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Discussion Starter #1 (Edited)
I am still somewhat new in the field and learn something new every day.

Todays delima is a 12yr old carrier heat pump. I have checked the thermostat programming. The air handler is fully functional, evap is clean, air filter is new, blower is working. Auxiliary heat is functioning. The issue is within the heat pump itself.

Manifold gauges are connected, indoor ambient temperature is 72* , outside ambient at the coil is 30*. Carrier charging chart for these temps provide with low pressure of 79 and high pressure of 293.

With the heat pump running continuous approx 20 minutes my low side pressure is 80 and high side is 225. High pressure line temp fluctuates between 96-103.

Normally a low high pressure line temperature would indicate to me the system is overcharged. If i recover refrigerant the temp drops, if i add refrigerant the temp will max out at 106 before dropping below 100.

I failed to mention the outside coil is clean.

Ok, back to the issue... I'm leaning towards possible refrigerant blow-by in the reversing valve, or possibly compressor failure. What's your thoughts?
 

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An RV that has internal blow by/leakage, would also cause the low side pressure to be high.

Is the LLFD inside or outside of the cabinet. Are checking the high side pressure at the liquid service valve, or the hot gas service valve.
 

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Discussion Starter #3 (Edited)
An RV that has internal blow by/leakage, would also cause the low side pressure to be high.

Is the LLFD inside or outside of the cabinet. Are checking the high side pressure at the liquid service valve, or the hot gas service valve.
Thanks for the quick response
Happy New Year!

The LLFD is located outside the cabinet, checking high pressure on gas side in heat mode.
 

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See how much of a preesure difference there is between the 2 lines. Could have a slight pressure drop.
 

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In short… high discharge temp can commonly be caused by
– Low charge (high suction superheat, low suction pressure, low subcool)
– Severe Overcharge
– Low condenser air flow
– Restricted metering devices
– Other restrictions (Liquid line drier, suction line drier, kinked lines, clogged screens)
Low discharge line temp can be caused by
– Overcharge (slight to moderate)
– Low load / air flow (in some cases)
– Compressor not Pumping (low compression)

Keep in mind that keeping discharge line and compressor temperature in check will greatly increase compressor longevity with refrigerant cooled compressors. It is worth noting that severely high compression ratios (low suction, high head) are more common in refrigeration applications as a cause of compressor overheating.

In A/C applications it is more commonly caused by the high suction temperature / low mass flow rate associated with low charge or restrictions. Though instances of overheating due to dirty coils and poorly insulated suction lines is also quite common.
 

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The compressor contactor controls how much power goes to your heat pump. If that’s damaged, it’s possible your heat pump could run all the time. You’ll need a professional to replace the part.
 
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