We have a Premier 2 Series Waterfurnace Model ATV040D110CLBX installed in 1996. We are seeing frequent shutdowns due to a water flow fault - steady red light on front furnace panel. If we clear the fault by resetting the breaker and restart the heat pump immediately, it will usually fault again in less than an hour or two. If we let it rest for 6-8 hrs, by using em heat, and then turn the heat pump back on, it will usually fault again after another 6-8 hrs. According to an older reply to a different post, the newer Envision models have the WF thermistor located on the refrigerant line, not the water line, so a WF fault indicates low refrigerant temperature. This could be due to low refrigerant or, by indirect inference, low water temperature. Can someone tell me if my Premier 2 Waterfurnace is configured in the same manner? I've measured the water temperature at the time of WF fault to be 35-37F. This is within a few degrees of the typical water temperature during normal heat pump operation. A local tech has measured the water temperature differential (pump inlet vs outlet) to be 3 deg F under normal operation. So it seems that my problem is not due to temperature below 15 F in the water line. I live in Eastern Washington where the outside temperature lately is a min in the mid-teens, high in the upper 20s. Our system is 2 horizontal 1200' loops with half of the pipe at 6' depth and half at 4' depth. Our system is 18 years old. Thanks in advance for information and suggestions.

Did your local tech perform a Heat of Extraction/ Heat of Rejection (HE/HR) ??
A 3 degree temperature differential seems a bit low, but that could be caused by too much flow.

Bergy

I suspect partial loss of charge or a metering device failure. Find location of sensor that triggers WF fault and independently measure temperature there.

A slow air coil refrigerant leak could cause subject condition...a competent tech should be able to top up refrigerant charge and detect leak.

Update 1-22-2014

The Tech came yesterday and checked that the thermistor is showing the correct impedance at 33 deg. He pumped the refrigerant out and added 6oz to bring it up to 5 lbs 5 oz specified weight, and repressurized. He checked that the DIP switch was set properly on 15F (loop) and cycled the switch multiple times. The heat pump WF faulted again last night, at 35F water temp, as usual.

I see 2 possibilities:

1) the control circuitry and temperature sensing is working ok, the refrigerant is getting too cold ~15F inducing a WF fault even though the water temp is ~35F (as measured with a recording thermometer with a probe). I suppose this could be due to a fouled heat exchanger(?). If so, what next? If not, what else?

2) the control circuitry is inducing a WF fault at a higher temperature than 15F. Either the thermistor doesn't behave properly at 15F even though its impedance measures ok at 33F, or the control circuitry is faulty. The tech (he's not a WaterFurnace repairman) says the circuit board(s) are not field-serviceable, though maybe a good WaterFurnace tech could do something here(?). Reading other forum threads I see that sometimes whole boards are replaced, without really knowing if this is the culprit. Seems a bit mindless to replace an expensive board without knowing in advance that it is faulty. Is there a straightforward way to determine this?

Maybe there are other possibilities? My concern is that we've eliminated the simple reasons for the failure, so finding the real solution may be much more difficult.

engineer, did I answer your concerns? Bergy, I don't know what a Heat of Extraction measurement is. We know the 3 deg temperature differential between entering and leaving water at ~36F. We know that the water flow appears reasonable, although the numerical value hasn't been measured. Why might a faster-than-normal water flow be a problem? In any case, doesn't this seem an unlikely result of an aging system?

thanks, engineer and Bergy, and thanks in advance to any other responders.

Did/can you measure the EWP and LWP. From the pressure drop you determine the flow.

The addition of refrigerant indicates a leak. Loss of refrigerant can cause your symptoms. Did tech find leak?

Thanks to everyone for their replies.

We had a different tech out yesterday. Our whole system had gone dead overnight. On em heat, it was blowing the 60A fuse. Tech found a loose connection that was sparking next to the fuse holder, causing the fuse to overheat and burn up! An easy solution to that problem.

Next, on the heat pump, he found the entering and leaving water pressure difference to be huge. He measured the specific gravity of the water and said it didn't have enough Enviro (sp?) antifreeze and the water was slushing up. Temperature in the water line was 23-27 deg, much colder than the 35F shown by my thermometer probe attached to the outside of the pipe. His thermometer went directly into the water via the access port. He will come back this week, hopefully, with his pump cart and more antifreeze.

The only puzzle to me is that he said his hydrometer indicated that the liquid was good to 45F. But how can the freezing temperature of the liquid be above 32F?? This doesn't make any sense to me.

Joe.ami, he didn't find a refrigerant leak, unfortunately. I'll have to ask him about this when he returns. My hope is that this drop happened over years during the previous homeowner, and the leak is so small we can live with it if it cannot be found.

Freezing temperature of liquid can't be over 32F but it sounds like you were lower than that.