Blowback on Woodgun

[emesine]

I own Woodgun E200. did a good job heating this winter.

However, it has a nasty habit of blowback when it shuts down then restarts within about 20 minutes. This only occurs with a hot, dry load of wood, and only under certain circumstances, but it can be impressive.

Does anyone know of a time delay relay that would keep the unit from turning on for 30 mintutes after high temp shut-down? I think that would be the easiest solution.

Thanks!

Andrew

 

[Fred61]

Get yourself some storage. It will give you longer burn times and longer idle time. I had the same problem with my E140.

 

[emesine]

Adding a sig. amout of storage to my system is going to cost upwards of a few thousand once I get the fittings, installed, etc. More importantly, it is going to complicate my system and lead to one more thing that can fail, rust, grow mold, get clogged, etc. If I can avoid it, I would prefer to go without storage.

Blowback occurs because there is hot gas in the woodbox. It only occurs when the unit turns back on within about 20 minutes of shutting off with a hot charge of wood. Electronically turning the unit off for 30 minutes after shutdown would fix the problem completely, and it would NOT add the complexities of storage. A proper electronic relay should be available to perform this function for less than $200. Can anyone help me with the part?

I can think of a way to do it with analog circuitry, but I would prefer NOT to get out the soldering iron and design my own PCB.

Andrew

 

[taxidermist]

Does it have a purge timer on the controller? I had to set mine on my eko to purge for 30 sec every 2 min to keep the boiler from blow back when starting back up from idle.


Rob

 

[emesine]

The woodgun does not have any physical way of purging gas out of the fire box, except to run that gas through the fire tube. That's exactly the problem- the firetube reaches the flashpoint of the gas in the firebox while there is still a good mixture of woodgas and air, which causes a flash, resulting in plume of smoke out of the air intake pipe- or singed eyebrows if you happen to open the door too soon (see my November post for a good laugh on this.)

The simpliest solution I can think of is to make sure the firetube is cool enough at the time of restart that all of the woodgas is purged before the flash occurs. Simply put a 30 minute lockout that keeps the unit from restarting within 30 minutes of turning off.

Is there another solution? Have the fan turn on for 10 seconds, off for 30 seconds, on for 10 seconds, etc. Would that work?

Again, adding storage would work, but I don't want to do that.

Andrew

 

[willworkforwood]

I normally don't post on threads dealing with boilers I know nothing about (and can't offer anything), but this has me scratching my head. My Econoburn occasionally has similar things happen during idling, where the unprocessed gas reaches flashpoint and ignites. Others describe similar events - we refer to this as puffing and/or explosions. So I know what you are talking about, but don't understand how you could unconditionally shut down your boiler for 30 minutes. What happens on a really cold day if there is a call for heat after, let's say, 10 minutes of shutdown? Or a DHW call (if that applies for you). Would you not be continuously falling behind on supplying heat on the really cold days if the boiler always waits 30 minutes before coming back online? In asking this, I'm equating shutdown to idling, even though I know the WG is different in that respect from most other gassers. Maybe that's why I'm not understanding how this would work.

 

[ewdudley]

A proper electronic relay should be available to perform this function for less than $200. Can anyone help me with the part?

I can think of a way to do it with analog circuitry, but I would prefer NOT to get out the soldering iron and design my own PCB.

Andrew

Requires a 24VAC-coil relay and a 120VAC-coil relay plus a ASY 3D power on timer delay relay, but does come in under $50 or so not counting an enclosure and your time.

(broken link removed to http://cgi.ebay.com/New-AC-110V-Power-Delay-Timer-Relay-1-999-Minute-/250692969515?pt=LH_DefaultDomain_0&hash=item3a5e77242b#ht_2665wt_922)


--ewd

 

[Fsappo]

Ahhh, I remember back in the 80's losin eye brows and eye lashes from those old wood guns.
Thanks to Dave Oneil for making me flinch every time I open a door now!

 

[boilermanjr]

Speaking from personal experience, make sure that your air valve is not leaking. Try burning wetter wood and/or bigger rounds. I know it sounds crazy, but it helps. The bigger wood burns less rapidly, producing less smoke, which reduces output and causes the boiler to run more continuously. Otherwise...thermal storage.

We used an E180 for about 20 years (30 pulp cords heating 10,000 square feet) and always had some trouble with back puffing. The back puffing was always worse the better our wood was. Our preferred piece was about 8" in diameter unsplit. We are now the Tarm/Scandtec/Froling importer and understand the value of split, dry wood just as we did when we ran the E180. It just worked much better with those big rounds.

By the way, thanks for bringing up Dave Oneil's name, whoever did that. Dave was certainly an early father in wood gasification technology in the U.S. Is Dave still selling remanufactured coal stokers?

 

[Fsappo]

No idea. I lost contact with Dave after I denounced the JW religion (which he was a part of) Once your out, the others cant talk to you. That was about 25 years ago. I do miss him though. He taught me a lot, he always had a smile on his face. My dad actually bought Warm Wood Stoves from him back in..84? They were very close for quite a while.