Pat53 said:
Eliot, here is what the inside of the White Rogers looks like.
thx, Pat
PS Eliot, if I can't use the White Rodgers, is there a a cheap substitute that would work to get me by this season?
Finding that you have a couple RA832A's was fortunate because they happened to have an extra set of contacts that does exactly what you need. You can continue to use the White Rodgers to control its circulator, but you'll need to add another relay to do what the spare contacts on the RA832A do for free.
The WR in the picture appears to be a normal SPDT relay. The normally open contact is used to switch the circulator on, black wire in, black wire out.
Note that the WR has no transformer. Only the two black wires are 110VAC, all the other wires on the right are 24VAC, and therefore the relay coil is 24VAC and the 24VAC power to drive the relay is coming from somewhere else.
This means the thermostat for the zone is being used to switch 24VAC power to the WR relay coil, which energizes the WR relay, which closes the WR relay contacts, which routes 110VAC power in one black wire and out the other black wire to the pump.
Since there is 24VAC power you can get at that's present on the low voltage terminals of the WR relay, all you need is another 24VAC relay that can be used to switch power to the transfer pump (in parallel with the two RA832A's). The existing thermostat can be used to switch both the WR relay and the new 24VAC relay together at the same time. (You may need to adjust the anticipator setting on the thermostat.)
One of those RIB 24VAC coil standalone relays would do the trick for $25 or so, since you're only switching a couple of amperes of locked-rotor inrush and a few hundred milliamperes steady state current.
--ewd