[Bldg-sim] Steam Boiler Efficiency Ranges

Jim Dirkes jim at buildingperformanceteam.com
Tue Jul 21 08:21:46 PDT 2015


Tom,

A Combustion analyzer tells only part of the story.

Some boilers cycle frequently due to being oversized (a common situation)
and (of course) when operating at part load.  The cycling brings some
inefficiency and it can be substantial. Hot water boilers, as I understand
it, are more impacted by these cycling losses than steam boilers.

For one of our projects, a steam boiler was losing water regularly via
condensate line leaks in a tunnel.  Our energy model, with pretty good
measurements of equipment power and other operating parameters, would only
match their utility meter readings when we used 52% peak boiler
efficiency.  The leaks apparently had  big impact on efficiency.

On Tue, Jul 21, 2015 at 10:35 AM, Davidson, Tom <TDavidson at dlbassociates.com
> wrote:

> Dear Bldg-Sim list,
>
>
>
> We are trying to determine the efficiency of an old gas-fired steam boiler
> that we plan to replace with a high-efficiency hot water boiler. We asked a
> company that tunes burners to take two combustion efficiency measurements –
> one before tuning and one after. Unfortunately the burner was operating so
> poorly prior to tuning that it messed up the combustion efficiency
> analyzer; it gave no readings and our opportunity to obtain a
> pre-implementation combustion efficiency value was lost. We do know that
> the burner was being starved of combustion air, but we aren’t sure by how
> much, or how low the efficiency of a gas-fired boiler can drop before its
> safeties shut it off.
>
>
>
> If anyone has successfully measured the efficiency of an operating boiler
> that is starved of combustion air, and is willing to share this efficiency,
> I would be quite grateful. I am looking your ‘worst of the worst’
> efficiency measurements. The rest of our energy model Is nicely aligned
> with facility usage, but we would need to drop the overall efficiency of
> this boiler to less than 50% to align with utility data, and even this
> value assumes that we are generous in terms of modeling warm winter
> temperature setpoints, high infiltration rates, etc.
>
>
>
> For reference the steam boiler we looked at is about 45 years old, made by
> the Federal Boiler Co. (Model AST 6 350).
>
>
>
> Thanks,
>
> Tom
>
>
>
> Thomas A. Davidson, PE
>
> *DLB Associates*  |  265 Industrial Way West  |  Eatontown, NJ 07724
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-- 

James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
1631 Acacia Dr, GR, Mi 49504

Direct: 616.450.8653
jim at buildingperformanceteam.com

Website <http://buildingperformanceteamcom>l  LinkedIn
<https://www.linkedin.com/pub/jim-dirkes/7/444/413>

 Life is not easy.  It’s never been easy. Expecting it to be easy is not a
healthy attitude.
Relax. Refresh. Regroup. Carry on.
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