All Replies on Reliant 3hp DC start capacitor help

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Reliant 3hp DC start capacitor help

by redham
posted 11-08-2018 03:22 PM

7 replies so far

View WhyMe's profile


1320 posts in 2446 days

#1 posted 11-09-2018 12:19 AM

I don’t think that run cap is way wrong for that motor. Just saying from my experience of run caps for 3Hp and smaller motors. The voltage just needs to be the same or higher than what the motor uses. The uf is more important.

View MrUnix's profile (online now)


8242 posts in 3084 days

#2 posted 11-09-2018 12:29 AM

This capacitor apparently did work for a while but has is bad again.
- redham

How do you know the cap is bad… did you test it? What are your symptoms. 16mf sounds about right though for a run capacitor (3hp typically uses around 20mf +/-), so if it really is bad, I’d just replace it with a similar one.


-- Brad in FL - In Dog I trust... everything else is questionable

View WhyMe's profile


1320 posts in 2446 days

#3 posted 11-09-2018 12:36 AM

I just checked the run cap on my 3HP compressor motor and it’s 20uf 370V. As MrUnix said 20uf seems somewhat typical for 3HP motors.

View redham's profile


50 posts in 1335 days

#4 posted 11-09-2018 05:36 AM

I bought it with the understanding that it “needs work”. The previous owner said he had changed the cap once before and that it work for a while before it went bad again. He did tell me that he had matched the replacement as close to the original as much as possible.

The unit needs a new power cord and plug so don’t have an answer on how it sounds. I will install the cord tomorrow.

Based on what with the previous owner said and what the specs for a new grizzly 3hp motor (40mf) was, I took a guess that previous owner may have made a mistake and replaced the original cap with an underrated one. The unit was used in a commercial closet fabrication shop so the owner may not necessarily be the person who used, maintained or repaired the machines.

This DC, if I can get it running will be a nice gem for +/- $75

View WhyMe's profile


1320 posts in 2446 days

#5 posted 11-09-2018 02:54 PM

Do a search for “Sizing run capacitor for 3HP motor” on Google and you’ll get some info that is helpful.

View splintergroup's profile


4059 posts in 2108 days

#6 posted 11-09-2018 03:09 PM

Caps are cheap so increasing the rating would be worth a try.

If your centrifugal switch is stuck, that could cause the run circuit to be engaged when it shouldn’t stressing the run cap.

View redham's profile


50 posts in 1335 days

#7 posted 11-10-2018 02:30 AM

Thank you all for your replies.

I changed out the power cord and put on a new plug. The cap connector for the ground wire was way too small for the 12 gauge wire that was used, so I sure there wasn’t a good contact there. I also re-seated the connector caps to the run capacitors.

Plugged the unit in without checking to see if on/off switch was in the “off” position. As soon as the plug made contact the motor roared to life and blew a plume of sawdust that made it look like I was in a Looney Tunes cartoon. The motor runs very smooth, even smoother than my 2HP Grizzly DC.

It appears that the previous owner either had someone else run the connections or wasn’t very careful with the connections.

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