Janitrol furnace burning in burner tubes, out of ideas

Reply

  #1  
Old 03-21-19, 04:52 PM
Member
Thread Starter
Join Date: Mar 2019
Location: usa
Posts: 5
Janitrol furnace burning in burner tubes, out of ideas

Installed used NG Janitrol gas furnace in my work shop. Made necessary conversions to gas valve (Honeywell V800A) and orifices (now size 55) to convert to LP, propane.

Plumbed gas supply lines from twin 100 lb. tanks, ran power and thermostat. Fired up and burner flames looked great, for about 30 seconds. Then individual burners began backfiring and when they did they continued to burn in the burner tube. Of course the perfect blue flame took on a yellow tinge and the burner generated a fairly loud roaring sound. There are 8 burner tubes. The order in which the burners backfire is fairly random and the first and last in line rarely backfire at all.

Checked output pressure and found it to be about 10" WC. Attempted to up the pressure at the gas valve but could not get above 10.5". No way to check input pressure on original valve.

Consulted with propane supplier, laying out all my actions and findings. They concluded that I need a new gas valve. Bought one, installed today (Honeywell VR8200) and guess what? Exactly same problem.

I was able to monitor both input and output pressures on the new valve since it did have both ports. Don't know what the readings reveal. Generally, I could adjust the output pressure from about 9" to 10.5". The input pressure measured 14.5" in static mode (burner valve closed), and dropped to about 11" when burner valve is open. After making various changes in output and input pressures, very little difference was seen at the burners.

Since the burners seem to burn perfectly for a short while when the furnace is first turned on and problem seems to occur more quickly when the burners are warm, I am wondering if the problem is linked to some change in the burner(s) when they get warm. There are no shutters on the burner tubes, so air-fuel mixture cannot be adjusted.

Supposedly, burning in burner tube is almost always attributed to low gas velocity. Since changing pressure the small amount I was able, made little difference, I'm wondering if the orifices are exactly the right size. Should I try larger or small orifices.

After spending, literally, days going up and down the ladder leading to the old furnace, I am desperate for new ideas.

Anybody?
 
Sponsored Links
  #2  
Old 03-21-19, 07:46 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 51,006
Likes Received: 163
Welcome to the forums.

Lot of guessing here. Do we have a model number for that Janitrol heater ?
 
  #3  
Old 03-22-19, 05:49 AM
Member
Join Date: Jan 2017
Location: USA
Posts: 487
what is the model number of the heater, it's rated input, the size of the gas line and it's length. From what you wrote, the input looks to be about 151,000 BTU's. based on a #55 orfice. A 100# cylinder of propane contains about 2,160,000 BTU or about 14 hours of run time per cylinder. There must be a regulator on the propane cylinder. See if can be adjusted to a higher pressure so the regulator in the gas valve has the ability to adjust to the required outlet pressure and be able to maintain a steady delivery pressure. BY the way; do you have some experiamce with furnaces and the like
 
  #4  
Old 03-22-19, 06:24 AM
Member
Join Date: Oct 2016
Posts: 1,162
Likes Received: 18
Does this thing start backfiring when the indoor blower comes on?
 
  #5  
Old 03-22-19, 07:20 AM
Member
Thread Starter
Join Date: Mar 2019
Location: usa
Posts: 5
Janitrol WH200

I think it's a Janitrol WH200. 200,000 BTUH input, net 156,000 BTUH.

Very little experience, compared to the last few weeks of trying to get this thing going.

No, the backfiring and internal burning occur regardless of whether the fan is going. As stated, the first popping and internal burning occurs within about 30 seconds of burners lighting. The blower usually doesn't start for several minutes.

I have tried upping the pressure on the upstream regulator at the bottles. Makes a little difference to the output pressure but symptom still persists. In fact the burner flames seem to be more yellow at the higher pressure, after they begin burning inside.

Thanks for your interest.
 
  #6  
Old 03-22-19, 09:35 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 51,006
Likes Received: 163
Typically..... not always.... a #50 is used for LP to attain an output of approx 25,000 but per burner.
Were the 55's included in the factory conversion kit ?

Did that heater have 45's or 47's for nat gas in place ?
 

Last edited by PJmax; 03-22-19 at 01:58 PM. Reason: correction
  #7  
Old 03-22-19, 12:19 PM
Member
Join Date: Jan 2017
Location: USA
Posts: 487
Looking at a propane orfice chart a #53 or a #54 drill size orfice is the correct size. No 2 charts are the same. One chart shows that a #54 orfice will flow 24,630 BTU's and another chart shows that a #53 orfice will flow 24,700 BTU's/ [email protected] 11.0 " WC. I would use the smaller size, the #54 to make sure that you do not overfire the unit. Your orfices are probably too small since the average flow using a #55 orfice is 18,850 BTU's /hour. Using a drill # chart, remember the larger the number the smaller the orfice hole. One more thing that you may want to consider is having a larger propane storage tank. Those 100# tanks will not supply a lot of flow at a low outside temperature. The removal of propane gas cools the remaining liquid and will drop the pressure quite quickly. Also you did not say what size the gas piping is. You may find that a propane heater is a pain in the a-- due to the complexities of a correct installation .
 
  #8  
Old 03-22-19, 04:41 PM
Member
Thread Starter
Join Date: Mar 2019
Location: usa
Posts: 5
The piping from the tanks to the unit is 1/2" black pipe, about 10 feet total length. Both original and new gas valve have 1/2" inlet and outlets. I think I bought the orifices from Supplyhouse separate from the valve conversion kit. Of course, the Janitrol heater is obsolete and found no support from the current owners of the brand.

One other new development after pittling with the furnace this morning. I figured I'm running out of options and nothing to lose, so I tried adjusting the air-fuel mixture by partially blocking the air supply at the orifice end of the burner tube. As stated, the burners do not have adjustable shutter, but they do have two approx. 1/4" holes on the top of the tube at the orifice end. The bottom of the burner tube is completely open.

I blocked off the small holes on top by placing a small piece of aluminum sheeting over them, crimping around the edge of the burner. Low and behold the burners did not backfire at all. Even after several minutes they burned fine. However, I was disappointed to hear them start to pop, though, once I replaced the access panel on the bottom of the furnace. Guessing with the panel in place the combustion air was directed more on the burner's orifice ends.

Figured I was getting very close to solving this problem, and tried changing outlet pressures but had little effect.

The backfiring now takes longer to occur and involves fewer burners, so I think we are getting close.

Per your analysis, moving up to a #54 orifices may do the trick.

Moving up to a larger propane tank may help as I was told by the supplier, but I intend to use the heater in my shop sparingly, and trying to keep my cost down as well. The new gas valve busted the budget on this project already. Too late to turn back now, though.
 
  #9  
Old 03-22-19, 04:55 PM
Member
Thread Starter
Join Date: Mar 2019
Location: usa
Posts: 5
Just checked. The original NG orifices are #42.
 
  #10  
Old 03-22-19, 05:01 PM
Member
Join Date: Oct 2016
Posts: 1,162
Likes Received: 18
I think playing with the burner like that is a very bad idea.
At a minimum you’ll need a combustion test to make sure the unit is burning clean.
If not, the unit will soot to a point that it will put most oil burners to shame.
LP, being its a petroleum byproduct, can and will soot very easily if not set up properly.
You’ll not be able to tell by just looking at the flame alone.
 
  #11  
Old 03-23-19, 05:10 AM
Member
Join Date: Jan 2017
Location: USA
Posts: 487
If you can, post a picture or the burner tubes in place and a picture of the top and bottom of the tubes. There may be parts missing. After making a few calls to heating associates I know They all said that a #53 orfice would pass about 24,700 BTU's @ 11.0 " WC and a #54 would flow about 21,200 BTU's @ 11.0" WC. Too much combustion air can cause the problem you are having. The #42 that you removed would flow about 24,800 BTU's of nat gas @ 3.5" WC. The Janitrol co was purchased by Goodman in 1982. A word of caution; check the overall chamber and flue passages for cracks that could put combustion products into the air stream and into your heated space. (very unsafe) check closely, they were known for this problem. my 2 cents.
 
  #12  
Old 03-25-19, 04:17 PM
Member
Thread Starter
Join Date: Mar 2019
Location: usa
Posts: 5
Near Solution

Name:  EntireBurner.jpg
Views: 33
Size:  87.8 KBName:  BurnerOrificeEnd.jpg
Views: 33
Size:  61.6 KBName:  BurnerOrificeEndTop.jpg
Views: 34
Size:  60.9 KBName:  BurnerOrificeHolesCovered.jpg
Views: 31
Size:  55.3 KB

Getting closer to solving this problem. It's looking more and more like I got some inaccurate info from my propane supplier when I first inquired about the correct size orifice when I made the conversion from natural gas.

Went back today and they realized their error. I need larger orifices. They drilled my #55's out to #54 and now furnace works perfectly. I realize I'm not completely out of the woods until it's tested under colder conditions. Currently it's about 50 degrees outside.

There was some concern about my 100 lb. tanks not being large enough to keep up with the 200,000 BTU furnace. Propane supplier suggested, if that problem develops, they would help me plumb the two tanks to act in parallel, which would provide the pressure I need, even when it's cold.

Thanks for all who helped me resolve my problem.
 
  #13  
Old 03-25-19, 04:21 PM
Member
Join Date: Oct 2016
Posts: 1,162
Likes Received: 18
Are you covering up the combustion air openings still with those covers?
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes