Boiler maxes out at 140*F, cycles on but will not fire.

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Old 10-05-14, 12:29 PM
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Boiler maxes out at 140*F, cycles on but will not fire.

We have a combined heating plus hot water boiler by Heatmaker (136K BTU). It's about 18 yrs old and has had blower, igniter, heat exchanger, release valve and other parts changed out over the years. Usually gives us endless hot water for a bath or shower.

About 1 week ago we noticed the hot water in out shower would last less then 5 min so I checked the guages. Pressure is OK but the system heats up to only 140*F and then just tries to cycle but flame stops within a couple of seconds of starting. Normally, it would max out at 180*F and then stop cycling. When I let the system cool down to 90*F and then restart it fires up and stays on until it reached 140*F (takes about 5-6 min). I've looked but cannot find the regulator valve/knob that sets the HW temperature.

The Heatmaker has seperate coils for the Heat and the HW. The 140*F seems to be enough to drive all the radiators in the house but the HW for the shower gives up pretty quick.

Can somone explain why the system will not fire above 140* and point me in the right direction as to where the problem may be. Are the continuous attempts to fire and immediately shut off possibly damaging the system as it is getting no rest cycle at all. I've been turning the system right off when we don't need HW to minimize possible damage. The heating season has not started yet so we're OK in that department for the moment.
Thanks, Gerry
 
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Old 10-05-14, 01:46 PM
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Gerry, do you have the full model number of the boiler handy?
 
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Old 10-05-14, 04:33 PM
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Hey Trooper, thanks for getting back to me on this.
Yes, the combination boiler is a Trianco-Heatmaker Model: HW-M2.
Then there is another set of characters after that but they have been scratched out. I remember the installer telling me the rating of the
furnace was as manufactured 110K BTU but they modified it (??) so
the actual installation was 130K BTU. It did not have any problems for
almost 15 yrs and in the last 5 we've replaced several items as listed in my
original posting.

I've ordered the various parts from a Massachusets supplier and a local
professional boiler guy I used to work with here, but who has quit the trade,
had done all the installations. The system still works great... when it works.
 
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Old 10-05-14, 07:01 PM
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Boiler maxes out at 140*F, cycles on but will not fire

Here are a few pics of the boiler I took this evening.Name:  Heatmaker 1.jpg
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Size:  39.6 KBName:  Heatmaker 2.jpg
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Size:  28.8 KBName:  Heatmaker 3.jpg
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Size:  29.8 KBName:  Heatmeker 4.jpg
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Size:  32.3 KB
 
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Old 10-06-14, 06:31 AM
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Scanned through the manual for the boiler last night...

My ideas would be the "Low Limit Control" or the "Priority Relay".

Take a look at the 'troubleshooting chart' in the manual. None of the symptoms seem to describe exactly what you are saying, but perhaps it will give you a direction to look.
 
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Old 10-06-14, 10:17 AM
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Hi Trooper,
I've found the boiler manual on line. Thanks for that simple recommendation.
I'll get a voltmeter and try to isolate where the problem is. You're probably
right as several problems point to the low limit switch. That's a $60 item and
I could live with that. If it's a combustion chamber problem I may be looking
at $600-$1000 and I don't think that's a good investment for a 20 yr old unit.

Have you had any experience with the Trainco Heatmaker boilers? Do they
tend to be reliable over 20-30 yrs or do they konk out after a certain period?

As I mentioned, I've already replaced the combustion heat/exchanger, gas
burner, blower unit, the igniter, gaskets, fan impeller, expansion tank......

Gerry
 
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