Home Improvement Stack Exchange is a question and answer site for contractors and serious DIYers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

My boiler is shutting down into lock out mode, but I don't know what's causing it?

It will start on reset but shut down after a few minutes, but as of now it wont kick on at all.

I checked the pilot and it is on and fine.

I would like to know if this type and model has a flash code to tell what's wrong.

By the vent there is some kind sensor/motor type setup that was making noise and now has stopped altogether.

It' a Pennco 15045vf- Series gas heater.

share|improve this question
that model does not have a draft inducer and pressure sensor – john Nov 6 '12 at 19:16
dont know? its almost soundes like a starter or something. – john Nov 6 '12 at 19:59
it stars before the boiler whould come on. then shuts itself off.. when the boiler kicks in now its not working at all along with the boiler not firing up. – john Nov 6 '12 at 20:01
I am 15yr exp. computer tech/hardware specialist.and can probably fix it.. but i first need to know whats going wrong? – john Nov 6 '12 at 20:08
Does the unit display any error codes? – Tester101 Nov 6 '12 at 20:38

Normal sequence of operation

  • Thermostat calls for heat.
  • Circulator is activated.
  • Water temperature is monitored to determine if thermostat can be satisfied, without firing the burner.

If the boiler must fire.

  • Damper opens.
  • Blocked vent safety switch is closed.
  • Gas valve opens.
  • Burners ignite.

Safety switches and limits

High limit sensor

If the boiler overheats, this switch will open and the burner will shut down. The burner will remain off until the temperature drops below the high limit setting, the circulator will continue to run until the thermostat is satisfied.

Blocked vent safety switch

If this switch is open (vent is closed) the system will shut down, and should not be run until the cause is fixed.

Flame rollout switch

If the flame or exhaust gas backs up, this switch will shut the system down. As with the blocked vent switch, the system should not be run until the cause is fixed.


From your description, it sounds like the damper motor is not functioning properly. This causes the blocked vent safety switch to stay open, which does not allow the furnace to fire. This could be caused by a bad motor, a stuck damper, a malfunctioning switch/sensor elsewhere in the system, or even a bad control board. You'll have to physically diagnose the system (which can't be done over the internet), or call an HVAC technician to service the unit.

share|improve this answer
ok thanks again.. will do. – john Nov 6 '12 at 20:47
dude thanks so much i called for a hvac tech to come look at it. – john Nov 6 '12 at 22:03
if im right setting it to manual i will loose about 5% efficiency from my boiler? the only reason im asking is because im gonna be going to school for hvac soon myself. and i want to learn as much as i can. – john Nov 6 '12 at 22:27

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.