Furnace installation mistake

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wakramer

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I recently noticed that when my furnace was on, there was air being drawn in from the garage through open vents on the return end of the furnace. This is a York furnace that was installed as downflow, which isn't the default configuration. I believe these vents were intended for the supply side combustion air and either should have been blocked off for the downflow configuration or the panel should have been moved to the supply end. I don't understand how the original installer or the subsequent installer who added air conditioning didn't notice this. Luckily we have carbon monoxide detectors throughout the house.

Should I now be concerned that the supply end doesn't have adequate combustion air since it doesn't have these vents? As far as I can tell, the only source for combustion air is the gap around the exhaust vent.

How much did these open vents on the return end affect the efficiency of the furnace and A/C? I assume the amount of return air from inside of the house would have been reduced by the amount pulled in from the garage.

1674321112374.png
 

WorthFlorida

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I had three homes with gas furnaces/airhandler so I'm a little aware on how they work. As far as down flow, the burners and plenum are the same, flames go up. it's the position of the blower and burner is changed, blower on top, burner on bottom. If the unit is multi position, then it is designed for combustion air to enter as needed. Without knowing your model number, many gas furnaces use a draft induced motor instead of a standard draft chimney that works on raising warm air. I do see a 3 or 4 inch pipe to the left. Is that the gas exhaust vent, then you have a draft motor. HE furnaces do pipe in fresh air for combustion and another for exhaust.

At the thermostat lower the temp so the heater doesn't turn on and change the FAN to ON. Now check the air flow from the garage. If it feels the same then it is the duct work causing it. If it is less then the furnace is draining the air, which I see as good. It allows the house to breath and the furnace is drawing needed air from the outside and not from heated space from windows and doors.
 
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wakramer

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I had three homes with gas furnaces/airhandler so I'm a little aware on how they work. As far as down flow, the burners and plenum are the same, flames go up. it's the position of the blower and burner is changed, blower on top, burner on bottom. If the unit is multi position, then it is designed for combustion air to enter as needed. Without knowing your model number, many gas furnaces use a draft induced motor instead of a standard draft chimney that works on raising warm air. I do see a 3 or 4 inch pipe to the left. Is that the gas exhaust vent, then you have a draft motor. HE furnaces do pipe in fresh air for combustion and another for exhaust.

At the thermostat lower the temp so the heater doesn't turn on and change the FAN to ON. Now check the air flow from the garage. If it feels the same then it is the duct work causing it. If it is less then the furnace is draining the air, which I see as good. It allows the house to breath and the furnace is drawing needed air from the outside and not from heated space from windows and doors.

Yes, position of the blower is now on top and burner is on the bottom. It does have a draft induced motor. Yes, the pipe on the left is the gas exhaust vent. This isn't a high efficiency model.

When the thermostat is on the fan position, garage air is drawn into the return air side through those vents on top, effectively bypassing the filter and blowing unfiltered garage air into the house.
 

wakramer

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Maybe this helps illustrate the problem better. You can see the filter at the top and the vents open to the garage which pull in garage air after the filter. This can't be right.
Screenshot 2023-01-21 120638.png


Here is the only spot in the installation manual that shows those vent holes and they are only shown on the supply end. This unit has been reconfigured for down flow so those vent holes are now on the return end.

Screenshot 2023-01-21 120938.png
 

wakramer

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It is NOT right. It is stupid and wrong if it is in a garage or unconditioned space.
Thank you. Confirmation that the contractors messed up when they originally installed it and that the A/C contractors didn't notice it either. This house has had some unconditioned and unfiltered garage air blowing through the vents for the last 11 years. I imagine this reduced efficiency not to mention it caused dirty air to be blown into the house.
 

Fitter30

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Take a piece of sheet metal block off the louvers on the bottom side caulk around the edges for a tight leakage free panel. Look at the blower wheel if it's dirty the blower needs to cleaned and if theres ac the evaporator is also dirty. The door might need some sort of foam gasket might find something in weather stripping. Yorks install manual doesn't show much is there a separate air intake for combustion air?
 
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wakramer

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Take a piece of sheet metal block off the louvers on the bottom side caulk around the edges for a tight leakage free panel. Look at the blower wheel if it's dirty the blower needs to cleaned and if theres ac the evaporator is also dirty. The door might need some sort of foam gasket might find something in weather stripping. Yorks install manual doesn't show much is there a separate air intake for combustion air?
I don't see a separate air intake for combustion air. There are no louvers on the cover either. The only place I see for combustion air to enter is the gap around the exhaust pipe.
 

Fitter30

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Pop out one of the caps where the flue could penetrate in the burner compartment for air. Surprised burner and heat exchanger aren't full of soot. Could call the installer back on the premise could of died by Co.
 

WorthFlorida

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Thanks for the picture.
The only manual I could find was at https://www.manualslib.com/manual/1037498/Coleman-Tg8s.html?page=3#manual. Coleman probably had a York unit relabeled. Very common in the HVAC industry.

Multi position does not mean any position and working for nearly forty years in telecommunications, I've learned that marketing and sales will do anything to make their numbers. Documentation, specifications and brochures will never mention what the product cannot do.

The only reference for down flow is a reference for combustion clearance but it looks more like a general table for any model. Everything else is horizontal or up flow. It doesn't look like your unit was designed for down flow. Normally the top half and botton would would be swapped with the cabinet. As far as air volume, the house was pressurized while the blower was running. You may have noticed air rushing out as you opened an exterior door.

As long as the burner has combustible air do cap off that grill as other have suggested. After 11 years the blower may really be dirty. The blower drum fins get filled with dust and moisture seem to turn it into a sold. If you can look in the blower wheel and it looks bad, you should pull the blower assembly. Even with a good filter regiment, fine particles will stick the the drum.

This is a simple video
 
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