fire place cycles

[bushrat]

Season Greetings

Got a Montigo fireplace (ME34DT-2) with a sit nova 820 valve.

Lites up ok, but after about 5mins, it starts to cycle on and off. The pilot stays lit.

Replaced both the thermal pile and couple (figured while I was there would replace both.)

Seamed Ok, then started to do it again. Checked the voltage of the thermal pile ~ 520 - 530mv on pilot only, but when I turn on the fire place, the voltage drops to about 220mv then slowly drops and stabalizes about 190mv.

Any Ideas would be appreciated

Cheers

[jtp10181]

does the TP mv stay at 190 while it is cycling? How fast does it cycle? Is the flame lifting or ghosting at all? Does it work with the glass off or cracked open a little on the bottom?

[oil lp man]

Switch or thermostat?
If thermostat, then the thermostat wire can't be too long or you will have voltage drop, like you have. 250 is normal millivolt reading with thermostat calling for heat.
Make sure you have millivolt thermostat, not a 24 volt thermostat.
If it is switched then the switch could have resistance causing voltage drop.
If it is a standard wall switch, not gold plated contacts, then this is common. If it is a factory toggle switch mounted on the fireplace then these frequently have problems too.

[oil lp man]

Originally posted by jtp10181
does the TP mv stay at 190 while it is cycling? How fast does it cycle? Is the flame lifting or ghosting at all? Does it work with the glass off or cracked open a little on the bottom?

I think you are more on the right track than I was since the longer it runs the lower the flame signal. Like the flame is being smothered.

[natgastech]

classic switch symptom....join the switch wires together and betcha it won't cycle.

[bushrat]

Thnaks for the replies.

No thermostat, just a wall switch - looks like just a normal light switch.

I turned up the pilot flame - seemed like it was a good size before -however figured more heat less voltage drop.
The voltage seems to stay above 200mv now and it SEEMS to have solved the problem.

HOWEVER - i'm not sure I've fixed anything, maybe just covered it up. Last year it worked fine with the pilot flame on a lower setting??????

I'll try the jumper idea as well.

Are there specific low resistant wall switchs for mV systems?

Interestinng idea about it being an air issue - I'll take a good look at the venting.

Cheers

[Edited by bushrat on 12-29-2005 at 11:12 AM]

[Collin]

Originally posted by bushrat
No thermostat, just a wall switch - looks like just a normal light switch.

I
Are there specific low resistant wall switchs for mV systems?

[Edited by bushrat on 12-29-2005 at 11:12 AM]

Flat style Decor switches are notorious for this problem.
Too much wire plus high switch resistance = trouble.

[blk]

get the volt meter out again & check your loss thru the wire & switch with switch on. if wires go directly from valve to switch (no safeties in=-between) your loss should be around 10mv. if greater then try flipping switch on/off several times and see if readings drop. If you cannot get them down to less than 20mv replace switch. You have checked all your wire connections & removed any un-necessary wire splices??????????

[natgastech]

Hey BLK, what units do you work on the most in Alberta?

[blk]

I work for the local utility, so we see just about every make and model out there. Most calls we get for them are usually no heat calls & check fireplace calls.One thing I have learnt over the years is that you can't properly trouble-shoot any unit without a good volt-meter and to know what your readings mean & where to take your readings. As you probably are aware, milli-volt systems(whether it's a fireplace,or any other appliance incorporating a milli-volt system) are very susceptible to millivolt loss for a number of different reasons , so knowing how to take proper readings is key to successful trouble-shooting. Our company used to sell&install gas fireplaces once apon a time, and we used to do warranty work on them as well as parts replacement, but since we do not sell them anymore we don't carry or replace parts anymore, other than thermopiles which we still carry on our service vehicles.

[natgastech]

BLK, ...After deregulation, the gas company (utility) here won't lift a finger to fix or lite anything. They just turn off the gas and say "yes you have a problem, call a local contractor." Does your utility just sell and distributed gas?

[blk]

Actually all our company does now is deliver the gas . At this time we are still doing service work although for how much longer well we'll have to wait and see. Things have definately changed with de-regulation here as well.We are still doing no heat calls, routine checks of appliances,gas odor + co calls ect. along with meter installs/exchanges(residential+commercial)and general maintenance to our system. I really enjoy the service work and will miss it if we loose it totally.