<div dir="ltr"><div><div><div><div><div><div><div>Tom,<br><br></div>That's why you should make a spot test beforehand (though it's more applicable to oil burners it doesn't hurt to do it) and always wear a CO monitor in the boiler room. If CO went so high as to damage the sensor in the combustion analyzer, you've got a significant risk of poisoning should there be any spillage of combustion air in the boiler room.<br><br><br></div><div>As Jim said, the combustion efficiency is only part of the story. And I would add that you should do your combustion test at different operating point if you have a modulating burner, at least at low and high fire.<br>On 'small' (=non industrial boilers), and this is probably your case here since your boiler is 350 HP and you're in the Northeast, you tend to have a single jack shaft that adjusts both combustion air and fuel valve via linkages and cam trims, and that's not very accurate and hard to tune (if the guy tried to tune it at all). What I pretty much always see if that people tune for proper excess air at high fire only (around 15%), and excess air is MUCH higher (50% to 150% sometimes) at low fire so that they're at least on the safe side to avoid incomplete combustion and its associated health and safety risks, and this degrades the efficiency quite a bit.<br></div><div><br></div>As far as efficiencies are concerned, combustion efficiency is definitely only part of the problem (and you're measuring it at one point in time too), especially on steam systems. The time of the 'Dead men' to quote Dan Holohan is no longer, and steam systems are never working as best as they could due to improper knowledge of its inner working and bad 'upgrade' or hot fixes throughout their lifetime.<br><br></div>Short cycling could and pretty much always is a huge problem, a lot more than on water systems, and even more so when there's a coil in the steam boiler providing hot water.<br></div>The pressuretrols are rarely tuned properly, even on ON/OFF burners, and if you add a second ptrol (either Lo/Hi/Lo or modulating) things get even worse and mains and differentials are very often incoherent leading to never modulating the burners,cycling on pressure very often, etc. Layer the aquastat controlling boiler water temp and therefore DHW production and it's a mess.<br><br></div>If you have DHW, summer efficiency is always really bad: your boiler is tremendously oversized for the task, even with a high differential on the aquastat (which is never the case, it's either fixed at 5F or the differential is set at 5F too...), so you get really bad short cycling on top of really high standby losses. Expect a summer energy factor of around 0.4.<br><br></div><div><br></div>Now for heating season: typically energy factors are around .6 to .7. Could be lower if short cycling, etc. <br>I would also check: proper weighting of the barometric damper, jacket
and back of the boiler insulation (back of the boiler insulation on scotch marine boilers is on
the inside of the back door and tends to fall off based on my experience),
air leakage at burner mounting and boiler doors (rope gaskets usually), and I'd inquire about when they last cleaned the boiler and tuned the burner, and whether they add chemicals for scale, bleed the boiler, etc.<br><br><br></div><div>The boiler is only one part of the equation. The distribution can also be very problematic. Among things I've experienced first hand:<br><br></div><div>The classics:<br>- The good old "double-hung zone valve" = people using windows as
temperature control (walk in the streets of NYC on a cold day and count
the number of open windows, it's horrendous), though that's more on the air infiltration side... (long ago EDR were sized to provide enough heating for apartments with open windows, as people once were scared of diseases from foul air, and I think it has remained this way)<br></div><div>- Uninsulated piping (sometimes thousands of feet of it in large garden style complexes)<br></div><div>- Busted air vents on one-pipe steam spitting everywhere, busted steam traps on two pipe<br></div><div><br></div><div>The more exotic ones:<br></div><div>- Cut-off condensate line going directly to the drain (I'm not even kidding: the boiler was taking so much city water that it was completely rotted and almost not working anymore)<br></div><div>- Automatic water feeder + long time lag distribution + improper piping arrangement on the return (the height between the main and water line wasn't enough to push the water back to the boiler): Condensate can't get back, boiler line drops too low => the boiler takes in city water, at end of cycle condensate would start to come back, overflow the condensate tank and discharge 180F condensate to the drain<br></div><div><br><br></div><div><div><br></div><div>When you say you need 50% efficiency to calibrate, if you're not modeling part load efficiency nor standby/short cycling losses, I'm not surprised at all, though I would make damn sure I don't have another hidden problem in my model before and investigate more (especially the above) in the field to see if I can justify this dramatic efficiency.<br><br></div><div>I hope this helps,<br></div><div>Julien<br><div><br><br></div></div></div></div><div class="gmail_extra"><br clear="all"><div><div class="gmail_signature"><div dir="ltr"><div>--<br>Julien Marrec, EBCP, BPI MFBA<br>Energy&Sustainability Engineer<br>T: +33 6 95 14 42 13<br><span style="color:rgb(0,0,0)"><br></span><span style="color:rgb(0,0,0)">LinkedIn (en) : <span style="color:rgb(0,0,0)"><a href="http://www.linkedin.com/in/julienmarrec" target="_blank">www.linkedin.com/in/julienmarrec</a><br></span>LinkedIn (fr) : <a href="http://www.linkedin.com/in/julienmarrec/fr" target="_blank">www.linkedin.com/in/julienmarrec/fr</a></span><br><span style="color:rgb(0,0,0)"><a href="http://www.linkedin.com/in/julienmarrec" target="_blank"></a></span></div></div></div></div>
<br><div class="gmail_quote">2015-07-21 17:21 GMT+02:00 Jim Dirkes <span dir="ltr"><<a href="mailto:jim@buildingperformanceteam.com" target="_blank">jim@buildingperformanceteam.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_default" style="font-size:large;color:#b45f06">Tom,</div><div class="gmail_default" style="font-size:large;color:#b45f06"><br></div><div class="gmail_default" style="font-size:large;color:#b45f06">A Combustion analyzer tells only part of the story. </div><div class="gmail_default" style="font-size:large;color:#b45f06"><br></div><div class="gmail_default" style="font-size:large;color:#b45f06">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.</div><div class="gmail_default" style="font-size:large;color:#b45f06"><br></div><div class="gmail_default" style="font-size:large;color:#b45f06">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.</div></div><div class="gmail_extra"><br><div class="gmail_quote"><span class="">On Tue, Jul 21, 2015 at 10:35 AM, Davidson, Tom <span dir="ltr"><<a href="mailto:TDavidson@dlbassociates.com" target="_blank">TDavidson@dlbassociates.com</a>></span> wrote:<br></span><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div link="#3333CC" vlink="#B2B2B2" lang="EN-US"><div><span class=""><p class="MsoNormal">Dear Bldg-Sim list,<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">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.<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">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.<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">For reference the steam boiler we looked at is about 45 years old, made by the Federal Boiler Co. (Model AST 6 350).<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Thanks,<u></u><u></u></p><p class="MsoNormal">Tom<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p></span><table style="border-collapse:collapse" border="0" cellpadding="0" cellspacing="0"><tbody><tr><td style="border:none;border-bottom:solid windowtext 1.0pt;padding:0in 0in 0in 0in" valign="top"><p class="MsoNormal" style="text-align:left" align="left"><span style="font-size:10.5pt;font-family:"Verdana","sans-serif";color:black">Thomas A. Davidson, PE</span><span style="font-size:9.0pt;font-family:"Verdana","sans-serif";color:black"> <u></u><u></u></span></p></td></tr><tr><td style="padding:0in 0in 0in 0in" valign="top"><p class="MsoNormal" style="text-align:left" align="left"><span class=""><b><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";color:black">DLB Associates</span></b><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";color:black"> | 265 Industrial Way West | Eatontown, NJ 07724</span><span style="font-size:9.0pt;font-family:"Verdana","sans-serif";color:black"> </span></span><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";color:black"><br><a href="mailto:tdavidson@dlbassociates.com" target="_blank">tdavidson@dlbassociates.com</a> | <a href="tel:732-927-5108" value="+17329275108" target="_blank">732-927-5108</a> | f: <a href="tel:732-774-5000" value="+17327745000" target="_blank">732-774-5000</a></span><span style="font-size:9.0pt;font-family:"Verdana","sans-serif";color:black"> </span><span style="font-size:8.0pt;font-family:"Verdana","sans-serif";color:black"><br><span class=""><a href="http://www.dlbassociates.com" target="_blank"><span style="color:#0e4ead">DLB Website</span></a> | <a href="http://www.youtube.com/user/TheDLBAssociates" target="_blank"><span style="color:#cc181e">YouTube</span></a> | <a href="http://www.linkedin.com/company/dlb-associates" target="_blank"><span style="color:#1d87bd">LinkedIn</span></a> | <a href="http://twitter.com/DLBAssociates" target="_blank"><span style="color:#55acae">Twitter</span></a> | <a href="https://www.facebook.com/DLBAssociates" target="_blank"><span style="color:#43609c">Facebook</span></a></span></span><span style="font-size:9.0pt;font-family:"Verdana","sans-serif";color:black"> <u></u><u></u></span></p></td></tr></tbody></table><p class="MsoNormal"><u></u> <u></u></p></div></div><br>_______________________________________________<br>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><p><span style="font-size:10pt;font-family:Arial,sans-serif;color:black;background-image:initial;background-repeat:initial"></span></p>James V Dirkes II, PE, BEMP, LEED AP<br>CEO/President<br>The Building Performance Team Inc.<br>1631 Acacia Dr, GR, Mi 49504<br><br>Direct: 616.450.8653<br><a href="mailto:jim@buildingperformanceteam.com" target="_blank">jim@buildingperformanceteam.com</a><br><br><a href="http://buildingperformanceteamcom" target="_blank">Website </a>l <a href="https://www.linkedin.com/pub/jim-dirkes/7/444/413" target="_blank">LinkedIn</a><p style="margin-bottom:0in;margin-bottom:.0001pt;text-align:center" align="center"><b><i><span style="font-size:14.0pt;line-height:115%;font-family:"MS Reference Sans Serif","sans-serif""> </span></i></b><span style="font-family:"MS Reference Sans Serif","sans-serif""></span></p><p style="vertical-align:middle">
</p><p style="margin-bottom:6.0pt;text-autospace:none"><span style="font-size:10.0pt;font-family:"Calibri","sans-serif""><font color="#0000ff">Life is not easy. It’s never been easy. Expecting it to be easy
is not a healthy attitude.<br>
Relax. Refresh. Regroup. Carry on.</font></span></p></div></div></div></div></div></div></div></div></div></div></div></div></div></div>
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