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HELP 2 SSRs used on 230V motor--do I need to protect against 110V?

For my boiler heat at home I have a 230V 1.75A AC water circulating pump (GrundFos UP26-116F) Here are the specs for it:

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Unfortunately the pump runs 24x7 during the heating season even when all 4 of the thermastats are open (which shuts down each of the water valves).

I have 2 Omron SSR (DC-RR010), here are the specs.

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I want to use the SSRs for the 2 hot leads of my 230V motor, which is simple enough... but what happens if one of the relays fail? Does the motor have built in protection of it's only receiving power from one of the power leads (in otherwords it becomes 110V), or do I need to build a circuit that protects the motor?

And if so, then how?

Thanks.

Reply to
Mark Main
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The motor needs only one lead switched to control it. You need a mechanical 2 pole disconnect switch to isolate both lines for maintenance, if you do not provide a separate circuit breaker for this small motor. And you need fuse or circuit breaker protection in both lines to account for the possibility that either side might short to ground. But I don't think you need a 2 pole control relay to turn the motor on and off.

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Regards,

John Popelish
Reply to
John Popelish

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The circuit breaker at the service panel is a "dual breaker" that covers both circuits going to the motor... so, if only 1 of these lines is hot and the motor is turned on, will that trip the breaker? It was my assumption that all 230V motors would be designed so that it won't burn out if only 1 of the circuits is hot... and if this is true, then it seems like I'm protected two different ways.

Reply to
Mark Main
[about a 230V appliance]

There's a misconception buried in there: a circuit is a full current-out/current-return path, and the usual

230V appliance has only ONE circuit. It has two LIVE WIRES, not two circuits.

A turnoff switch needn't disconnect all live wires from the motor to perform its function. One SSR will control your motor (or water heater). To make the wiring safe, however, your circuit breaker DOES disconnect all live wires. In case of fault, to prevent fire, that's useful. In case you want to work on the wiring, to prevent shock hazard, it's useful.

The SSR (solid-state relay) isn't reliable and fail-safe the way the circuit breaker is intended to be, so it cannot do the same job as the circuit breaker in any case. Thus, "double SSRs" isn't useful.

Reply to
whit3rd

If its single phase ( 2 wires only from service) you need only to open one side. Your service should have a dual breaker for this line so even if the motor should short to ground the lead that stays connected, it'll simply popped the breaker for you in which case you would need to service the motor any ways.

P.S. You may want to consider a motor starter contactor over using a SSR. they come with various selections of coil voltages to energize the relay. You can even op for a motor over load on the starter.

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Reply to
Jamie

Why would one of the lines at the box be hot, and the other one not?

Why would it trip the breaker? Unless there was a short, the motor was locked rotor, or some other failure.

Why are you saying "1 of the circuits", as if there were two? There's one circuit, a 240 v two wire feed. That other, third wire, is a ground.

I'm not sure what you are protected against!

Reply to
PeterD

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