Dehumidifier Coils Freezing over

[LincolnCont.]

I know this isn't an HVAC question but since it contains a compressor and refrigerant I figured this was the best place to ask for solutions. My Coils keep freezing over and I think it is because my compressor stays on constanly instead of shuting off when it begins to frost. Here's what's happening
1. I turn the machine on and the fan starts then the compressor.
2. The first and second coils begin to frost.
3. It is very hot/humid and very little H20 is condensing.
4. After it frosts over I quickly turn the switch off/on
5. The fan kicks on and the ice melts rapidly
6. The Compressor clicks on and the first two coils frost over and if i let continue without turning it off/on the third and fouth coils slowly frost over aswell

Any suggestions on what's causing it/what needs replaced?

 

[oltruckag]

A frosty evap is caused by 1 of 2 things - low refrigerant or restricted airflow.

Does the unit have a filter? If it's dirty it might not be getting enough airflow.

Dehumidifers aren't really my specialty, but refrigeration systems all work on the same principals. How old is the unit? It may have just given up the ghost...

 

[LincolnCont.]

A frosty evap is caused by 1 of 2 things - low refrigerant or restricted airflow.

Does the unit have a filter? If it's dirty it might not be getting enough airflow.

Dehumidifers aren't really my specialty, but refrigeration systems all work on the same principals. How old is the unit? It may have just given up the ghost...

Its clean as a whistle plenty of air flow. Its 24yrs old

 

[jm1fd]

Systems using R-22 tend to freeze the evaporator over when they're low on charge. Yes...I know...totally counterintuitive.

 

[oltruckag]

Its clean as a whistle plenty of air flow. Its 24yrs old

Plenty of airflow and old... Could be a bit of compressor restricting the orifice (hence the instant frosting of the first few loops) or there is a leak in the system and the charge has leaked out.

Probably time to start looking for a replacement - depending on the size of the system the repair will probably not be cost effective.

(that's my 1000 mile diagnosis anyway )

 

[A_Pmech]

On most better dehumidifiers there's a "frost guard switch" or relay on the evaporator coil wired in series with the humidistat. It causes the compressor to trip out when the evaporator gets too cold.

Are the contacts welded closed?

If you don't have a frost guard switch, disregard the above.

 

[fpianka]

I just went through this with a portable unit. If you suspect the frost guard switch (it sits on the coils and is easily removed, even if you have to snip a couple of wires) you can connect an ohmmeter to it and stick the frost guard switch in the freezer. As the temp drops, the switch should open (to turn the compressor off). Mine was fine, so I was off to buy a new unit. Got 12 years out of the Kenmore, so got another, but it's a lot more hi-tech. I'd be surprised to get a even a few years out of the new one, but you never know.