New gas valve & aquastat...wired valve incorrectly and transformer burned up in New stat

Klingler1970

TThrough our church we do a lot of boiler/furnace repair for those without means for a new system. Monday we went to a home with a very old torridheet boiler that was experiencing delayed ignition intermittently. The aquastat was the oldest I've ever seen and the gas valve was at least 30 years old. I suggested replacing both including thermopile. Easy right? Got a Hydrolevel 3200 stat for a reasonable and replaced the old Honeywell vs820a with a Robert Shaw 700-506. Circ pump wasn't too old but rewired it as it was sketchy. New wired from stat to valve. Upon powering up the stat started smoking almost immediately. I knew it was fried and removed it. I had a used HW L8184 for oil but added a transformer to a knockout and tried again. Same deal…burned up secondary side of former. I started tracing and checking all wiring and found I had placed the 24v wired to the gas valve on TH & TP instead of TH and TH/TP!! Could that have possibly been the reason for blowing transformers? I had one more super old WR 24v Astat and before I found the mistake I wired it and hit the power but only for a second…it's transformer was buzzing like crazy. If that were the case of blowing the corners do it likely cook the valve too? It's our mistake and our cost…It's and old but solid boiler and should outlive her if I can get this figured out. Thanks in advance

Klingler1970

"if that were the case of blowing the transformers did it likely cook the gas valve too" sorry…darn fat thumbs and

109A_5

Hello Klingler1970,

With reading the data sheets for the gas valves you are playing with (Honeywell vs820a and Robert Shaw 700-506) it appears they are for a 700 millivolt, Power Pile systems and NOT for 24 VAC systems. Putting 24 VAC into these gas valves is going to destroy something, maybe a few somethings.

A 700 millivolt system can be controlled by 24 VAC controls if wired up correctly with a relay to isolate the two electrical systems.

Originally it may have just needed a new Power Pile or securing a loose connection and you could have walked away, re-engineering the system can take you down a 'Rabbit Hole' you don't want to go down.

The way I see it, you need to put the system back the way it was (electrically speaking) and replace the defective and smoked parts, or possibly convert it to a 24 VAC gas valve with a thermocouple.

exqheat

Check all wires with meter for voltage and resistance before attaching to instructed terminals. Colors can be wrong.