i.e., if you can use radiant floors for a bit of summertime cooling - up until but below the point where condensation would occur?

Summer time cooling. This is a topic more directed to human comfort. Like a warm floor in the winter taking advantage of radiance, convection and contact heating makes us feel comfortable. The humitity in winter tends to be lower as water vapour in our atmosphere is condensated out,on the ground as rain or snow. This same air we warm in our homes making it relatively drier. This drier air makes us feel cooler at a modest temp because our skin is still perspirering and this is why we either run the temp a little higher or add humitity.
The summer for the human comfort we need to lower the humidity and by temperature to get the water out. This way as our skin perspires we feel cooler and more comfortable. That is why say in Arizona at 100 degs "it a dry heat" and feels not too bad. but say in the Amazon rain forest 100 degs wow. Our skin sweats but unable to cool the skin (lack of evaporation too much water in the air already)/not nice.

The problem with just cooling the floor in the summer is we still have the humidity and the condensation point can occur very close to the ambiant temp. The floor will condensate and you have cold wet feet and still feel uncomfortable. In stead of cooling media running in the floor run it through a air handler and distribute through the house. This removes the moisture, lowers the temp and as the cool air sinks, the floor becomes quite cool and remains dry.

One thing I'm going to try in the next week or two is to run only the ground loop water/glycol through the shop air handler to see if it will air-condition without the GSHP operating.(not hacked yet) I'm willing to bet the ground temp alone may do the trick. This way only a few watts for the circulation pump and fan motor.


Randen

[Drake]

Dew points can change in most places faster then hydronic slabs can change temp so cooling condensation would be hard to control except stably dry climates.

[AC_Hacker]

Originally Posted by randen

The humitity in winter tends to be lower as water vapour in our atmosphere is condensated out,on the ground as rain or snow. This same air we warm in our homes making it relatively drier.

I think the mechanism at play here is that warm air is capable of holding more moisture than cold air. The term 'relative humidity' takes this into account. The 'relative' part is relative to the maximum moisture air can hold (100% RH) at a given temperature.

When cold winter air is brought into the house and warmed up, even though it has the same amount of moisture as it had before, it is now warmer and capable of holding more moisture, so it's % RH is lower.

In the summer, warm air (which can hold a lot of moisture) is brought into the house and cooled off, thus lowering it's moisture holding capacity. If it's moisture holding capacity is lowered to the point that it reaches 100% RH, the moisture leaves the vapor state and enters the liquid state (AKA: condenses).

The rest sounds pretty good...

Originally Posted by randen

One thing I'm going to try in the next week or two is to run only the ground loop water/glycol through the shop air handler to see if it will air-condition without the GSHP operating.(not hacked yet) I'm willing to bet the ground temp alone may do the trick. This way only a few watts for the circulation pump and fan motor.

Randen,

I have the same idea myself, I'm just waiting for some warmer weather to try things out. It's been a long, wet, cool spring here...

Be prepared for the event that your shop air handler will condense a lot of water, due to the lowered RH.

I came across a web posting from a guy that did this very thing. He modified an aluminum fin condenser coil to fit his needs, and pumped ground water through it. He had to put a pan with a tube leading outside, under his condenser to drain the water.

He reported that his best results were from re-circulating the air inside, rather than bringing in air from outside.

An additional benefit is that you'll be putting heat into the ground for wintertime use.

-AC_Hacker

[peacmar]

This is an amazing collection of information. I've been feverishly reading this thread every opportunity I get. it is long, but very informative. Congratulations to everybody in their success thus far! And many thanks to AC and everybody else who have contributed to this cause. I have searched for months for DIY gsph info. I am what I consider to be an extreme DIYer. With solar, wind, and high efficiency solid fuel under my belt. But those are all for different blogs on another day. I hope I can contributed to this adventure also. I am still educating myself as far as refrigerant handling goes, but have 15+ years in the welding trade and specialize in non-ferrous metal work and repair, with heat exchanges and radiator building and repair being ine if my favorite subject. So I feel the actual hack will be a sinch once I has found a suitable done to experiment with. Best of luck to all and thanks once again. My time free can be limited occasionally but I hope to become a contributing member of this discussion.

-mark