48V relay question [RE-wrenches]

[Windy Dankoff, Dankoff Solar]

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Darryl and others,

I have used the same principle to fill the need for a 48V relay by 
obtaining a 120VAC relay. I find that an AC-coil relay works fine on 
approximately half the voltage DC. In fact, it seems to get more 
voltage than it needs, so for 48VDC, I've had to add a small 
resistance to keep the coil from running hot.

Rather than explain this to people in such uncertain terms, I have 
taken to suggesting 2 24V relays with coils wired in series (per my 
previous message). It's fool-proof.

Windy



At 9:05 PM -0700 10/17/03, Darryl Thayer wrote:
>Hi
>Here is what I would do. 
>First I would not use the float switch to control the
>load, as you suspect it might be short lived. 
>
>All AC relays will work on DC except that you need a
>resistor in series with the coil because you need less
>DC voltage.  Choose a relay with the contact ratings
>you want, find the coil current data, then measure the
>coil resistance with an ohm meter.  You want the same
>current when operating with 48 volts DC.  Use ohms
>law, E=I*R; that is E/I=R so 48volts/coil current=(R
>of coil+ R of added resistor)
>
Daryl

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