# Heating Zones and simple relay?

Discussion in 'Electronic Basics' started by OceanGeek, Mar 27, 2007.

1. ### OceanGeekGuest

I have a house with 5 heating zones, some radiant heat some cast
iron. Each zone is controlled with a standard 24V thermostat. I
would like to create a simple circuit that would make a zone (or two)
slaves to another zone.

Example

Zone A calls for heat (thermostat closes) i would like this action to
cause Zone C to come on (via a relay??) for as long as Zone A needs
heat. Zone C would still be a discrete zone.

Does any of this make sense?

2. ### Rich GriseGuest

Sure. Just energize a relay with zone A's 24V, and put its contacts
in parallel with zone C's own thermostat output.

This is assuming ordinary bimetal thermostats - if they're electronic,
then we'd need more information (i.e., make, model, wiring diagram,
overall wiring diagram, etc.)

Cheers!
Rich

3. ### OceanGeekGuest

The other thermostats are electronic but they run off batteries so
they are really just a switch, right? Will the 24V circuit have
enough mA to close the relay? I dont want to start blowing the fuse
(1A) on the control box. Am i over thinking this?

Thanks

B

4. ### ehsjrGuest

Do this - it places no load on your control box:

AC in----o--- < existing zone A switch
^---o
|
+-------------+
| |
| |
+-------------+
|
AC in ----------+

Pick a relay whose coil voltage matches the
AC applied to the zone A load (a circulator,
I assume, but it doesn't matter).

When zone A turns on, the relay will energize.
Wire the contacts of the new relay in
parallel with the zone C switch, like this:

o--- < new relay contacts
| ^---o
AC in----o--- | < existing zone C switch
^---o
|
|
AC in ----------+

You can slave any number of zones you want.

Ed

5. ### Rich GriseGuest

You're not overthinking it at all, but to come up with a realistic
answer, we need to know exactly what you have now. It's impossible
to tell from here how much current your 24V supply can supply unless
you tell us, and that sort of thing.

Do you have model numbers, manufacturers, specifications, etc?

Thanks,
Rich