How do you handle this???

Mark Eatherton

During my tours for the State, I am coming across numerous manufacturers of 82%, multi stage, multi fan assisted construction from numerous well known manufacturers. No need to mention them by name, because they and we know who they are, and they are all dealing with the same situation.



One of them required a minor air shutter adjustment to clean it up, but when I got nearer to a clean burn, the onboard pressure sensing switch kept dropping out with an error of Low Air... These manufacturers need to remember that high altitude works differently on their small diaphragms, and they need to offer a high altitude "fix" kit for those boilers being used above a certain altitude.



But what really caught my attention was a DHW, 4 stage, fan assisted boiler. Granted, it was not in the utmost ideal settings (it had a Tjernlund inducer, a barometric, and was drawing outside air for combustion), but it was in compliance, and had all the right pressures in the right places. This particular appliance had 2 blowers, for 4 gas valve/stages. It had settings varying between 120 degrees F and 140 degrees F, with each stage occupying about 5 degrees F between stages. (120, 125, 130, 135 with 5 degree differentials).



The boiler spent most of its time running on one stage of burner during the day, recovering small usages and system standby losses. At that point, the CO in the flue gas stream was around 2,400 ppm AF of CO. No adjustment of it could be done to make it right, because any adjustments with just one burner lit are going to negatively affect the other burner when it comes on. The only way the system burned clean was to have all burners and fans on at the same time. The CO dropped to 50 ppm with all four stages on line.



So, what's a feller to do? Damned if you do, culpable if you don't.



With the ECM technology being what it is, I would think that it is possible to stage blower speeds commensurate with burner stage operation, no? It is obvious that the excess air being introduced by the fixed fan speed was the major contributor to the CO production.



Suggestions?



TIA



ME

Mark Eatherton

Check this out ...

As found in a major boiler manufacturers I&O manual.



If no combustion analyzing

equipment (CO2 or O2) is available then a proper

adjustment of the air/fuel ratio (CO2 or O2) cannot be

accomplished. However, by briefly sniffing the flue

gases it is possible to determine if the CO2 or O2 is

within the proper range.



Really? A sniff test?



Glad I have an analyzer. The flue gas on the boilers I was testing today was well over 2,000 ppm. One of them spiked at 3,000 ppm.





SNIFFFFFF, clunk....



I guess their lawyers haven't read their O&M manuals, yet.



ME

Oak Park Electric

The knucklehead test

I almost find that amusing...  too bad it's NOT.  "If you do not have proper equipment, place nose and mouth directly over open flue outlet of unit, then inhale deeply.  If monoxide levels are within limits, you will remain conscious."   Reminds me of the time spent in HVAC / stationary engineering training.  We had several   "just kidding" diagnostic methods.  One was The Ol' Grab The Pipe Test, which involved grabbing the pipe and using the highly accurate human perception of temperature to check things like evaporator superheat, condenser subcooling, TXV operation, steam trap operation, and others.  Then there was The Polish Burning Test, applied when wiring a unit. 

1.  Do your wiring   2.  Turn power on   3. Sniff    4. If it smells like electric fire, you did something wrong.  

Mark Eatherton

We call that first test the oooh, ooooh, AHHH!!! test.....

'Cause that's what you do when your hand hits the REAL hot spot. AHHHHHHH!!!



The other test, we call the smoke test. Everyone knows that electricity is just in our imagination. It's actually smoke that the power authorities send through the wires. You can see them controlling it at the smoke stacks at the power plant. And when working on electrical equipment, if you let the smoke out, it's toast And it's done. And you're done, and on your way to find a new less defective component :-).



Welcome to the Wall by the way.



ME

Steamhead

Red-Tag it, Mark

that's the only way you will avoid liability if something goes bad. 

Oak Park Electric

Thanks

for the welcome, Mark.  I was a Wall Wart for a long time, and just recently started posting.  This site is such a great collection of knowledge and capability, I'm really glad I found it back when.