CO Testing Hole

In several of the inspections I have preformed, the furnaces have been tested for CO. Several had some cheap non thermal duct tape on them which has failed or is missing. The last home I was at has a 3/8 inch hole but doesn’t look to have been covered up at all, why furnace was operating you could feel quite jet of air / exhaust coming out of it. is this a problem? Its a reem furnace with pvc inlet and duct work and I thought you could test it outside for CO because it is a closed system?

anytime a system isn’t working as designed it’s a problem. a symple fix, yes, so me, i’d tell them how to fix it and suggest buying a c.o. alarm.

If the hole was in the discharge pvc it would be a big problem. In the ductwork it may be a test hole. Most test holes are smaller than 3/8 inch 1/4 usually. Could be where someone had checked deltaT. CO testing would be done on the inside.

Is it normal for a Inspector to drill a hole in the discharge pvc, while preforming a buyers inspection without permission to do so by the seller of the house?

My second question what is the recommended way to seal the hole in the pvc pipe? I’ve seen sealant, duct tape, metal backed tape and just nothing used to cover the hole. All the holes have been 3/8 to 1/4 on these type of furnaces.

not me. my inspections are “non-invasive”. meaning i don’t drill, cut, or dismantle anything. but removing a service panel that is meant to come off as part of normal use and care is o.k.

I certainly wouldn’t drill any holes either. To answer your other questions about holes in the ducts. I had a new 90 plus installed 3 years ago, I have a sevice contract on the furnace. Last year when they serviced the furnace they drilled a hole in the exhaust (PVC) and put a threaded nut in it. They also drilled a smalll hole in the heat duct to check for CO. When they finished they sealed the hole with clear caulk. When their here again on the 21st I plan to be here to see if they seal up the hole (I assume they will) I also plan to find out why the hole was drilled in the exhaust. I wasn’t here when they did the last maintenance.

I’ve never personally seen or used a CO detector that would fit (the probe) in a 3/8 hole. Maybe they were using a combustion analyzer. Checking flue gases for CO is pointless. You will find it.

:roll: Don’t know why a home inspector would drill a hole in the exhaust pipe, but hvac companies that have been trained in co/combustion analysis test in the exhaust. By testing for co from burner start up, blower turn on to burner shut down the condition of the furnace can be determined. Misaligned/dirty burners. Cracked heat exchanger leaking seams. Gas valve not shutting off fully.

Drilling a hole in the pvc is an accepted trade practice. Some localities require a threaded plug other allow hi temperature silicone sealant covered with a waterproof tape. Have copies of the letters from the manufacturers of B vent stating practice of drilling atest holes in B vent
nd sealing test holes in their product.

Exactly, I’ve tested combustion (mainly fuel oil). It hasn’t been a practice for the companies I’ve worked for to test gas fired (residential) furnaces. They burn very clean right out of the box and a lot of the new ones have no provision for making adjustments to fuel air mixtures. All this was in my former life as an HVAC tech.

That has been the case in the past with gas heating equipment. However there is a small core in the HVAC industry that are pushing to test gas just like oil even though the only adjustments that can be made is gas pressure. It’s an uphill battle to convince some that these tests need to be done and some days you fell like you have been ](*,) . Personally I have found a brand newly installed furnace creating high co in the flue. Everytime the blower came on the flame would be slowed down. You couldn’t see the flame very well through the burner observation box. The only way this was found was buy testing the flue gases. On removal of the heat exchanger and teardown found that someone at the factory had left a screw out to attach the primary cell to the transfer box to the secondary heat exchanger.

Just read the other day over at Heating Help dot com of a tech that tested a new boiler on startup producing over 4,000 ppm co. An orfice washer was left out of the burner assembly.

So don’t panic if you see drilled and plugged vent pipes the hvac folks that know what they are doing are making sure the equipment is safe.:wink:

Great that they are testing its the fact that they place a little bit of duct tape over the hole or nothing, Today did two inspection and found one with small hole drilled into the pvc exhaust pipe, no tape or plug or sealant applied to it. While furnace was on u could feel the warm exhaust blowing out the hole ‘hole found in pvc exhaust pipe, suggest hvac contractor inspect and repair as needed’ photo included in report.