I have a boiler that is controlled by a 120VAC T-Stat. The unit plugs into the wall (120VAC) and on the unit there are two terminals. One is hot 120VAC at all times and the other, when hot, fires the unit.

What I would like to do is control this from a "traditional" 24VAC T-Stat.

I believe I would need a relay that could take the "signal" (on/off) from a 24VAC T-Stat and "trip" a 120V relay, hence turning on the unit.

So. First we need to take 120VAC and transform it to 24VAC in order to have the proper power to supply the new T-Stat, correct? Then from there we need the relay that switches the 120VAC on, correct?

So my question(s)... how do you wire it and what are the "proper" names for the relay, etc. I need?

Thought I'd see if anyone knew...

Thanks,

Pete

Might want to contact Allied Electric (Google 'em for web site) and describe to a tech what you want. They'll get you the right goodies.

You'll need a relay such as this: They come in all kinds of different control and output voltages. You'll probably want a base for it as well, rather than soldering directly to the pins.

Of course, you'll also need the 120v/24v transformer. Allied would have that. Also any HVAC supply, electrical supply and even sLowes or Home Despot should have them.

edit: once you get your parts, I can draw you a wiring scheme.

__________________
1998 E300 +310,000K
1996 E300 +460,000K

Lux!

Thank you SO much.

Ok. I just spoke with them. Seems to be the best way to go is with a relay that is coil voltage of 24VAC and 120VAC on the other side (correct?) An example would be found:

886-2381 KRPA-11AY-24 3-1393104-7 24 VAC DPDT 5

For the relay... (page 1117)

http://www.alliedelec.com/catalog/pf.asp?FN=1117.pdf

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That relay (as an example) would plug into this base:

Use:

886-2488 27E122 1393143-6 8-Pin Octal Screw Term. KRPA, CB, CD, CH, CS, CNS

(page 1121) for the base (nice screw terminals for the socket.)

http://www.alliedelec.com/catalog/pf.asp?FN=1121.pdf

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And for the transformer:

Any of the 24VAC Secondary ones here (all we have to do is juice the t-stat (and in turn trip the relay) with it... I'll leave that up to you as far as which one is best. They can be found on page 926.

http://www.alliedelec.com/catalog/pf.asp?FN=926.pdf

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Thank you!

Pete

That looks like the ticket.

What kind of thermostat do you plan to use?

__________________
1998 E300 +310,000K
1996 E300 +460,000K

A simple 24VAC 2 wire t-stat. Let's say a honeywell "round"...

Ya know... something like this:

http://www.homeandbeyond.com/prod-0071154.html

Thanks again!

Can't get much more simple than that!

__________________
1998 E300 +310,000K
1996 E300 +460,000K

Yup... a simple 2 wire heat-only t-stat... I'll admit that I have no idea how to wire the relay end of things...

Thanks again,
Pete

Lux,

Question.

Could we use a simpler solid-state relay instead? Just reading and wonderin'

Pete

As long as it triggers at 24V and can handle thru-put of 120V.

__________________
1998 E300 +310,000K
1996 E300 +460,000K

OK... the wire-up would be the same... so lead the way boss.

Pete

I'd stick with a contact relay for that job. No need to make it sensitive to voltage spikes.

The wiring for this is very simple. I'll let Lux draw it up for you (out of laziness of course) but you'll slap your forehead when you see it.

Thanks for the tip Matt. I'll stick with the contact relay then. There are SO many of them!

This is a 12VDC set up... but I'm learnin'

Me thinks I taught me-self, yes?