Burned up Taco SR506 relay

srafferty05

Got a call for no heat at my rental.
1yr old Peerless 4 zones, 4 circulators. 
Breaker was tripped and then found this mess.
Any idea where to start?
Did this relay just fail, or possibly something else cause the failure?

MaxMercy

srafferty05 said:

Did this relay just fail, or possibly something else cause the failure?

Open neutral?? Wow. Anything else in the rental damaged electrically?

What I would do is demount the circuit board and wash it in the sink with hot water and strong detergent with a stiff paint brush. Most of what looks like damage is carbon residue from whatever let the smoke out. Once it's clean, we can see where on the board the problem is.

It could have been a safety device like an MOV on the board. Sometimes they put on a show when they go bad. It could also have been a loose AC wire on a terminal or bad solder on one of the circ relays. With an inductive load like a circulator motor, you can turn 120VAC into a few thousand volts when you start an arc.

EDIT: Take a close look at zone 4 wiring. It's hard to see, but it looks like the black hot wire was loose on the zone 4 terminal and started a arc at that point and destroyed the terminal board. Once the arc is started, it will keep going as long as the zone is calling, or until the wire gap opens too far or until the AC is interrupted. Looks like a loose wire on zone 4 hot was the cause.

STEAM DOCTOR

Wow. You certainly need a professional in there. Can't tell from here but near 100%  certain that the relay was not the source of the problem. More the symptom of some problem. Did this ever work? If yes, then you should look into whether one of your tenants is an amateur electrician and did some electrical work that was over there heads. Any construction done recently? Someone drive a nail into some wiring? Could be anything. Whatever you do, don't replace the control until the source of the problem is found. Could be a loose wire in the control. 

pecmsg

Is that mounted directly too the boiler or is there an air gap between?

How hot does that side get?