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Phil, Mechanical Engineer
Category: Electrical
Satisfied Customers: 8682
Experience:  Retired electrical contractor, 51 years experience.
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Trying to install a low water cutoff on a gas boiler. The

Customer Question

Trying to install a low water cutoff on a gas boiler. The new one I purchased is a MM
and it is replacing a safgard 550. The MM has yellow wires that are supposed to connect to the boiler panel but the wire from the panel are black and white. What should I do?
Submitted: 1 year ago.
Category: Electrical
Expert:  Phil replied 1 year ago.


Please attach a well focused, close up photo of the wiring diagram glued inside the service panel,you can use the paper clip-icon at the right end of the toolbar at the top of this dialog box

If there is no paper clip-icon, look for the '+attach files' link at left of your send button.

I can mark it up with trouble shooting instructions.

Customer: replied 1 year ago.
Customer: replied 1 year ago.
one is a diagram I found online and the other is off the device.
Customer: replied 1 year ago.
are you there?
Expert:  Phil replied 1 year ago.

Hello again, I have to come and go to do research and juggle several questions at a time.. right now I need the model number of the "MM" low water cut off control.

Expert:  Phil replied 1 year ago.

oops I see the MM is mc***** ***** RB 122

It will take me a while to look both of them up and sort out the wiring.

Expert:  Phil replied 1 year ago.

I am going to make a CAD drawing for you, its going to take me half an hour or so.

Expert:  Phil replied 1 year ago.

I need a photo of the boiler wiring diagram to be sure that I integrate new level control properly. There are more than a few options.

Customer: replied 1 year ago.
Sorry- I had to runs some errands
Expert:  Phil replied 1 year ago.

Hello again,

Here is your connection diagram, the dark diagram on the right is a screen shot the wiring diagram

you posted.

Thanks for letting me work with you. When we are finished, if my answer has been polite, professional,and thorough, please click one of the ratings . If you still need help let me know!. Expert is not paid for assisting you until you rate answer. Feel free to follow up for30 days at no additional cost.

Customer: replied 1 year ago.
Hi there,
The yellow wires are very short and the probe is far away from the boiler wiring. How can I resolve that issue? Also,
there are two yellow wire. Do I connect both?
Sorry - I am not very wiring savvy.
Expert:  Phil replied 1 year ago.

Hello again, That low water safety cut off switch is a *critical safety device, a licensed boiler service person needs to do that wiring if there is any confusion what so ever.

It will be quite easy for you to make a fatal mistake if you are not very wiring savy.

If you can rate my work positively for the superb CAD drawing I sent you, I will appreciate it, that is how I earn my living. The wiring itself in this case needs to be done by a pro boiler tech.

If you need help locating one, tell me which direction you are from the center of the nearest city and I will get you a short list of the best rated ones in your area.

I will put the rating box up now.