Heat pump problem

sktn77a

One of our heat pumps started giving us problems yesterday. We live on a lake in the Roanoke, VA foothills and had a cold evening and morning. About 10.00am I noticed the air from the vents didn't seem warm and went outside to look at the condenser unit. It was covered in ice/frost. All 4 sides of the coil and all of the internal pipes and componets were covered. The heatpumps were just serviced 2 months ago (2 systems - both bottom of the line Carrier systems, 5 years old) - 2 new capacitors and one of them, don't know which, had 1.5 lbs of r22 added. I know that it is common for this to happen in AC mode when the refrigerant is low but don't know if this applies in heatpump mode? Could also be a bad de-frost system? The unit hisses for a minute-or-so after the compressor switches off.

I'm going to call the folks back that serviced the units in November but wanted some trustworthy thoughts here before doing so.

Thanks in advance,

Keith

biggles

that hissing when the compressor shuts off is the freon equalizing thur the valves if for example your running R-22 you might be looking at 250/65 running on pressures... so that's that.that whoooosh you hear is the reversing valve swinging from cooling to heating or heating into defrost...that defrost cycle should of kicked in as the ice builds up in the heating cycle with the colder the outside air the more your going to defrost.a quick check for you to do when running in heating mode is to try to grab the insulated line into the air handler on a fully charged heat pump in the heating mode you shouldn't be able to do that...thats direct compressor superheated freon 170Fplus into the coil there..if it is warm then a charge is low .don't let people just add freon without making an effort to check for leaks they know where the common points are and make them take temps of pipes air inot of unit inside and outside and record the guage pressures/days temps on the invoice...tell the tech to grab that line into the air handler...he screams your charged up

sktn77a

Thanks Biggles! So is the feezing over possibbly due to low freon charge? Could this happen if the defrost system is working properly (ie do I have a non-functioning defrost system) or would the defrost cycle just kick in to prevent freezing over like this even if the charge is low? (I'm not at the house during the week so can't check the insulated pipe temperature until next weekend).

Keith

biggles

when the unit is in heating mode the outside is the evaporator and is running 40F with the inside taking the discharge freon to heat the show....the defost cycle is sensed from a resister within the condenser coil (brands differ)something has to tell the defrost board to swing the reversing valve to defrost mode so the compressor freon melts the ice off the condenser..then swings back to continue heating in the winter.that 40F outside on the condenser in the heating mode when it is below that outside there is no load as the temps drop below 40F so ice forms as in a refrigerator....at 20F a HP will run but the defrost cycles increase in happening...to see if the charge is short and a system switch if you see this condition again and the house is warmed up swing the stat to cool and you'll force a manual defrosting in that mode.if the charge is within the unit keep a mental time it takes as the ice melts off the condenser...when the ice is not seen flip it back to heating and check that insulated line at the air handler...or outside right out of the unit ...if the heat is there the charge is there then it's the board????NOTE:the reason you can't check the discharge line in the cooling mode is it is within the condenser going right to the coil turning into liquid freon with less heat at 85F during the summer.the only thing producing heat on any system cooling or heating is the freon being compressed...if the charge is lit then the heat temp also will be lower 90F-100F that you can grab no problem...freon is like air in a car tire it's there or it isn't,and constant top offs is a PITA as filling a low running tire...right

harleyrider

I'm going to call the folks back that serviced the units in November but wanted some trustworthy thoughts here before doing so.

Thanks in advance,

Keith[/quote]

You should NEVER have to add freon to a system, if its installed correctly. The exception to that rule is of course over time a leak develops.If you develop a leak, and a technician discovers that leak then he should make you aware of it an advise a plan to REPAIR the leak. Leaks allow dirt/air/moisture into the closed side of a refrigeration system and promote the development of acid, once you have acid in your system its a slow and expensive death for the system. removing and cleaning up acid in a system is a painstakingly expensive venture,and it almost always is fatal to a small residential system.

When the company come back out and if they say that you are low again on freon, I would insist that a leak search be performed, the leak found and properly repaired.

sktn77a

Will do, Harleyrider.

Thanks Biggles - will check that this weekend

Keith

sktn77a

One last question - this is a new house (to us - it's about 5 years old, lived in for 1 year but the heat was on low for the winters to prevent freezing). The previous ownes didn't have any filters in the system (return air filters) and there are no filters anywhere else in the ductwork or air handlers. The filter sizes are 14x14 and 20x24 upstairs and a 14x24 downstairs. The downstairs filter seems too small for a 3 ton heatpump? Would restricting airflow cause the outside unit to freeze over (like it does with an AC)? I plan to increase the return air at the earliest time possible but in the interim wanted to know if the filters I put in could have reduced the airflow and caused the problem with the 14x24 system.

keith

biggles

air restrictions are minimal unless they were dirty..trick hold it up to the lights if you can see light air will pass thru it.that icing issue is totally on the outside condenser during a winter heating run...and that you said he ran it with no filters as found might want to check the A coils on top of the air handlers migh be matted with dust/dirt that needs to be eyeballed.you might notice a slower LO air movement in the heating mode compared to a HI fan air during the summer...depending on brand a slower air is used so the air can heat up more... might be LO/LO MED wired in the fan.to check it when in heat just switch the FAN?ON from the stat and you might hear a speed change...to test the return grill sheet of newspaper should hold it up heat or cooling..check the rounds on the supply fan squirrel cages also...for dirt/dust

sktn77a

UPDATE:

Well, turns out the defrost board and sensor were bad. The service guy replaced those and everything appears fine now. Thanks for your help Biggles and Harleyrider.

Keith