These Combustion Test Results OK?

Boilerpro_5

and is not preferred for the triangle tube Prestige if maximum efficeincy is wanted. Add a Wilo stratos and away you go.

Boilerpro

<A HREF="http://www.heatinghelp.com/getListed.cfm?id=393&Step=30">To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"</A>

D107

1981 Weil McLain gas-fired CGM-7P1 with draft hood.

9-25-07 combustion test, 11:46am, outside temp 72?
stack temp: 382; amb temp: 76; O2: 11.7%; CO2: 5.2%;
CO 21ppm; 0% COR CO: 49ppm; Eff: 77%; EX Air: 113.7

Unfortunately no draft test was done. CO2 seems low to me; perhaps due to warm day? Chimney is internal, about 33ft high 7x11 inside. Burner tubes recently thoroughly cleaned, no FAI in 1920s house--boiler room band joists uninsulated.

Thanks,

David

Steamhead (in transit)

Well, the CO readings are low enough

to be safe, but there are definitely more-efficient boilers out there now....... there's lots of excess air going thru that boiler, and as is sometimes the case on atmospheric gas boilers you may not be able to do anything about it.

In that case, I'd consider replacing it.

"Steamhead"

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

D107

thanks; trying to keep it another 5 yrs, then go mod-con

Have to repipe basement since prior owner had gravity conversion done and piped zones in series--rad to rad.

I thought it unusual that a combusion test wouldn't include draft test....

Hard to believe eff is as high as 77.3%. Dividing DOE output of 165K by firing rate 210K = 78.6%. Only lost 1.3% in 26 yrs?
(not to mention system efficiencies.)

Good thing about waiting a few years is that by then, those micro vari-speed pumps should be widely available and wallies will have figured out a way to officially avoid primary secondary with mod-cons.

thanks,

David

Steamhead (in transit)

You won't read much draft

between the boiler and the draft hood, but it should have been tested. There should of course be more draft in the chimney, and the tech should have ascertained that flue gases weren't spilling from the draft hood.

Once you get the piping redone properly, the system will work much better.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Steamhead (in transit)

Dave, what if

the head and flow rate thru the modcon and that of the system are different? I would assume P/S would be a great way to decouple the two.....

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

D107

I guess I have been intrigued by the many wall discussions

on the subject, though your point is certainly an excellent one. If I recall I think Mark Eatherton's Munchkin is running without P/S. Of course with my limited knowledge I may be planning for something that may not work with my system. Only have about a 40K loss though. Also have become a fan of buffer tanks.

I regret our schedule of other imminent and ongoing house projects will prevent us from installing a new boiler for now so we're stuck with about 900 therms a year usage for heating. A mod con and ventless attic sealed with icynene and I'd bet we cut usage in half.

Thanks again,

David

singh

You mean

5.2% O2 and 11.7% CO2 .


"9-25-07 combustion test, 11:46am, outside temp 72? stack temp: 382; amb temp: 76; O2: 11.7%; CO2: 5.2%; CO 21ppm; 0% COR CO: 49ppm; Eff: 77%; EX Air: 113.7"

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

tim smith

Comb readings

Singh, he is correct, w/ the high 02 and the low co2 with that much excess air. I would check my gas pressure on this boiler. It very likely is low or maybe it has air shutters on it and could be adjusted. I would like to see at least 6.5 to 7 C02. Tim

Mitch_5

O2 typically 6 - 9%

did you check manifold pressure I have seen alot of cases especially with high pressure systems that the regulator was faulty or set wrong only getting 2.5" or less on the outlet side.

You seem under fired, keep in mind that most analyzers test O2 and calculate CO2 as a mirror image.

Mitch S.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

D107

thanks much for your responses

I also noticed the CO2 and O2 numbers seemed to be reversed, but that's what the Bacharach printout receipt says. If this is underfired capacity-wise (ironic since at 210Kbtu it is certainly OVERfired for heating purposes) perhaps that is due to the gas line being 3/4" with about a 30ft run. Plus there's also a 40Kbtu direct HWH, 22Kbtu dryer and max 60Kbtu oven/stove attached. Been working fine for years, but even when an 80K btu modcon was sized, we knew the gas line had to be upgraded to 1".

Also, the house next door just had a gas line put in from the street --not yet activated--but I hope that wouldn't affect anything.

I give the testing company credit that they had digital equipment, but their inability to interpret and fully test things like draft, CO spillage in room, manifold pressure etc. is not good. (Though I gather testing draft OB with a draft hood may not be so easy--perhaps a probe hole must be drilled into horizontal breaching just before the brick wall?)

I guess one thing I can do myself is check the gas meter movement when firing. See attachd photo. Dial on left -- 1/2cu ft? moves faster than one on right 2 cubic ft? So if I clock dial on right for 2 cu ft then multiply time lapsed by 50 that's 100 cu ft or 1 ccf? and that's 100K btu, yes? which for a 210K firing, should take a little less than a half an hour to reach.

Thanks,

David

Unknown

David,

use the half foot dial, and let it do two rotations and time it. Then divide those seconds into 3,600 (number of seconds in an hour)and multiply your answer times the BTu content of gas in your area probably around 1025 to 1050 BTU's per cubic foot. That will give you what the unit is firing at in BTU's.

This package seems to have excessive excess air and needs a professional gas combustion tech to take a look at it.