Relay sizing question for well pump

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Old 07-06-16, 12:40 PM
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Relay sizing question for well pump

Greetings,

I have a well pump that is cycled via a relay, and want to get some feedback as to whether or not I am using an adequately sized relay.

The pump in question is a Grundfos 7S10-19 - 1hp, 230v.

I have a 24v circuit controlling the coil on this relay, which I have wired to control both hot leads of the 240v (US - Spokane, WA) circuit:

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It has been in use for roughly 9 months. Yesterday I discovered the pump was not coming on, and when I pulled the relay, I found this:

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The black lead, in addition to having obviously gotten very hot, was also quite corroded:

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I had a spare relay and base, so I have installed those temporarily.

So, my first-and-foremost question is: am I using a relay that is adequately sized and proper for this application? If the type of relay looks correct, could a faulty relay have caused this result?

Secondly, any thoughts on the corrosion issue? I am guessing it is probably related to the different metals coming into contact... though it is a rather humid environment as well if that may be relevant. Does one perhaps use something along the lines of dielectric grease to seal up the contacts, after all the connections have been made?

Lastly, a confession, since it may well be relevant as well. The contacts on that relay base are just a little bit too small for 10-gauge wire, so I did have to modify the wires just a tad to get them to fit. I will be getting a new base with proper-sized contacts ASAP (as well as a new relay, if need be).

I would appreciate any feedback - let me know what other information I can provide that may be of use.

Edit: thought I would add that the pump in question is barely a year old, as well.
 
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Old 07-06-16, 12:56 PM
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I'd say what you have is under sized. A 1hp motor at 230 volts pulls about 8 amps when running but much higher when starting. I would feel more comfortable with a relay and base that had a rating twice the motors operating load, so I'd look for a 15 or 20 amp relay and base. The larger size would also accommodate larger size wire.

Corrosion, loose or otherwise a poor connection can cause resistance which creates heat. So, your relay might have survived but it looks more like a problem with the wiring connection.

If the connection is tight it should be gas tight and not allow corrosion between the mating surfaces. I've seen some really corroded wires & connections that worked fine and when disassembled the part of the wire in the connector was in surprisingly good condition. The problem is if the wire and connector had corrosion before they were assembled together. That could cause a lot of heat to be created and allow corrosion to continue.
 
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Old 07-06-16, 02:26 PM
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Thanks for the input! I've been doing a bit of searching... not finding many 20-amp relays out there, but plenty of 15-amp ones, so I will probably lean that direction. This one, for example, is rated 15A @ 277v:

https://www.grainger.com/product/DAY...In-Relay-1EHL4

And the matching socket (https://www.grainger.com/product/DAY...y-Socket-1FC13) is rated for 16A/300V, so I would certainly expect it to be able to accommodate 10-gauge wire. If I were to go through Grainger, I could pick it up locally and I could take a scrap of wire with me to make sure.

That reminds me, any suggestions on go-to places for this sort of thing? Or don't-go-to places, for that matter?
 
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Old 07-06-16, 02:37 PM
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Ditch the octal socket and use something like this:

https://www.grainger.com/product/DAY...er-Relay-1EJH6

You can get a socket for it, but easier just to crimp on terminals. You would use yellow terminals for 10 ga wire.
 
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Old 07-06-16, 02:45 PM
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You really need to be looking at relays that are rated in horsepower rather than in amperes. Air conditioning condenser contactors are often a less expensive relay that is rated in horsepower.

You are probably not experiencing corrosion. The green color is indicative of overheating and over heating comes about because of using a relay with insufficient contact mass as well as an under rating according to amperes drawn by the load. Unfortunately, you will now have to replace all the wire that has been subjected to the excessive heat.
 
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Old 07-06-16, 03:08 PM
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Corrosion, loose or otherwise a poor connection can cause resistance which creates heat. So, your relay might have survived but it looks more like a problem with the wiring connection.
I agree. The issue is not with the relay, it is the base terminals. A poor connection is what caused the overheating. I would consider using a RIB (relay in a box) (Example): https://www.platt.com/platt-electric...px?zpid=698139
 
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Old 07-06-16, 03:21 PM
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Ah... I am beginning to think it was the fact that I was filtering for 'plug in' style relays that was keeping the higher amp ratings from showing up! I was filtering for plug-in relays with finger-safe sockets just on the off-chance that I have to talk a family member though fixing something. But, that is really unlikely, and the fuse box is literally right next to the relays - I can just tell them to throw the breaker and wait until I get home!

Fortunately this is a very short run, so replacing all the wiring is really not that big of a hassle. Honestly, it hadn't occurred to me that the cable that wasn't visibly damaged might still be questionable!
 
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Old 07-06-16, 03:40 PM
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The RIB relay has wire pigtails on them for easy wiring. No exposed energized parts will be accessible. Wires might be long enough so you might not need to splice on new wires to the field wires. Just cut off the damaged wire and restrip.
 
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Old 07-06-16, 03:46 PM
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In a damp or corrosive location you don't want to use plug in relays.

Someone mentioned an A/C contactor. That's what I would use. For about $20 you can decent two pole HD relay.
 
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Old 07-06-16, 04:33 PM
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Not really a damp or corrosive environment - maybe a bit humid at times is all.

It also just so happens that I work at a rep firm for HVAC manufacturers... I am going to have to see what I might be able to come by via one of the lines that we carry.
 
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