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Old 11-22-2006, 05:29 AM   #1
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Greetings,

On my 01 UA have basement air/heat pump. Air works awesome, heat pump works, but noticed the last couple nights it started making a wierd noise when the temps got below 40 degrees. Not that it should get that cold in FL, but it has been rather chilly. In any case, duing the day, I don't notice it. When it is cold out, I hear this ultra high pitched but faint whine, almost inauible, but once I notice it it is quite annyoing.

Thought it might be filter related, pulled the filter, didn't go away.

Is this normal? is the heat pump just reaching its limit of working capacity and can't keep up? It sounds like it is a freon related problem, not a mechanical noise, and certainly doesn't sound like a bearing or fan motor going bad.


Thanks for you help

John

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Old 11-22-2006, 05:29 AM   #2
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Greetings,

On my 01 UA have basement air/heat pump. Air works awesome, heat pump works, but noticed the last couple nights it started making a wierd noise when the temps got below 40 degrees. Not that it should get that cold in FL, but it has been rather chilly. In any case, duing the day, I don't notice it. When it is cold out, I hear this ultra high pitched but faint whine, almost inauible, but once I notice it it is quite annyoing.

Thought it might be filter related, pulled the filter, didn't go away.

Is this normal? is the heat pump just reaching its limit of working capacity and can't keep up? It sounds like it is a freon related problem, not a mechanical noise, and certainly doesn't sound like a bearing or fan motor going bad.


Thanks for you help

John

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Old 11-22-2006, 06:02 AM   #3
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John,
The whine you hear is probably the gas furnace coming on. The heating system is smart enough to adjust for the reduced efficiency of the heat pump at lower temps and turns on the gas furnace to augment the heat pump. At some low temp, (I would have to dig out the Black Bag to find the exact answer) the heat pump will not even come on.
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Old 11-22-2006, 06:46 AM   #4
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Documentation on my '02 says 36 Degrees F. However, when the gas furnace comes on, it is apparent from the additional airflow (coming from the floor vents vs. overhead) and you can usually hear the gas burner come on. There is a 'turbine' sound from the fan in the gas furnace.
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Old 11-22-2006, 07:27 AM   #5
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No, I am certain the gas furnace isn't coming on. I know what it sounds like, and the sirflow is still only from the ceiling, not the floor vents. the noise clearly is coming from under the bed/engine compartment....

I was talking with a fellow RVer at the park and he said his makes the same noise when it is chilly out, so I am hoping it is a normal situation. Thanks for the quick replies... I am sure you all know how it is with somehting "different"... I get worried when I don't fully understand what it is tring to do.

John.
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Old 11-22-2006, 10:40 AM   #6
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John,
Don't know if your 40J is set up like mine, but I have 2 furnaces. The one in the bedroom is controlled by a separate thermostat from the one up front. The front furnace is controlled by the Coleman Mach thermostat that also controls the heat pump. When the front furnace comes on it sounds just like what you described.
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Old 11-22-2006, 12:16 PM   #7
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Yes Mine is set the same way.

The rear furnance is off, so it can't be that.

The Front furnance, wasn't on on either occuance. I tried it today with an outside temp of 59, and it ran normally. I am not sure what the temp was last night, but it did get quite cold for FL. My understanding of the unit is that it will kick on the gas furnance if there is a 5 degree difference between the set temp and the room temp. Both times it was less than 5 degree difference, plus, as I said earlier, I am certain that it wasn't the gas furnance kicking on. That sound is quite different than what I am hearing.

The Noise I am hearing is very high pitched, but very faint. We'll see if it does it again tonight, I don't think the temp will drop quite as far as last night.

A good note is that it seems to be operating properly, atleast it is keeping the house warm.

Thanks,
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Old 11-22-2006, 12:49 PM   #8
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John,

It may be the reversing valves, they are what make the heat pump part "work". As the ambient temperature falls, the pressure rises in the system. What you are hearing is the sound of the refrigerant moving thru the reversing valve, at increased pressure due to the lower ambient.

Normal operating condition as far as I know.

HPotIW
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Old 11-22-2006, 04:48 PM   #9
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Your statement that as the ambient temperature drops the pressure increases.
I do not think so,as the ambient temperature drops the freon pressure decreases at the outdoor coil less heat is being transfered at this coil therefore less heat is being created at the indoor coil.At a given temperature as Smlranger stated 36 degrees the gas furnace comes on.That is because there is so little ambient heat left to transfer thru that outdoor coil."Low Freon Pressure"
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Old 11-22-2006, 05:48 PM   #10
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Indeed Ed, I missed that one.

Turns out that sound may be liquid not absorbing enough heat to expand to a gas state and gurgling in the system (if I have read heat pump system theroy correctly, it's a little confusing)

I actually know John (moder2) and am certain its not his furnace coming on, as he states. He's a pretty sharp guy, and can tell the difference.

My heat pump makes the same noise, and the RVP tech told me it was refrigerant making noise due to pressure, and I incorrectly assumed it was high pressure, not low.

Anyone have a better working understanding and could provide a clearer picture for us?

Thanks Ed!
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Old 11-22-2006, 09:43 PM   #11
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I will take a stab at this.

If the whine is associated with a low outside temp, I think it is coming from the metering valve. This valve delineates the HI Pressure Liquid from the Low Pressure Liquid in the system.

There is a tubing connection between one side of the indoor coil and one side of the outdoor coil which does not go thru the compressor or reversing valve. In the tubeing is the metering valve, more than likely located where the tubing enters the indoor coil. This valve shuttles back & forth, depending on which way the freon is flowing IE cooling mode or heating mode.

Now to see how this works.

In the cooling mode, compressor sucks low pressure gas from the indoor coil and outputs hi pressure gas thru reversing valve to outdoor coil where it turns to hi pressure liquid as it travels thru. This liquid goes thru metering valve turning into low pressure liquid and then into low pressure gas as it travels thru the indoor coil.

In the heating mode, compressor sucks low pressure gas from the outdoor coil and outputs hi pressure gas thru reversing valve to indoor coil where it turns to hi pressure liquid as it travels thru. This liquid goes thru metering valve turning into low pressure liquid and then low pressure gas as it travels thru the outdoor coil.

In the cooling mode, because of the higher temperatures/pressures involved, the metering valve will always be metering liquid.

In the heating mode, because of the lower temperatures/pressures involved, the metering valve may be metering gas. If the hi pressure gas entering the indoor coil does not condense into liquid before it reaches the metering valve then it will transition from hi pressure to lo pressure as a gas.

This may be what you hear.

Sorry for the long wind.
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Old 11-23-2006, 04:22 AM   #12
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Your understanding of how a Heat Pump operates is close.
But the last part (in the heating mode)there is a metering device of some type when the system is in heat.Either the freon is passing thru the cooling metering device via a internal bypass or there is a check valve routing it around it.
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I just thought of something,the indoor fan speed is selected at the thermostat,try operating on "low speed".Most of the time I know that mine is set on "high speed".In the heat cycle you would want the air moving slower therefore you pickup more heat from the indoor coil.
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Old 11-23-2006, 07:23 AM   #13
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Good morning ED,

I agree that if the True-Air heat pump was a more sophisticated unit it would have 2 separate metering devices or Thermal Expansion Valves with associated check valves and bypass tubing. But the True-Air Data Sheet identifies the metering device as a BiFlow Restrictor. I believe the same device meters the freon in both directions. I suspect that it is designed in a way which it meters a different amount in heating than in cooling, but won't swear by it.

It is true that running the indoor blower on lo speed will make the air warmer. But the True Air will not allow that selection. In the heating mode, stage 1, it activates both compressors, both reversing valves & puts the indoor & outdoor blower motors on Hi speed.

I believe they do not allow a lo speed in the heat mode because when the unit is operating and the outside air temp increases the slower air movement over the indoor coil will not be sufficient to remove enough heat. This will cause the compressor head pressure to rise to the point of tripping the hi pressure switch. If the switch would fail, you could exceed the presure limits of the coils.
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