# Can I cut into the side of a furnace?



## reload (Jun 3, 2011)

I just purchased a new (downflow) system for my "split-level" house including the a-coil, furnace and condenser unit. The old system was configured with the a-coil under the house, which I am not wanting to do anymore because of servicing issues.

Unfortunately, the new coil and furnace are too tall to go in the existing space without modifications. Also, as you can see from my drawing, I still need the plenum box at the bottom, so I can't really get rid of too much vertical distance on the supply end.

One thing I though about doing was to "cut" into the side of the furnace for the return air and then just plug the top. That would save me all that wasted space above the furnace.

I would love to have an opinion from the experts on this board, before I start cutting into my new furnace 

Also, just FYI, the blower motor is on the opposite side of where I would be cutting, so at least the air would be going directly into the side of the blower.

I can provide better explanation on any of this, if needed.

Please see my attached drawing, or if it is not attached, I will try to figure out another way to post it.

thanks!


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## Doc Holliday (Mar 12, 2011)

Yes, you can cut the side and mount a return air duct directly to the side of the furnace and blank off the rear. We do it all the time.


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## reload (Jun 3, 2011)

Thank you sir! Can you recommend a good tool to do the cutting?


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## Doc Holliday (Mar 12, 2011)

reload said:


> Thank you sir! Can you recommend a good tool to do the cutting?


 
Certainly. There is a tool made specifically for cutting holes, attaches to a drill. You'd have to be careful as the metal on a furnace is thicker than on a plenum so you run a greater risk of breaking the bit. 









If you use the above type hole cutter make certain you get one that cuts to your return duct size as the one pictured above is not the biggest one available.

Or you can just use some good old fashioned tin snips. Trace your collar which you can mount directly to the furnace and cut it by hand. 










They even make metal sheers in drill attachments or one piece hand held drill sheers.


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## reload (Jun 3, 2011)

Thanks a million! This is a great board and an incredible resource. I hope to return the favor to somebody, someday.


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## Doc Holliday (Mar 12, 2011)

It got better once I arrived. 

Come back if you have any problems, questions or concerns and we'll be glad to help.


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## angelas111 (May 27, 2011)

i used my angle grinder with a cutoff wheel to do the return hole in the furnace because it is a much thicker gauge steel than the plenum and i got too fatigued trying to use the tin snips. lots of sparks but it was a easy and clean hole to cut.


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## rlfranklin2 (May 21, 2014)

I see this as an old message, but one may also use a RotoZip tool with a metal cut off, please watch eyes! Suggest wearing long sleeves for metal bits and eye protection Always! In addition, one may use a saber saw with a metal saw blade attached, 14 teeth per inch should be good to use.
Cheers!


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