Probably silly question – installer / service coming Monday, but here is the situation. Teach me something.
I have been working on and off at a new McMansion since June. I show up yesterday and hear a clanging noise as I get out of the truck. Follow the noise to one of the heat pump compressor units and find it covered in ice on the inside of the coils to the point where the fan blades are hitting the ice pack and producing the racket. I pulled the disconnect at the unit to shut it down.
The house has 2 heating / AC zones each with it’s own pump / air handler / auxillary electric heater. The 2nd floor zone is working fine, only the unit for the 1st floor was iced (larger of the 2, if that makes any difference).
This unit (Trane) was installed about May of this year, AC worked fine all summer; has been in the heating mode only for about 6 weeks. The weather for the last two days has been a light drizzle, high in the mid-40’s down to low 30’s overnight.
The 1st floor is currently being heated via the auxillary electric heater ( built in to the air handler) so the lady who lives there is not freezing. House temp held steady all day yesterday while I was working. I guess it is just as well the installer could not make it until Monday as that will give the ice a chance to melt out of the unit.
So what causes a heat pump to ice up?
Jim
Never underestimate the value of a sharp pencil or good light.
Replies
A heat pump ices up since it takes the out door air and runs it through the "evaporator coil" in heat mode where it steals 5-15* out of the cool outdoor air. To do this the temp at the refrigerent tubing/fins gets below freezing. With a lot of humidity in the air, frost/ice will form. The unit should be sensing this as performance begins to suffer and lower pressure occurs in the system; it should be going into a defrost mode to melt the frost/ice. Obviously, something's amiss with a sensor or the program in the brains of the unit.
Thanks, sounds like a defective sensor or circuit board or something inside the unit, installer will find it on Monday. The HO was asking me if she would be having this problem whenever it was cool/cold and it rained - I plead ignorance, but said I didn't think so.
Sounds like a warranty issue since the age of the unit is only 7 months or so.
Jim
Never underestimate the value of a sharp pencil or good light.
One also needs to tell the HO that when the HP is fixed and goes into defrost mode, there is often a big steam cloud at the end of the defrost cycle when the fan comes back on (normal ) ; but, have heard of more than 1 HO calling fire dept. first time they saw the HP at their new house go into defrost.
Oohhhhhh! I didna know dat!
Thanks for that info, I will be sure to warn her as she is the excitable type.
Jim
Never underestimate the value of a sharp pencil or good light.
Mine sets off the corner flood light motion sensor with the steam cloud. Awesome first time you see it and do not expect it.
Thanks for your info, you were right on the money. Sensor problem.
The rest of the story - the service guy shows up, pops the cover off and finds the sensor wire dangling - plugs it back in and the unit works great. Talk about me feeling like a dope!
Jim
Never underestimate the value of a sharp pencil or good light.