Help design my new system please

[Mikesolar]

Originally Posted by buffalobillpatrick

refrigerant/water

6 gpm should be easy even with a low power pump like a Taco 006 with 1" x 10' pipes & no head loss on either ends at the tanks. The HX's have very little head loss @ 6 gpm.

6 gpm x 10* F delta x 500 = 30K btu/hr

I'm wondering about pulling the water out of the bottom of the solar tank?
More even temp. over more hours, & yes, I know it's normal to pump your hottest water into a HX, but in this case, maybe 180* water is too hot for heat pump?

BBP

This is why I mentioned using a thermostatic valve on the input to the HP from the solar tank. 180F will drive the head pressure crazy and the HP doesn't need it anyway. 100f max is more than hot enough.

[Mikesolar]

Originally Posted by buffalobillpatrick

http://ecorenovator.org/forum/attachment.php?attachmentid=4141&stc=1&d=139466771 2[/IMG]


This is evaporator 30 Bar 4.7 Ton, condenser not here yet = 40 Bar 9 Ton

Is there a distributor on the refrigerant inlet on the HX? Alfa Laval had a lot of problems years ago by not ensuring that the refrigerant was evenly distributed amongst plates. They had lots of freezeups and splits.

It is interesting that the Europeans are nearly entirely plate heat exchanger users and we are the other way around, using a coax HX. There must be a reason.

[buffalobillpatrick]

I found this: Mueller 1/2" OD ACR Copper Tubing is rated to only 363psi.

Mikesolar, don't know? They are made in Germany sooo I assumed that they are the Shiznet.

BBP

[buffalobillpatrick]

From another site:

"R290 and R22 have different liquid densities, and different enthalpy change in the evap. The result is that a TXV rated for R22 but used with R290 will have ~3.5 times the capacity"

[NiHaoMike]

That's not correct. R290 is very close to a drop in replacement for R22, R433b even more so.

[dhaslam]

If the input water is hot enough it should be diverted into the heating circuit and bypass the heat pump. At intermediate temperatures the input temperature can be regulated by mixing the input with the return from the heat pump. I use a small buffer tank for the input side which keeps the input temperature stable and also allows a high flow rate.

[buffalobillpatrick]

dhaslam, I agree & that is in my plan.

If Solar tank > 80*F, I will pull heat out via a HX of 3/4" x 500' loop of o2 barrier pex, this goes directly to Taco ODR TMV to radiant floor.

But there is more to it, this new heat pump will also be used to heat my Thermal Accumulator that is also my DHW tank.

An aqustat on Thermal Accumulator can call for heat from heat pump concurrently with the above, direct to radiant operation.

BBP

[buffalobillpatrick]

interesting reads on R290:

http://www.danfoss.com/NR/rdonlyres/...ompressors.pdf

http://www.hydrocarbons21.com/news/view/3367

[buffalobillpatrick]

It looks like 2 x parallel loops of 250' of 3/4" pex,

with flow of 3.65 gpm in each loop

at Delta T of 20* F , (tank vs. water inside pex)

should transfer about 15 Tons of heat = 180K btus

At a head loss of 7.65'

HL = K x C x L x F^1.75
K = .0034, C = .933, L = 250, F = 3.65

Way more than enough HX for radiant floors.

BBP

[NiHaoMike]

If you split the loop into more parallel sections, you can reduce the pump power requirements.