Sequence of cutoff devices in wiring

[Deleted User]

The wiring of my ancient boiler is an amateur rat's nest of wires hooked together with tape and hanging all over, with some of the insulation flaking off. I'm planning to rewire it using a barrier block to make everything organized and labeled.



My first instinct would be to wire it in the same sequence as it is now. You can see that in the diagram. The low water cut-off is wired through the pressuretrol. The LWCO is really last in line if you consider the R terminal to be the start.



Problem is, I was reading some installation manuals for these LWCOs online, and it says they are supposed to be the first one from the hot terminal, which should be R. So should I leave it in the current sequence, or put LWCO first from the R terminal?



Edit: forgot to mention, if it matters, the LWCO is combined with auto water feed. But I don't see why it should matter what order they are in in the series. If the circuit is broken anywhere, nobody's getting any current, right?

Jamie Hall

Just so long

as they are in series, as you show, I can't see that it would make any difference -- unless the LWCO's autofeed wiriing requires that it have a hot connection at all times.  I wouldn't think it would -- it would mean that there would pretty well have to be a third terminal wired to neutral for it to make any difference. That would be the only consideration that I could see.

EBEBRATT-Ed

wiring

THE R TERMINAL SHOULD BE YOUR HOT FROM THE TRANSFORMER. c FROM THE TRANSFORMER SHOULD GO TO THE GAS VALVE.

YOU DIDN'T MENTION IF YOUR WATER FEEDER IS MECHANICAL OR ELECTRICAL. if IT'S ELECTRICAL IT WOULD HAVE TO BE CONNECTED TO c AS WELL.

if YOUR WATER FEEDER IS MECHANICAL JUST REVERSE THE C AND R WIRES AT THE TRANSFORMER AND YOU SHOULD BE OK.

wITH AN ELECTRICAL WATER FEEDER WE USUALLY MAKE THE LOW WATER CUTOFF THE FIRST CONTROL SO IT CAN POWER THE FEEDER IF NEED BE OTHERWISE WHEN /IF THE BOILER IS OFF ON PRESSURE THE FEEDER CANT WORK.

[Deleted User]

I think it is mechanical

Thanks. I don't fully understand though Ed. The water feeder/cutoff is McDonnell & Miller No. 47. I think it is mechanical. Below is my current plan. Does that look OK?



A strange coincidence happened today. We woke to a cold house, 56 F in the bedroom and 50 in the kitchen. I checked the transformer, it still had 24 volts. I checked the pilot light, still on, so I knew there was gas. So most likely a wiring problem. I jiggled the mess of wires and the burner flashed on momentarily. I was able to find the bad connection and fix it. And I hadn't messed with the wires yet. Guess I'm doing this at the right time!

[Deleted User]

All done

Job went well, though I am a little spooked by the fact that, after who knows how many years, the crappy old wiring job finally gave out the eve of the very day I was going to replace it.



I'm now convinced that, just like house wiring, all the switches (LWCO, pressuretrol, thermostat) should be in the hot line before the gas valve. The old wiring was just the opposite, the hot wire went straight to the gas valve and all the switches were in the neutral side.



One advantage of this rewire is that diagnosing electrical problems will be easier, using the terminals on the block.



Here are some pics before and after wiring the new board. As always, the help is really appreciated!