Negative pressure gas valves

Brad White

the best way to check this was to search for information on a boiler that has a negative pressure gas valve. The Hydrotherm KN uses a Dungs gas valve (as does the Munchkin and others but of a commercial range). This is what was said in a press release as one source:

<i>Commercial Boilers maintain max combustion efficiency.
December 1, 2005 - Rated at 99% efficient, gas-fired KN-6 and KN-20 utilize Tru-Flow(TM) Technology, which automatically adjusts fuel to match changes in air-flow for conditions such as temperature, <b>altitude</b>, and air-inlet or flue-outlet blockage. While KN-6 offers 600,000 Btu capacity and 4:1 turndown ration, KN-20 offers 2 million Btu capacity and 5:1 turndown ratio. Latter can accept 10:1 variation in water flow and has no return water temperature limitations.</i>

What I do know about these boilers and gas valves is that they are tolerant of very low gas pressures, essential when connecting to some of our older gas lines where you are lucky if the utility guarantees you more than 4.5 inches WC of gas pressure. It makes sense that altitude would be less of a problem but I am eager to learn more of the details myself.

Bob Sweet

Went to a boiler

class tonight and got to talking about neg. pressure gas valves. The instructor (who was very good) said that at altitude, no compensation was needed for de-ration with his particular equipment. If the input rating is 100000 btu at sea level it would be the same at 7500' above sea level.

Thats tough for me to grasp. Living at altitude has always been a factor when sizing a boiler. If it's correct it'll be a major plus.

Any thoughts on this?

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