Electric Motor Question

[Steve@Advance]

Monday evening the run capacitor on my HVAC compressor unit went out.

It had a double, a 45/5 mfd. The supplier I use was out of that one, but they had a 45/7.5 mfd.

I went ahead and used it, but now there is a different sound, like a high pitch whine I assume is coming from the condenser fan motor. I can't read the label on the fan motor to check the amp draw without taking the thing apart.

Do you think it will hurt to leave the 7.5 on it?

Thanks!

 

[Geo-TH,In]

My experience, the 7.5 will cause the fan to overheat.
Just get a 5 mfd. You don't need a combo 45/5. You can use 2 separate caps.

 

[Janicholson]

Agree. The difference is enough to cause incorrect phase alignment and add heat to the run mode. Jim

 

[Geo-TH,In]

Some motors have a one time thermo fuse.
Measure motor temp with an IR thermometer.

 

[seb52]

(quoted from post at 04:13:48 07/26/23) Monday evening the run capacitor on my HVAC compressor unit went out.

It had a double, a 45/5 mfd. The supplier I use was out of that one, but they had a 45/7.5 mfd.

I went ahead and used it, but now there is a different sound, like a high pitch whine I assume is coming from the condenser fan motor. I can't read the label on the fan motor to check the amp draw without taking the thing apart.

Do you think it will hurt to leave the 7.5 on it?

Thanks!

hi using a 45/7.5 mfd capacitor instead of the recommended 45/5 mfd may be causing the unusual high-pitched whine. It's best to stick to the manufacturer's specifications to ensure optimal performance and safety. Leaving the 7.5 mfd capacitor might strain the fan motor, potentially leading to issues.

 

[Steve@Advance]

OK, I ordered a 5 mfd cap. There is room to split them up and have the compressor on the 45 and the fan on the 5.

That will probably help with the heat too. The unit is on the west side of the house, up against a brick wall, the evening heat is brutal there! This is the 3rd cap in 6 years.

Thanks everyone!

 

[buickanddeere]

If there is a cap available in a higher voltage rating . They will usually last longer .

 

[guido]

Steve@Advance,

You are hearing an unhappy motor. I would get the right one,

Guido.

 

[Jerry/MT]

+1

 

[jniolon]

When you get it right, order two more and put them where you can find them for next time

j

 

[Janicholson]

Put a window awning over the unit. Direct sun degrades performance enough to warrant shade. Jim

 

[da.bees]

You didn't say which has been going out but my hunch is the compressor cap. If you add a start cap with relay for momentary help at start up the run cap will last longer,like from now on. For future reference 10% larger replacement cap is allowable per majority of motor/compressor mfgrs.

 

[guido]

da.bees,

YEP! that is what my Modern refrigeration and air conditioning text book says. Was written by three authors. You will find different OPINIONS on this forum though,

Guido.