Off Topic: Capacitor / Electric Motor

[tb lilley]

Apologies, as this is hopelessly off topic ...

Central heating boiler hasn't been working. Fan motor not firing up, so boiler locking out.

Motor has a large cap bolted to side of it. On examination cap has leaked badly. Rated 4.5 uf. I slotted a 3 uf in as a replacement and boiler has been running fine for a day and a half now.

If it aint' broke, don't fix it ... but am I risking any damage by running an out of spec cap on this electric motor? The voltages on both caps are the same.

 

[Mitchell Gant]

It sounds like a motor run capacitor that has failed, and your 3uF replacement is good enough to kick it into running and keep your boiler running while you need it this cold weekend.

But I'd be looking for the proper rated 4.5uF to fit as it's probably designed to use this value:

"Choosing a wrong capacitance value for a motor can result in an uneven magnetic field, which can be observed as uneven motor rotation speed, especially under load. This can cause additional noise from the motor, performance drops and increased energy consumption, as well as additional heating, which can cause the motor to overheat."

https://eepower.com/capacitor-guide/applications/motor-starting-capacitor/#

 

[tb lilley]

Thanks! Yeah, I'll get through the next few days then fit a 4.5 uf. It is so cold right now I daren't go anywhere near it .....