boiler shuts down and restarts near end of heat cycle.


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Old 10-20-10, 01:44 PM
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boiler shuts down and restarts near end of heat cycle.

it is a wtgo4/l8124a.5 yrs old.had the annual last wk.not a big problem but wonder why it doesnt get up to hi temp,seems to cycle 160 to 170 w/ the hi lim at 200.the lo at 140 w diff at 10.the circ runs when the boiler shuts down.
 
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Old 10-20-10, 04:15 PM
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klockk, who set the high limit at 200? Turn it back to 180.

Are you using this boiler for your hot domestic water? or do you have a separate water heater?

I ask this because I may make some recommendations on the other two settings also... but I need to know if you are making hot water for the home with it.

You say the circ runs after the BURNER shuts down? For how long? until the thermostat is satisfied I presume?

The temperature gauge may be inaccurate. The aquastat may be inaccurate.
 
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Old 10-21-10, 05:26 AM
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thanks for reply.it is used for hot water summer&winter utilizing elec hot water htr,which is turned off.on a call for heat,the circ.&boiler start.when cold water is returned,the circ cycles&boiler keeps running.{normal}after the return gets warm,the boiler shuts down and restarts immediately{after purge}.the circ keeps running.it will do this 2,3,or more times at about 5-10 min intervals till the thermo satisfys and both the circ&boiler shut down.you say set it back to 180 ok.i tried all the way to 220-same results.
 
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Old 10-21-10, 05:34 AM
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Has this setup worked properly for you in the past? Or did this just start after the annual service?

Does the burner run for a long time before the boiler temperature reaches 160-170? If it does, I am wondering if it has some sort of max duty cycle. My dad has a Weil Mclain that will only fire for a certain amount of time before the burner shuts off.
 
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Old 10-21-10, 10:24 AM
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i think it always did it. for sure 3yrs ago. its 6th yr.coming up.i dont think it runs a long time.30 to 45 mins maybe.an hour tops.we have enough heat.it bothers me when it shuts down and starts right back up.
 
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Old 10-21-10, 04:24 PM
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What you are describing sounds as though it could be ALMOST normal operation, in certain cases. But, I'm not sure that the weather is cold enough yet for this... let me explain:

When the boiler gets a heat call, of course the burner should fire and the pump should start.

The water in the system starts heating up... and that heat is pumped to the home.

As the water temperature reaches the HIGH LIMIT setting, the BURNER will shut off [NORMAL] and the circ will continue to run, as long as the heat call continues.

There is a differential built into the HIGH LIMIT circuit. This is NOT the differential that is associated with the LOW LIMIT, and adjustable on the DIFF dial. The HIGH LIMIT DIFF is FIXED and NOT adjustable. The DIFF dial will have NO EFFECT on the HIGH LIMIT.

The HIGH LIMIT DIFF is 'typically' 10° on most aquastats. Some are 15°

As the system continues to run after the burner has shut off on High Limit, the water will cool because it is giving up the heat to the home.

When the water cools past the HIGH LIMIT minus the FIXED DIFF, the burner will fire again [NORMAL] and again heat the water to the High Limit, and shut down again.

This will continue as long as the thermostat calls for heat. It is doubtful that there is any 'timer' on the burner firing cycle.

The reason that I said it ALMOST sounds normal is because you said this:

shuts down and restarts immediately
Restarting IMMEDIATELY is NOT normal.

You also said "(after purge)" and this leads me to believe that you have an OIL fired boiler. Is that correct?

If this IS an oil fired unit, it is possible that the burner is shutting down for a reason OTHER than hitting high limit. When you had your annual, did you explain this to the tech? Did he shrug his shoulders and ignore you?
 
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Old 10-21-10, 04:27 PM
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In this weather, it would not be at all unusual for the water to not get very hot. The water is only going to get as hot as it needs to before the thermostat satisfies, and this will usually NOT be as hot as the high limit is set.

You may in fact have a problem with the burner losing it's flame.

You may have a problem with the aquastat, or primary control.

OR, you may not have a problem at all.
 
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Old 10-22-10, 11:23 AM
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thanks for the clear description i understand and agree.it is oil,a w/m wtgo4 w/ a riello f-40 burner which has an integral lockout{reset}for flameout.i dont reset it.i asked the tech and he said he"d heard of some doing that,sort of looking at the L8124a.if it was really hi-limit,shouldn"t there be a time lapse before restart?
 
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Old 10-22-10, 03:18 PM
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I'm not a Riello guru, but I can tell you that the controls on some of the other burners feature both 'soft' and 'hard' lockouts. Also, if there is a 'flameout' while running, the control will attempt to restart the burner a few times before locking out. If the restart is successful, it won't lock out.

Maybe that's what you are seeing...

if it was really hi-limit,shouldn"t there be a time lapse before restart?
Yes... that's why I stressed "ALMOST" and "restarting IMMEDIATELY" in my previous post. Burner shutting down and restarting immediately is NOT normal.

From what you've said so far, I don't have a lot of confidence in your tech.
 
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Old 10-23-10, 02:04 PM
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hello thanks for reply.not cold enough now.will see what happens later in the season.
 
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Old 11-21-10, 09:26 AM
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now that its colder,i can add a little.i've installed pilot lites for circ and the boiler and both stay on when the shutdown-restart occur.i dont think its a flame-out,it's very smooth.i'm thinking the riello is timing out?{30-40mins]any info would be appreciated.tnx
 
 

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