I was working on a Jotul B vent stove yesterday and I came across a problem that I could not figure out...The customer stated that the unit would shut down if they operated the unit on high but other than that, the unit is fine. This stove is at least 20 years old. Put the stove through a service to include cleaning the pilot and ran the unit. Everything worked fine on high and I concluded a dirty pilot to the drop. Almost cleaned up and then the pilot started to drop. Main burner flame looks good but when the unit gets hot, the pilot will start to turn yellow and come off of the TC, turn the unit down and the pilot comes back. Cool everything down and works fine on high until the unit gets hot again. Going to replace pilot assembly but now Im guessing and I dont like to guess. Anybody have the same problem before???
Low gas pressure. Send me $150 in the mail. (:
I was thinking that but a few things were throwing me off. I was only losing the pilot when the unit gets hot, the main burner flame did not change, once cooled down after 8-10 min, everything was fine till it got hot again. No test ports on the valve so I cant monitor the valve pressures. At this point the customer does not want to put any money into it but I was looking for suggestions to keep in the back of my mind.
Once the unit heats up the draw up the vent lifts the weak pilot flame off the TC. Another thing could be that the unit doesn't vent well on high and could heat up the spill switch and shut down.
The first would have a tall straight vertical chimney, the second scenario may have a short rise, horizontal run and/or short chimney. There are some service calls where you may have to "stop the clock" to find the solution. For myself, resolution comes first and then the money will follow (with referrals, etc).
The yellow pilot is a sign of lack of pressure/volume. I had a DV today that had a yellow pilot and I pulled and cleaned the pilot orfice and that did not help. I pulled the pilot line and blew it out with compressed air and no more yellow pilot. Maybe something is blocking the pilot's gas supply when it gets hot.
That was my thought or something in the valve becomes blocked when hot...like I said, the main burner flame is not affected at all, no ghosting or anything. Thanks for the replies.
Check the orifice to ensure no one drilled it out. Clock the meter to ensure not over the max. firing rate. Check vent for obstructions in either intake or exhaust.
I've seen units with weird airflows in the combustion chamber. The pattern of the logs can have a great impact on this so ensure they are positioned per the mfr. Same for embers. Make sure any lint screen around the venturi is clean and properly positioned.
When pilots start acting up, techs start making pilot shields--I recommend you don't. I know every old timer has his success stories with shields but they are hit or miss and can cause other problems
Try to scope out the air intake baffles into the combustion chamber to ensure no blockage such as bugs or insulation.
Ensure the floor penetrations are gooped where the TP was replaced as too much air can be a problem, too. Ensure the fit of the glass.
Perform combustion analysis at cold start them progressively until pilot changes.
Conduct full load test on house gas. See if any appliances have been replaced recently.
A valve can get clogged up with crud to where it works sporadically. In this case, most combination valves are rated 175F. If the heat signature of the Fp changes, so can performance. Also, these valves have a pilot filter much like cigarette filters that can clog over time with oils and crud.
Being a B-vent, you always need to consider the air flows in and out. Combustion gases should exit the collar through a draft hood area into the vent and out. If there is a problem with venting, you can get a reduced flow of exhaust gases, which could acct. for the phenomenon you describe. If the vent is overdrafting, you can get a 'curtain effect' where room air is venting through the draft hood up the B-vent but the unit is venting out elsewhere, which is a real hazard. That's why the combustion analysis testing.
You want to test down by the air intake to see if the O2 drops below 20% as this occurs or the unti heats up. You of course want to test for CO spillage there and at the draft hood and glass seals, and test for flue gas analysis.
A yellow flame could be a drop in gas pressure but I would fist look at the air flow to the pilot and how it changes as the unti heats up.
Keep the fire inside the fireplace.
I think I would clean the pilot again. Have had many I thought I had cleaned and missed just a little lint. Does the pilot shrink at all when burner comes on??
Pilot did not change size until the burner was good and hot. I have not been back yet due to the busy time has just started for us in ohio.