Cap Overkill

[RTECHSC]

I went to one of those great warranty calls. 2 1/2ton with a 45+5 cap... The compressor calls for a 35... Would an increase of the amount eventually damage the compressor? Thanks once again!

[beenthere]

Yes it can.
The motor won't run at its design RPM under its normal loads. So the windings could over heat.

[ga-hvac-tech]

Just for discussion purposes, what happens when a compressor is 'under-capped'? I have seen a few this year with a cap 5 MFD low (guess the tech put in what was on the truck).

[beenthere]

Varies a bit with the load the comp is under.
Lower RPM, higher amp draw.

[ga-hvac-tech]

THX Been.

[udarrell]

Just for discussion purposes, what happens when a compressor is 'under-capped'? I have seen a few this year with a cap 5 MFD low (guess the tech put in what was on the truck).
Regarding Run capacitors, the rule I went by was +10% MFD, zero under.

The run Rated MFD would have to be 50-MFD, or higher for a +5MFD to be acceptable.

However, I would use a 45 & add a 5-MFD in parallel to get to the a required 50-MFD.

I never wanted them above either, I always bought 440-volt caps & carried enough MFD spreads to meet the correct rating.


I went to one of those great warranty calls. 2½-ton with a 45+5 cap... The compressor calls for a 35... Would an increase of that amount eventually damage the compressor? Thanks once again!
The 5 was probably for the fan motor. 35-MFD times .10% = +3.5-MFD.

A 38.5-MFD would be the limit above, even a 40-MFD would be too high. The 45-MFD should be replaced ASAP. - Darrell