CO Reading Fluctuates

kirby96

Hi-

I just had my older (~20 year) furnace (err, boiler for radiant heat) cleaned/tested, and it passes CO testing, but the readings seem to fluctuate between 50 and 70 ppm. We tested on 2 different days, and the furnace has been running, and the two tests were consistently inconsistent (both tests went up to 70ish, back down to 50ish, and so on). The tester wasn't sure what might be causing this, so I've been searching the web for clues but haven't gotten anywhere. Any insight here?

Thanks,

Kirby

mikeapolis

Did the technician test the gas pressure inlet and outlet while the boiler was operating? Windy day during test, how is the venting? What is the boiler brand/model
Thanks

Zman

There is probably a variable like draft, gas pressure or air temp in play? Is it a 2 stage boiler? Does it stabilize once it has been running a while? Does the fluxuation coincide with someone opening and closing a door in the house? Where does the CA come from.
Not sure it is an issue, it does sound a bit unusual.

icy78

Pics of the installation please.
What is the time cycle of the C0 fluctuation?
What does the 02 reading show? (In tenths also please)
What tool were they using?
On your pics, show where the analyzer probe was.
Can you give a pic of the printout?
Some equipment will exhibit that action, BUT it's very important that the 02 also only varys by, say, a tenth also. 
    In other words, they'll follow a shallow sine wave action.
    If it's an atmospheric boiler,  a barometric conversion is always good to do.

kirby96

Thx for the feedback. When I get done with work today, I'll post some pics and answers to those questions!

EBEBRATT-Ed

Combustion changes from day to day. Fuel temperature, draft, boiler water temperature, air temperature etc etc all can affect combustion readings.

You are looking to keep the equipment operating in a safe range.......not at any specific point

captainco

We call that the combustion roller-coaster. As long as it never rises higher the next time it is okay. If it even goes up 1ppm higher than before there is a venting problem. Not unusual on a windy day.

Zman

captainco said:

We call that the combustion roller-coaster. As long as it never rises higher the next time it is okay. If it even goes up 1ppm higher than before there is a venting problem. Not unusual on a windy day.

Huh?

captainco

Huh?- Yes this is such a thing. The dangerous roller-coasters are the ones that get higher and higher- 20-10-25-20-30-20-35 etc.

icy78

captainco said:

Huh?- Yes this is such a thing. The dangerous roller-coasters are the ones that get higher and higher- 20-10-25-20-30-20-35 etc.

X2
For example, 
If you see a low slow up and down of the same low number and the same hi number then it will pass saftey inspection.
But ANY rise above that peak will have me watching it like a hawk, because it will often keep climbing then. This results in NON steady state so would be a dangerous way to leave the appliance.

GW

Z, the Captain has spoken, let it be😀