Aquastat/Relay: Stumped!?

adambuild

Got a no-heat call last night at midnight and replaced a bad aquastat/relay on a hydronic boiler by 2:30am! Relay coil was fried, replaced with new Honeywell L8148E 1265. Today, get a no-heat call again. Go to home and new relay coil is fried!? 3 Taco 571-2 zone valves are on separate xfmr, checked end switch wires and got no backfeed voltage, voltage to boiler is 123vac. Any ideas?

Empire_2

Adam....

Sounds like something has to be shorted out. The only thing is that it seems to take a while to do so. Have you checked what each zone is doing as amps on the boiler circuit? (I know you said the t-stats are on their own t-former) but what are you getting amp wise on each zone that calls?

Mike T.

adambuild

Wait a minute........

I just looked up the wiring for Taco 571-2 and it shows stat on 1&2 and end switch on 2&3. Presently, stat is wired to 1&3!? I just inherited this job, but it seems like it's been like that for a long time!? Could that be?

mike from pa.

How is the circ. pump? Is the motor ok on the burner?

Joe Mattiello

Same circuit?

Are you working off the same circuit? The controls are interfaced through the low voltage terminals.

Danimal

Taco correct wireing

a thermostat goes in series with the 24v side of step down transformer to terminal 1 on the taco zone valve. termianl 2 goes to other side of step down trans former. The purpose of this circuit is to supply power to a heat motor. When the heat motor heats up enough to melt the wax in the zone valve (Appx. 1 to 2 Min.)it opens the zone valve and closes the end switch. Also another wire goes from terminal 2 to one side of relay coil. then from the other side of the relay coil connect to terminal 3. the end switch closing (on the taco zone valve) completes a path for current to flow to and through the relay coil.
There are a couple different way to to wire taco zone valves to make the burner run and cirrculator run but with out a doubt there is only one right way to wire them to get correct sequence of operation.
1. Check voltage at transformer
2. Check for end switch connection When the end sitch is closed can be closed mannually should have a Zero ohm reading.
3. And My biggest suggestion would have to be check you wiring.
4. Also a maximmunm of 3 taco zone valves can be used with a 40va stepdown transformer.