I have preexisting 110volt> transformer> 3 relays to 3 B&G pumps. 1 thermostat 24volt wire. I am installing a new WeilMcLain package boiler. Do I need 110 to boiler also? If not what do I do with 2 black-1 white- 1 yellow coming out of boiler ? Have installed many boilers ,but only am used to wiring to 1 pump in ordinary fashion.This wiring system was in operation with a similar older package boiler but did not see the hookup since the boiler was yanked before I saw it. Thanks.

Do I need 110 to boiler also?

Yes read the electrical part of the wiring diagram that came with the boiler.

I suggest buying a three zone panel to complete your install. It makes all the wiring easy and neat.

Naturally this is a guess since no one really knows what you have there or how it was wired before. A ON SITE survey by a competent boiler control expert would actually be your best bet.

NOTE: Now is the time to upgrade your customers system to allow zoning. You need to discover what pumps are designated to the different sections of the building. You also need to discover weather or not the system has a indoor/outdoor boiler water temp control. This alone will save big $$$ on there utility bill.

Naturally these items cost more and will be an add on to your bill but most customers will understand saving $$$.


ALSO see your other post on the same subject.

https://www.askmehelpdesk.com/heating-air-conditioning/3-circulators-1-new-weil-mc-clain-boiler-265399.html