Heat pump with low suction pressure

[PalmettoMaintPro]

Sorry to be a thread hog just my brain is cooking this one. Split systems are best charged by subcool or superheat IMO. Weighing a charge should be for something that there is not a variable in ,i.e. ice machines and package units or fridges. The line set of a split system is a variable unless you know for a fact EXACTLY how long the lines are. Which makes weighing a charge for a split a tad trickier to do. It can be done ,but only with accurate math.

[chuckcrj]

I should have mentioned I have done that, that was the first thing we did. I am starting to lean towards a check in the outside txv that is not opening, also on this ruud there are small strainers braized in on either sid of the txv outside. possibly a issue there but i dont have a noticiable temperature change from one side to the other of the strainers, but maybe i am wrong in thinking i should. trying to decied what the next move should be or if im missing something.

You checked static, what was it?

You have low airflow or refrigerant restriction, but you will have to give us SC and SH to know for sure which.

[sgagne199]

if the txv was not feeding properly or you had a restriction in the system wouldn't you see higher head pressures than normal and 180 is certainly lower than normal for 22. sounds to me you either have low load aka airflow or low refrigerant charge

[TriWorksInc]

I had a Ruud heatpump this summer that I went on a no cooling call to find the indoor expansion valve slammed closed, thought it was a slam dunk diagnosis, but nooo. I put the new expansion valve in, and blam the same freekin problems, same issues presented. After doing major testing and checking. The second expansion valve was bad. Ruud sent me a new one (3rd) and the problem was solved. Crap Happens, I thought only to me!

[PalmettoMaintPro]

I had a Ruud heatpump this summer that I went on a no cooling call to find the indoor expansion valve slammed closed, thought it was a slam dunk diagnosis, but nooo. I put the new expansion valve in, and blam the same freekin problems, same issues presented. After doing major testing and checking. The second expansion valve was bad. Ruud sent me a new one (3rd) and the problem was solved. Crap Happens, I thought only to me!

I saw a bad one in couple of new Rheems , Txv that is . guess it can happen to any brand though , dont wanna rheem bash , worked for a dealer for a year . they make a really solid product . as does Ruud, which are restickered Rheems in a nut shell

[TriWorksInc]

I was just letting him know that there is always a possibility that a new part is bad. Ruud is a solid piece of equipment and they do not make the expansion valves, but they stood behind there equipment warranty and there tech support helped too.

[PalmettoMaintPro]

I was just letting him know that there is always a possibility that a new part is bad. Ruud is a solid piece of equipment and they do not make the expansion valves, but they stood behind there equipment warranty and there tech support helped too.

agreed whole heartedly , Rheem and Ruud are always great as far as warranting thier equipment

[timebuilder]

What is the return air temp?

In cooling mode, you need to get heat into the refrigerant in the indoor coil. If you have low suction pressure in cooling mode, then you are not getting enough heat in there, most likely because of poor return airflow.

Post return air temp, static across the evap, and subcooling.

Make sure the txv is properly installed, bulb correct and tight. You can test the txv using ice water and warm water, dunking the bulb.

[Ford3517]

if the txv was not feeding properly or you had a restriction in the system wouldn't you see higher head pressures than normal and 180 is certainly lower than normal for 22. sounds to me you either have low load aka airflow or low refrigerant charge

From what I was taught and my experience, the only restriction that should give you a high head pressure would be a compressor discharge line restriction. A restriction anywhere after the condenser would not result in a high head pressure. When you pump a system down you completely block the flow of refrigerant and you do not get a high head pressure. Refrigerant condenses and turns to liquid and once the low side is in a vacuum there is nothing left to pump.

PS I should add that in some cases this may not be true but most of the time it is.

[timebuilder]

From what I was taught and my experience, the only restriction that should give you a high head pressure would be a compressor discharge line restriction. A restriction anywhere after the condenser would not result in a high head pressure. When you pump a system down you completely block the flow of refrigerant and you do not get a high head pressure. Refrigerant condenses and turns to liquid and once the low side is in a vacuum there is nothing left to pump.

PS I should add that in some cases this may not be true but most of the time it is.

Here we go again.....

[PalmettoMaintPro]

From what I was taught and my experience, the only restriction that should give you a high head pressure would be a compressor discharge line restriction. A restriction anywhere after the condenser would not result in a high head pressure. When you pump a system down you completely block the flow of refrigerant and you do not get a high head pressure. Refrigerant condenses and turns to liquid and once the low side is in a vacuum there is nothing left to pump.

PS I should add that in some cases this may not be true but most of the time it is.

if the suction line is stopped up,(unlikely,but ya never know) the head pressure is still going to be high because it can't get thru the suction line ,backing up and resulting in high head pressure. When you pump a unit down the compressor and every thing is assumed to be working fine the reason you dont see the head pressure going up when you pump down a unit is because the accsess port is AFTER the shut off valve. It is physics,when the pump runs it is pushing liquid and pulling vapor and any blockage in between said push and pull ports is going to adversly effect pressure. A restriction is usually going to cause the symptoms orriginally described in this thread . Cause if that pump is still pumping and it cant get thru to the pump return , the pressure is going to rise BEHIND the point of blockage and the pressure AFTER the blockage is going to be low. Remember the lines make a loop to an from the compressor being that that is where the magic happens. The whole pump down thing is bad example IMO. I base this on what I said about the accsess port being being AFTER the valve

[bob_scheel]

if the suction line is stopped up,(unlikely,but ya never know) the head pressure is still going to be high because it can't get thru the suction line ,backing up and resulting in high head pressure. When you pump a unit down the compressor and every thing is assumed to be working fine the reason you dont see the head pressure going up when you pump down a unit is because the accsess port is AFTER the shut off valve. It is physics,when the pump runs it is pushing liquid and pulling vapor and any blockage in between said push and pull ports is going to adversly effect pressure. A restriction is usually going to cause the symptoms orriginally described in this thread . Cause if that pump is still pumping and it cant get thru to the pump return , the pressure is going to rise BEHIND the point of blockage and the pressure AFTER the blockage is going to be low. Remember the lines make a loop to an from the compressor being that that is where the magic happens. The whole pump down thing is bad example IMO. I base this on what I said about the accsess port being being AFTER the valve

A suction line restriction won't cause high head pressure. The condenser will just condense the additional refrigerant. Then as the suction drops the head will also drop.

[bob_scheel]

From what I was taught and my experience, the only restriction that should give you a high head pressure would be a compressor discharge line restriction. A restriction anywhere after the condenser would not result in a high head pressure. When you pump a system down you completely block the flow of refrigerant and you do not get a high head pressure. Refrigerant condenses and turns to liquid and once the low side is in a vacuum there is nothing left to pump.

PS I should add that in some cases this may not be true but most of the time it is.

On systems without a receiver (or too small of one) a liquid line restriction could cause high head pressure if the line set is long enough after the restriction to cause the condenser to flood.