Combustion analysis

Jim Davis_3

It seems that the boiler industry or at least the newer type boilers, Veismann, Munchkin, Buderus do give more information on combustion setting than others. Unfortunately it is impossible to drill 2 burners orifices identical. The BTU's of gas fluctuates all over the country. And as S Ebels, Mitch, etc. have stated, unless you test you don't have a clue. "Air Free" CO can sometimes be misleading because it is "Calculated". Which is better? - 12% O2 & 100ppm "CO Air Free" or 5% O2 & "110ppm CO Air Free"? O2, Temp & CO all have to fall in a good range or none of the numbers will mean anything.

Pete_23

Combustion analysis-Munchkin

I know all these new condensing hi-eff boilers should be set up with a combustion analyzer. My question is do most boilers require an adjustment after checking with a combustion analyzer? or are the factory settings usually correct.
thanks

S Ebels

Good question

Simple answer

Any and all combustion appliances, be they boilers, furnaces, water heaters, kitchen stoves, gas fireplaces, oil burners............you get the point, must be tested. If you don't test, you don't know. Doesn't get any more basic than that.

As far as factory settings go.........Some manufacturers will really expend serious effort to get their product "dialed in". Viessmann comes to mind here. Nearly all manufacturers will ship their product out at a preliminary setting that will asure that the burner fires. In truth, that's about as close as they can come at the factory. There is no way they can anticipate the field conditions in which an appliance will be installed. Too many variations in vent length or chimney, fuel pressure, atmospheric conditions etc. Rarely, and I mean very rarely do we come across any type of burner that requires no adjustment. Maybe one in 200, tops! The only exception to this would be the VIessmann Vitodens boiler. They are self regulating provided your gas pressure is correct and they'll even compensate for that to a point. Never had to adjust anything on one of those. CO runs <10ppm or less. (I'm wandering again, talking about my favorite boiler, Viessmann, sorry)

That being said, I feel that it's mandatory to test everything we lay our hands on. This is our "rule of thumb" even on stuff we didn't install. It's just the best way and........ the only way I can sleep at night.

It's also priceless to see the look on a customers face when you show them a before and after printout of their equipment.

Mitch_6

If you don't test you don't know.

All installs should be tested for safety you may find a boiler has the wrong orifice or similar issue and a proper combustion analysis will show this.

Mostly I find most of my boilers fine out of the box, the main issues I find on an install besides combustion air which can be factored before the install are.

1) low gas pressure on natural gas services I have come across several cases of poor pressure due to regulator failure. This will show up on a combustion test as under fire but I also check with a manometer for comparison.

2) I have had several boilers that even after a proper chimny sweep and inspection have had excess draft in the chimny causing either a curtain effect on the draft hood or in one case pulling the flame off the logs.

So while allot of the basic package boilers do not seem to need gas valve adjustment (typically all have been 3.5" wc on the nose outlet). I do find other issues that justify a full combustion test.

Mitch S.

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jeb

Munchkin

Do most Munchkins come set from the factory correct?

Cosmo_3

I think you got your answer Pete

That is, unless you check you don't know.

Sorry to be so blunt but thats the way it is


Cosmo Valavanis

Rudy

The thing I wonder about....

Right in their instruction manual they list the desired CO reading of (If I remember correctly) 80 to 120 ppm on high fire.

What they don't specify is if this is the 'diluted' reading or the CO air free reading.

Anybody have any idea?

Mitch_6

co readings

I am familiar with munchkins but install have installed Weil Mclain / Burnham and Trianco condensing boilers.

Readings they look for are usually low O2 about 3 to 5% on high efficiency condensing boilers

Co2 about 8% and co under 100 ppm in fact most protocols state any co over 100 ppm free air the equipment should be repaired and any co over 400 the equipment should be made inoperable until repaired or replaced.

Mitch S.

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S Ebels

You know what bugs me......

A lot of manufacturers don't even publish desired test results in the owners manual. You have to call their tech service line get 'em. Sometimes trying to get the info from them is like pulling teeth, especially the furnace people.

Mitch_6

manufacturers

do publish gas pressure and draft specifications and allot of installers do not even check that. Very few people I know will put a draft gage on (usually just match test) or check gas pressures unless they "see" a problem.

In fact most gas equipment installers do not own a manometer set to inches w.c. or a draft gage.

As to combustion readings of natural draft equipment I just look for the industry standard readings, only on high efficiency equipment does it seem to vary from the norm.

Mitch S.

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Mark Hunt

Answer is


Undiluted/air free.

That is the CO number that should be used.

Mark H

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