Are the individual contactors inside the transfer switch replaceable? And does a 50 amp system use 220v contactors? Are they difficult to replace?thanks,Ron

Probably 120 volt. Probably easier to replace whole switch. Probably have to remove it anyway to replace one of the contactors. Have you opened it up to take a look?What issue are you having?

It might well vary depending on the model of transfer switch. If they are replaceable, they would presumably have to be swapped only for a precise exact replacement to maintain safety and safety certifications.The coils for the relays (contactors) would be 120V coils because otherwise 30A shore power or many RV generators would not work (as they connect both hot lines to the same phase). The contacts I would think would have to be rated for 240V operation in as much as the hot lines, at least, could see that voltage across them depending on the precise timing of the opening of the other contacts. The difference between contacts rated for 240VAC and those rated for 120VAC is probably as much regulatory paperwork as anything; it's not a huge physical change.

Both contactors will be three pole, normally open contacts. The contacts must be rated at least 50 amps. The coil voltage will be determined by the type of transfer switch you have. Some may be 120v, and some may be 24v. It will say the voltage on the old coil. Replace it with the same voltage. The typical contactors will be what is known as "IEC" style as opposed to "NEMA" style. It would be difficult to find one that isn't rated with a high enough voltage on the contacts. The highest voltage you will see at the contacts is 120v to ground.

A 50 amp transfer switch uses (2) three pole relaysSome new coils are DC with a rectifier control board, eliminates hummingThe older versions all use 120v coils in the relaysThe really good ones have mechanical interlock between the two contactors, do only one can pull in at any time"Todd" Transfer switches were Built that wayFinding a single replacement part could be hard to do

The contactor is labeled "Chint NC1-5011" and does not have the voltage labeled on it. It does indeed have three connections ( 2 each hot, 1 neutral). Since there is nothing in the motor home that uses 220/240v, I would assume that the contactor should be rated only for 110/120v. When looking at these on Amazon, they look identical and are the same price but only the 220v is available. Does it really make a difference which one is used? I could see not using a 110v unit on a 220v system, but I don't see where using a 220v on a 110v system would matter. I would think only the contact would be more robust to handle the extra voltage.However, it looks like it has been "tripped" as the center elongated section is sunken down into the unit by about a 1/4". Can this be reset? Also, there is a cover on the unit that is held down by two screws and seems to be holding down the center section.....can I removed the cover and reset the unit that way? Mandalay Parr on 12/19/16 03:29pm Probably 120 volt. Probably easier to replace whole switch. Probably have to remove it anyway to replace one of the contactors. Have you opened it up to take a look?What issue are you having? The whole switch runs about $300 bucks....the one contactor runs about $75. Nope, don't have to remove the whole switch to remove the contactor. Yes, I've opened it up and taken voltage measurements.The issue is that 120v is going into the contactor but nothing coming out. Hence, no 120v shore power. Generator contactor works just fine.Thanks for replying... appreciate it.Ron

Transfer Switch Contactors | Good Sam Community

25 Replies

Mandalay_Parr
Explorer
Dec 23, 2016
Ron,
Contactors have a rrating for both the contacts and the coil.
In your case,the contacts can be 240volts 50amps.
The coil 120 volts most likely.
As stated above some may have D.C. Coil to eliminate humming.

If your switch has only one contactor, it is normally de-energized when connected to shore power and engerized when the generator is running. Any contactor can have both mechanical problems as well as electrical issues.

I think you would be best served to replace the whole switch
time2roll
Nomad
Dec 22, 2016
Consider getting the top dog 100 amp rated.

http://www.bestconverter.com/100-Amp-Transfer-Switch_c_195.html
MrWizard
Moderator
Dec 22, 2016
cliky
onecb
Explorer
Dec 22, 2016
I put this one in mine two years ago:https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=PMTS-50+Power+Max+50+Amp+Transfer+Switch&rh=i%3Aaps%2Ck%3APMTS-50+Power+Max+50+Amp+Transfer+Switch
Works just great. Alvin
Cydog15
Explorer
Dec 21, 2016
lanerd wrote:
Just as an update, I've decided to bite the bullet and just replace the entire transfer switch. Sorry to put everyone through all my questions.

Thanks to all...

Ron

Probably the best idea. Get it from these guys, they are known for great service and helping folks here.
Bestconverter
lanerd
Explorer II
Dec 21, 2016
Just as an update, I've decided to bite the bullet and just replace the entire transfer switch. Sorry to put everyone through all my questions.

Thanks to all...

Ron
mbrower
Explorer
Dec 21, 2016
lanerd wrote:
D.E.Bishop wrote:
lanert, wouldn't the amperage rating be more important. Most relay contacts are rated in amps, the relay coils are rated in volts. So you probably need 120vac relays with 60 amp or better contacts.

But the relays are rated at 50 amps in either 120v or 240v....no amperage is specified. Plus amperage is applied with the load, so initial connection would be almost 0 amps....only after you start turning things on will there be current draw. If the relay is rated for 50 amps (max in our motorhomes), either relay (120 or 240) should work.

Since using either 15 amp, 30 amp or 50 amp services.....all are 120v. That tells me that any voltage over it's rated capacity, the relay will fail. So if I have a 240 v relay and I only apply 120 volts to it, I would think it would work just fine. So far I haven't found or heard where it won't.

My problem is that I can purchase a 240v relay but can't find a 120v anywhere. So my question is can I use a 240v relay?

Ron

You must have missed my other post. This Link will take you to a 120V 50A transfer relay. Works well and has very good reviews.
MrWizard
Moderator
Dec 20, 2016
ON further inspection, I've noticed that the center section (like a push-button circuit breaker will depress when power is applied and will pop back out when power is removed. Is this normal operation of the relay? I'm thinking about starting the generator and see if that relay does the same thing.

Yes that is the energized coil pulling the contacts together

quit worrying about voltage rating
You can use a motor contactor rated at 220v
But it must have the correct coil voltage
In this case 120v coil
Many motor contractors used in machinery have 24v coils
You can not use one with a 24v coil
Your replacement must have a 120v coil
If you buy from an RV supplier, likely no problem
If you are searching on line for the best deal
You need to pay attention to the coil voltage and the physical size
Or it may not fit
dougrainer
Nomad
Dec 20, 2016
lanerd wrote:
D.E.Bishop wrote:
lanert, wouldn't the amperage rating be more important. Most relay contacts are rated in amps, the relay coils are rated in volts. So you probably need 120vac relays with 60 amp or better contacts.

But the relays are rated at 50 amps in either 120v or 240v....no amperage is specified. Plus amperage is applied with the load, so initial connection would be almost 0 amps....only after you start turning things on will there be current draw. If the relay is rated for 50 amps (max in our motorhomes), either relay (120 or 240) should work.

Since using either 15 amp, 30 amp or 50 amp services.....all are 120v. That tells me that any voltage over it's rated capacity, the relay will fail. So if I have a 240 v relay and I only apply 120 volts to it, I would think it would work just fine. So far I haven't found or heard where it won't.

My problem is that I can purchase a 240v relay but can't find a 120v anywhere. So my question is can I use a 240v relay?

Ron

Where and Why do you think there will be NO LOAD???? IF you have the roof AC's on and other appliances. THAT Load(about 35 to 50 amps) will be causing the contac points to arc when the appropriate relay opens or closes. THAT is what causes Transfer Boxes to fail(usually). Doug
DrewE
Explorer II
Dec 20, 2016
lanerd wrote:

But the relays are rated at 50 amps in either 120v or 240v....no amperage is specified. Plus amperage is applied with the load, so initial connection would be almost 0 amps....only after you start turning things on will there be current draw. If the relay is rated for 50 amps (max in our motorhomes), either relay (120 or 240) should work.

Since using either 15 amp, 30 amp or 50 amp services.....all are 120v. That tells me that any voltage over it's rated capacity, the relay will fail. So if I have a 240 v relay and I only apply 120 volts to it, I would think it would work just fine. So far I haven't found or heard where it won't.

My problem is that I can purchase a 240v relay but can't find a 120v anywhere. So my question is can I use a 240v relay?

Ron

You very much can have 240V RMS applied to a set of relay contacts on a 50A RV even if nothing in the RV is operating at 240V. You have a 240V supply (well, a 120/240V split phase supply). Should the neutral connection open first, whichever hot opens next will have the full 240V line voltage across it. (Of course, what that voltage is depends on the timing of the contact opening with respect to the AC cycle timing; it could be anything from 0V to about 340V, the peak voltage.)

In short, the contacts should be rated for 240V RMS minimum. There is no problem with using 240V contacts on a 120V circuit; the voltage ratings are maximums. It would also work equally as well on, say, a 24 VAC circuit. (DC circuits are somewhat of a different matter because the DC waveform doesn't periodically cross zero volts, which means that arcs when the contacts open continue longer rather than breaking down when the voltage crosses zero.)