Ultra Boiler Modulation

[Michael Gallagher]

Hello,

I am the proud owner of a Weil Maclean Ultra 105 boiler; it was insalled this past May. Generally, I like the unit, but I am confused about modulation: The literature says it has "20-100% modulation." Does that mean it fires at any rate between those two? Or at JUST 20% and 100%?

Thanks,

Mike

[Edwin Pawlowski]

Any modulating boiler I'm familiar with is a variable firing rate. The W-M uses a mixing venturi to send the gas/air mix to the burner with a 5 - 1 turndown ratio

[Michael Gallagher]

So for clarification, bearing in mind I am not up on the terminology, you are saying it can fire anywhere between 20% and 100% inclusive?

[Edwin Pawlowski]

Yes. Most of this type of boiler senses the temperature and will trim the fire to maintain a steady water temperature as opposed to the older methods of turning the burner off, starting it back up again when the temperature comes down, shutting off again, and repeating.

I don't know the exact setup WM uses, but let's say the maximum temperature is going to be 185 degrees. At about 180, it may go down to 20% fire and let it creep up slowly. On a very cold day, the water coming back to the boiler may be 120 degrees and that will cause the burner to go back up to

100% until it reaches a warm enough water temp to start backing down. The result is more even heating, less temperature swings.

[Michael Gallagher]

Thanks for the clarification; I have a better idea of what's going on.