Ranco, Johnson or other control for Parallel pump?

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goosegunner

Minister of Fire
Oct 15, 2009
1,469
WI
I am trying to decide how to control a Parallel pump for my system.

I would like it to be independent of my boiler system so it could also function as a back-up in a power loss.

I want to be able to;

1. Sense temperature near boiler in supply.

2. Near boiler Idle temp start the parallel pump.

3. At set drop or differential stop the parallel pump.

4. Wire the controller and pump to a battery backup system to run during a power loss if set point hit.

Looking at either a Ranco ETC-111000-000 or Johnson A419ABC-1C Digital control

Both are 120/240V single stage temp controller.

Would this be what I am looking for? Or are the better options?

gg
 
I think either would work fine, as would a mechanical strap-on aquastat. I didn't look at the specs for either the Ranco or the Johnson. My preference is always for a SPDT relay due to possibility of future use for something else and the flexibility that SPDT provides. In your use SPST would work, but if you had SPDT, you could hook up (for example) a green pilot light when the parallel pump was "off" and a red pilot light when it was "on." This would give you an immediate picture of operational status. You may find other uses for the SPDT wiring as well.
 
I think I am going with the Johnson. It seems to have a few extra features as far as I can tell.

Mainly, You can switch from either cut in to cut out at set point for both heating and cooling.

So I would actually use the Cooling Cut-in

Cooling/Cut-in mode the differential is below Setpoint. The output relay energizes and the LED illuminates when the temperature rises to Setpoint. When the temperature drops to Setpoint minus the differential value, the relay and LED de-energize.

gg
 
good choice & agree on use of cooling mode.
 
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