r407c heating problem

[marinetech]

I received 2 calls today regarding boats with self contained reverse cycle AC units with water cooled condensors both using 407c. The problem is both boats are complaining that they are not getting heat. One boat is in Tennessee and the other is in South Carolina. Water temperatures are around 55 degrees for both. Reported pressures are 25 psi suction 170 psi discharge. Do these pressures sound right? Everything I have read about 407 says the pressures should be close to what they would be using r22. These seem low. How efficient is 407 compared to r22 as far as heating is concerned?

[Gary]

My guess would be frozen coils. Try putting them in A/C mode for about 15 minutes or so to defrost the coils... then see if the heating works.

[nike123]

If I understand correctly, this is water to air heat pump.
I would first check water flow (filters) and air flow! Temperature difference across water heat exchanger should be between 8 and 15 degrees F. Your suction pressure is too low. It should be above 50 psig. That could be because of low water flow. As Gary said, could also bee that exchanger is frozen.
Efficiency of R407 is about 5% lower than R22.

[Gary]

Yes, the frozen coil is most likely caused by low water flow... and we might also wonder why the system isn't automatically defrosting itself.