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Old 03-24-2009, 08:03 PM   #1
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Is it the usual "leak"???


Hi guys. New to the forum and hoping you all can help offer a second opinion.

I have a 2.5 year old frigidaire 3.5 ton heat pump (model FT3BA-042KA). Live in Alabama. Unit is still under parts warranty. Ran the heat all winter long at 71 degrees with no problems. New Years eve weekend was particularly warm and we had guests over so we set the t-stat to cool and lowered the temp to 66. Fan came on, compressor came on, but house didn't cool. We called a service tech.

They told us that we were low on (nearly out of) refrigerant, but after 3 hours of searching couldn't find a leak. Recharged the system and happily handed me a bill. Over the last three months now, we've had the system either off or on heat and have held a comfy 70 degrees.

Once again, it's time to switch to cool and we've got nothing. Again, the compressor kicks on and the fan is spinning full speed. We've got plenty of air coming through the vents. I temped it at 74 degrees regardless of the t-stat setting. Air return filters are changed regularly.

Any ideas before I call another service tech? I don't even know whether I should be trusting the same company we originally called or not. I just can't figure out how the house heated if the refrigerant had leaked out. Our power bill doesn't suggest the heat strips were running, but I'm not sure how else to tell.

Thanks in advance and sorry for the long post.
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Old 03-24-2009, 08:11 PM   #2
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Is it the usual "leak"???


If it's out or low on refrigerant It won't take long for the suction line large line / condensor to ice up... Leaks can be difficult to locate sometimes. I would suggest the company put a nitrogen test from the outside ( lineset) to the inside coil... That would be a start

Last edited by kenmac; 03-24-2009 at 08:14 PM.
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Old 03-24-2009, 08:39 PM   #3
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Is it the usual "leak"???


Thanks kenmac.

I should add the supply line (isn't that what the main, insulated copper pipe running to the outside unit is called) doesn't get hot or cold when the unit is running.
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Old 03-24-2009, 08:44 PM   #4
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Is it the usual "leak"???


Quote:
Originally Posted by kastnna View Post
Thanks kenmac.

I should add the supply line (isn't that what the main, insulated copper pipe running to the outside unit is called) doesn't get hot or cold when the unit is running.


The insulated line is the suction line.. If you had the a/c on and this line freezes over the unit is low... This line is usually cold>
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Old 03-24-2009, 08:44 PM   #5
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Is it the usual "leak"???


The large line is a vapor line in cooling mode.

And a Hot gas line in heating mode.
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Old 03-24-2009, 08:53 PM   #6
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Is it the usual "leak"???


okay thanks.

So what does it mean if the suction line isn't getting hot or cold? Maybe I'm mistaken and the compressor isn't coming on. Like I said, I'm not an expert and this is definitely a job for a pro. I just don't want my ignorance to get me ripped off.
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Old 03-24-2009, 09:10 PM   #7
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Is it the usual "leak"???


If you have a pressure switch on the unit.. The compressor may not be comming on
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Old 03-24-2009, 09:20 PM   #8
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Is it the usual "leak"???


If you are low on refrigerant, the suction line will not be cold during start up (cooling mode). It will take a long time before the line will ice up. Basically, the coil will start to ice up at the metering device. It will then slowly ice up the coil blocking off air flow. Eventually, the suction line will form ice at the air handler and make it way back to the outdoor unit.
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Old 03-24-2009, 09:36 PM   #9
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Is it the usual "leak"???


If they never fixed the leak in the first place it has most likely leaked out again and is shutting off from low pressure on the low pressure control. One of the best methods for leak checking is to pump up the system to about 150 psi with dry nitrogen and a trace of refrigerant. Amazing how hard it is to find small leaks without that much pressure. I have had cold weld leaks start to show up much better at that pressure. Be careful not to overpressurize the compressor. Low side of the compressor not rated the same as the high side. Check the pressure rating on the model # sticker for more info.

Last edited by yuri; 03-24-2009 at 09:48 PM.
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Old 03-25-2009, 09:03 AM   #10
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Is it the usual "leak"???


Thanks for the advice everyone. I have somebody (different) coming next week.

can anyone explain why the heat pump successfully heated the house all winter? I thought refrigerant was responsible for both heating and cooling. Was it the heat strips?

I didn't notice a spike in my power bill, which I was told is common if the heat strips are running. And for the record, the heat won't warm the house above 74 degress (doesn't matter whether it's 32 or 72 degrees outside).

Thanks again. I let you guys know what the service tech has to say.
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Old 03-25-2009, 09:19 AM   #11
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Is it the usual "leak"???


Probably a combintation.

The strip s were helping to heat.

Plus. In heating mode, a HP requires less refrigerant in heat mode then in cooling mode.

Some systems use a charge compensator because of that different requirement of refrigerant.
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