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Posted by on November 1, 2006, 6:10 pm
>
>Pappy,
>Thanks for the advice to look at the simple stuff; I would like an easy
>answer to this. The indoor coil has a fccv, not a txv, but the heat
>pump does have a txv, don't all heat pumps have one? I did not check
>any pressures in heating mode.
>
>The indoor coil is clean as new; the outdoor coil looks good but could
>stand to be washed. I did not think much of it because of the
>extremely low high side pressure in cooling. Also, the only returns in
>the house are high air returns.
>
>Bubba, The details of how I determined airflow were; I used a
>"magnehelic" to measure static pressure from below the coil to a
>reference point at the filter. The needle actually bounced between 0.4
>to 0.5 depending on how the sensing ends were placed in the air stream.
> I am aware of the difference in using the different motor speeds taps
>in heating and cooling and moved the taps to see the effect on my
>readings. The Trane "service facts" sheet has a nice table listing
>the airflow at the different motor speeds at a given static pressure.
>
>To double check I measured the temperature rise in heating with the
>furnace running.
>The Output BTU is specified at 63000 Btu/hr, I did not measure this,
>and my temp rise was 47 deg (measured return air boot to plenum delta
>T) I then used CFM=BTU/hr divided by temp rise times 1.085.
>63000/(47x1.085)= 1235 CFM
>
>The unit is rated at 2.5 ton (the 30 in the part number TWR030C)
>
Wide open metering device or stuck reversing valve.
>What can cause a low High side pressure and a high low side pressure in
>cooling mode, in a heat pump, and cause very low btu/hr output in
>heating mode?
>
>What things would check, in what order, and how?
>
>Thanks,
>Dave
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