Water source heat pump high head pressure

[PolarBearAir]

Hey there,
I was working on a water source heat pump Trane serial number# W04C11546 MN# GEVB02411J0110TL. The unit is an upflow with the compressor compartment being on the bottom and the fan and coil on top.

The problem is that the unit will run for about one minute in cooling mode then goes off on high head (400 psi r-22). Unit runs fine in heat. I replaced the txv to no avail. Believe the problem is the reversing valve at this time, but was wondering what else could possibly be the cause as I normally work on standard split systems and package units.

I am only working on this for my friend who has a loft in downtown LA. I run my business in the 'burbs, and water source heat pumps are rarely seen here.

[hvacrmedic]

This is mostly due to low or no water circulation. Sometimes it's due to a bad pressure switch, overcharge, or excessive inlet water temp. A bad (bypassing) RV causes low head. HTH.

[couand1217]

Is there a strainer in the cond water line that could be stoped up?

[HuNGRYTeCH]

I agree with the other two that a lack of water flow is the most likely culprit. Is there a circuit setter in the system that is to set correctly, or a restriction somewhere in your piping. Check your inlet and outlet water tempature. You should have a resonable delta t, a very low delta might tell you have to much flow, a very high delta might tell you don't have enough flow.

[marsmech]

To be sure that the lack of water flow is causing your problem there is more information needed. Think about it...the tube in tube or what ever the exchanger is would also be used in heat. If the strainer or flow was reduced then the unit would most likely also fail in heat due to low temperature cutout. If for some reason it did not fail you would notice that your suction pressure was being effected by the decreased flow. Are you seeing the a low suction pressure in heat? Are you seeing 400 psi on your gauges during cooling or is this the cutout point of the switch? Let's start there first and go from there.

[BKS60]

I have seen many of these units that after multiple loss of water flow for whatever reason the high discarge pressure causes the inner tube of the condensor to completely flatten not allowing any water flow. You can check your entering and leaving water for flow and pressure drop.

[HJ Controls]

good way to get a lot of guessing is to ask a question and give no info.
what is your entering and leaving water temp, superheat ,subcool,suction and discharge pressure, do you have a condenser water regulating valve of some sort. without info all your going to do is change a bunch of parts.

[PolarBearAir]

When in heating, the outlet water line gets nice and cold. - didn't take the temp of it, but it seems as though the water is flowing correctly. In cooling the opposite it true, outley water line gets very warm.

I have seen reversing valves on standard heat pumps be functional, but not open all the way.. What troubles me is that when I've run into that in the past,the suction pressure was through the roof. On this unit my low side is at the standard 65 psi. I don't have instrumentation for superheat/subcooling numbers, which I know would really help.


My temperature splits are right where they should be in heat and cool. 21 degrees in cooling , and 32 degrees in heat. I will also add thatwhen I was recharging the unit after replacing the txv, it would have high head pressure but not go all the way up to 400. I ran it undercharged for about 15 mins and the suction was at 40 psi with the head pressure hovering around 290- 310.


I did purge the water lines in my initial diagnosis. There was a significant amount of small debris in the bucktet afterwards. Is there a strainer or filter in the water line?

[Dallas Duster]

When in heating, the outlet water line gets nice and cold. - didn't take the temp of it, but it seems as though the water is flowing correctly. In cooling the opposite it true, outley water line gets very warm.

I have seen reversing valves on standard heat pumps be functional, but not open all the way.. What troubles me is that when I've run into that in the past,the suction pressure was through the roof. On this unit my low side is at the standard 65 psi. I don't have instrumentation for superheat/subcooling numbers, which I know would really help.


My temperature splits are right where they should be in heat and cool. 21 degrees in cooling , and 32 degrees in heat. I will also add thatwhen I was recharging the unit after replacing the txv, it would have high head pressure but not go all the way up to 400. I ran it undercharged for about 15 mins and the suction was at 40 psi with the head pressure hovering around 290- 310.


I did purge the water lines in my initial diagnosis. There was a significant amount of small debris in the bucktet afterwards. Is there a strainer or filter in the water line?

In a perfect world there should be a strainer on the inlet of the unit. I think your condenser water side of the unit is where your problem is. :bump:

[XcelTech]

If your reversing valve was bad both pressure would be overly high. Something like 350/120 or it would not be changing from heat to cool.

Your water flow is not high enough, your water enter is to hot, or you have non-condensables in your refrigerant.

If you truly blew out the heat exchanger and your not over charged it has to be one of those three problems.

Make sure you don't have a water actuator with a delay in start and/or your compressor is starting after the actuator is 100% open.

My money is on the water is too hot. Your friends loft is probably connected to a water tower that is most likely not getting the chemicals it is suppose to be and the tower fins are covered in scale.

[marsmech]

When in heating, the outlet water line gets nice and cold. - didn't take the temp of it, but it seems as though the water is flowing correctly. In cooling the opposite it true, outley water line gets very warm.

I have seen reversing valves on standard heat pumps be functional, but not open all the way.. What troubles me is that when I've run into that in the past,the suction pressure was through the roof. On this unit my low side is at the standard 65 psi. I don't have instrumentation for superheat/subcooling numbers, which I know would really help.


My temperature splits are right where they should be in heat and cool. 21 degrees in cooling , and 32 degrees in heat. I will also add thatwhen I was recharging the unit after replacing the txv, it would have high head pressure but not go all the way up to 400. I ran it undercharged for about 15 mins and the suction was at 40 psi with the head pressure hovering around 290- 310.


I did purge the water lines in my initial diagnosis. There was a significant amount of small debris in the bucktet afterwards. Is there a strainer or filter in the water line?

From this post it sounds like there are two water lines connected to the heatpump unit. (Water inlet and water outlet) There should really never be a need to have an actuated valve on the main loop lines due to the fact that the water is only meant to be a stable source of temperature media and it is supposed to be kept clean and pure. On a typical system the entering water temperature is kept between 70-80 degrees at all times of the year. The leaving water temperature should have a temp difference of 6-8 degrees in heat mode and 10-12 degrees in the cooling mode. I am beginning to believe that incoming water and flow may be an issue. If the inlet water was higher temperature than the recommended and the flow was reduced then your suction pressure has the chance to be near normal ranges. The load would still be present, even though the flow is reduced it is at a higher temperature which would make up for the loss of flow. In heating the air coil is your condenser and the water coil is your evap. I believe (without being on site) that you could maintain running without issue during heat mode because of this higher loop temp. But when you switch to cooling and your water coil becomes your condenser the lack of flow and the higher temp is detrimental because you can not remove the heat and lower the pressure from the heat pump and the unit subsequently trips off. I was surprised to read the temp differences of 21 and 32 as this numbers are high to begin with and they should be reversed meaning your outlet main water loop should be higher in cooling not heating. Cooling - water coil - condenser - (hot) removes heat lowering the high side pressure in the heat pump refrigeration cycle.
Heating - water coil - evaporator- (cold) adds heat and raises low side pressure in the heat pump refrigeration cycle.

Check your inlet water temps and verify your outlet temps and see where you stand good luck.

[Drazen]

you can measure temperature by any kind of wrap-on sensor, and before that you are guessing, and, what is frequent problem in maintenance work, if you stay stick by unproved hypothesis for too long, it can drain your energy.

are you sure in any way that your heating mode is working properly? i mean if you are in some warm area, and outdoor temperature is very high now, you can hardly check how heating system works with no load imposed on it.

[PolarBearAir]

I was surprised to read the temp differences of 21 and 32 as this numbers are high to begin with and they should be reversed meaning your outlet main water loop should be higher in cooling not heating. Cooling - water coil - condenser - (hot) removes heat lowering the high side pressure in the heat pump refrigeration cycle.
Heating - water coil - evaporator- (cold) adds heat and raises low side pressure in the heat pump refrigeration cycle.

Check your inlet water temps and verify your outlet temps and see where you stand good luck.


The temperature differentials I was referring to was for the air, not the water.

Yes there is a big cooling tower on the roof of the building. But wouldn't everyone in the building be experiencing issues as well?

Is it possible that my supply and return water lines were crossed during installation and im trying to cool with water that has already had a bunch of heat dumped into it from other tenants?

I guess my starting point should be to get some pressure and temperature readings on the water inlet/outlet. Temperature is easy, but what should i use to get the pressures? There are shutoff valves on both the supply and return water lines that have hose bib attachments. Do they make a pressure gauge that fits?

Thank you all for your responses, very much appreciated. Wish I had more experience with these things.

[XcelTech]

T
Yes there is a big cooling tower on the roof of the building. But wouldn't everyone in the building be experiencing issues as well?
.

Not necessarily, if your friend's apartment is further down the pipe circuit or if your friend requires a lot of cooling. The other side of that is that you blew out the pipe but you don't know what kind of calcium build up is inside and your not gonna get all the calcium out with a high pressure purge.

Pop open one end of your pipe and let the water drain into a bucket for 10 secs measure the amount of water in Gallons and then times it by 6. That is a quick and dirty way but it will get you what you need.

[Tommy1010]

You should have an access tee with a shut off valve somewhere on those water lines.

1st try BACK flushing the lines. (rinse out in opposite flow)

If that dont do anything, try some scale remover solution with a submersible pump.

If you resort to this, always reflush with some baking soda and water.

It neutralizes the chemical left over in the pipes, and stops corrosion in the future. I've experienced cracked heat exchangers from not doing this. Before you know it, you have a water breach. And then your changing a whole hell of alot more than you planned on.

What kind of pipe is it? If its copper pipe or pvc, you shouldnt need to use chemical.
But if its black pipe (schedule 40 or suttin), you can have alot of crud.

[Dallas Duster]

Let's get the make and model of this thing maybe the manufacturer will let us freeze up the condenser to clean her up.

[johnnyonetruck]

I agree with some sort of water flow issue. You most likely do have a strainer on the inlet water to the unit. Your lines could be crossed but not likely if it has been working for any period of time before you began working on it.

WSHP's are prone to having fouled/stopped up condensers if the tower water is not maintained properly. Based on what you have posted so far, I would imagine you have a stopped up strainer, mineral/crud build up in the condenser, or a combination of the two. As stated earlier, get it cleaned up ASAP but make sure you get all cleaning residue out of the system.......maintenance crew on an "unnamed military installation" near me cleaned 10 WSHP condensers and did not get cleaning residue out of them.........10 compressors went swimming from the inside..........and refrigeration oil in your condenser water is a little messy as well.

All that being said, it sounds like water flow issues of some kind. Not likely that your unit has any sort of automatic water flow control valve, but likely has a circuit setter. You should be able to check your pressure drops across condenser at PT ports (normally Trane supplies supply and return ball valves with built in PT ports along with flexible connnections for each unit). If the installing contractor did not buy the connection kits with the units, then hopefully they installed PT ports on the pipe somewhere near the unit supply and return connections.

Good luck.

[SwampTromper]

Surely water flow issue. Just check the in and out temp, it will probably have a large td. Then like everyone said, check for strainer, purge both ways, and you'll most likely need a chemical soak and flush because thats some nasty water and the unit has clearly not been maintained. If you still dont have around ten degree td then its most likely a charge issue, but hooking up gauges with a dirty or clogged condenser is a waste of time. Check for gpm specs but if theres any damage to the condenser youll ned to adjust flow to get desired temps. And like johnny said, any cleaner that will work well is very acidic and needs to be thouroughly rinsed.

[Hardwater]

The temperature differentials I was referring to was for the air, not the water.

Yes there is a big cooling tower on the roof of the building. But wouldn't everyone in the building be experiencing issues as well?

Is it possible that my supply and return water lines were crossed during installation and im trying to cool with water that has already had a bunch of heat dumped into it from other tenants?

I guess my starting point should be to get some pressure and temperature readings on the water inlet/outlet. Temperature is easy, but what should i use to get the pressures? There are shutoff valves on both the supply and return water lines that have hose bib attachments. Do they make a pressure gauge that fits?

Thank you all for your responses, very much appreciated. Wish I had more experience with these things.

Have you checked the loop circ pmp discharge pressure? this should give you a starting point. Does the unit have a circuit setter? if it does it should have the test ports you can use.