Ultra Boiler Modulation


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
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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
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wrote:

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?
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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.
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wrote:

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