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Help on Weil Mclean WM97+ 155 derated to WM97+ 110"HA"

Bart56 Member Posts: 4
When my WM97+ was installed, the distributor gave my contractor a WM97+ 155 instead of a 110 like he ordered. He did not charge me extra (he said so) but derated it to a 110 by changing settings in the controller. My old boiler was a 100K gas boiler and the house BTU sizing showed that's all that was needed.

The contractor is out of business now but he had a lot of trouble getting it to fire up quietly - making a loud boom when it fired. He called tech support and ended up having the regional WM tech support guy show up. They changed settings and finally decided that the igniter needed replacing which was installed a week later. It starts up ok but often Booms or growls when first firing.

I'm looking at doing annual maintenance and I noticed that it was set for High Altitude when I live about 300 ft elevation. This doesn't seem right and I wonder if this may be causing the occasional booms on firing. A clean igniter helps calm down the booms.

There are no WM Preferred contractors in my area and wonder how to ensure the system is set up correctly. I could do a factory reset then derate it to 110 and see how it performs, WM Support won't give me any support because I'm not a contractor.

I haven't had very good luck choosing a random HVAC contractor. The last one I called for a boiler tune-up didn't bring his CO meter and wanted to charge me for a second visit to do so.

I'm not complaining, just a little uneasy about finding a contractor that knows Weil Mclean systems well.

Any advice is appreciated.


  • Jamie Hall
    Jamie Hall Member Posts: 20,803
    If it booms or growls on startup -- the combustion settings are way off. You really need to find someone who can adjust the system properly; You can't do that without the various test instruments -- or which a CO meter might be one, but not the only one.

    I suspect what your installer may have done to "derate" the unit is to simply limit it's maximum firing rate.

    Pretty much any good technician experienced in maintaining gas fired boilers should be able to help. One of the problems with getting support from the manufacturer -- besides the fact that they don't like to work with unlicensed people for very good reasons -- is that that boiler has been discontinued.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Bart56
    Bart56 Member Posts: 4
    Thank you Jamie.

    I am aware that it has been discontinued and after reading the boiler service manual, setting it from the 155 to the 110 adjusts the firing rate and then also setting it to High Altitude derates it further.

    Good info on the possible cause of the booms and growls - thanks for that.

    Also, you're giving me confidence to find the right tech, regardless of WM experience.

    EBEBRATT-Ed Member Posts: 13,331

    Did you try "find a contractor on this site" ? Also post your location someone may have a rcommendation.

    Isn't it nice that Weil Mclain refuses to help out. I can understand them not passing technical information out but they should assist you in finding a list of qualified contractors instead of abandoning you. Maybe that why people both contractors and homeowners like Energy Kinetics
  • Bart56
    Bart56 Member Posts: 4
    Yes, I did try find a contractor and a commercial steam contractor was the only listing that showed up.

    I actually expected Weil Mclain to let me as a homeowner know if my contractor had set it up correctly. I do know he worked with WM Tech Support during install, but obvious things like "Boiler Model settings" are set against the instructions in the manual. It says the model setting MUST be the same as the stamped nameplate model but it's not (nameplate says model 155, but the controller is set to model 110. It also says High Altitude is only to be used above 5500 ft only while I'm at 350 ft.

    Even if Weil Mclain support said those are not right and we'll have a trained contractor call you would have been a much better response.