carbon monoxide detector setting

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What is the best setting for a co detector at a boiler.  I have one that sets of a alarm at 25 ppm, the gas company and energy audit guys are going around telling everyone they need  a new boiler or service above 35ppms. 

so what is the best setting when you check a boiler before the alarm goes of on your detector?

Tim McElwain

Pretty tough when

you place the CO detector near the boiler. If it has a draft hood it will typically spill for a few minutes before it starts to draft. This will cause some detectors to go off if too close to the boiler or furnace or any other equipment. CO detectors belong at the locations were we live for real protection. I suggest if you have to have a CO detector near the equipment get it at least 25 feet away from the draft hoods on the equipment.



The target for CO Air Free in the flue is 100 PPM or less for both gas and oil. If inspectors and audit personnel are shooting for 35 in the flue they would shut off just about every Mod/Con made.



This is not the first time this has come up with energy audit personnel and inspectors, someone is giving incorrect teaching on combustion analysis, but I am not surprised



If you are however having long term accumulation in the ambient air of 35 PPM Air Free then you need to address combustion issues with the equipment.

Jean-David Beyer

If inspectors and audit personnel ...

"If inspectors and audit personnel are shooting for 35 in the flue they would shut off just about every Mod/Con made."



Can you explain that for this non-professional? Do you really mean in the flue? I may be confused because my boiler has no draft hood.



I have a W-M Ultra 3 in my garage. The garage has two louvered vents that apparently pass code for running an oil boiler that gets its air from the space it is in. At least, the inspector never complained about it. Not sure how swift the inspectors are around here. I bet it does not really pass the code, since the high one is more than 12 inches from the ceiling, and the low one is higher than the top of the boiler, not within 12 inches of the floor. If the low one was within 12 inches of the floor, it would be below the snow level much of the winter.



My Ultra 3 gets its air from outside and it exhausts to outside. PVC pipe. It seems to me that even if the boiler is misadjusted and is putting out 1000 ppm of CO, I should be OK (except for my gas bill and what I am doing to the enviroment), unless the exhaust piping leaks. Spec says the combustion should be adjusted so that the CO is less than 60 ppm.

Tim McElwain

All equipment makes some CO

which is typically removed with the rest of the flue products such as CO2,O2,  water vapor, nitrous oxides etc. Many of the specifications for Mod/Cons when being adjusted and tested call for around 100 PPM air free CO or slightly higher. So 35 PPM would require all them to be shut down.



The Ultra along with many other Mod/Cons get their air for combustion from outdoors and vent flue gases to outdoors. The old requirements for air for combustion (12" from the ceiling and 12" from the floor) do not apply. These units still require annual cleaning and maintenance and a combustion test and any adjustments that must be made at that time.

Jean-David Beyer

Thank you.

As I suspected, then, my house probably violated code in several ways from when it was built until I had the old oil burner removed: Unless there was no code in about 1950.



1.) No pressure relief valve in boiler.

2.) No Low Water Detector on boiler.

3.) No anti-backflow valve in the supply. There was a pressure reducing valve, and what I thought would be a pressure relief valve (an assembly, painted red, with a big tag saying that valve was NOT the pressure relief valve required by the code).

4.) Boiler got its make up air from the room (garage) it was in, and the vents were improperly located. Furthermore, I never checked if the vents were large enough. And the former owner blocked off the lower one next to the boiler so the cold air coming in would not freeze the old style expansion tank. Since the new gas boiler is the sealed combustion type, the inspector said it might not need such big vents, but said I was not to close them off. I would not have bothered anyway.



That boiler, a downdraft GE, did not have a draft hood. Sometimes a technician would put in one of those things with a flapper so air from the room could be sucked in when the boiler stopped firing so the draft up the chimney would not cool off the boiler. At other times, the technician would remove it because he said a downdraft boiler did not require it (smoke pipe came out the bottom of the boiler).

rlaggren

From my lessons on codes and gas appliances...

At various times in my plumbing career, I'd say numbers 2-4 probably did not violate code at the time it was installed. #1 I'm not sure about, but in general codes have always been a place to _start_ when planning an installation, not a blue ribbon spec - IOW, they've always been lowest common denominator. But they _do_ keep getting stricter, although not always more sensible, so today we generally have better installations, by code, than in the past.



There is language about combustion air that states the openings must be above usual snow levels. There is also language which allows combustion air to be take directly from indoor space (with no special openings or ducting) if the space meets certain requirements - cubic volume per BTU being one of them and probably a max BTU. It's been years since I dealt with large spaces and I don't recall the specifics. Everything seems to be in a closet these days.



Rufus

Tim McElwain

JDB all that is in the past, I hope

you are happy with your gas equipment.



However to answer perhaps your past concerns # 2 and #3 were not always required and so due to its age may not have been code at the time.



I have a feeling the "Red" thing was a relief valve just not sized correctly perhaps for the boiler.



The fact that your oil boiler was in the garage presents other issues that thank goodness are not an issue with the new unit. That is that equipment installed in garages is required to be 18" off the floor. I do not know if that always applied to oil systems and just how far back it goes.



"That boiler, a downdraft GE, did not have a draft hood.  OIL BOILERS DO NOT USE A DRAFT HOOD ONLY GAS.Sometimes a technician would put in one of those things with a flapper so air from the room could be sucked in when the boiler stopped firing so the draft up the chimney would not cool off the boiler. At other times, the technician would remove it because he said a downdraft boiler did not require it (smoke pipe came out the bottom of the boiler)" THE THING WITH THE FLAPPER WAS PROBABLY A BAROMETRIC SINGLE SWING FOR OIL. I AM NOT SURE WHAT THE SPEC ON THAT REVERTIBLE FLUE BOILER WAS FOR OIL BUT FOR GAS CONVERSIONS WE HAD A SPECIAL ADAPTER WE INSTALLED INTO THE FLUE CONNECTION TO INSURE DRAFTING.



Wish you well with the new gas installation.

Jim Davis_3

CO alarm levels

Technically vented equipment should never put enough CO into a mechanical room to set off a detector at any level.  BPI has come up with a new CO standard that doesn't want more than 25ppm of CO in the actual flue gasses.  They really want to screw up equipment if they try to make it lower.  The most popular standard in the field today is 100ppm.  For this to set off an alarm in a room it would have to spill 100% for several minutes if not more.  CO dilutes considerably in free air so it takes a while to build up measureable levels unless it is producing a lot more than 100ppm.

Tim McElwain

Jim this BPI thing has come up several

times recently with inspectors doing energy audits and shutting off Mod/Con equipment with over 35 PPM air free. Now the National Grid people are doing the same thing. I have had several calls from factory reps wanting to know what I teach. I tell them 100 PPM or less is still my standard. Is someone mistakenly using the OSHA workplace standard for an eight hour period rule?

Jim Davis_3

BPI

When non-experienced HVAC persons start making rules things are going to get screwed up.

The fact that some CO analyzers can read 10-30ppm of CO higher than others because they are not NOX compensated makes it even worse.