# Rooftop or indoor furnace??



## andy.t (Jul 18, 2013)

Hey guys, ive been doing service on some light commercial air handlers and rooftops in our city and im running into a little debate of what to either new install or replace units. Im thinking rooftop all the way for indoor air quality with the make up air. Theres pros and cons for both but always good to hear some feedback, experiences and input!


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## johnh (Jul 6, 2013)

not knowing your heat loss but I would prefer a 90 percent efficient furnace installed indoors. It's more efficient, easier to maintain. A rooftop unit always goes down on the coldest day of the year. The standby heat loss on a indoor unit is considerbly less than a outdoor unit. my thoughts


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## PlungerJockey (Feb 19, 2010)

Your in Canada eh.

I would go indoor. Servicing a roof-top furnace on a cold Canadian day is not my idea of a good time.


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## andy.t (Jul 18, 2013)

ya eh! ha ... thats where the conversation is leading in our shop. nothing like a faulty code in -35..(...or i should say -31f) Other than the freezing serviceman on the roof though?.. i am a fan of a roof top...no mechanical room, air make up..?


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## CaberTosser (Mar 7, 2013)

I always wonder why every rooftop HVAC unit I've ever seen is so poorly insulated. I'd love to see some video from a FLIR camera on a police helicopter in the winter, every rooftop unit would be as bright as the freaking sun. They're easier for access for sure, but a miserable task to do in -35C. One thing you're not noting is that the building owners have them up there for a reason: square footage. Why put mechanical equipment in leasable space? Every square foot taken by equipment is space they're not able to collect rent on; they could give a rats patootie about a service techs convenience.


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## andy.t (Jul 18, 2013)

good point on the info red...and good thing most customers dont have choppers.. 
square footage is huge.. money money money... 

on a side note..any suggestions on insulating duct when there is return and heat exposed to the extremes? ive heard of a spray foam barrier that does a seal on it...of course r values are only as good as the thickness...ive heard of a quote...big dollars wasnt worth it..would make or break a tender.


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## Atomic Bearcat (Aug 9, 2013)

*From Experience*

If there's an RTU already in place, keep it. As others have said, why take up leasable space indoors? Not to mention the duct modifications/transitions to the new AHU. Most commercial space requires a certain amount of fresh air for the occupants. Packaged equipment is an extremely economical way to heat/cool a space as well as provide minimum OD air requirements.


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## rjbphd (Feb 5, 2010)

andy.t said:


> ya eh! ha ... thats where the conversation is leading in our shop. nothing like a faulty code in -35..(...or i should say -31f) Other than the freezing serviceman on the roof though?.. i am a fan of a roof top...no mechanical room, air make up..?


You can have all the RTU... I worked on them and don't enjoy carry and set up ladder and its freakin cold or freakin hot with wasp nests inside..


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## Catlin987987 (Nov 12, 2010)

I doubt you will find a furnace that can flow the cfm most RTUs move.


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## Atomic Bearcat (Aug 9, 2013)

Catlin987987 said:


> I doubt you will find a furnace that can flow the cfm most RTUs move.


Up to about 7.5 tons would be ok, but I think ESP on the duct system might be a bit out of range, depending on how much ductwork would need to be installed to reach the existing duct from the RTU.

Anything above 8 tons, and I think the expense of pulling the RTU off the roof, capping the curb watertight, installing the AHU, and adding a duct furnace or hot water coil, in addition to the ductwork would be excessive.


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## andy.t (Jul 18, 2013)

Ya I can see where higher cfms are needed a RTU is the way to go. Lots of good feedback guys. Thanks !


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