# HTP Elite ModCon banging at ignition



## markb (Jun 11, 2009)

Hey ya'll,

Just got my gas ticket and am getting sent to service boilers we have installed in the past. Piping boilers and system design is my forte, service is something I have limited experience with. (been a licenced plumber for all my adult life....before someone tears my head off and blocks this thread).

I was sent to service a HTP Elite 299,99 today. Boiler makes "whoosh" sound and bangs at ignition. I ran a combustion analysis. CO and CO2 are within range at high fire and low fire. The only reading I see off the charts is during ignition, the CO PPM jumps to over 700PPM (supposed to read less than 100). I spent 30 minutes adjusting the gas valve, but very little change. Any advice from experienced gas techs would be very much appreciated.


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## plumbdrum (Nov 30, 2013)

What's your gas pressure reading on a manometer?


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## markb (Jun 11, 2009)

10.5"


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## CTs2p2 (Dec 6, 2011)

Rough age of the unit?
And did you check the ignitor?


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## plumbdrum (Nov 30, 2013)

LP or nat gas?


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## Plumber patt (Jan 26, 2011)

HSI or Spark ignition?


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## markb (Jun 11, 2009)

One year old. Ng. Spark


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## markb (Jun 11, 2009)

Did not check ignitor


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## Plumber patt (Jan 26, 2011)

Vfd ?


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## markb (Jun 11, 2009)

No video. Just imagine what a stick of dynamite sounds like


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## Plumber patt (Jan 26, 2011)

No, does it have a VFD for modulation?


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## markb (Jun 11, 2009)

not sure


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## Plumbworker (Oct 23, 2008)

Have you checked the gapping of the spark rod? excessive gap can cause delayed ignition aka bang. The burner tube also needs to be removed and blown clean from inside of burner tube with compressed air on a annual basis. The swirl plate between combustion blower and gas valve should also be checked and any build up cleaned.


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## bct p&h (Jan 19, 2013)

Is the gas pipe sized correctly?
Is there a regulator at the meter? If there is, how much pipe is between the regulator and the boiler?
Intake and exhaust clear? Is the venting done correctly?
Like others have said, check the igniter gap and clean the burner.
If you still can't figure it out call tech support or Emerson Swan in Massachusetts.


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## plumbdrum (Nov 30, 2013)

bct p&h said:


> Is the gas pipe sized correctly? Is there a regulator at the meter? If there is, how much pipe is between the regulator and the boiler? Intake and exhaust clear? Is the venting done correctly? Like others have said, check the igniter gap and clean the burner. If you still can't figure it out call tech support or Emerson Swan in Massachusetts.


If he bought the HTP from a supplier they rep Emerson Swan will help, if not he has to call whoever supplies it locally, or HTP.


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## Catlin987987 (Nov 12, 2010)

We have opened many of them and found them clogged up with debris and some kind of build up. 
We clean them out with Terosol cleaner then wash them out thoroughly, blocking the condensate and filling them/draining them multiple times.


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## bct p&h (Jan 19, 2013)

plumbdrum said:


> If he bought the HTP from a supplier they rep Emerson Swan will help, if not he has to call whoever supplies it locally, or HTP.


Never had that problem. Even when servicing htp boilers that I didn't install and had no idea where it came from they never turned my questions away.


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## PlumberDave (Jan 4, 2009)

By sound I'd say the boiler gas and air are mixed before being shoved through a flame arrestor screen into the firebox. But the flame arrestor screen has a few larger holes burnt into it causing whoosh boom sounds as the gas in the premix chamber is lit up on startup. No mater how you look at it, you are getting a build up gas before ignition.


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## Catlin987987 (Nov 12, 2010)

Well what ever happened to it?


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## markb (Jun 11, 2009)

My boss sent one of the more experienced guys to looks at it. Ill let you know what happens when I ask him next time I see him. 

Thanks for the suggestions, most likely a delayed ignition issue due to a dirty burner (they just did some landscaping work beside the vent and air supply terminations). Boiler probably sucked in some debris. Fan humming could probably be associated with debris as well considering the fresh air is blown into boiler casing and not directly into burner. 

I fell like a useless apprentice all over again! :thumbsup:


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## markb (Jun 11, 2009)

Turns out it was a problem with the regulator. Not enough gas. Had to increase gas size from 3/4" - 1" as well because of the gas tite. There you have it.


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