Looking for a Relay

[emtunderwood]

Looking for a 120v coil relay that when the 120v power is broken the 48v will close and power the repeater. I've looked all over I've found a couple I think that might do that but not for sure. I'm sure someone knows a few off hand.

Thanks

 

[prcguy]

Looking for a 120v coil relay that when the 120v power is broken the 48v will close and power the repeater. I've looked all over I've found a couple I think that might do that but not for sure. I'm sure someone knows a few off hand.

Thanks

There should be hundreds of relays that will work. Search for 120VAC coil, a SPST would work if the contact ratings are 15A or more for your repeater that will draw a max of 10A @ 48VDC. Personally I would search for a DPDT, 120VAC coil with at least 20A contacts. I would then parallel the contacts. They are everywhere online or at any electronic store or Graingers, etc.

 

[emtunderwood]

Idk maybe I'm stupid I can find 120vac coil relays but none that allow 48vdc to pass. Or would it be easier to take a 48vdc coil coming off the main PS that feeds the DC PS of the Radio and use the relay there and have the batteries connected there and if something happened to the 48v PS the batteries would kick in? And honestly I have no clue how to wire it..

 

[buddrousa]

You are more concerned with the 15 to 20 AMPS than you are voltage.

 

[RFI-EMI-GUY]

Idk maybe I'm stupid I can find 120vac coil relays but none that allow 48vdc to pass. Or would it be easier to take a 48vdc coil coming off the main PS that feeds the DC PS of the Radio and use the relay there and have the batteries connected there and if something happened to the 48v PS the batteries would kick in? And honestly I have no clue how to wire it..

You need a relay with a 120VAC coil that is rated for continuous duty as it will be energized forever.

Then you need contacts that are current rated for the 10-20 amp 48V DC supply of your radio. Check current specs and select a higher rated relay. You need at minimum a SPDT so that when the coil is energized, the DC connection from the power supply to the radio is opened (The NO contact) and the 48V battery then applied to the radio (Via the NC contact). The contacts of a DPDT relay can be doubled up to make a more positive connection. Or one set of contacts used to provide an alarm that the radio is on battery. NO = normally open with coil de-energized. NC = normally closed with coil de-energized.

 

[prcguy]

Idk maybe I'm stupid I can find 120vac coil relays but none that allow 48vdc to pass. Or would it be easier to take a 48vdc coil coming off the main PS that feeds the DC PS of the Radio and use the relay there and have the batteries connected there and if something happened to the 48v PS the batteries would kick in? And honestly I have no clue how to wire it..

You need a 120VAC coil to switch the relay instantly on AC power failure. Relay contacts are not rated for a specific voltage, just a maximum so any relay contact rated 20A or more will handle way more than 48V. You don't want to use a 48VDC coil as that may take a few seconds to switch as the 48V power supply ramps down with an AC power failure then you would have to use diodes to isolate the coil from the battery power that gets routed to the repeater with the relay.

I would get a DPDT relay with some easy mounting feature. 120VAC coil. 20A or 30A contacts. Wire the common contacts to the repeater 48VDC input and the NC contacts to the battery. Wire up a charger directly to the batteries. Power up and test by removing AC from the 48V power supply then pulling the plug on the relay coil. If you plug the relay coil and 48V supply into the same AC outlet you can better test by turning off the circuit breaker to that outlet which will closely simulate a power failure.

 

[AK9R]

The issue with contact rating is that it may handle the amps, but may not have sufficient flash-over rating to handle the voltage.

Here's one in the Mouser catalog that may be overkill, but would do the job. It has two Form C contacts so DPDT, coil is rated for 120 VAC, contacts are rated for 30 amps and can switch up 600 volts AC or 125 volts DC, $68.48: https://www.mouser.com/ProductDetail/TE-Connectivity-PB/PRD-11AG0-120?qs=wvf%2BmaPDr9NpRr6QrJwuog==

Wire the 120 VAC supply to the coil of the relay so that when the 120 VAC drops, the 48 VDC is applied to the repeater. But, what is powering the repeater when you have 120 VAC supply?

 

[prcguy]

The issue with contact rating is that it may handle the amps, but may not have sufficient flash-over rating to handle the voltage.

Here's one in the Mouser catalog that may be overkill, but would do the job. It has two Form C contacts so DPDT, coil is rated for 120 VAC, contacts are rated for 30 amps and can switch up 600 volts AC or 125 volts DC, $68.48: https://www.mouser.com/ProductDetail/TE-Connectivity-PB/PRD-11AG0-120?qs=wvf%2BmaPDr9NpRr6QrJwuog==

Wire the 120 VAC supply to the coil of the relay so that when the 120 VAC drops, the 48 VDC is applied to the repeater. But, what is powering the repeater when you have 120 VAC supply?

Relay contact flash over is not a problem under a few hundred volts, even on a small relay. Since you will be installing a 48VDC input Quantar power supply inside the repeater you can just wire the external AC powered 48V power supply right to the internal Quantar supply. When AC fails the external 48V supply will shut down and will not care when the battery gets routed to the Quantar internal supply. You could wire the external 48V supply to the NO contacts of the relay which would disconnect the external 48V supply from the internal Quantar supply during AC power failure but it’s not necessary.

 

[emtunderwood]

The issue with contact rating is that it may handle the amps, but may not have sufficient flash-over rating to handle the voltage.

Here's one in the Mouser catalog that may be overkill, but would do the job. It has two Form C contacts so DPDT, coil is rated for 120 VAC, contacts are rated for 30 amps and can switch up 600 volts AC or 125 volts DC, $68.48: https://www.mouser.com/ProductDetail/TE-Connectivity-PB/PRD-11AG0-120?qs=wvf%2BmaPDr9NpRr6QrJwuog==

Wire the 120 VAC supply to the coil of the relay so that when the 120 VAC drops, the 48 VDC is applied to the repeater. But, what is powering the repeater when you have 120 VAC supply?

The 120vac initally goes to a PS that supplies a 48v dc PS in the quantar. WE have 48v battery system there. In case of a inverter failure or 120v to 48v dc psu failure the relay will engage the 48v direct from the battery bank.

 

[emtunderwood]

The issue with contact rating is that it may handle the amps, but may not have sufficient flash-over rating to handle the voltage.

Here's one in the Mouser catalog that may be overkill, but would do the job. It has two Form C contacts so DPDT, coil is rated for 120 VAC, contacts are rated for 30 amps and can switch up 600 volts AC or 125 volts DC, $68.48: https://www.mouser.com/ProductDetail/TE-Connectivity-PB/PRD-11AG0-120?qs=wvf%2BmaPDr9NpRr6QrJwuog==

Wire the 120 VAC supply to the coil of the relay so that when the 120 VAC drops, the 48 VDC is applied to the repeater. But, what is powering the repeater when you have 120 VAC supply?

This is what I was looking for and could not find it..

Thank You!!!

Both you and PRC for everything...