Unit heater in garage

Started by Mmtc79, October 06, 2017, 09:59:58 AM

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Mmtc79

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 ?

Admin

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.

QuoteDue 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.

QuoteHorizontal 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.

QuoteCategory 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.

QuoteCategory 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;

QuoteClause 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.

Mmtc79


Admin

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.

Mmtc79

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

Admin

Yes, the Mr. Heater manual I read (MHU50/80) says a drain line is only required on commercial installations.