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Furnace air return port must be located at least 10’ from the combustion chamber(s) (where the burners are) of gas burning appliances or in a separate room. The exception from this requirement is when the furnace and other appliances (within that room and 10′) are using combustion air from the outside.
10′ distance or return air port located in other room is to prevent bi-products of combustion process from being sucked into the air circulation system and contaminating the apartment.
This next item is an extremely common and dangerous issue and in some way another variation of the first one. The furnaces are often manufactured and delivered for the installation without the bottom plate (under the blower). This feature allows to connect air return duct to the bottom of your furnace.
However, whenever this bottom connection is not used (air return duct connected to the furnace side wall), there must be a special metal plate installed over the opening to prevent bi-products of combustion and dust, lint from being sucked into the circulating air.
Look for a small push-button type switch along one of the edges of the blower compartment opening – this is a safety cut-off switch which disconnects the power to the furnace as soon as the blower compartment cover is removed.
The reason I asked you to use furnace service switch first is that installers tend to tape or by-pass this safety device when testing the new furnace during installation, and than forget to put it back in service.
If your condo has a single air return port (all rooms have only air supply registers), make sure that the bedroom and bathroom doors have at least ¾” of a clearance between the bottom edge and floor surface / threshold
Look where the PVC vent pipe connects with the furnace induced draft motor enclosure discharge which is usually at the furnace enclosure wall penetration. Most of the high efficiency furnace manufacturers recommend this joint to be sealed with high temperature RTV type sealant (not a regular silicon). The are two benefits from such connection;
Unfortunately, I rarely see an installation done correctly. It’s either loose / not sealed with anything (try to pull the PVC pipe from the joint), or it’s been bonded with PVC type solvent cement and already leaking condensate around the seam. Problem with the PVC type solvent cement is that it doesn’t bond properly to the other piece of plastic which is not a PVC type, and responds differently to exhaust gases temperature. Cement might hold for some time, but the joint will eventually crack and start leaking (look for stains around the seam).
Some manufacturers / designs require use of a rubber sleeve and metal clamps on this first furnace PVC vent pipe connection – make sure that clamps are tight – you should not be able to pull it apart (don’t force it). If it is loose, all you need to do is tight the clamp with a screwdriver.
Run furnace for 30 minutes and check connections on PVC pipe for any leaks / condensation buildup – they must be air tight and replaced if leaking (silicon repairs are not acceptable). You should check PVC vent pipe joints periodically for leaks.
Turn OFF the furnace, remove service panels (might be single or two) and check for any moisture, corrosion stains inside the enclosure. High efficiency / condensing furnaces produce acidic condensate during the combustion process which sometimes deteriorates seals, starts dripping onto the furnace components and accelerates corrosion.
If you spot any moisture stains inside the furnace enclosure, whatever is causing it must be serviced to prevent more and sometimes permanent damage to the furnace components.
All furnace metal vent pipe connections (single wall pipe) must be secured with screws (there should be 3 per connection), no duct tape (any kind) on vent pipe joints
If there are small gaps between the furnace vent pipe and an induced draft motor collar, it might be just missing a high temperature rubber gasket. Connection on the picture has an orange-red colored gasket but it requires reducing coupling between 3″ collar and 4″ diameter vent pipe.
Vent pipe connection between the furnace equipped with an induced draft motor and a tank type water heater must be WYE shaped / not a T type connection. This is required to prevent furnace exhaust gases from being pushed back into the the water heater vent pipe.
Furnace gas connection – no flexible appliance type gas connectors are permitted in Chicago (and Illinois). Peoples Gas allows CSST (Corrugated Stainless Steel Tubing) as a final connector for permanently installed appliances, such as water heater or furnace but I’ve seen only a few.
Gas supply line must have a so called drip leg installed to collect moisture from gas lines before it contaminates furnace gas valve
Furnace air filter, filter compartment and blower compartment
For furnaces installed on upper floors and / or in closets above the ceiling in your condo, there should be a drip pan under the air conditioning coil section (where two AC copper pipes penetrate furnace enclosure wall).
It must be plumbed to its termination point where it can be safely discharged. In such installations you should be able to see two drain pipes, one attached to the furnace enclosure (coil section) and second to the drip pan.
Some of them are very cheap and will give you very little or no benefit at all. Other waste gallons of water per day of operation.
Those were the most common problems I see during my Chicago condo furnace installation inspections.
There’s much more stuff to inspect in your condo -
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Jake bf2s.com
7 months ago
Very useful information looking to install a new furnace!!! thx for the info and the pics were fantastic!