# High Efficiency and Combustion Air from Inside...thoughts



## jar546 (May 29, 2012)

From what I understand, the manufacturer's do not consider this a HE furnace anymore.


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## jar546 (May 29, 2012)

Oh yeah, and the receptacle is not TR or GFCI like it is required to be and NO it was not part of the furnace assembly, it was put there by the installer


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## globe trekker (May 29, 2012)

jar,

Is this installation the way the manufacturer requires it?   Shouldn't both pvc pipes extend

to the exterior?


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## Gregg Harris (May 29, 2012)

jar546 said:
			
		

> From what I understand, the manufacturer's do not consider this a HE furnace anymore.


Still listed and labeled as high efficiency installed as a single pipe or dual.


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## Gregg Harris (May 29, 2012)

Also look at NEC 422-12 Central heating equipment under exception #1 if the receptacle is part of the individual branch circuit does not require it to be GFI


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## jar546 (May 29, 2012)

Gregg Harris said:
			
		

> Also look at NEC 422-12 Central heating equipment under exception #1 if the receptacle is part of the individual branch circuit does not require it to be GFI


Don't see that.  What year?  Certainly not 2008


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## jar546 (May 29, 2012)

And certainly not 2011 NEC


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## jar546 (May 29, 2012)

Gregg Harris said:
			
		

> Also look at NEC 422-12 Central heating equipment under exception #1 if the receptacle is part of the individual branch circuit does not require it to be GFI


Nor 2005, 2008, 2011 NEC


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## jar546 (May 29, 2012)

Please stop me!

Not in 1993, 1996, 1999, 2002, 2005, 2008, 2011


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## Doorman (May 29, 2012)

Well, how about  ’49, ’50, ’51, ’52, ’53, ’54, ’55, ’56, ’57, ’58′ 59′? Or maybe ’60, ’61, ’62, ’63, ’64, '65, '66, ’67, ’68, ’69, ’70 ...

With apologies to Johnny Cash.


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## jar546 (May 29, 2012)

Doorman said:
			
		

> Well, how about  ’49, ’50, ’51, ’52, ’53, ’54, ’55, ’56, ’57, ’58′ 59′? Or maybe ’60, ’61, ’62, ’63, ’64, '65, '66, ’67, ’68, ’69, ’70 ...With apologies to Johnny Cash.


I went back to 48.  Not kidding


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## Papio Bldg Dept (May 29, 2012)

Doorman said:
			
		

> Well, how about  ’49, ’50, ’51, ’52, ’53, ’54, ’55, ’56, ’57, ’58′ 59′? Or maybe ’60, ’61, ’62, ’63, ’64, '65, '66, ’67, ’68, ’69, ’70 ...With apologies to Johnny Cash.


was that a JC's reference for "one code at a time?"


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## Francis Vineyard (May 29, 2012)

It's gets confusing to remember it all with every code change cycle and even more so if a locality is enforcing one version of NEC and a different year of IRC.

The 2011 added exceptions for the TR and the 2005 had an exception for GFCI:

*2001 NEC*



*406.12 Tamper-Resistant Receptacles for Dwelling Units.*

In all areas specified in *210.52*, all nonlocking-type 125-volt, 15- and 20-ampere receptacles shall be listed tamper-resistant receptacles. 

_Exception: Receptacles in the following locations shall not be required to be tamper-resistant: _

*Changed From 2008*

• 406.12 & Exception: Revised to specify that the requirement applies to “nonlocking” type receptacles and to add a new exception providing specific conditions under which receptacles are not required to be tamper-resistant 

_(1) Receptacles located more than 1.7 m (5½ ft) above the floor. _

_(2) Receptacles that are part of a luminaire or appliance. _

_(3) A single receptacle or a duplex receptacle for two appliances located within dedicated space for each appliance that, in normal use, is not easily moved from one place to another and that is cord-and-plug connected in accordance with _*400.7(A)*_(6), (A)(7), or (A)(8). _

_(4) Nongrounding receptacles used for replacements as permitted in _*406.4(D)*_(2)(a). _



*2005 NEC*

*210.8 Ground-Fault Circuit-Interrupter Protection for Personnel *FPN: See *215.9* for ground-fault circuit-interrupter protection for personnel on feeders. 

*(A)* *Dwelling Units* All 125-volt, single-phase, 15- and 20-ampere receptacles installed in the locations specified in (1) through (8) shall have ground-fault circuit-interrupter protection for personnel. 

(1) Bathrooms 

(2) Garages, and also accessory buildings that have a floor located at or below grade level not intended as habitable rooms and limited to storage areas, work areas, and areas of similar use 

_Exception No. 1 to (2): Receptacles that are not readily accessible. _

_Exception No. 2 to (2): A single receptacle or a duplex receptacle for two appliances located within dedicated space for each appliance that, in normal use, is not easily moved from one place to another and that is cord-and-plug connected in accordance with __*400.7(A)(6)*__, __*(A)(7)*__, or __*(A)(8)*__. _

Receptacles installed under the exceptions to *210.8(A)(2)* shall not be considered as meeting the requirements of *210.52(G)*. 

(3) Outdoors 

_Exception to (3): Receptacles that are not readily accessible and are supplied by a dedicated branch circuit for electric snow-melting or deicing equipment shall be permitted to be installed in accordance with __*426.28*__. _

(4) Crawl spaces — at or below grade level 

(5) Unfinished basements — for purposes of this section, unfinished basements are defined as portions or areas of the basement not intended as habitable rooms and limited to storage areas, work areas, and the like 

_Exception No. 1 to (5): Receptacles that are not readily accessible. _

_Exception No. 2 to (5): A single receptacle or a duplex receptacle for two appliances located within dedicated space for each appliance that, in normal use, is not easily moved from one place to another and that is cord-and-plug connected in accordance with __*400.7(A)(6)*__, __*(A)(7)*__, or __*(A)(8)*__. _

_Exception No. 3 to (5): A receptacle supplying only a permanently installed fire alarm or burglar alarm system shall not be required to have ground-fault circuit-interrupter protection. _

Receptacles installed under the exceptions to *210.8(A)(5)* shall not be considered as meeting the requirements of *210.52(G)*. 

(6) Kitchens — where the receptacles are installed to serve the countertop surfaces 

(7) Laundry, utility, and wet bar sinks — where the receptacles are installed within 1.8 m (6 ft) of the outside edge of the sink 

*Changed From 2002*

• 210.8(A)(7): Revised to add laundry and utility sinks to the GFCI requirement. 



Francis


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## north star (May 29, 2012)

*= = =*

Papio,

Here's a link to Johnny's song... "One Piece At A Time" song

[ the consecutive,  muti-year variety  ]

*http://www.opel-p1.nl/onepieceatatime/index.htm*

*= = =*


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## MikeC (May 30, 2012)

While I know nothing of electrical requirements, being a "direct vent appliance", combustion air shall be provided per the manufacturer's instructions (IRC G2407.1).  In this case, the unit appears to be a Trane XB90.  Installation instructions do allow for indoor combustion are to be used as long as the criteria is met.  One of those criteria being 50 cubic ft per 1000 btu.

You will find that quite a few of these high efficiency appliances allow for the use of indoor combustion air.  It is still a high efficiency appliance, but the potential need for make up air to come from the outside may offset the high efficiency of the unit.  In some cases, manufacturer's will send you back to the "local codes" if indoor combustion air is used.  This really screws things up because it is a direct vent appliance and the code says to follow the manufacturer's instructions.


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## Papio Bldg Dept (May 30, 2012)

north star said:
			
		

> *= = =*Papio,
> 
> Here's a link to Johnny's song... "One Piece At A Time" song
> 
> ...


One of my all time JC favorites...thx north star!


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## Paul Sweet (May 31, 2012)

The high efficiency furnaces I'm familiar with require both pipes to terminate outside and within a foot or two of each other.  This is so wind gusts don't create unequal pressures that might trip a safety switch and shut the furnace down.


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## ICE (Jun 2, 2012)

Paul Sweet said:
			
		

> The high efficiency furnaces I'm familiar with require both pipes to terminate outside and within a foot or two of each other.  This is so wind gusts don't create unequal pressures that might trip a safety switch and shut the furnace down.


Some but not all.

http://www.inspectpa.com/forum/showthread.php?5619-Combustion-air&highlight=pressure+zone


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## Daddy-0- (Jun 2, 2012)

You can take combustion air from indoors if the room is large enough. This makes it a "non direct vent" appliance and changes the vent pipe clearances. Look for the non direct vent charts in the installation instructions.

Love me some Johnnie Cash too. "Life ain't easy for a boy named Sue."


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## MikeC (Jun 2, 2012)

I can only echo what Daddy-O- posted.  This is a catagory IV appliance regardless of where the combustion air comes from.  The fuel gas code is quite clear that it is to be installed per manufacturer's installation instructions.  In this case (for this individual appliance), so long as you don't encounter one of the requirements mandating outdoor combustion air, indoor air is okay.  It still allows for low temp venting through PVC or ABS.  The only difference I see between the indoor vs. outdoor is the maximum vent length.  Any time you encounter a catagory IV appliance, be sure to open the manual that should be attached to the appliance.  This is where you will find all of the information you need.


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## TheCommish (Jun 3, 2012)

regardless of the code(s) requiremnts, it seem to me that taking combustion air from the inside of the house and exausing it to the outside is a waste of energy, could cause back drafting of other apliances or problems with the combustion appliance if another  exauste fan pulls  the air out ot the space such as a jenaire grill or some of the monstorh ove the cook top fans I have seen.


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## Francis Vineyard (Jun 3, 2012)

Commish I agree with your sentiments and MikeC's

A leaky or drafty house may use more fuel to heat the home but it will not make the furnace less efficient; it still consumes less fuel per BTU’s.



The appliance efficiency doesn’t change because of where the combustion air originates. The real value in efficiency is based on annual energy consumption. In a perfect Energy Star home would be constructed air tight; all gas fired appliances would be direct vented and a high efficiency mechanical ventilation (ERV OR HRV) exchanges and provides fresh make up air.

Francis


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## Gregg Harris (Jun 4, 2012)

Other major issues that effect the efficiency of the HVAC system is that the airflow is rarely checked in heating or cooling. The gas pressure is rarely checked, and less than 5% of all gas appliances are set up with a combustion analyzer to adjust the combustion process of the appliance.


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## Keystone (Dec 10, 2012)

Expanding on JAR's example, with the furnace being assumed as installed within a basement would the basement now be considered a plenum?

IPC 502.2 Rooms used as a plenum.

Water heaters using solid, liquid or gas fuel shall not be installed in a room containing air-handling machinery when such room is used as a plenum.


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## ICE (Dec 10, 2012)

Keystone said:
			
		

> Expanding on JAR's example, with the furnace being assumed as installed within a basement would the basement now be considered a plenum?IPC 502.2 Rooms used as a plenum.
> 
> Water heaters using solid, liquid or gas fuel shall not be installed in a room containing air-handling machinery when such room is used as a plenum.


No.

*Plenum*.

An air compartment or chamber including uninhabited crawl spaces areas above a ceiling or below a floor, including air spaces below raised floors of computer/data processing centers or attic spaces, to that one or more ducts are connected and that *forms part of either the supply-air, return-air or exhaust-air system*, other than the occupied space being conditioned.


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