What happends when your Home Cental Air unit freezes?

[jams]

I have a feeling this is going to cost me.

What happens when your central air unit freezes? My unit came with the house and is 11 years old. The outside unit has frost all over it.

What can be done. I have a service contract on the unit but they can't come until Monday. I was thinking of cycling the unit on every few hours and then give it time to thaw out. Will this harm the unit.

Thanks

[Quik289]

When the unit freezes up it is low on freon. Cycling the unit shouldn't hurt it if it is just a little low. Don't know what might happen if the system has a big leak (from a new hole in the condenser), but you probably won't get much cooling in the house if you have a big hole and all the freon is gone. Of course a big enough leak means no cooling and no freezing either. I am currently cycling my dehumidifier in the garage because it is freezing up - low on freon too.

[392cobra]

Originally Posted by Quik289

When the unit freezes up it is low on freon. Cycling the unit shouldn't hurt it if it is just a little low.

+1

Yep,you're low on freon.Been there..done that.

When was the last time it was serviced and has freon been added in the last year or two ?

[jams]

Thanks guys. It has never been serviced. I guess I am not that proactive.

[392cobra]

Originally Posted by jams

Thanks guys. It has never been serviced. I guess I am not that proactive.

It could easily be a normal loss of freon after years of use and not a major problem.
Except that the cost of the freon will be high.

I have mine serviced twice a year,Summer & Winter.Have a Service Contract as well.

[gunn427]

First thing to check is your furnace filter, blower belt (if it's not direct drive). If the air flow is reduced across the evaporator the suction pressure will be reduced and along with it the evaporator temp. This is the most common cause of ice ups. Most coils run at 34F, if you don't flow enough air that temp will fall below 32F and will build frost,as the frost builds, less air, the ice begins to build and will travel back the suction line to the compressor. If your air flow checks out you may indeed need a tech. If its a filter or belt, change it and your good to go.

[Jamo]

Well, there ya go...sounds like it's time for a family get together!

[undy]

Several items will cause your A/C evaporator to freeze up (40 years as a mechanical contractor) I had a dozen of these problems with customers last week

1) As said, low on freon

2) clogged air filter.

3) defective t-stat (causing the outside unit to run, but not the indoor fan)

4) defective TDR (time delay relay) or other fan control in the air handler,
causing the fan to stop.

5) Indoor fan with excessive bearing wear intermittently dropping off line
and causing a freeze-up.

There are other "unusual" problems that will cause this but these are the ones most prevalent.

[Joe Wicked]

I just had mine charged from being really low. The tech told me to de-ice the inside unit by running just the fan to cycle the warm air inside the house across the iced up inside unit.

[trularin]

Undy has a nice list.

What is NOT happening is the freon is being "changed".

If it freezes up, IE ice forms on the compressor parts, that means there is not enough conversion taking place. Does the fan blow in the furnace/air unit?

In a recent set of events for our family, the blower motor was drawing too much current causing the system to shut down the motor. No air across the coils makes the system ice at the compressor because there was not enough conversion taking place.

Insufficient freon should be low on the list of problems...unless something happened to cause the loss.
Electrical - like a motor being shut down - is probably higher in the list.

I do not know how technically inclined you are, but some of these guys can get big money to do a small thing.

I hope this helps!

[undy]

Originally Posted by trularin

I do not know how technically inclined you are, but some of these guys can get big money to do a small thing.

...and frequently do! Heck it pays for the Cobra, the Z06 and last but not least, the girlfriend



On an older residential system refrigerant loss is by for the most common culprit when coil/line freeze-up is the symptom.. With Freon 22 having gone the same route as the dinosaur and Freon 12 it's sometimes the best thing to bite the bullet and recapitalize. It can nickel, dime and dollar you to death ... and ... you still end up replacing it. I could write a book on the subject.

The new systems take R-410A and the major components in most cases aren't interchangeable with R-22 components.

[jams]

Well the verdict is in......

It was a bad circuit board that didn't allow the blower motor to circulate air as mentioned above. Looks like some arcing took place by one of the relays.

Its blowing cold I just have to wait as the temperature slowly lowers from 90 degrees inside the house.

Thanks for all of your excellent advice and insight. I always like to get educated before the repair man comes, so I can talk intellectually and not be taken advantage of.

So far so good. Once I get to about 75 degrees I will be happy.

[undy]

Ahhhh... reason #4 takes the flag this time. Glad it wasn't a loss of freon, that's more problematic ... and more expensive.

[Joe Wicked]

I have a leak in mine and has always been there. I have fought with the builder on this, and they have brought techs out, and I have hired techs, who can't pinpoint the leak. Best answer so far is "it is probably in the wall somewhere".

[undy]

Originally Posted by Joe Wicked

I have a leak in mine and has always been there. I have fought with the builder on this, and they have brought techs out, and I have hired techs, who can't pinpoint the leak. Best answer so far is "it is probably in the wall somewhere".

Depending on the rate of leakage, the constant loss of refrigerant is eventually going to send your compressor to an early grave. ($1K+ repair)

Here's the way to go at the fix...

1) Recover all refrigerant from the system & kill all electrical power.

2) Cut (tubing cutter) the two copper refrigerant lines (liquid and suction
lines) going into your air handler or evaporator coil.

3) Cut the two copper refrigerant lines going into your heat pump or A/C unit.

4) Silver-braze access fittings (Schrader valves) into one end of the
copper liquid line, one end of the suction line, one of the copper lines for
heat pump or A/C and one of the copper lines for the air
handler/evaporator coil.

5) Crimp and silver braze the remaining ends of the copper lines (4)


6) Charge each of the 4 components (liquid/suction lines & A/C or heat pump)
with 300 psi of nitrogen.

5) From there you just watch which of the 4 items loses pressure.

The above process takes me about 45 minutes once I'm at the job site.
If it is one of the refrigerant lines running in the wall you WILL KNOW which one it is and which one you need to re-run. There are esthetically pleasing line-set covers for running lines down the building's exterior. You can always open up the wall(s) to find the leak in the respective line if running a new refrigerant line is out of the question. A good builder would have gotten this done for you.

[Joe Wicked]

I agree a good builder would have gotten it done, but mine just followed the law and serviced it while it was in warranty.