[Equest-users] Furnace AFUE, Et, HIR and furnace fuel auxiliary

[Bishop, Bill]

Thanks Bruce.

 

I appreciate your insight on the reasonable range of furnace
efficiencies. I was more concerned with how to model the baseline per
minimum ASHRAE efficiencies. Using my question numbering, I'm going with
these answers:

1.)    Warm Air Furnace

2.)    No pilot light

3.)    HIR=1.25

 

Bill

 

From: Bruce Easterbrook [mailto:bruce5 at bellnet.ca] 
Sent: Tuesday, June 21, 2011 8:57 PM
To: Bishop, Bill
Cc: eQUEST Users List
Subject: Re: [Equest-users] Furnace AFUE, Et, HIR and furnace fuel
auxiliary

 

Hi Bill,
I don't have a project to pull up to get to these inputs.  I believe I
normally enter the AFUE, and 78% is an medium oil number and a low gas
number.  Typically most gas units on the market will give you a 92% AFUE
for a condensing unit and a few are running in the 94% range.  Oil you
can get into the 84% range.  Don't do condensing oil, no one is using
the correct steel in the heat exchangers and they rot out after a few
years.  No units run with a pilot light anymore and you can see why, it
is all spark ignition.  I normally use a warm air furnace on a PSZ.  Use
78% for oil and 92% for gas, no pilot light for either.  You can adjust
everything later on the heating/unitary power tab.  Grain of salt, I
don't do LEED work, just 90.1.  For the project I have open I have a HIR
of 1.08 and 0 auxiliary, gas.   So I probably input 92% AFUE in the
wizard, no pilot light.
Bruce Easterbrook P.Eng.
Abode Engineering

On 21/06/2011 10:12 AM, Bishop, Bill wrote: 

When selecting "furnace" for the heat source, eQUEST adds 800 Btu/h for
furnace fuel auxiliary (pilot light) as default. The default 800 Btu/h
adds 12% to my baseline heating energy, so it is not trivial.

ASHRAE Standard 90.1, Table 6.8.1E lists minimum furnace efficiency
requirements.

What should I enter for Furnace HIR and Furnace Fuel Auxiliary for
Baseline System 3 (PSZ-AC) and the new 90.1-2010 Baseline System 9
(Heating & Ventilation; Warm-air furnace, gas-fired)?

 

First, which equipment type applies? Table 6.8.1E has three gas-fired
equipment types - Warm Air Furnace, Warm Air Duct Furnace, and Warm Air
Unit Heaters. I think both Systems 3 and 9 would be Warm Air Furnace,
since packaged (System 3) and ventilation (System 9) systems would seem
to preclude duct furnaces and unit heaters.

 

Second, does the note, "Units must also include an interrupted or
intermittent ignition device (IID)" mean that no pilot light should be
modeled? This note to Table 6.8.1E does not apply to Warm Air Furnaces
<225,000 Btu/h in 90.1-2004 or 90.1-2007, but applies to all Warm Air
Furnaces in 90.1-2010. This is a LEED 2.2 project but the building is
currently under construction.

 

Third, Warm Air Furnace minimum efficiency is 78% AFUE or 80% Et .
Should I use HIR=1.282 (78%) or HIR=1.25?

 

Thanks for your thoughts,

Bill

 

 

 

 
 
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