Damper bypass wiring (molex jumper settings) - for common Honeywell/WM control

willrr

Trying to swap out old Weil Mclain 511-330-095 control unit for same in existing steam/gas/intermittent system for old Peerless G (trying to get through the season).

Damper was unplugged and old control unit has damper molex jumpered between pints 2 and 5 (molex has two rows of 3 plugs and center of each row is jumpered).

New unit has jumpers between pins 2+3

My guess would be to jumper as in current setup but I can't find anything out about jumpering pins, only pug it in or not...

Thoughts?

109A_5

Hello @willrr,
I think you will find (if you do some research) the jumper that comes with a new Ignition Module (or Aquastat) and the jumper on a cable going to a Damper unit serve two different purposes.

The jumper on a new (or never used with a Damper system) Ignition Module allows the Ignition Module to function properly (No Damper).

The jumper on a Damper cable (once used on the Ignition Module) blows a internal fuse in the Ignition Module so that the module can no longer be uses with the original Ignition Module supplied jumper. The Ignition Module now has to see the End Switch closure (Damper Open) in the Damper unit to work. It is essentially a safety lockout feature so the Damper (which could be closed) can't be electrically disconnected and the burner fired up with the original jumper supplied with the Ignition Module.

Hope this make sense to you.

willrr said:

Damper was unplugged and old control unit has damper molex jumpered between pints 2 and 5 (molex has two rows of 3 plugs and center of each row is jumpered).

It appears someone bypassed the safety lockout feature I described above.

willrr

Thanks! Yes, from what I found, both jumpers do the same thing but one has a fuse in its path. Now I found a diagnostic that said the old jumper config could be used temp for diagnostics - so it doesn't sound like it's blowing the fuse but to fool the boiler to think there's a damper. The new jumper follows the same path but not through the fuse. But the real question is - can I use either or should I use the one that was there previously (same identical control units, I just don't have the wiring for them). Or does it matter?

109A_5

Hello @willrr,
I would expect this, jumpers between;
Pins 2 and 3, no Damper, factory jumper that come with the Ignition Module or Aquastat.
Pins 4 and 3, is for the purpose of blowing the Damper safety lockout fuse (part of the Damper wiring harness).
Pins 2 and 5, bypasses the Damper End Switch functionality. Not safe unless the Damper is removed.

willrr said:

Now I found a diagnostic that said the old jumper config could be used temp for diagnostics - so it doesn't sound like it's blowing the fuse but to fool the boiler to think there's a damper.

No it would not blow the fuse since the fuse is already blown and 2 to 3 won't work any more. And is just used for diagnostic purposes.

willrr said:

The new jumper follows the same path but not through the fuse.

I think the Gas valve load goes through the fuse. Jumper 2 and 3, no Damper ever in the system.

willrr said:

But the real question is - can I use either or should I use the one that was there previously (same identical control units, I just don't have the wiring for them). Or does it matter?

I would use the jumper that comes with the New Ignition Module (2 to 3) and remove the Damper unit if it is failed and the costumer does not want the Damper replaced or repaired. You don't want to defeat safety lockouts (other than testing). And you are the last person to touch it, CYA.

willrr

Yep, thank you very much for the help and advice. It was quite hard to find any info on this unit but the same type of control has been used for a long time. I do really appreciate the time and help, Happy (and warm) Holidays!