A good friend and I have been conversing over his problem. I'm a GC and sub all my HVAC/tinning work... so I'm a layman in this regard.
Jim may have gotten long winded in his e-mail, but I've tried to synopsize it: as follows......
Have a situation and would appreciate input from you.
(Lots of background and then just a simple question.)
Last December, we had the crawl space and attic sealed and insulated. The company that did the work (GB3 Energy Solutions) preformed before and after CO and air leakage tests and installed two outside combustion air vents for the furnace, boiler and water heater. We also purchase a CO-Experts low level CO monitor.
We recently (on Oct 18th) had a new high efficiency furnace installed by Walrath Heating.
Since that time, the CO monitor alarm has gone off several times with readings of 58, 20, 17, 37 & 39 ppm.
A Walrath tech came out using a Bacharach Monoxor III which reads as low as 1 ppm and checked the new furnace, the boiler and the hot water heater, but was unable to get any reading. He suggested that perhaps the monitor was defective.
Meanwhile, early morning on 11/30, our Kidde CO monitor alarms went off. They go off at a level of 70ppm. We opened doors and windows, went outside and called 911. Fire Department came but by that time could only get a reading of 12 ppm in the crawlspace.
They called Xcel who sent a tech out and checked all three appliances and again could not find any readings.
We again called Walrath who sent another tech out. He spent a couple of hours testing and checking stuff and came to the conclusion that there is not adequate combustion air being provided to the boiler and water heater. He surmised that since most of the alarms were going off early in the morning that when those devices were firing up early in the morning, the vent stack was cold and we were experiencing back-drafting. He proposed running additional combustion air vents. He also left a CO-Experts model 2014 CO Monitor.
That monitor alarm promptly went off the next morning with a reading of 13 ppm.
The rep from Walrath called me on Monday, restating what the tech had said. . It was suggested that I contact GB3 to see if they would stand behind their work and install the additional venting.
One of the owners from GB3 called and scheduled an appointment yesterday morning to find the source and cause of the CO.
That tech ran numerous tests on the devices and determined (and then showed me the tests and readings) that the problem is not inadequate combustion air, but rather that the new furnace fan is so much more powerful that the old furnace fan that it is creating negative pressure in the crawl space as it is drawing air from the gaps in the return ductwork which in turn is causing the water heater to back draft. The recommended solution is to seal the return air ducts.
The GB3 owner called this afternoon to confirm the techs findings. He indicated that since they are in the business of sealing homes, they need to be aware of air flow requirements, etc, and are trained and have the equipment to run the tests.
Thanks in advance,
UPDATE: Since this time, or at my questions, some other points.
1) Jim had (GB3) do his return airducting in the crawl space completely sealed (in hopes of alleviating an negative pressure and backdrafting)
The co monitors still went off at 25-50 ppm, even with his trap door open to the crawl space.
2) Both companys have inspected his current boiler and WH venting and found it to be properly functioning.
3) His new furnace is a 96% Rheem with dual stage, properly vented to outside. Jim did mention that it was very noisy and seemingly more powerfull blower than old furnace, when he had no problem and it was conventionally vented thru a separate chase than the boiler and WH currently.
4) Although a big crawl space, it was insulated and sealked, but the GB3 put in both a high and low 6" combustion air supply venting.
5) The new furnace is horizontally set, and there appears with testing to be no leaks causing a negative pressurization.
6) The new furnace has a PSC motor... not a variable speed... but I am unaware if that can be set to different speeds with jumpers. Jim notes that it blows like all hell.
Any ideas.... Jim is about to install more combustion air venting (after sealing the crawlspace which runs under main living quarters
)
TIA
Peter
EDIT: Additionally, the CO going off does not seem related to any strange windy occurances.
