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Gas Assist For Large Log Burners W/Safety Features
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BBQMAN
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Joined: 13 Jun 2005
Posts: 15470
Location: Florida

PostPosted: Sun Aug 22 10 3:07 am    Post subject: Gas Assist For Large Log Burners W/Safety Features Reply with quote

I've been asked often over the years to post "how to" info on my log lighters.

I'm loathe to do so because of safety concerns.

Now that's not to say it can't be done, because I've been using a simple log lighter (low pressure valve, venturi, pipe with holes burner) for years and have had no issues.

Many pit manufacturers offer a log lighter option- Lone Star, Lang, DP to name a few.

But make up air, a smothered fire, etc. are dangerous combination's with any any LP device that in all reality has no safety other than common sense.

And this can be the end result:

http://www.thesmokering.com/forum/viewtopic.php?t=51291&postdays=0&postorder=asc&start=0

It's no secret that I cook a lot of BBQ.

And I fully well know how to burn logs without outside help from LP...............................but sleep is not overrated!

I contacted the head of the service department at Ole Hickory earlier this summer. I can't say enough about the top-notch assistance I got from them.

Apparently, I'm not the only BBQ nut that has made the request for their tried and true gas burner set up.

So here's how we did it:

Resources:

Ole Hickory:
www.olehickorypits.com

Watlow:
www.watlow.com

Cole Parmer
(example of simple temp control- digital are also available)
http://www.coleparmer.com/catalog/product_view.asp?sku=8900212

Grainger:
http://www.grainger.com/Grainger/wwg/search.shtml?searchQuery=solid+state+relay&op=search&Ntt=solid+state+relay&N=0&sst=All

http://www.grainger.com/Grainger/wwg/search.shtml?searchQuery=type+j+thrermocouple&op=search&Ntt=type+j+thrermocouple&N=0&sst=All

McMaster Carr

http://www.mcmaster.com/#ceramic-insulation/=8klurh
Insulation for back of firebox/electronics enclosure
Part #93235K11



Back side of unit (comes pre-wired ready for input AC) You are looking at a Honeywell electronically controlled gas valve, spark unit, and control box.

Note: Gas input is low pressure LP




"Delivery" side of the assembly- no spark/gas/ignition sensed at the pilot and the main valve does not turn on.

Also shows the blower that supplies the correct air to fuel mixture need for correct burn.




Type "J" Thermocouple w/4 foot lead.

Note: thermocouple should be long enough to connect DIRECTLY to the controller with no other connections.

If you use common wire for an extension, accuracy WILL suffer.




Omron 110/220V Solid State Relay



Watlow 935 Series Temp Controller w/PID and alarm features

Note #1: I already had the controller from a previous project. An alternative would be to get a controller (either electronic or analog) with a built in relay.

Note #2: I prefer SSRs due to their long longevity for on/off switching over standard "ice cube" style relays




Wired up!

2nd pic shows the output wires that go to the pre-wired burner package.






Basic wiring schematic:



So there you have it.

From the assembly point that this is at, all that is needed is a box to mount the burner, the correct wiring links and AC supply, and gas hookup to a low pressure regulator.

I bench tested the entire setup earlier (yes, it works)!.

I'll post a few "action" pics when the entire kit an caboodle gets installed into my cooker next week.

Part II The install:


This could be mounted to just about any cooker with a large enough firebox to support it.

Mine is 24x24x30

Stainless component box left over from another project:



It was too deep, so we cut 1 1/2 inches off the back side, and welded a new back on with side "ears" to mount it.

Also cut some scrap plate and covered all the extra holes. Silicone from the inside (this application doesn't need to be air-tight)



Cut the 4 1/8" hole in the component box after carefully locating where it needed to be in relation to the firebox:





Located the hole placement on the firebox, then drilled the pilot for the hole saw mandrel FIRST.

Double checked the placement from the inside of the firebox BEFORE drilling the final hole.


Much easier to re-locate the hole if it's a 1/4 inch rather than 4 1/8". Wink







Mounted the box with high temp ceramic insulation to protect the electronics from heat:





Gas line routed in through the bottom, electric through the side. Empty 90' cord grip is for air intake





Installed the control panel on top of the cooker:



And mounted the thermocouple in the cooker.


Not shown but I wire tied it to the middle of the rack support. I purposely got the cable long enough so I could move it IF I wanted to.



Houston, we have liftoff!






The "money shot".

Slow smoked ribs about 6 hrs at 250.

Very tasty, and hardly any propane flavor! Wink Rolling Eyes Laughing Laughing Laughing






A few "after notes":

My LP use was about 20 pounds for 14-15 hour cook. YMMV due to style of cooker, weather conditions, etc.

Of course the more wood you use, the less gas you need.

The controller needed very little fine tuning.

I set the offset to 10' to cover the difference between the analog and digital gauge temps.

I also set the hysteresis at a 20' set point so the controller did not rapidly cycle off/on/off/on/off/on etc.

The set-point is where the burner cuts off, then the temp drops 20' before it turns back on.

If I set it for 260 it stays right at 240-260 the whole cook.

And all kidding aside, there is no gas taste. The burner burns hot and clean like it should.

I own a gas oven (so do many folks and upscale restaurants) and I have never detected a gas flavor in that either.

Purists will debate that, so YMMV once again (MDN).

Happy cooking, and thanks for looking!
Cool

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Last edited by BBQMAN on Sat Jun 04 11 4:46 am; edited 9 times in total
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k.a.m.
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PostPosted: Sun Aug 22 10 3:43 am    Post subject: Reply with quote

Mike that is a serious set up. Thanks for sharing and I just bookmarked it. Very Happy
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seattlepitboss
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PostPosted: Sun Aug 22 10 5:58 am    Post subject: Reply with quote

Is that a temp controller or does it just shut things off if something isn't right? If it's a temp controller, it would have to have a pilot light, right? Can you post a picture of your burner showing the pilot light arrangement clearly?

If anyone wants to duplicate this do NOT go buy a gas valve. Thousands of those are thrown away every week as plumbers upgrade gas hot water heaters. Simply call a plumber and ask him to give you the next gas hot water heater he scraps out, and make sure you tell him you need the gas valve. It will save him dump fees and he will be glad to do it!

seattlepitboss
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BBQMAN
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PostPosted: Sun Aug 22 10 6:27 am    Post subject: Reply with quote

Quote:
Is that a temp controller or does it just shut things off if something isn't right? If it's a temp controller, it would have to have a pilot light, right? Can you post a picture of your burner showing the pilot light arrangement clearly?


Yes, it's a temp controller.

A cheaper version (electronic) can be had for under $100.00.

Watlow makes a simple analog version for about $150.00.

The gas valve is NOT what is found in most gas water heaters- which usually have a standing pilot light.

The gas furnace in my home is also far simpler- standing pilot there as well.

Unlike the above appliances which are readily open to outside air, a firebox is not the same animal (see note below).

I'm not going to disassemble the snout of the burner, but you can see the components.

The sequence is:

The controller senses a low temp through the pit thermocouple.

It in turns sends juice to the the relay, switching power directly to the burner.

The burner immediately turns on the fan, and a spark unit.

The spark unit lights a pilot.

Approximately 30 seconds later, if the thermocouple in the snout sees flame, the gas valve is allowed to send a rush of gas to the main burner.

When the temp in the pit is reached, the temp controller shuts off the AC to the burner assy, and the entire things shuts down.

The system "fails" in the open (no power) applied state.

No flame, no gas flows.

Further, the burner and oxygen source to run it are independent of the firebox. Note: this is one of the biggest problems that is overcome with this setup as opposed to others. Most firebox's are MUCH more airtight than your average gas grill. Gas flame and a low oxygen supply are a very dangerous combination

The obvious advantage (other than more even pit temps) is that I can burn logs same as always, and not worry that my temps fluctuate much do to the logs being spent.

I have friends out West (where wood is scarce and expensive) that swear by their OH and SP pits.
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Last edited by BBQMAN on Mon Aug 23 10 6:58 pm; edited 3 times in total
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BBQMAN
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PostPosted: Sun Aug 22 10 6:40 am    Post subject: Reply with quote

A note to do-it-yourself types:

As a tech with a background in automated machinery I of course thought of going that route.

The cost of the valve, Honeywell spark controls, the conversion box, along with the actual burner and modified blower add up to enough money that it just wasn't worth the $$ saving to have to dicker around getting things "just right".

For instance I had no idea the CFM requirements for the fan.

Plus the time involved in wiring etc.

It just wasn't worth the hassle (to me)

This unit is tried and true through both OH and SP.

Now you HVAC pro's that can get-r-done without going the pre-packaged route kudos to you.

The "average Joe" with "some" skills could do this modification in a safe manner.

In all honesty this isn't a project for a beginner, and it was (is) costly.
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Last edited by BBQMAN on Sun Aug 22 10 10:45 am; edited 1 time in total
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Hell Fire Grill
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PostPosted: Sun Aug 22 10 10:44 am    Post subject: Reply with quote

Are you going to take pics of your gas mod as you go? I'm interested in seeing the progress. Im not interested in gassing mine I just like to see stuff modded.
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BBQMAN
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PostPosted: Sun Aug 22 10 10:54 am    Post subject: Reply with quote

Hell Fire Grill wrote:
Are you going to take pics of your gas mod as you go? I'm interested in seeing the progress. Im not interested in gassing mine I just like to see stuff modded.


Of course, me too! Razz

I've been out of town the last few weeks and had some serious catching up to do when I hit the ground.

My buddy modded a stainless box to house the burner while I was away, and my Grainger box had arrived as well.

Spent some time today (just couldn't resist) putting things together and making sure everything functioned properly.

I'll show the box and holes blown through the firebox wall, mounting, and final results when I'm finished.

When the burner lights up it's like a jet on after-burner.

Bet it looks cool after dark!

I'm enthused about this project to say the least- it's been a long time coming. I still debated spending the jack to make it happen.

My busy season starts in October so the timing is just about right.
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daddywoofdawg
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PostPosted: Sun Aug 22 10 12:05 pm    Post subject: Reply with quote

So is this just a log lighter or would this work on my Gasser?when I'm away I'm afraid of the flame going out in the middle of a cook and looking for something to keep the flame lit or turn off the gas if the flame goes out.Would this project do that?
Do you have part numbers for this project and or source.
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jeepdad
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PostPosted: Sun Aug 22 10 9:53 pm    Post subject: Reply with quote

Mike, you should have a second unit to mod the lime tree....in case of frost....gotta save the lime tree! Very Happy Nice post.

--Dan
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BBQMAN
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PostPosted: Mon Aug 23 10 12:01 am    Post subject: Reply with quote

daddywoofdawg wrote:
So is this just a log lighter or would this work on my Gasser?when I'm away I'm afraid of the flame going out in the middle of a cook and looking for something to keep the flame lit or turn off the gas if the flame goes out.Would this project do that?
Do you have part numbers for this project and or source.


As stated at the title, this is a gas assist and would work just fine for your use (I'm familiar with your cooker).

The idea is (like an oven) you set the temp and walk away knowing that it will maintain said temp wood or not.

It is also a log lighter in the respect that anything you throw in front of it will burn.

I'll post links to the suppliers at the original post.

The thermocouple is available in various lengths, and as stated in the original thread choice of controllers will determine relay style (if any) and price.

I prefer quality parts, and this mod reflects that.
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seattlepitboss
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PostPosted: Mon Aug 23 10 12:33 am    Post subject: Reply with quote

Of course, such a system means you MUST be within reach of 110V power. Since I do a lot of cooking in sites where there isn't any power available, this wouldn't work for me. The surplus water heater types don't require any power, you have to manually light the pilot light which has to stay on for the duration of the cook. There is a thermopile above that pilot light which generates enough power to actuate the gas valve. If the flame goes out, the gas valve automatically shuts off. Temp control is achieved in the normal ways, which include varying gas pressure, opening or closing a gate valve to modulate gas flow, or modifying the air flow through the cooker.

I think the powered temp controller idea is great. You could bake bread in your smoker, in fact it simply becomes an outdoor oven to which you can add smoke. The use of a bang-bang temp controller means there will be swings in the temperature (minor) compared to the PID controllers, which can control temperature much more closely. For gas heat, though, those generally require a standing pilot light as well. Brewers use those, and it's really cool to watch the flames flickering off and on as the controller varies the pulse width to keep temps constant.

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BBQMAN
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PostPosted: Mon Aug 23 10 12:45 am    Post subject: Reply with quote

seattlepitboss, you make a good point, and yes that method would work.

Big disadvantage- once the pilot light goes out (for whatever reason) your done.

Furthermore, that's a realistic possibility in an enclosed air-poor firebox with a smoldering fire.

Reason #2 if the pilot goes out (do to the above situation) and the thermocouple in the burner snout still see's heat from the smoldering fire in the box., the gas comes on....................................not good.

This unit eliminates that problem as well (yes, I thought about it).

Most of us with commercial equipment have access to A/C and/or own gensets.

If the power goes out, everything re-sets when it comes back on.

Or, for fail safe operation use a UPS.

Need a remote setup and don't own a genset?

A deep cell battery and the proper size inverter would work as well.

Then again, a small genset is close to the cost of the above..................
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Last edited by BBQMAN on Mon Aug 23 10 7:01 pm; edited 1 time in total
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milt
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PostPosted: Mon Aug 23 10 1:59 am    Post subject: Reply with quote

I've been asked often over the years to post "how to" info on my log lighters.

I loathe to do so because of safety concerns.



Great topic Mike. I have never gone into great detail
about the gas hookups on my rigs for the same reason
since I don't have any safety backups on them. I also
don't have any hair on my arms or any eyebrows. Shocked Wink
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BBQMAN
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PostPosted: Wed Aug 25 10 5:33 am    Post subject: Reply with quote

Three solid days of rain here! Mad

Should have some install/action pics in the next couple of days......................
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vexter1
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PostPosted: Thu Aug 26 10 7:13 am    Post subject: Reply with quote

Awesome write up Mike!! Thanks for sharing - that is very cool!

Quick thought...

You know I see a lot of BBQ teams using Ole Hickory and Southern Pride pits on the circuit (they must do some catering on the side - that's a lot of pit for competition!) - and most of them run on forced air no propane to stay legal - I wonder if your setup could be retro fit to run like that as well?

Thanks again Mike!
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BBQMAN
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PostPosted: Sat Aug 28 10 10:52 pm    Post subject: Reply with quote

vexter1:

Good question!

I'm not sure on the answer, but would assume that it could be done (because it is by the commercial guys).

I would imagine it would be as simple as not turning on the gas, turning the power off to the igniter (it has an automatic repeat cycle if it doesn't see flame) and providing a secondary relay to run the fan only if the previous were in a shut off condition and the thermocouple/controller saw a low heat condition.

Hell Fire Grill:

I'll have the rest of the build pics up next week.

I'm waiting to get some high temp resistant ceramic type insulation for the air-gap between the component box and the firebox.

Temporarily using fiberglass but it's not a permanent solution....................

I did get the system up and running, and did a rib cook yesterday as an experiment.

Cooked a whole hog overnight for an event this evening and boy is this setup SWEET!
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BBQMAN
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PostPosted: Fri Sep 03 10 3:33 am    Post subject: Reply with quote

I'm done for now and the rest of the pics are posted. Cool
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killswitch505
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PostPosted: Thu Sep 23 10 4:00 pm    Post subject: Reply with quote

where the hell have i been this is the first time i've seen this Confused Confused ultra clean setup !!!! this is a must for my trailer rig!!! thanks BBQ man
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hvac81
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PostPosted: Sun Sep 26 10 7:21 pm    Post subject: Reply with quote

Good job Mike.
Thats the exact same setup I used for my Rotissery Pit.
100% safe and imparts no noticable flavors.



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BBQMAN
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PostPosted: Wed Sep 29 10 7:27 pm    Post subject: Reply with quote

killswitch505 Thanks brother! Not bad for a hack-n-wacker industrial electrician! Wink Cool

hvac81 I thought of you during this build as I've enjoyed seeing some of your fabulous projects over the years!
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