Home designed and built heat pump!

[The MG Pony]

Well after assessing my needs I have determined the min/max deltas for the water inside to achieve a 21 - 25C room temp, I figure a 30C delta should be enough. To achieve this with good convection air flow. My water has to be from 50 to 70C. After determining the needed condensing temps, I searched for refrigerants with favourable pressure ranges and this is the list I compiled so far What you guys think?

R134a NBP: -26.1C; Ct:101.1C; Cp:589psi; BTU/Lb:1,806
R152a NBP: -24.0C; Ct:113.3C; Cp:656psi; BTU/Lb:7,481
R401a NBT: -34.4C; Ct:105.3C; Cp:669psi; BTU/Lb:- ---
Least ideal far as Ct and Cp go
R022- NBP: -40.8C; Ct:096.2C; Cp:600psi; BTU/Lb:0,946
R290- NBP: -42.2c; Ct:096.7C; Cp:616psi; BTU/Lb:21,625

Ct = Critical Temperature
Cp = Critical Pressure
NBP = Normal Boiling Point

R-152a so far looks like it will have the lowest head pressures at a condencing temp rang from 50-70C being its Ct is 113.3C and it has good moving capacity per Lb.

Max evap temp will be closely tied to the ambient air temps, the absalute min here in BC will be -10 and rarely at that, average is -05C for midle of winter So again its evap pressur looks to be faverable for the average winter temps. Only concern is I only have access currently to R-12 and R-22 TXVs, I suspect they should work after the necicary super heat corrections are made to the TXV providing they are at all needed!
------------------------------------------------------

Ok got a base line.

Air source evap/Condenser:
7.034Kw/H (2Ton)
Water source Evap/Condenser:
5.28Kw/H (1.5Ton)
Compressor:
4.98Kw/H (1.42Ton)

Target room temp: 25C (77F) max ,((Heating mode))
Target water temp for heating mode 50C (122F) - 60C (140F) realistic?

Temp range on the air source Cond/evap -10C (14F)max to a max of 40C (104F)
I think it best to use some thing to ensure sufficient super heat during heating mode for when the weather gets warmer, to ensure it stays within range for cooling the compressor, like using a PWM that slows the fan as super heat goes up.

Now how do I determin air speed needed for thees values? If you can help point me in the right direction to calculating it out. Thanks.
--------------------------------------------------------

So Ok select a TXV with an MOP. Now the water exchanger will be using a head pressur modulated flow control valve, I plan to set it to fix the head the best it can to a stable High side, with this wouldn't the TXV all ready be stable?

As for the fan I was going to use a thermaly controlled PWM unit scaled to the PT chart of the refrigerant I'm planning to use, would this not be good enough?

Part Numbers & Specs
- Coax-2150-S-08-108 Coaxial heat exchanger, 1.5Ton

- V46AC-1C Head pressure modulated, flow control valve (3/4 NPT)

- 2K17C3R126A 17000BTU/H @ 54F evap R-22 rotary

- Temprite 340 series Oil sep 1/4 ODS

Apartment chararistics:
Window surface area total: 285.75 M^2 (937.5 F^2)
Floor Surface area total--: 214.27M^2 (703 F^2)
Air Volume total----------: 1,714.195M^3 (5,624F^3)
Room Width: 5.79M (19')
Room Length: 11.28M (37')
Room Hieght: 2.44M (8')
Room wall thickness .127M (5") R-20

Windows are all single pain with wooden framing and no sealing, Walls have a Delta of 13.4C (56F) between inside & out side. Roof is R-50 about 2 feet thick.

So with that I estimate heat loss for the whole place + 25% to be 1.75Kw/pH (5,958.4 BTU/pH) Using the formula: U * A^2 * Dt(F) = BTU/pH


This is from another thread that I sort of hijacked from US Iceman (Sorry!) So I figured I should move it to its own little thread. Any help or pointers will be greatly apreciated, this is the first such project of this scale other then making chillers!

[Abby Normal]

Check the math on your load

Walls have a delta of 13.4C? A differential? Meaning its 20 inside and 6.6C outside?

or is a diference of 56F so a differential of 31.1C?

20 inside and designing for -11.1 C outside?


Assuming it is a 56F differential then allow for air infiltration, you have a volume of 703 x 8 =5624

If you are not noticing condensation on those single pane windows it is because the place is not very air tight.

Air leaks out of the space and is replaced by that dry BC winter air which keeps humidity down.

Could be 1/2 an air change an hour so

5624/2 x 0.075 x 0.24 x 56 = 2834 Btu/hr for air infiltration alone

Your load just seems low maybe it is because you used a celsisus differential of 13.4C which is what you would see used in Miami. No need to subtract 32 when converting F to C differentials just use 1.8

[US Iceman]

This is from another thread that I sort of hijacked from US Iceman (Sorry!)

No problem. Just let me know where to send the invoice to...

[The MG Pony]

The windows are mini water falls! tons of humidity!

temps are calculated as follows: Inside +25C Out side: -10C, intended opperating temp for inside +21C.

BC dry air? No BC is very very humid! 85-95% humidity all the time. I thought the load seemed rather small as well.

For current weather look here! (Note humidity) > http://www.weatheroffice.ec.gc.ca/ci..._metric_e.html

[Abby Normal]

Well the dewpoint is about 1C, it was showing 87%RH,

RH is relative humidity, relative to the temperature. The warmer air is, the more moisture it can hold.

Heat that outdoor air to 21C and the RH drops to less than 22%, Cold air is dry air. Does not get that humid in the summer either.

[The MG Pony]

then why are my windows coated in fog dusk till don? Thats what gets me.

I normaly run adehumidifier durring the night and it is nearly over flowing in the morning!?!? Erf this whole humidity thing seems rather confusing, plus the head cold isn't helping understanding atm!

[Abby Normal]

open a window and run a bathroom fan, RH will drop, windows will clear up

[The MG Pony]

Heating bill will go up. lol, I'm plotting a way to rig up a system to recover all the heat from the exhaust air once the system is built. It will be sort of like a pre-evap be for the main air source one that all the exhaust air will flow through.

[Abby Normal]

humidity will go down and air quality will go up. Nothing free in life. passive heat reclaim is on the market already

[The MG Pony]

this would be more active heat reclaim in a sense

[Abby Normal]

http://www.refrigeration-engineer.co...ead.php?t=6234

[The MG Pony]

Ah thanks, that will help.

[The MG Pony]

Well I got more parts for the project but I'm having trouble selecting a valve to modulate between hot water duty and heating duty.

The problem is I'm setting the cut out at 45C, I want the unit by default to work on heating domestic water first to 45C then change over to heating the house to 45C but to do it all along the heating curve.

In example, as the tank gets hotter it phases the flow over to the room heating loop so at some point the HWT tanks flow is mixed with room flow (Probably in the mid point of the valve phasing over) at which point the valve will shift to 100% HTW duty and may interfere with the RTT of 45C on the thermostat and cut the compressor off be for any stable set point is met!


I still haven't been able to get much details for the compressor I have either <_< So far all I know it uses a run cap any where from 30 to 35Uf perminant split.

So far I have a Johnson Controls V48 series 3 way acting head modulated water valve that I may use, or use two solenoids with their own basic thermometor to switch from tank heating to room loop heating, though I want to try and make the system more gracefull then that.

[Freonboy]

Daikin have a heat recovery exhaust and fresh air supply unit VAM and Toshiba used to sell a good one which was the same size as a normal extract fan.

[The MG Pony]

Finaly scored a cheap reversing valve so now I'm actualy constructing the "out" door unit.

Here it is so fare

[The MG Pony]

Got the vacuum breaker installed on the water discharge side, have yet to install the check valve, got the reversing valve all brazed in (It did not go smoothely but non the less got it in and leak free, hope fully it still works after all that!) Right now got 200psi Nitrogen in and its holding (Well slightly under 200 but the needle hasn't moved a mm for several hours now!)

Here are the new picies!