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Scenario with Heat Pump System. (currently not maintaining heat @ 68F when cold

Scenario with Heat Pump System. (currently not maintaining heat @ 68F when cold


Old 01-29-18, 12:27 PM
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Scenario with Heat Pump System. (currently not maintaining heat @ 68F when cold

Scenario with Heat Pump System.

New Construction Home (2015) heated/cooled with Goodman 2-ton Heatpump first and 2.5 ton on second. Both have aux heat strips. The issue seem to appear after the 3amp fuse blew. (had several power outages around same time period). The fuse has not blown since nor prior. So it may be related. Live in Winston-Salem area of North Carolina. The first winter (before fuse blew), I called the company the installed the system and they told me there was nothing wrong with operation. We only had one or two cold odd day Winter 2015-16.

Replaced basic thermostat with programable ones Fall 2016Ė same model on both floors. Fuse around same time. It was late fall so I am not certain if it was before, after or during replacement of thermostats. Winter 2016-17 was first full winter. I once again called the company the installed the system and they once again told me there was nothing wrong with operation.

This past summer (2016) the first floor (2ton) was blowing heat when in cooling mode. The tech could not figure out why the reversing valve was not operating. First he blamed the thermostat, but when I explained I reversed the thermostats, back and forth the problem was also on the first floor and did not move he though it could be a wiring issue. He tried may things and could not identify what was the issue, but when he jumpered the reversing valve (orange and red at the outside unit). The house cooled fine. My Electric bill was normal and comparable to previous summer.

Winter 2017-18, here in Central NC, it has been much colder than typical of the area. The 2nd floor maintains temperature very well, even if set back is used. We keep the first floor @ 68F. When (outside) temps drop to around 20F, the unit will start to have trouble maintaining temp. When temps drop to mid teens it will not maintain 68F. When outside temp dropped into the middle single #ís. The inside temp will drop to about 60F. During the day time the temp will recover to 68F. Measuring temps at the register vent with an infrared gun, will often show very low delta T (someone basically 0). However, the delta T will rise briefly to 15-20. The delta T on 2nd floor is normally slightly better when temps outside are above freezing. I know the Aux is on the majority of the time when cold on first floor, but not 2nd floor. (of course this is in part because heat rises). I have to wonder if the defrost cycle is competing with the heat strips and that is why I get low delta for long periods.

First, could the reversing valve problem be related to the heat performance issues? Could this indicate low gas? Could this be a Defrost board issue. The other thing I considered is that the unit is similar undersized. The house was built with a sunroom addition that is mostly glass might contribute to the problem. The current Dec-Jan bill, I would estimate to be nearly double ( over $350 vs any prev. high month ($200), I should be getting email in couple days to know for sure.. A low month is under $120. The house is 2925 total sq.ft. The first floor is about 1300 sq.ft. including sunroom due to garage. Both units are Goodmanís.

My questions.

If it is a defrost board issue, that would seem to be a simple fix Ė would this also cause the summer issue with reversing valve not working right when not by passed?

Is something else cause the unit/heat pump not to run correctly? (such as low gas)

Is the unit simply undersized and has difficulty when temps drop to around 20F?

I donít mind paying someone to fix the problem, but I donít like paying someone to scratch their head.

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Old 01-29-18, 04:33 PM
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Welcome to the forums.

A lot of questions there and most should be addressed by the installing company.

I can tell you this.... when the room temperature is 3f or more below the set point..... the AUX is turned on. For this reason set back is not recommended on a heat pump system. If your system spent a lot of time running the AUX heat.... that would raise the bill considerably.

If the defrost board has to be bypassed to get the unit to cool..... that is an issue.
Old 01-30-18, 05:00 AM
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The installing company told me there was nothing wrong twice, so I called another company which could not figure out what was wrong. I do not use set back during winter any longer on first floor. I am aware 2 degree will normally trigger AUX hear (which should be avoided unless system in "normal" defrost cycle). A 50% increase of any high usage month over past 2 years would seem to indicate a problem.

Thanks for your comments.
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