Janitrol furnace issue...........................(Starch)

Craig R Bergman

Have you tried to clean the pilot assm.? If the pilot isn't burning good the main burner can "suck" the pilot flame out.

Bergy

Joe Brix

Ok, I'm throwing in the towell.......

....client of mine bought a two story rental a couple years ago. Upper floor is heated by a newer Rheem 80% draft induced furnace, lower level by an old Janitrol model 20-100 natural draft. Both are tied into a common vent (which is another issue altogether, I have to look up the vent tables).

A year and a half ago, the gas company red tagged the janitrol for a leak. We found the gas valve bad, and replaced it. Everything has worked fine until a couple weeks ago when we were hit with a bit of a blizzard. Now, the pilot light will get blown out when the main burner ignites.

Gas pressure is good, draft downstream from the hood is a steady -.05" (and doesn't change a bit when the other furnace kicks on btw), heat exchanger is clean and draft is evident at the burners. I couldn't read the actual over fire draft, but "smoke tested" and don't see an issue with back pressure or the like.

When the burners light, there is a brief (and I mean VERY brief) flame rollout back into the manifold area - the flame will lick out about a half inch, and then "suck" back into the flues and behave normally. When the rollout occurs, the pilot gets snuffed. Sometimes it will relight, but usually won't. I have no idea why this started happening, or what may be causing it. I'm wondering if the original valve was a "slow opening" type?? That wouldn't explain, though, why the problem took 18 months to show up!

I'm throwing up my hands. Any thoughts?

Starch

Craig R Bergman

Pilot Assm.

Have you tried to clean the pilot assm.? If the pilot isn't burning good the main burner can "suck" the pilot flame out.

Bergy

Joe Brix

It's new...

...we replaced the pilot as'sy. about a month after changing the gas valve, as the old one had clogged. I should have mentioned that.....sorry!

The pilot flame is good and strong, and hitting both the thermocouple and the pilot train properly.

Starch

Ed_26

pilot

Has the hx been checked? Sometimes there is a buildup of soot/powder @ the top of the hx just below the baffles where the hx transitions to the draft hood. Or, the hx has deformed enough to slow the initial draft just enough. Also.. perhaps the manifold press. has changed?

don_185

If.

If the burner tube and tracks are all clean then, I would put the slow opening valve back inplace.

Its in there for a reason.The reason being the problem you are now having.

Joe Brix

Well......

...I am not sure if the original valve was a slow opening type or not! I was hoping someone here might have some old specs on this furnace.

don_185

Sorry John

I misread your post.Looked in some of the books I have and only thing I can get from your numbers is that its a 5 ton drive and firing 100000 btus.

Are you getting the rollout when it first start with no blower.Or with the blower running when it fires?

Any other lettering like gdt,gmp?

Joe Brix

No problem, Don!

The nameplate was very difficult to read, so that's the only number I could make out. It did say 100K input, 80K output, and a reference to the "Midland Ross" company in Columbus, Ohio. I was not able to see any other information.

To answer your other question, the rollout occurs ONLY on burner lightoff, regardless of whether the blower is running or not. As soon as the burners are lit, the flame then behaves as you would expect. As said before, I couldn't get an over fire draft reading, but "smoke" testing at the burner area showed draft through the heat exchanger before and after burner lightoff. My tech who istalled the gas valve was with me when we looked at it today. He "doesn't think" the rollout occured when he initially replaced the vavle. I'm wondering if replacing the pilot assembly with a standard Honeywell unit may be contributing to the problem - maybe the OEM one was designed differently?

I would love to just tell the guy he should have us replace the furnace, and I certainly will suggest doing so. If, however, this problem is actually a result of our putting in the "wrong" gas valve, I feel I should correct it. I just wish I knew if the original valve was a slow-opening type before I waste any more time.....

Starch

Dale

rollout

Couple of things, first confirm inlet and manifold pressure when the furnace comes on. Problem seems to be a lack of venting up through the heat exchanger sections, how do the burners look,clean and rust free? As a quick TEST try it with the vent pipe off, same rollout and a partially restricted heat exchanger. There are flow restrictors at the top of all old heat exchanger sections,take the top sheet metal off to pull them out, may be rusted up. Clean as much as you can from the outside. Let us know what you find. good luck.

jim lockard

Change the furnace


Do not waste your time trying to figure it out. Best Wishes J.Lockard

Unknown

John put a

step opening gas valve on the unit and that might help considerabley. Those units when they get old tend to have some swelling in the heat exchanger which changes the pressure in the chamber.

I also find that -.05 draft to be too high which could be resulting in "Curtain Effect" taking place. What is the draft before the draft hood (in the sections before the dilution air is mixed)?

lchmb

standard

I believe I have the book on that unit in the office and can look tomorrow, but I do believe the original valve was a step opening...Good luck...Either way, like Tim mentioned, it will probably solve your problem..