3 h.p. Single Phase Compressor motor question

[wmgeorge]

Here's the wiring diagram,there is also a centrifugal switch in the motor that can cause starting issues.

https://www.grainger.com/ec/pdf/5K675_6.pdf

OK if it has the switch there is no starting or potential relay. OP has got it running and just using one leg of the motor starter, and that is ok too. It would be better to have both OL heaters inline but there are thousands of HVAC compressor single stage 220 volt that have only one hot leg switched. I do not like it because it leaves the other leg hot all the time, but they come wired from the factory like that.

[wierdscience]

Here's the wiring diagram,there is also a centrifugal switch in the motor that can cause starting issues.

https://www.grainger.com/ec/pdf/5K675_6.pdf

[Danl]

Once connections have been overheated its hard to get them cleaned up again. You can have voltage and no or not enough current to run the motor, if connections are bad. As long as the motor windings are not burnt, or open, capacitor is ok, and you have the info on the starting relay and all checks, I would buy the motor contactor Paul found for you. You do need to know the coil voltage on the old one and get the same.

That makes perfect sense. Once I get back out there, I plan on taking more photos of the relay wiring so I can reconnect everything properly after I remove it, clean all contacts and repair the T1-L1 buss if I can. The motor is back in operation now, due to the fact that I temporarily jump wired the T1-L1 terminals. I may end up buying the $60 magnetic switch after all, but I will first see if this is worth repairing. I'll bet the old relay is at least 40 years old, and has given me no troubles over the 10 or 12 years I've owned it.

[wmgeorge]

Once connections have been overheated its hard to get them cleaned up again. You can have voltage and no or not enough current to run the motor, if connections are bad. As long as the motor windings are not burnt, or open, capacitor is ok, and you have the info on the starting relay and all checks, I would buy the motor contactor Paul found for you. You do need to know the coil voltage on the old one and get the same.

[6PTsocket]

So the start capacitor is not even used in this setup?

I'm hoping there is something I can use instead of this old thing, since it does not appear to be repairable.

Dan L

Of course the start capacitor is used. 5k675k is described as a capacitor start,capacitor run motor. In spite of my best efforts, I could not pull up the wiring diagran for your motor. Other Dayton motor owners said they called Grainger ( Dayton is their brand) and were able to get a diagram. Some of us are more sure than others as to how it is wired but it would be good to have some documentation to be sure. Make sure it is the full disgram and not just what is on the plate. The info is free for the asking.

Sent from my SM-G900V using Tapatalk

[Danl]

Jerry, when I found voltage on the terminals, they were all connected to the relay wires, so either it was being passed through the fields somehow, or I was confused (probably the most likely).

As it turns out, that L2 terminal is in fact a dummy. I may take it apart to see if I can repair the dead contact like PSTechPaul suggested. I was looking at the eBay item when you posted your response, garagemark. I don't see why that wouldn't work. On my current unit, the power switch is also the leg that goes through the pressure cutoff switch.

It is cold out in the unheated area of my shop right now (25°), otherwise I'd try to see if I can clean up the inoperative contact inside the relay to resurrect it. If not, I will probably buy one of those eBay units for $60. It has provisions for adjustable maximum amperage and a pressure cutoff switch.

Dan L

[J Tiers]

I thought you found voltage on the motor terminals? If so, then how can something before that be shot and not passing current?

Are you now saying that you do not get continuity through the relay? Or at least voltage does not appear on the motor?


Anyhow, just because, you may try going through the unit, removing wires one lug at a time, cleaning them up, and replacing them in place. Might fix matters, unless you know there is a more serious problem.

[ww_big_al]

You can check and see but L2 might be a dummy terminal as this is only single phase. The starting relay and cap would be after this contactor. The two spring looking things are overload heating elements.

You may be right. Never thought about it being a dummy terminal.
Might want to check that Red wire. It looks like it's been smoked.

[garagemark]

If you're not a Chinese hater, you can pick up the whole shebang for under 60 bucks with no shipping.

http://www.ebay.com/itm/MAGNETIC-MOT...-/321134649990

[wmgeorge]

You can check and see but L2 might be a dummy terminal as this is only single phase. The starting relay and cap would be after this contactor. The two spring looking things are overload heating elements.

Do a google for potential starting relay. Here is one > http://www.achrnews.com/articles/924...tarting-relays

[PStechPaul]

That appears to be a thermal motor overload relay, with two "heaters" (the spring-shaped elements), that trip the relay if the motor takes too long to start or otherwise draws too much current for some period of time. Such units can be repaired, and it may be that the contacts need to be cleaned up or there may be dust and dirt or even bugs that cause failure. The heaters are also replaceable, although it may be hard to find ones for something so old. They are rated for current and should match the motor FLA (Full Load Amps).

I found a similar device on eBay for $75:
http://www.ebay.com/itm/ARROW-HART-C...-/291805798913

Here is a heater element but I don't know if the rating matches yours:
http://www.ebay.com/itm/New-Arrow-Ha...-/191716081292

I tried to find a suitable motor starter for your 3 HP compressor, but it's a bit complicated. You may need a 120V or 240V or even 24V coil, and you may need an overload with a contactor. For 3 HP and 240V single phase you need something like 10-15 amps. Here are some items that should work:

https://www.automationdirect.com/adc...s/GH15DN-3-10A (16 amp contactor $57)

https://www.automationdirect.com/adc...ads/RTD32-1400 (10-14 amp overload $67)

[Danl]

If L1 is shot just move it to L2. You are only using 2 out of 3 contacts now.

I'll try it, thanks.

[ww_big_al]

If L1 is shot just move it to L2. You are only using 2 out of 3 contacts now.

[Danl]

Actually a motor that size uses a potential or voltage relay that picks up the voltage across the start winding and drops out the relay/start cap. I forget all the details and Jerry can fill in what I missed.
That is not a potential or starting relay but a contactor or heavy duty relay, in any event it looks shot.

So the start capacitor is not even used in this setup?

I'm hoping there is something I can use instead of this old thing, since it does not appear to be repairable.

Dan L

[wmgeorge]

Actually a motor that size uses a potential or voltage relay that picks up the voltage across the start winding and drops out the relay/start cap. I forget all the details and Jerry can fill in what I missed.
That is not a potential or starting relay but a contactor or heavy duty relay, in any event it looks shot.