Refrigerant Charge

[EnergyWiz]

I was wondering if anyone here could tell me how you can tell you have a low refrigerant charge on a DX cooling system? We have a water source heat pump (brand new) that tripped on Hi/Lo (Trane alarm)... Any thoughts?

[jayguy]

check the IOM...it will give you pressures/temps. also check the water temp and glycol concentration. i had a job where everyone and their brother just kept resetting the unit...turns out the glycol concentration was at 5% instead of the 30% it was supposed to have, and the water was at 29-30F. square ice does not go through round tubes very well.

[psychometric]

I had a mammoth water source hp last season, brabd new, tripping head pressure over 400 psi immediately on startup. Turns out check valve was hanging up. If your system is new with the old piping, check the temp through the water coil. If using flexible hoses, make sure they are new and clean. As far as the refrig charge, just make sure superheat is ok, delta T, etc. I'd be concerned more with the condenser water side to start with.

[EnergyWiz]

Thanks for the input. We are okay on the water loop side. We have 22 other heat pumps that are working fine. We are currently in the cooling mode, so no problem with glycol. We did check the glycol freeze point... I don't trust any of those expensive instruments. The solution froze at 15F in a walk in freezer. We cannot get the unit to run long enough to check pressures before it trips on high-pressure. It turned out to be a leaky shrader valve. This may have gotten stuck open when we checked the refrigerant pressures the first time.

[jdcoolj]

The unit you are working on sounds like it probably has a factory charge less than 10LBS of refrigerant. To take the guess work out I recommend recovering and weighing the charge. Weigh back in the exact charge with a digital scale. At least you eliminate refrigerant as a promblem.