I woke at 5:00 this morning and the house felt cold. When I checked the the thermostat it read 66 degrees which is 3 degrees lower than my normal set point. Outside temp is 8. It was around 18 all day on Thursday.

I went downstairs and looked at the unit and the zone control was showing that it was operating in second stage with aux heat. I stuck the probe from my digital thermometer between the insulation and the pipe and got the following readings: EWT 37 and LWT 36. Temp readings were EWT 57 and LWT 48 on Sunday when outside temp was 30.

The thermostat is set for 69 degrees 24/7. There is no set back. I went to bed at 11:00 and noticed that the unit ran without aux heat the entire time I was home.

My zone control is set so the 2nd stage doesn't kick in for 15 minutes and aux heat doesn't kick in for 30 minutes. Could these setting be leading to my reduced indoor temperature?

Any ideas?

Is compressor actually running? LWT=EWT suggests zero heat from ground - you are on aux only.

Test by reducing thermostat setpoint to 1 degree above house temp - see if register air is warm with just stage one. I'll bet it won't be - something is keeping compressor from running or pumping heat (loss of refrigerant, stuck reversing valve.

Unit may have gone out on low EWT and needs to be reset (cycle power). If loop is just water (no antifreeze) or heat pump is configured via dip switches for plain water it'll cut out at 32 or so to prevent freeze damage.

Just some possibilities...

I agree.
Sounds like compressor lock-out.
Turn power off and then restore it.
- temps may require aux heat sooner than 30 minutes.
Keep us posted.
J

UPDATE

The owner of the installing company was out to look at my system last week.

Checked pressure and temp in EWT and LWT lines. Ran some calculations and everything was within spec as shown in the Climate Master book.  EWT was 38 and LWT was 34. I don't recall the pressure.

Entering temp from desuperheater was 123 and exiting temp was 125.

He checked the air temp in the supply and return duct and the temp change was greater than what was in the Climate Master book.

What he finally found was that the AUX heat wasn't working correctly. Apparently, there is a 5 KWH heat strip and a 10 KWH heat strip. The 5 KWH strip would kick on but the 10 KWH strip would never activate. He indicated there's a time delay between the 5 & 10 KWH heat strips but timer must not be working. He rewired so the 10 KWH comes on first and is reordering a circuit board. Once he rewired the strips and kicked on the AUX heat, the supply duct temps shot way up.

Hopefully this will solve my cold house problems on those 5 degree days.

Nowhere in that explanation do I read an answer / explanation for the original observed condition of EWT=LWT. Aux won't affect EWT / LWT

Was LWT=EWT adequately explained along with reconfiguring the strips?

Did he check the fault code history with you?
Average tech not likely to catch that coil problem. That's encouraging.
J

My method for checking EWT & LWT was done by inserting the temp probe from my digital oven thermometer in between the insulation and the pipe which is probably not the best way to do it. I was a little alarmed when I found that there was only 1 degree of difference which coupled with the low interior temperatures prompted my post.

When the temps were checked the other day it was done through the ports in the lines which I assume will provide a better indication of the actual temps. The unit was also checked for any error codes and there were none present. After checking all of the normal operations and finding nothing out of the ordinary he started checking the current in the lines with a clip on meter and found the problem with the AUX.

Would have expected the 1* temp difference indicated lock out. Had you killed power to unit before he checked for fault codes?
J

No. I never turned off the power to the unit. I left for Florida when all this was happening and met with the installer the day I returned home.

Still like his heads up on the subtle coil malfunction, so am inclined to wait and see with you monitoring the system. 1st stage with a lot of flow could have a very low delta t between entering and leaving water, so make sure you have good contact with the thermometer and measure back and forth more than once. Also not thrilled with temps on DSH.
Keep us posted,
J

Agreed - I missed the 2 deg Delta T on DSH - normal is 10 ish...

Actually, upon reflection, maybe not in this case - DSH in 120s may be quite near compressor gas discharge temp, so low heat transfer. My DSH maxes out at 115-120 after an all night run in low stage on a below-outdoor-design day. My new 410a system with TXV has hot gas about 40 deg below than the 20 year old R22 unit in the old house.

Tranquility 27 HWG has a high limit temp switch factory set @ 125 F, but it is located on HWG heat exchanger "water in" line.

Regards, Masoud