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Question DetailsAsked on 7/22/2016

I replaced a unit with R22 to a new unit with R410a but it is not able to cool as well, why?

I had new AC unit installed Rheem model rawl-090az using R410a to replace an old unit: Rheem rawd-091caz serial # 7335f320709077 that I had since 2007 and was using R22. I had no problems getting the old unit to cool down 3000 sq.ft. to 75f and below. the new unit can only cool the space down to 79f and it works constantly to maintain 79f. why? the installer does not want to do anything about it...what can I do?

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2 Answers


I presume the new unit is actually a RAWL-090-caz, not just az - meaning 208/230v power.

Could not find the RAWD-091 caz - must be too old to be in their documentation any more, so can't tell what the 091 designated in terms of rating - the 090 is 7.5 ton rated. If you look in the owner's manual if you still have it (for the old unit) or if you have a photo of the old unit model/rating plate, if the rated 'tonnage" was 7.5 tons or less, then the new unit should be able to keep up.

I am assuming he replaced the evaporator coil too - in the ducts or air handler unit - because if not, since R-410a is about 15-20% less efficient as a refrigerant than R-22, your unit would be dramatically undersized compared to what you were running beforewithout a higher-capacity evaporator. Also, not knowing what lineset size you have (the tubing) larger (commercial) units like yours commonly need the next larger size lineset to operate right.

Since it is not cooling correctly I would get on the installer's case - and if not luck there, then your recourse is to get manufacturer input (they might send out a factory rep depending on your area), filing a claim with the contractor's bonding company to get it fixed, or under warranty state in writing to the contractor that it is not performing as the old one did so you want your money back (meaning presumably they take the unit back).

Oh - BTW - the "rating" of the unit, in terms of "tons" of air conditioning per hour, 1 ton = 11,917 BTU/hr (British Thermal Units per hour) - rounded off to 12,000 usually. Even though the R-410a unit has a less efficient refrigerant, if the new unit is rated for the same or higher tonnage than the old one (whatever it was) then the new unit should perform as well - will have to move more refrigerant and usually have a larger evaporator, but if rated the same should perform as well.

One caveat - because of the energy transfer difference, the newer unit might require higher airflow to give the rated cooling - so the furnace or air handler blower might be undersized for the job now if that was not changed or at least checked for adequate airflow capacity. For instance, the old unit might have had a flat-panel or "brick" evaporator and the new one an "A-coil", which looks sort of like a letter A or an A-frame building and has two panels (one on each side of the "A" which the air flows through. A-coils typically require a greater fan pressure than a brick because it is pushing the air throufgh two panels, so staying with the old fan could end up with an undersized heat exchange capacity.

Of course, there is also the possibility he did something wrong - has the wrong throttling orfice in the evaporator, wrong amount of refrigerant in the system, wrong pressure (high and/or low side) because of mis-set or wrong TXV valve, wrong fan settings on the condensor fan, etc. Lots of possibilities.

Answered 3 years ago by LCD



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Answered 3 years ago by Member Services

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