Author Topic: Unit heater in garage  (Read 490 times)

Offline Mmtc79

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Unit heater in garage
« on: October 06, 2017, 09:59:58 AM »
Just to clarify unit heaters vented horizontally must be stainless correct if cat 3 appliance
But yet I see so many with bvent out sidewalks ?

Offline Admin

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Re: Unit heater in garage
« Reply #1 on: October 06, 2017, 10:30:32 AM »
Yes, horizontal venting must be stainless steel on residential installations.  B-Vent can be used for vertical venting on most residential unit heaters I see.

Essentially, the CSA removed the UL listing from horizontal B vent installations for residential unit heaters.

Unit heaters are usually listed as Category I appliances for vertical vent installations.

All residential horizontally vented units manufactured after July of 2011 must be vented as a Caterory III Unit/Utility Heater in compliance with UL 1738 & ULS636.  For horizontal residential installations these units are certified as Category III appliances.

The Mr. Heater manual I see seems to contradict itself, and I don't do commercial work.

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Due to changes to Z83-8 2009 CSA2.6-2009, the use of single wall B-Vent is no longer permitted as an acceptable material when venting horizontally, this change covers both residential and commercial installations.


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Horizontal commercial installations are for buildings which are not attached to living spaces. The vent may be single wall vent material. 
  For some reason they refer to B-Vent as single wall.

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Category I appliance — an appliance that operates with a nonpositive vent static pressure and with a flue loss not less than 17%.
Note: This category consists of draft-hood-equipped appliances, appliances labelled as Category I, and fan-assisted appliances for venting into Type B vents.

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Category III appliance — an appliance that operates with a positive vent static pressure and with a flue loss not less than 17%.

The biggest challenge is satisfying Clause 7.28.3;

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Clause 7.28.3 - When installed in a garage, a minimum clearance of 8 ft (2.4 m) shall be maintained between the base of the heater and the garage floor. The minimum clearance may be reduced when a substantial guard is provided to prevent vehicles from striking the heater. See also Clause 4.16.

Offline Mmtc79

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Re: Unit heater in garage
« Reply #2 on: October 06, 2017, 10:54:21 AM »
Cheers thanks for your info

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Re: Unit heater in garage
« Reply #3 on: October 06, 2017, 11:41:47 AM »
I called Mr. Heater Tech Support 1-800-251-0001 to ask about horizontal venting in commercial applications. 

They said they made a mistake in the manual and that BOTH residential and commercial horizontal venting must be stainless steel.

And they confirmed they refer to B-Vent as a single wall vent.

Offline Mmtc79

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Re: Unit heater in garage
« Reply #4 on: October 06, 2017, 03:18:23 PM »
Yeah talked to them also what did he tell you about the condensate drain only needed for comercial ? One I'm looking at has no floor drain thinking condensate pump with a heat tracer on the pipe sounds like over kill

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Re: Unit heater in garage
« Reply #5 on: October 06, 2017, 06:35:53 PM »
Yes, the Mr. Heater manual I read (MHU50/80) says a drain line is only required on commercial installations.