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

[Nick Caton]

Hi all, 

 

The advice to invert the efficiency and zero out the pilot light is solid and something I've put into practice before as well... if anyone was still on the fence =).

 

If anyone's interested, on a related note I've got a top-secret baseline system calculator project... one of those pet projects I'm sure many of us have undertaken...  It's not complete yet (and likely will be ready to go as soon as 90.1-2010 makes it obsolete), but I along the way I have dug up and kept reference of a good resource for turning AFUE ratings into HIR inputs:

 

HIR = f(AFUE):  [Reference: California Energy Commission's 2005 "Nonresidential Alternative Calculation Method (ACM) Approval Manual"]

For single packaged central furnace (baseline system #3):  HIR = (.005163*AFUE+0.4033)^-1

For Boilers where 75 ≤ AFUE < 80 (Baseline systems #1, #5 &#7): HIR = (0.1*AFUE+72.5)^-1*100

For Boilers where 80 ≤ AFUE < 100 (Baseline systems #1, #5 &#7): HIR = (0.875*AFUE+10.5)^-1*100

 

~Nick

 

 

NICK CATON, P.E.

SENIOR ENGINEER

 

Smith & Boucher Engineers

25501 west valley parkway, suite 200

olathe, ks 66061

direct 913.344.0036

fax 913.345.0617

www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Carol Gardner
Sent: Thursday, June 23, 2011 2:01 PM
To: Bishop, Bill
Cc: eQUEST Users List
Subject: Re: [Equest-users] Furnace AFUE, Et, HIR and furnace fuel auxiliary

 

Yes and the quote from the calculator "furnaces & boilers after 1980 are to not have pilot lights" backs it up. So we all agree. I'll get right on those crankcase heaters for you.....



On Thu, Jun 23, 2011 at 11:02 AM, Bishop, Bill <wbishop at pathfinder-ea.com> wrote:

Carol,

 

I'll defer to Bruce's expertise on furnaces. Between his comments below, and the note in 90.1, Table 6.8.1E that I quoted below (in my second question), it would appear that we should use 0 as the default eQUEST value for Furnace Fuel Auxiliary. You can still enter a non-zero value if modeling an old furnace, using your pilot light calculator to show savings as an ECM. Now Google "energy use of air conditioner crankcase heater" and help me figure out the eQUEST default for CRANKCASE-HEAT. ;)

 

Bill

 

From: Carol Gardner [mailto:cmg750 at gmail.com] 
Sent: Thursday, June 23, 2011 1:43 PM
To: Bishop, Bill
Cc: Bruce Easterbrook; eQUEST Users List


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

 

Hi Bill,

I agree with your conclusions but got curious about boilers and pilot lights and their usage. I have to admit to being fairly ignorant when it comes to gas using equipment. So I did what I usually do and Googled energy use of a pilot light and came across this nice little website:
http://energyexperts.org/EnergySolutionsDatabase/ResourceDetail.aspx?id=4407
that had a link to a nice little calculator that can be used to calculate pilot light energy use:
http://www.wisconsinpublicservice.com/home/gas_calculator.aspx
When you are in the calculator there is "more info" next to the furnace line and it includes the following information "natural gas furnaces and boilers have been required to have pilotless ignitions since 1980". That would mean that the eQUEST default should be modified to be 0, right?

Carol

On Wed, Jun 22, 2011 at 6:43 AM, Bishop, Bill <wbishop at pathfinder-ea.com> wrote:

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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-- 
Carol Gardner PE




-- 
Carol Gardner PE

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