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Automatic Transfer Switches
I have the old Mavrick ATS switch still in coach and it still works, I’ve had a couple of problems with the voltage protection orange little box with black knob, I’m sure the contacts in relays are getting there to. If I was to replace it before it dies, who could recommend a good solid ATS box, it does not need surge protection because I use a in line surge protector. I was looking on line and Esco ES50M-65N looks OK but it can only handle a 12KW gen and we all have larger gens, I had 1 In the Foretravel that was in a gray electrical box that was good and solid don’t see any on line in a gray box, Any thoughts ??
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6 Replies
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Most transfer switches are little more than an assembly of electrical contactors and relays. I would not replace an entire unit, but would have no problem suggesting a replacement of contactors and relays and a close inspection of terminals and connections.
Sounds like a good bench project for a rainy day in the garage.
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Buy 2 of these
https://www.amazon.com/gp/product/B00206LZWY/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
and one relay that I will have to send you model number. I’m traveling and don’t have access to the info until next week. I can send a wiring diagram as well.
You should be able to reuse a metal box to mount everything in.
This will give you a 75amp rated transfer switch.
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Please correct me if i am wrong but i was under the impression that transfer switches had to be failsafe in that the contactors are mechanically connected in a way that prevents both contactors being closed at the same time. Like a 2 position multiple pole switch with only one signal input. Not 2 indepenently operated magnetic relays. I may be wrong but this is important to verify. Gerald, Threegreens? Jeff Rowe? Please opine…
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I have what appears to be a Liberty designed transfer switch and I do not see how it can present a potentially dangerous problem unless multiple simultaneous failures occur.
The relays which I assume are time delayed engage the contactors and unless a contactor fails to release or open the circuit and then the generator is started while still on shore power there might be an issue. I think.
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Mine are not physically linked. I thought they were when I started my rebuild. Found out different.
They are electrically linked. If Art goes this route he will also need 1 Normally Open aux contact for those contactors listed above. This reminded me of that since I don’t have the schematic with me.
When I rebuilt mine I went thru a failure modes and effect analysis to ensure I understood both how it worked normally and when the relay and aux contacts failed either independently or at the same time. As an engineer who works with safety class systems, it is simple and effective. The version I have does not have a timer to delay switching when the generator starts (it is generator priority) nor any under/over voltage nor surge protection.
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I read that info about mechanical interlocking a long time ago. It was likely spec requirements for an institutional application where standards are more stringent. What Jon and Joe are saying sounds reasonable and Joe has obviously done his homework. Sorry to muddy up the works. I just don’t want Art to get hurt before he gets every part on his coach replaced. Im sure hes getting close. Thanks.
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