Chicago Condo Furnace Installation Most Common Problems


This chapter of the Chicago new condo inspection covers most common furnace installation issues (based on my inspections).

Condo furnace inspection - air return should not be placed closer than 10' from any area of combustion, or should be located in a separate roomCondo inspection - furnace combustion air and air return through the same louver doorsFurnace 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.

Chicago condo inspection - furnace air return compartment with a side duct and left open bottom / missing required metal plateCondo furnace inspection - air return compartment warning information tagThis 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.

Condo furnace inspection - missing bottom closure plate inside the air return compartmentHowever, 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.

  • Before you remove the furnace bottom cover to check for that closure plate, turn the appliance OFF – there must be a ON-OFF service switch mounted on the furnace enclosure or within the furnace closet – this is also a requirement.

Chicago condo furnace inspection - furnace blower compartment safety switchLook 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.

Chicago condo furnace inspection - with a forced air heating system and a single air return port installed in your condo, entry doors to heated - air conditioned rooms should be undercut three quarters of an inchIf 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

New condo high efficiency furnace with PVC vent pipe – most common issues

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;

  1. provides required air tight seam which is resistant to acidic condensate from the high efficiency furnace exhaust gases
  2. allows for easy separation for servicing purposes

Condo inspection - furnace PVC vent pipe must be sealed at furnace first connection with a high temperature RTV type sealantChicago condo furnace inspection - leaking PVC pipe joint at furnace wall penetrationUnfortunately, 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).

Condo furnace inspection manual - PVC vent pipe connected with rubber sleeve and metal clamps - one is missing
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.

Chicago condo furnace inspection -broken seal on high efficiency  furnace PVC vent pipe connection
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.

  • Furnace PVC vent pipe must be always sloped towards the furnace at ¼” per foot (minimum) to drain condensation through the furnace internal tubing system. If your furnace high efficiency vent pipe slopes down towards the exterior wall, there’s a possibility of ice buildup during the cold season which could block the exhaust pipe and shut down the furnace.

Chicago condo furnace inspection - corrosion caused by leaking connections inside the high efficiency furnaceTurn 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.

New condo regular furnace / metal vent pipe most common issues

  • Condo furnace vent pipe must always run upwards at a minimum of ¼” raise per foot

Condo new furnace inspection - all single wall vent pipe connections must be secured with screwsChicago new condo furnace inspection - furnace metal vent pipe joints must be secured with screwsAll 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

  • Condo furnace metal vent pipe must be the same size as the induced draft motor discharge end. If larger size pipe is used, such connection requires reducing coupling – look at the connection from underneath.

Chicago new condo furnace inspection - gas furnace metal vent pipe must be the same size as the induced draft motor discharge end. If larger size pipe is used, such connection requires reducing couplingIf 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.

  • Furnace double wall vent pipe connections have a twist and lock design and should not be secured with screws
  • Wherever the furnace vent pipe penetrates closet / utility room side wall or ceiling surface it must change to double wall before penetration, minimum 6” clearance to combustible materials for a single wall pipe / never inside the wall or ceiling
  • Your furnace vent pipe must be adequately supported along its entire length

Chicago condo furnace inspection - improper type of a connector used between the WH and an induced draft furnace - must be WYE type.Condo furnace inspection - WYE type connector is required between the furnace and a water heater 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.

Chicago new condo furnace inspection - flexible gas connectors are not permitted
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.

New condo furnace inspection - missing condensation drip leg on furnace gas supply lineChicago condo furnace inspection - white Teflon tape on gas pipe connections is not permitted Gas supply line must have a so called drip leg installed to collect moisture from gas lines before it contaminates furnace gas valve

  • No white Teflon tape is permitted on appliances gas pipes connections. There is a special yellow tinted Teflon tape designed for the gas pipe joints or several different types of sealants (paste like).

Some other issues to look for on you new Chicago condo furnace

Furnace air filter, filter compartment and blower compartment

  • Make sure that you can pull the filter out and install it without disassembling half of the furnace or destroying the filter in the process.
  • Blower compartment and furnace should be clean. They are often heavily contaminated after the construction and even changing several filters won’t prevent your new furniture from getting a white coat of plaster powder.

New condo furnace inspection - missing condensate discharge pipes on furnace installed above the bathroom ceilingFor 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.

  • Furnace humidifiers – a few different types so check my whole house humidifier post and let me know what you have so I can give you more details. If possible, ask the developer or his representative to explain how to operate and maintain your particular type of the whole house furnace humidifier.

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 –

Chicago Condo Inspection Manual

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1 Comment
  1. Jake says

    Very useful information looking to install a new furnace!!! thx for the info and the pics were fantastic!

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