Burnham CHG DV boiler goes on...then goes off


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Old 12-19-10, 12:47 PM
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Burnham CHG DV boiler goes on...then goes off

Here are the specs...
Burnham CHG boiler
Direct Vent
forced hot water

Issue...
the boiler goes on...i see a nice blue flame. a few seconds later i hear the fan but the fan looks like it blows out the flame so the flame goes out and click the boiler is off again.

no error codes. it just calls for heat and the circulator keeps going.

moments later the boiler refires and same thing happens again.

any ideas?
it fires no problem...just won't stay fired/lit.
 
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Old 12-19-10, 12:58 PM
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That's this boiler for natural gas?

http://www.usboiler.burnham.com/pdf/CHG_lit.pdf



What fan is it that you hear turning on?

The only fan I'm aware of is the inducer motor which should be on before the burners light up.
 
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Old 12-19-10, 01:13 PM
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yes that's the boiler and yes it's natural gas.

it appears that there's a combustion air blower but i see the flame that's nice and blue and few seconds later i see the flames starts to get weak (looks like someone is blowing on it) and eventually die out...then click everything is off again.

from the manual....
The sequence of operation for a CHG series boiler on a call for heat from a thermostat is as described below:
a) When power is first turned on, 120V is provided to the MCBA, the combustion fan and the LWCO transformer.
A separate 50VA transformer, connected directly to the MCBA, powers all other low voltage circuits.
b) For the first few seconds after power-up the control module goes through a self check.
c) When there is a call for heat, the control module checks to make sure the air pressure switch is open. If it is, the
combustion fan will be energized and will ramp up to ignition speed. When the air pressure switch closes, a 10
second prepurge is activated.
d) After the prepurge, the control module energizes the gas control valve and the spark for 4.5 seconds. If a
flame is established and proved, the control allows the flame to stabilize for 5 seconds at the combustion fan
ignition speed setting. If the flame fails to prove, the control module will attempt to light the burner 4 more
times. If a flame is still not established, the control will lockout.
e) Once the flame stabilization period has ended, the MCBA allows the burner to modulate. The actual firing rate
is dependent upon the measured current and recent differences between the set point temperature and the supply
temperature. If an outdoor sensor is connected to the control module and the boiler is responding to a call for
heat, the set point temperature will be determined by the outdoor reset curve shown in Figure 11.4.
f) Once the set point temperature is reached, the MCBA will turn the burner off and allow the combustion fan to
operate in postpurge for 35 seconds before it turns off.
g) The central heating pump will continue to operate until the room thermostat has been satisfied.
h) A demand for domestic hot water (DHW) is given priority on CHG series boilers. If a call for DHW is received
while the boiler is responding to a call for heat, the heating circulator is deenergized until the call for DHW is
satisfied.
 

Last edited by mktbully; 12-19-10 at 01:36 PM.
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Old 12-19-10, 02:46 PM
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So is the fan turning on before the burners light as it should? You aren't hearing it start? Is it then speeding up to a higher speed that you do hear?
 
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Old 12-19-10, 08:06 PM
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Originally Posted by SeattlePioneer
So is the fan turning on before the burners light as it should? You aren't hearing it start? Is it then speeding up to a higher speed that you do hear?
yes the flame goes on...i hear the fan go on. everything sounds fine but then the fan picks up in speed and the flame goes out.

this happens in matter of 10 seconds...from the lighting and shutting down. the actual fire doesn't stay lit for more than 4-5 seconds and poof it's out. right before the flame going out i hear the fan picking up speed. it's almost like the flame is not strong enough or the fan is going way too fast.
 
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Old 12-20-10, 01:20 PM
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just to close the loop on this issue. the tech came in and it was discovered that the concentric exhaust/tube is leaking. so the exhaust is leaking into the intake which starved the boiler for fresh air (oxygen) hence it couldn't stay lit.
 
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Old 12-20-10, 03:31 PM
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Your repairman gets an A+ for nailing that one!
 
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Old 12-20-10, 06:32 PM
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3 calls to burnham tech, 4 hours, and $400 later.
still left with a leaking concentric vent (condensate is leaking out from it also). tech got the boiler's pulling air from the basement and left to go on another no heat call.

not that i'm not willing to pay for their time but it feels like i'm paying for the guy to do on the job training.
 
 

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