CAT IV Termonology

[Michael Thomas]

Is the fan on a CAT IV furnace still called the "inducer fan"?

[Bruce King]

I think induced draft fan is the correct name.

[Michael Thomas]

Thanks... I want this CMA report item to be 101% accurate: Cat IV furnace pulling combustion air from the utility area with no elbow to prevent debris entry (checked, the manufacturer allows CA from the interior)...

"Observation: Sounds of loose material tumbling around in the induced draft fan (the same principle as loose coins in a clothes dryer) were present when the furnace was operating.

Analysis: At the time of the first inspection drywall and other debris were noted at the air intake. Per contractor, between the first and second inspections debris was removed through the intake vent opening by developer's HVAC contractor by inserting the hose of a "shop vac". Debris was still present behind the access door at the time of the second inspection, and was visible withing the intake when examined with a "SeeSnake" remote viewing device. Per client request and with the consent of the developer's HVAC contractor (who was present at the second inspection) the furnace was operated during the second inspection in heating mode long enough (approximately 10 minutes) to establish that heat was present at all registers. Throughout the entire time the furnace was opening in the heating mode debris could be heard tumbling within the fan's housing. This indicates that debris has been sucked into some operating components of the furnace. This material could shorten the furnace's operating life and/or void the manufacturer's warranty if furnace operation is continued without its removal. (The manufacturer specifically prohibits the use of their furnaces as "construction heaters").


Recommendation: The furnace should not be further operated in the heating mode until it has been disassembled as required for removal of debris from all operating mechanisms, inspection for possible damage, and repair as required by a qualified, licensed and insured HVAC contractor."


The inducer obviously still contained a *lot* of construction debris, but the buyer insisted he wanted it run and the HVAC guy insisted it was fine to do so.


I do *not* want to get dinged by the buyer if this furnace fails prematurely - first time I've ever felt I should have a way to attach an audio recording to a report...

[Bob Harper]

An "inducer" induces a draft in a Cat.I fan assisted furnace. A Cat. IV appliance, venting with positive pressure, uses an " exhaust blower".

I don't care what the mfr. says, installing it with a depressurization fan is bad. If there are other atmospherically vented appliances in the Combustion Appliance Zone (CAZ), it can be deadly. If there is a second such furnace, one can backdraft the other. Ditto for a water heater. I've proven it before on actual cases.

There is no acceptable reason not to provide outside combustion air for a Cat.IV furnace directly. None.

Regardless, if there is debris in the blower, it must be repaired or replaced. Even if the debris is removed, it has probably damaged the impeller sufficiently to shorten its useful life. Should the exhaust blower fail, you are relying on the pressure switch and high limit switch to shut it down. However, due to the opening to the CAZ, this unit could continue to fire, venting into the home without tripping the safeties. If the ductwork isn't sealed, it will inhale the combustion gases and provide a nice CO distribution system for the home.

They need a low level CO monitor in that home, too. No UL 2034 junk.

HTH,
Bob

[Michael Thomas]

Bob,

Thanks for the reply.

If I get the chance, I always ask why they didn't install the second (intake) pipe, The usual answer (in the Chicago condo conversions ) is: "The inspector would not let me vent horizontally, so I had to go out the roof. He wouldn't let me have the intake through the wall if the exhaust is on the roof, so I would have had to run a second pipe to the roof."

On these El Cheapo conversions everything is about saving a buck - and pity the poor buyer: these are "starter" purchases, most buyers don't stay more than a few years, and it's going to be very difficult to get the association to pay for currently necessary repairs, let alone "preventive maintenance". This was worse than most - I actually thought at one point things were going to get physical with the developer.

[Michael Thomas]

"They need a low level CO monitor in that home, too. No UL 2034 junk..."

Buy a $120 CO alarm?

It will be major progress if I can convince them that that they need to get the developer to move these two smokes! (And yes, they are both smokes, NOT CO alarms).

[Don Matthews]

Michael,

I am relying on my somewhat feeble memory at the moment, but I believe that the IRC requires smoke detectors be installed within 2 feet of the highest point in a room and no closer than six-feet to a ceiling fan.

Maybe someone with a better memory (or a copy of the code book close at hand) can verify this information.

Has a CO been issued for this residence? Did the inspector conduct his inspection from the comfort of his vehicle?

[Jerry Peck]

The IRC states:
- R313.1 Smoke detection and notification. All smoke alarms shall be listed in accordance with UL 217 and installed in accordance with the provisions of this code and the household fire warning equipment provisions of NFPA 72. Household fire alarm systems installed in accordance with NFPA 72 that include smoke alarms, or a combination of smoke detector and audible notification device installed as required by this section for smoke alarms, shall be permitted. The household fire alarm system shall provide the same level of smoke detection and alarm as required by this section for smoke alarms in the event the fire alarm panel is removed or the system is not connected to a central station.

NFPA 72 states to the effect of: when on a ceiling no closer than 4" to the closest part of the smoke alarm to a wall; when on a wall, no closer than 4" to the closest part of the smoke alarm to a ceiling and no further than 12" to the closest part of the smoke alarm to a ceiling; peaked ceilings are addressed, but I've forgotten those dimensions right now - not closer than 4" to the peak to the closest part of the smoke alarm (I think), but there is also a maximum distance down (which I think is where the two slopes are 3' apart, but am not sure); not within 3' of a supply, tips of ceiling fan blades, and, for homes prior to 2007, not within 3' of a return (but this was dropped in the later edition).

Used to be basically not within 3' of an air disturbing source, now being within 3' of returns is okay.

Also, the 'not within 3' of a supply' also states 'not in the direct flow from the supply, so 'being 3' out in front of where the supply is blowing is not acceptable either - must also be off to the side and out of the supply air stream.

[Michael Thomas]

Manufacturer's installation instructions for the alarm in the picture: