"Home made" 150 kW heat pump

[SteinarN]

I constructed a fairly large water/water heat pump in November -05. It heats an assisted living facility of 4,900 m2, that is 52,700 ft2, two ventilation systems of a combined 9 m3/s capacity and 300 m2 heated outside area.

The heating capacity is between 140 to 155 kW dependent of the ground loop temperature and the outlet water temperature. It extracts heat from 19 wells, each 155m deep, 508ft, total 2950m, 9678ft.

The return temperature in the ground loop water/glycol mix is 5C in the autumn at the start of the heating season and drops to -1.5C in the spring. Flow is 10.5 l/s, 2.77 US Gal/s. Dt is 3.5C at full capacity. Heat extracted is 110 to 125 kW.

Outlet water temperature on the warm side is regulated dependent of the ambient temperature, varying between 21C at 20C ambient and 32C at -20C ambient. Warm side flow is roughly 8 l/s.

It is equipped with a liquid refrigerant subcooler connected to the water return from one of the ventilation system heating coils. This cools the liquid refrigerant from between 26 to 36C down to 20 to 21C. This cooling of the liquid/heating of the water yields an additional up to 20 kW heating capacity without affecting the compressor power consumption. The COP is 4.6 to 5.2 dependent of the water temps. This is a very high COP.

The compressor is an eight cylinder Copeland Discus compressor, the 2nd largest. Displacement is 2,060 cm3. Max amps is 152 A at 230 V. 50-75-100% capasity steps. Power consumption under actual running conditions is 31 kW at 100% capasity.

Pictures: http://s684.photobucket.com/albums/vv206/SteinarNo/150%20kW%20heat%20pump/

[nh3wizard]

Nice job, wish I had your brains.

[desA]

Hej SteinarN,

Bravo!!! A really nice job you've done. Takse mukke.

Are you willing to share some ideas on your electrical control details & wiring layouts? Interesting to me at this point.

desA

[SteinarN]

Hi desA.

It was a VERY interesting project to do. Both the mechanical building, the refrigeration side of it and the electrical/PLC side.

I draw the electrical schematic myself and got an electrical company to build the switchboard. I also made the program in the PLC and the HMI.

Regarding the control details, the main goal is to control the warm side water outlet temperature. This setpoint is continously calculated based on the ambient temperature and two manual inputs, namely what water temperature shall be at 20C ambient (currently set at 21C I think) and a percentage input (currently set at something like 27% (that is, for every degree the ambient deviates from 20C, 27% of that deviation is added or subtracted from the actual setpoint).

Example, -10C ambient:
21C + (20C - (-10C) *27%) = 21C + 8,1C = 29,1C.

This calculated setpoint and the actual water outlet temperature is the two values which is input to the PI regulator determining the compressor loading.

The first 50% output from the PI regulator engages the compressor in 50-75-100% steps. 50-100% PI output range opens the 3-way valve for additional heating from a boiler. This capacity is only needed when the ambients is below -11C.

Any time the ambient is above 0C the neded capacity is less than 50% compressor load. This brings the compressor to start (in 50% capacity mode) and stop repetedly. I have a minimum run and stop timer currently set at 600s each to avoid short cycling.

I have set the superheat as low as possible. This brings the real possibility of flooded starts. I have programed a function which opens and closes the liqiud solenoid valve based on the actual evaporator pressure compared to the evaporator pressure just before the compressor stopped last time. This function is only active for a set amount of time after compressor start and is terminated when spesific values is meet.

When the compressor is stopped for a considerably lenght of time like several days there might be a possibility for the evaporator to be completely filled with liquid refrigerant.
I have programed a function to avoid the possibility of liquid slugging at start up in such a case. When the compressor has not run for a set lenght of time (currently set at 24h I think) and is to start it only runs a couple seconds (currently 3s) and then stops for 30s. This repeats up to ten times until the suction pressure comes below a set value, currently 4,3bar. The liquid solenoid valve is of cource closed all the time. When this 4,3bar suction pressure is meet the solenoid valve opens and the compressor no more stops.

I have also programed a couple low pressure/frozen evaporator/lack of evaporator flow safetys like unloading at low suction pressures and compressor stop before the mechanical LP/HP activates. Also compressor unloading at high HP before the mechanical HP activates.

The ground loop pump is controlled by the PLC and is started 5s before the compressor.
Various time counters for compressor run time in the possible load steps. Average load the last two hours and a lot of other small functions.

[Quality]

What coolant are you using in the ground loop ?

[SteinarN]

What coolant are you using in the ground loop ?

20% ethylene glycol. The total volume is about 9.500 liters.

[andywill]

Looks like a nice job indeed but I couldn't help noticing the orientation of the discharge vibration eliminator. I was always trained to install these perpendicular to the compressor crankshaft.
http://www.universalmetalhose.com/pdf/Bulletin_302.pdf

[multisync]

Our local church is looking at a very sized similar project. I would love to hear about costs as they have been quoted huge sums for this job.(I would be happy to put your name forward ;-)

I'm wondering if inverter driven scrolls would increase performance even further?

[SteinarN]

Looks like a nice job indeed but I couldn't help noticing the orientation of the discharge vibration eliminator. I was always trained to install these perpendicular to the compressor crankshaft.
http://www.universalmetalhose.com/pdf/Bulletin_302.pdf

Yes, you'r right.

I assumed the deviation from the pependicular direction wasn't large enough to cause any problem. It was difficult to get it perpendicular because of the odd direction of the discharge outlet and the fact I had installed the receiver before the vibration eliminator.

Under normal running the compressor is virtually without any vibration what so ever. The reason for the vibration eliminator is to take up the movement when the compressor start and stops. When I manually moves the compressor as much as it moves itself when it starts there seems to be no stress to the vibration eliminator. The compressor moves freely within the range for the start and stop jump.

[nike123]

Impressive work SteinarN! You should be proud at yourself. Kind of set of same interests like I have, but here we don't use ground loop heat pumps (climate is mild). What is PLC and HMI used for control?

Few thoughts of mine:


Isn't Copeland Discus to expensive for such use? Why you choosed semi hermetic? For capacity control reasons?

Regarding of vibration eliminators. They are placed perpendicular to compressor shaft and that could lead to premature damage of them. That mounting position makes them streching and contracting and they are not designed for that. They can only eliminate axial vibrations by bending its axle.

Isn't this switching of compressor ON-OFF for liquid start prevention somehow bad for compressors.
Maybe you should switch ON-OFF (for few seconds intervals) liquid line solenoid guided by suction pressure, to achieve same goal


Edit: I see that others are already addressed matter of vibration eliminator during my typing of this post.:D

[Peter_1]

Wow!!!! :cool::cool:
Steinar, what size can you bend with a bender?
Am I right seeing 1 1/8?

[nike123]

Looks like a nice job indeed but I couldn't help noticing the orientation of the discharge vibration eliminator. I was always trained to install these perpendicular to the compressor crankshaft.
http://www.universalmetalhose.com/pdf/Bulletin_302.pdf

It is not supposed to be mounted perpendicular to compressor crankshaft but perpendicular to direction of vibration.
Since vibration in compressor is perpendicular to crankshaft, then perpendicular to perpendicular mean parallel to compressor crankshaft.;)

http://farm4.static.flickr.com/3545/3374508385_da8422b829_o_d.png

[andywill]

I can see what you mean, there is not much room to play with.The only real way to know for sure is if you have a premature failure of it but then again it could last for many years to come.

[SteinarN]

Our local church is looking at a very sized similar project. I would love to hear about costs as they have been quoted huge sums for this job.(I would be happy to put your name forward ;-)

I'm wondering if inverter driven scrolls would increase performance even further?

The copeland Discus is overall the most efficient compressor series I'm avare of. Some scrolls MAY be more efficient at some specific operation conditions, but as the operation conditions change the scroll easily come outside it's most efficient area and become less efficient than a Copeland Discus. However there is large differences between different compressors in the same series so it is not possible to give an general answer. It is necessary to do a comparision in every particular case.

At -9C evaporating, 33C condencing, 5K superheat, 10K subcooling, R404A, the Discus range has a COP ranging from 4,37 for the D8DJ-600X up to 4,81 for the D3DC-100X. The compressor in this heat pump is the D8DH-500X with a COP of 4,61 at these operation conditions.

In the scroll range it is only one compressor with a COP above 4,81, namely the ZF13KVE-TFD EVI with economizer. Evaporator capasity only 11kW. Would need 12 of these compressors for this heat pump. The other scrolls has a COP ranging from 4,23 up to 4,71.

Only 8 out of 36 Copeland scrolls have equal or better COP than the D8DH-500X in this heat pump, including the economizer models.

[SteinarN]

Wow!!!! :cool::cool:
Steinar, what size can you bend with a bender?
Am I right seeing 1 1/8?

The largest bent tubes you see is 1-3/8" hard copper tubes for the water tube conection on the subcooler PHE heat exchanger in the upper right in some of the pictures. That is the largest I can bend with my current tool.

[Peter_1]

What type of bender are you using then Steinar?

[SteinarN]

Nike, the HMI is an Exor CP10G-04 with 4 lines, 16 characters/line display.

The PLC is a Hitachi EH150 with a 316 CPU, analogue in and out modules, digital in and out and one temperature module, 5 modules total. Program size 2.500ksteps if my memory serves me right.

[SteinarN]

What type of bender are you using then Steinar?

http://www.refrigeration-engineer.com/forums/showpost.php?p=96988&postcount=7

[nike123]

Isn't this switching of compressor ON-OFF for liquid start prevention somehow bad for compressors.
Maybe you should switch ON-OFF (for few seconds intervals) liquid line solenoid guided by suction pressure, to achieve same goalSorry, I did not write what I have on my mind here. I mean If you install solenoid valve in suction line, you could switch off and on that valve in short intervals guided by suction pressure (or superheat) and in that way avoid compressor switching ON-OFF. Also it could be always closed when compressor is OFF and in that way you eliminate migration of liquid refrigerant in compressor.

[SteinarN]

I dont have any valve in the suction line.

I calculate the say 5 extra starts maybe only 10 times in a year is of no significance. In the winter times the compressor can run for a month or more without any stop. The total number of start/stopp in a year is still very moderate.

[nike123]

Nike, the HMI is an Exor CP10G-04 with 4 lines, 16 characters/line display.

The PLC is a Hitachi EH150 with a 316 CPU, analogue in and out modules, digital in and out and one temperature module, 5 modules total. Program size 2.500ksteps if my memory serves me right.

Can you tell price range for that combination of PLC, HMI and modules? Also, did you purchased software for programing PLC and HMI, and if yes, what is price range for that?

[SteinarN]

Nike,
I always install the vibrasorber perpendicular to the cranckshaft. I know they will be subjected to some stretch/compression, but compared to the stretch caused by the pressure inside a discharge vibrasorber I assume the stretch caused by compressor movement at start and stop is an order of magnitude smaller than the stretch caused by the internal pressure.

On small compressors I often install double lenght vibrasorbers in a 90 degrees turn. Therby the vibrasorber easily takes up the movement in any direction without any stress whatsoever.

[SteinarN]

Nike, I don't remember exactly. The HMI cost maybe 750 Euros, the Pt100/1000 4 sensor temp module was maybe 150 Euros, the digital in and out was cheap, maybe 80 Euros each, analogue in and out maybe 150 Euros, The CPU maybe 300 Euro, power suply maybe 80-100 Euro and the back plate for 5 modules maybe 100 Euro. The back plate is in 3, 5 and 8 modules versions.

Free software included for the HMI, dont remember, maybe the Pro-H for the PLC cost 100 Euro. However there is no code on the Pro-H software so no problem in installing on different computers. ;)

[nike123]

I dont have any valve in the suction line.

I calculate the say 5 extra starts maybe only 10 times in a year is of no significance. In the winter times the compressor can run for a month or more without any stop. The total number of start/stopp in a year is still very moderate.

Ok, but you stated that compressor is operated like this:





When the compressor is stopped for a considerably lenght of time like several days there might be a possibility for the evaporator to be completely filled with liquid refrigerant.
I have programed a function to avoid the possibility of liquid slugging at start up in such a case. When the compressor has not run for a set lenght of time (currently set at 24h I think) and is to start it only runs a couple seconds (currently 3s) and then stops for 30s. This repeats up to ten times until the suction pressure comes below a set value, currently 4,3bar. The liquid solenoid valve is of cource closed all the time. When this 4,3bar suction pressure is meet the solenoid valve opens and the compressor no more stops.




To me, that doesn't sound good, since compressor should not have more than 10 starts per hour, and minimum run time is too short. I think that that will overheat windings and lubrication is not good, since in 3 seconds oil could not be distributed to all lubrication channels.

But, that is only my theoretical observation based on compressor manufacturer recommendations. Maybe your practice shows that is perfectly OK run it in that way.

[nike123]

When I install vibration eliminators, I imagine long flexible stick who could bend in any direction but could not change its length. Than I choose how to install it, and that always end by parallel to crankshaft position.

[SteinarN]

Nike,

Copeland standard series is cheaper than the Discus series, but the reduced power consumption in this case is something like 15.000 kWh per year. The price difference between the standard and the Discus is paid back in a year only. Besides I like the better numbers for the overall COP :cool:

Why not hermetics? Partly for the same reason. If one hermetic then no capacity regulation. If several hermetic then more complicated system, either several independent systems or considerations for oil equalization etc. In any case mere tubes, more vibrasorbers, more electic motors to fail, more of everything.

[nike123]

Nike, I don't remember exactly. The HMI cost maybe 750 Euros, the Pt100/1000 4 sensor temp module was maybe 150 Euros, the digital in and out was cheap, maybe 80 Euros each, analogue in and out maybe 150 Euros, The CPU maybe 300 Euro, power suply maybe 80-100 Euro and the back plate for 5 modules maybe 100 Euro. The back plate is in 3, 5 and 8 modules versions.

Free software included for the HMI, dont remember, maybe the Pro-H for the PLC cost 100 Euro. However there is no code on the Pro-H software so no problem in installing on different computers. ;)

Thanks, now I have some reference to compare with new supposedly cheaper Telemehanique PLC-s.

[nike123]

Nike,

Copeland standard series is cheaper than the Discus series, but the reduced power consumption in this case is something like 15.000 kWh per year. The price difference between the standard and the Discus is paid back in a year only. Besides I like the better numbers for the overall COP :cool:

Why not hermetics? Partly for the same reason. If one hermetic then no capacity regulation. If several hermetic then more complicated system, either several independent systems or considerations for oil equalization etc. In any case mere tubes, more vibrasorbers, more electic motors to fail, more of everything.


Good point!
Do you planing to make it as commercial product or is it only one time custom made order?

[SteinarN]

When I install vibration eliminators, I imagine long flexible stick who could bend in any direction but could not change its length. Than I choose how to install it, and that always end by parallel to crankshaft position.

That's a reasonable way to see it. However I also see it in such a way that the vibrasorber is torsionally completely stiff. Then the vibrasorber cant flex when the compressor jumps at start and stop when the vibrasorber is paralell with the cranckshaft.

[SteinarN]

Ok, but you stated that compressor is operated like this:




To me, that doesn't sound good, since compressor should not have more than 10 starts per hour, and minimum run time is too short. I think that that will overheat windings and lubrication is not good, since in 3 seconds oil could not be distributed to all lubrication channels.

But, that is only my theoretical observation based on compressor manufacturer recommendations. Maybe your practice shows that is perfectly OK run it in that way.

Every thime this occur the compressor motor is cold as it has been stoped for at least 24h. When it finaly start the minimum runtime timer forces it to run for 10min. It then stops for a long time because the heat produced is to much based on the PI regulator requirements. The PI regulator doesnt require an other start for a very long time. Therefore no more starts within that hour.

In practice the 3 second start happens 4 to 5 times before the suction pressure comes low enough to deactivate this feature. So in total, 5 short starts 10 times a year gives a total of 50 extra starts a year.

[SteinarN]

Thanks, now I have some reference to compare with new supposedly cheaper Telemehanique PLC-s.

This is Norwegian oil economy inflated prices. Probably cheaper in other European countries.

[SteinarN]

Good point!
Do you planing to make it as commercial product or is it only one time custom made order?

Most likely a one time custom made project.
However one local hotel/resturant is planning to expand. Maybe I get involved there. But that's at most a 60kW heat pump.

[icecube51]

Nice doing Steinarn, got my hands on a complete chiller of 85Kw this weekend.has 2600 running Hrs on the teller.got it from a factory ware it was to small. they put in a new one and was planning to dump it in a container for scrap metal.
i think i have a very good idea what to do whit it now. thank U very mutch.
going to do some calculations first,make a few plans,but keep every one posted.(think i need some help to ;-)..)

cya, Ice

[fowlie]

we used to have problems with a hussman super plus pack running on d8 comps and we found the only way was as said start comp for few seconds then off do this a few times and bobs your uncle,could you also not fit more unloading valves and start comp fully unloaded then gradually load it up.
nice job take my hat off