Cost to clean a heat exchanger?

Pricing is not discuss on this site .

Also the sooting is generally the result of overly rich combustion, not the cause. I'd have that looked into.

Did the tech leave behind a printout of the combustion test? At 3 years old, that boiler should be spotless inside. At 20 years it should be spotless. If there's soot, then the tech needs to find out why, not just clean it.

or it is lacking combustion air or it is massively underfiring for some reason like inadequate gas supply or a problem with the gas regulator or something clogging the burners.

the condition of the HX us related to the life it has lived, as @Alan (California Radiant) Forbes suggested

A site visit and some troubleshooting is required to know the answer

Maybe get a second opinion, now that you have some tips on what to ask the service person

It is certainly possible to plug or foul a HX in a years time or less if the equipment was not installed and set up properly

It is on gas not LP, correct?

Gas pressure and draft needs to be tested/adjusted.

Combustion is way off. I don't see a HX getting dirty with those #s but anything is possible.

CO needs to be below 100 below 50 is better and it should be a lot lower than that like 10

Co2 should be more like 9

O2 maybe 5-6

So your way off I am surprised it ran

But check the service manual for what the combustion #s should be mine are just a reasonable guess.

Something is way off and I suspect they never combustion tested it at start up.

They don't make a more simple boiler. That's an open draft hood, so I hope the tech got the probe up over the top of the block. With those numbers, it seems the techs sampling was diluted. Atmospheric oxygen at sea level is about 21%, so getting 16.58% during a combustion test means the tech didn't stick the probe where it needs to be stuck.

@Evan0307 , did you see for yourself the dirty flue passages in the boiler? Dollars to donuts its clean as a whistle.

The CO reading at that location is maybe 2 or 3 times higher in the boiler which makes it deadly. You have been lucky so far

don t post to often but i will state in 40 years plus i have only seen 1 or 2 sooted gasfied hot water boiler . 1 lack of combustion air 2 bad gas valve

Its very rare that atmospheric gas fired boiler gets sooted not for nothing i know things are slow every where and the bigger a company is, the more over head the more they feed off of unknowing home owners and every service call must produce x revenue plain and simple .It,s sicking. Combustion testing in the wrong spot is the first indication of the wrong company wrong guy wrong training . I believe that if they aint doing oil fired equipment service then they aint to familar w combustion testing at least w old timers . I say this from experience and working in the phvac field for close to 40 years ,my experience is most of all the plumbers i have worked w would not even know how to do nor cough up for a combustion analyzer unless for free and or where forced at gun point to buy one or by law . i say this because i worked for some who did service and did not even own a electrical meter **** brought one a fluke meter and case for him zero thank you too ,i know this as one of buddha four noble truths . This is not to put all of them in one bunch there are a few but in the grand sense most say there s no need . lol Remember in the father land plumbers do waste and vent thats thats and heating are heating tech different animal and there heating tech make us look silly for sure .

Personally the bigger the company the more the eye is off the ball and detail are forgotten and workers are a number and profit is king there are exception but be sure that it will cost $.

PS get a half way decent co detector plug in battery back up ,it may only alarm at 40 to 50 ppm but its better then waking up stupid or dead ,basement boiler room area ,bed rooms

peace and good luck clammy

can you look inside the boiler? you are looking up the draft hood up the vent. the collector box on top of the boiler connects in to the side of that box, can you look in there? there is some soot there which shouldn't be there. not enough to affect operation, at least here, but something is happening to make it.

you can also take the front cover off and take some pictures around the burner and up the bottom of the heat exchanger.

turn the switch off before you start sticking your hand and face inside so it doesn't accidentally fire with you in it.

Would you recommend a Harley, or an Indian, or are the foreign motorcycles like Honda OK? The passenger side mirror on my MiniVan says "OBJECTS IN THE MIRROR ARE LARGER THAN THEY APPEAR". Will that one work too?

But seriously: As other's have explained you do have a draft hood and the combustion test was taken from the wrong location. here are 5 diagrams from the instructions of a combustion analyzer that show the different types of gas heating appliances, and I have put Red Arrows to indicate the test location. If you look at the 4th diagram of a furnace with a similar draft hood to your boiler's draft hood you can clearly see that you need to place the probe inside the furnace from the underside of the box type draft hood. In that illustration there are 3 openings to that draft hood box where you need to take readings.

I have added one more illustration that depicts your boiler's draft hood, and the arrow showing the test location for CO, CO2, O2, and stack temperature from each separate section. this may reveal that the boiler is operating perfectly in all the sections but one. then you can look at the burner that feeds the one problem section.

Certainly some black soot there. If that is the top? how does it look from the bottom with a mirror?

I'm not sure about the yellow color, @captainco will know.

it is probably caused by lack of return water temp protection, the boiler is probably staying too cold and is condensing. it needs to have a thermostatic bypass or at least a manual bypass to keep the boiler temp up with all the mass in that system. is it a gravity conversion, are the original mains huge?