Heating, Air Conditioning, Fridge, HVAC/Noisy AHU heat mode


Looked at a system the other day. Like you Craig, Im Industrial/Commercial Tech 30+yrs. Not an expert on small res. HPs. Most of my experience has been in Colorado, Now I have returned to Florida after 24 years. So Air cooled HPs are a weak spot for me.  History!! Rudd AHU UBHA 17J11NFGAI (whats the tonage?) Its a friends Rental home. When he bought the place...the copper thieves stole the CU.
He had a Company replace the CU (used) Rheem 3ton HP. Its still in decent condition. Found it off on HP safety. would not reset, determined its faulty. By-passed for trouble shooting. Tenet stated it made a really loud noise from the AHU. Gauged system (R-22), Suc psi at approx 70, LL psi rose rapidly and I heard the noise from the AHU.
When I ran the system in Cool mode, the suc psi was at 60, LL at 168. OSA at just around the 60-64f mark. It appeared slighty low. I did not do SH Delta-T or sub temp readings, suc was cool to touch and some condensation and no temp differential accross the reversible dryer.
Switch back to heat mode and the head pressure rose rapidly and noise returned at AHU. Evap Coil was not all that dirty and air flow was good. Im leaning toward the TEV.
Have you experienced this issue, Could the AHU be undersized? Gratefully seeking your thoughts and advise.

Rheem/Ruud liked to use different model numbers for their air handlers.  I am not sure what the tonnage is.  I would call the local wholesaler and ask them.

With the outdoor temp in the 60's, it is hard to determine if it is charged right in cooling mode.  I would have to block off some of the air flow to get the head pressure up to check it.  Also keep in mind the evap coil does not have the same heat rejection at the cond. coil.  There is an outdoor temp limit for running the heatpump in heat mode.  Carrier states not to run in heat mode above 66. The noise could actually be normal.  Does the A/H contain a TXV?  There may not be anything wrong, just seems louder because of the higher outdoor temp.


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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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