Gonna try to build it myself BUT,

[RufusToad]

Hi all, my name is Todd and I live in Nashville IN.
I’m running an old TimberWolf draft boiler that’s just about done for, so I’m planning to build a new stove from scratch. The new setup will have an O₂ sensor, a VFD fan, possibly a flame eye, several temp probes, and it’ll be multi‑fuel capable. I’m also planning to install a diesel-fired hydronic heater inline for backup/makeup heat. I travel a lot, so this gives my wife some breathing room to keep the house at a steady temp without babysitting the stove. I’ll admit — once you automate things, it makes you a little lazy.
Where I’m stuck is deciding between a gasifier and a multi‑pass boiler.
I love the efficiency and wood savings of a gasser, but I’m also a procrastinator and worry I won’t have enough wood stored to feed it all season. Reliability is a big concern too — this system needs to be rock solid. On the other hand, the simplicity of a multi‑pass design is really appealing.
In a perfect world, I’d buy something like a Portage & Main unit without the controls and then modify it myself. There’s a big farm machinery show in Louisville, KY in a couple weeks, and a lot of the major boiler manufacturers will be there. I’m hoping I might be able to work out a deal, though I’m not holding my breath.
So I’d love to hear from folks who own or have run a gasser. What are the real-world pros and cons? Anything you wish you’d known before buying/building one?
Also — if anyone has plans, drawings, or build notes they’d be willing to share, I’d really appreciate it. I’m still trying to wrap my head around sizing the orifice and heat‑exchange tubes.
Price isn’t unlimited, but I’m not looking to cut corners on this build either. This is going to be my summer project, so I am just now getting things lined up to start the process.

 

[andym]

What exactly are you trying to build that isn't already on the market? Why not just buy a multi pass Heatmaster boiler and be done with it? I can understand trying to save some money, but you've indicated that budget is no problem.

 

[RufusToad]

What exactly are you trying to build that isn't already on the market? Why not just buy a multi pass Heatmaster boiler and be done with it? I can understand trying to save some money, but you've indicated that budget is no problem.

I would definitely purchase a multi pass if I could find one without the controllers but that is tough to do. I have performed some tests with the boiler I have and there are ways to increase a multi pass fuel usage by piping warm air into the inlet and by slowing the flow air just for starters. You can also slow the flow of the exhaust with a damper that induces a bit more heat into the water.
Something else I was contemplating was lining the wall of the fire box on the outside with refractory then another liner before the water to trap heat but not sure that would work. Lastly it would be a bit more difficult to incorporate a diesel heater if the stove is already built although I could still make it work just not optimal.
So moral to my story is I would absolutely purchase if I could find something I am looking for.
I want to incorporate WiFi as well and that’s not an option on anything I have seen except for Central and nothing they have is cheap

As I said in my previous post I am really confused on whether a gasser or multi pass is the way to go.

 

[brenndatomu]

IMO if you are buying, go gasser, if building, go MP...just WAY too many variables to DIY a super reliable gasser...heck it takes even the big 3 OWB mfrs years to dial them in perfect!

 

[hobbyheater]

Where I’m stuck is deciding between a gasifier and a multi‑pass boiler.
I love the efficiency and wood savings of a gasser, but I’m also a procrastinator and worry I won’t have enough wood stored to feed it all season.

Don't worry about keeping up with the wood , a good Gasser with storage will burn 1/4 of the wood that a non gasser wil burn!

 

[sloeffle]

I want to incorporate WiFi as well and that’s not an option on anything I have seen except for Central and nothing they have is cheap

The new Heatmaster G (gasifier) boilers are WiFi enabled. Much better design, and quality than Central.

 

[hedge wood]

Hi all, my name is Todd and I live in Nashville IN.
I’m running an old TimberWolf draft boiler that’s just about done for, so I’m planning to build a new stove from scratch. The new setup will have an O₂ sensor, a VFD fan, possibly a flame eye, several temp probes, and it’ll be multi‑fuel capable. I’m also planning to install a diesel-fired hydronic heater inline for backup/makeup heat. I travel a lot, so this gives my wife some breathing room to keep the house at a steady temp without babysitting the stove. I’ll admit — once you automate things, it makes you a little lazy.
Where I’m stuck is deciding between a gasifier and a multi‑pass boiler.
I love the efficiency and wood savings of a gasser, but I’m also a procrastinator and worry I won’t have enough wood stored to feed it all season. Reliability is a big concern too — this system needs to be rock solid. On the other hand, the simplicity of a multi‑pass design is really appealing.
In a perfect world, I’d buy something like a Portage & Main unit without the controls and then modify it myself. There’s a big farm machinery show in Louisville, KY in a couple weeks, and a lot of the major boiler manufacturers will be there. I’m hoping I might be able to work out a deal, though I’m not holding my breath.
So I’d love to hear from folks who own or have run a gasser. What are the real-world pros and cons? Anything you wish you’d known before buying/building one?
Also — if anyone has plans, drawings, or build notes they’d be willing to share, I’d really appreciate it. I’m still trying to wrap my head around sizing the orifice and heat‑exchange tubes.
Price isn’t unlimited, but I’m not looking to cut corners on this build either. This is going to be my summer project, so I am just now getting things lined up to start the process.

First of all. Welcome to the forum. You didn't say if this is going inside or outside. If you have room for something inside I would give the Switzer wood boiler a look. Gary runs controls on his like you want to run. I wish back in 2009 when I bought my Garn I would have went with a Switzer instead. His systems are closed also. I would never have one with a open system again. You can buy you a MP PM with a boiler commander on it and do what you want to do with the controls. I think you will find out in a hurry unless you use recycled material and your time is worth nothing you won't build a rock solid no fuss wood boiler for less than you can buy one for. At least that's what I found out in 2009. Also make sure your insurance is all good with a homebuilt boiler mine wasn't

 

[Tonty]

I have a Switzer. It's a multi-pass batch burner with built in storage that burns through the batch of wood with automatic controls once you light the batch. Every system has its pros and cons, I suppose, but I am very happy with my setup. To me it sounds like a Switzer is exactly what you will try to build, but the only consideration may be space since they have water storage built in. They can be built with a fuel oil burner installed for back up. My flue gas temp runs around 260*-270* running flat out, so I don't think you'll get much more efficient than that with wood. As far as wifi connectivity, I'm not sure what you are looking for there. I have added some probes to my unit so that I can keep track of storage temps, flue temps, etc. The one thing I'd like yet is a temp before the flue gasses pass through the storage, but I think that could be 2,000* or more and with the location I'm not sure how to make that work.
But they aren't cheap. https://switzerswoodburning.weebly.com/

 

[RufusToad]

This is fantastic information and thank you. I have been looking at the HeatMaster, Portage & Main, and Crown. I believe the Central system is kinda like buying a JD. as that name is a few $$ alone. My setup is a bit unique—my stove is technically both indoors and outdoors. I built a small building around it that also stores seven or eight ricks of wood. The structure isn’t insulated, but it’s fully enclosed with a concrete floor and a roof.

I even built a tube‑and‑shell box on top of the stove so that when there was a call for heat, a squirrel‑cage fan would kick on and warm the building while using the excess hot air to feed the boiler. I added a remote‑control car servo to the draft door, and once the exhaust temperature climbed high enough, the program would gradually close the draft and redirect more hot air into the room. Surprisingly, it worked really well. I’ve always heard that pulling cold outside air into a combustion chamber can cost you 2–4% in efficiency compared to using warmer air, so this setup seemed to help.

Does anyone know how long gasifiers have actually been on the market? I don’t remember seeing them when I bought my current boiler, but I assume there’s only so far you can push wood‑burning technology. I’d like to think the serviceability and reliability are pretty dialed in by now.

My goal is for this next system to be the last one I ever buy or build—simple, dependable, and something that saves me from all the heavy wood cutting. I’ve got an endless supply of wood anyway, especially after a tornado hit last year and left hundreds of trees on the ground.


One question: what exactly is a batch‑burner system?

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[hedge wood]

One question: what exactly is a batch‑burner system?

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Do a search on Google and on this forum for Switzer wood boilers and for Garn wood boilers and you will learn all about batch burning wood boilers. You should run across all the problems I had with my Garn. Do your self a favor and buy a Switzer and it will last you till your done with wood.

 

[Tonty]

https://www.hearth.com/talk/threads/my-switzer-install.189820/
Here's a link to my install. I can do an explanation on a batch burner yet. Right now it's time to go let the students into the school I teach/principal at. Have a good day!

 

[salecker]

I believe batch burning refers to the ability to store BTU's for use later after the fire is gone.
I batch burn with my Econoburn (gasifier) and 1000 gallons of insulated storage.
A normal winter day/night at -20C/ 4 below F...
I start a fire at 5PM when i get home, i reload about every 2 hours and the fire is out around 11 PM.
The house then draws from the heated storage for the remainder of the 24 hours till i restart a fire at 5 PM the next evening.

 

[Tonty]

Yes, a batch burner uses water storage as thermal "battery." In a Switzer, the water storage is integrated into the unit. Mine has 600 gallons of water storage, so it is a "small" one. The larger ones will have 1,000-2,000 gallons of water storage or even more. More storage equals a longer time in between burns. When it is cold, I typically burn twice a day, once in the morning and once in the evening. For example: I wake up and find my water storage temp is 120*. My Switzer heats the water 1* per pound of wood (when no heat is being used), so I will weigh out 80lb of wood and start the burn. Once it is lit, I can leave the premises if I wish because this burn is automated, and the whole load of 80lb will burn out in about 2 hours. Then my storage will be at 200*, and whatever heat method I use will draw from that thermal storage "battery" throughout the day, In the evening, I will check my storage temp again and do another batch burn. There is no active fire in the firebox other than when I do the batch burns. If you have a larger unit, you may have to burn a batch of wood only once every 24hrs. or maybe you can even wait longer than that.

 

[RufusToad]

Wow this is excellent. I am learning a bit here and I appreciate the links.
I am going to assume the amount of water in the system is because of the batch burning? The 3K gallons had me worried until Tonty linked his as I don't see a smaller unit on the website and I don't have near the space to house this size boiler. I am going to assume this is a $15-20K boiler?
So if the boiler flame is out at 11pm and the heat load is more than the stored energy how does the storage not deplete the heat before you restart again? I run approx 250g now and would think I would deplete all that water temp within 3-5 hours at a 0°f day. I could be missing something here.
I am wondering if Switzer will be at the show in Louisville next week?

 

[Tonty]

Here’s how my system works. Mine was an install in a new house, so I could build it this way. I have hydronic in floor heat, so the water circulates through that on its own pumps/thermostats. Furthermore, I also have a propane forced air furnace. There is a hot water coil in my furnace that I can circulate hot water from the boiler through. The pump for that is tied to a separate controller/pump that I can set a temp on. If the water is higher than that set temp, the pump runs, circulating water through the coil and the force air furnace fan runs as heat is called for. If the water temp is below the set temp, that circulating pump does not push hot water through the furnace coil. Instead, if the furnace thermostat calls for heat, the propane burners in the furnace will kick on to heat the house. That rarely happens. I use maybe 125 gallons of propane a year, and most of that is in the fall before I have started my boiler.

I don’t have a back up oil burner in my boiler. If I did have one with an oil burner in it, that would automatically kick on to keep my water temp in the boiler at whatever temp I had it set to.

Edit: It also heats all of my domestic hot water, but that’s only in the winter for me. I don’t run year round like @hedge wood did.

 

[Tonty]

Switzers can be custom built, so Gary could possibly build one to fit your space. I don’t know what kind of price they have on them by now.

 

[hedge wood]

Wow this is excellent. I am learning a bit here and I appreciate the links.
I am going to assume the amount of water in the system is because of the batch burning? The 3K gallons had me worried until Tonty linked his as I don't see a smaller unit on the website and I don't have near the space to house this size boiler. I am going to assume this is a $15-20K boiler?
So if the boiler flame is out at 11pm and the heat load is more than the stored energy how does the storage not deplete the heat before you restart again? I run approx 250g now and would think I would deplete all that water temp within 3-5 hours at a 0°f day. I could be missing something here.
I am wondering if Switzer will be at the show in Louisville next week?

You are learning how batch burning works. You have to decide how big your water storage needs to be to get you threw until you want to do your next burn. My Garn had 2000 gallons and I had to fire it three times a day when real winter hit in my area. I was burning 10 to 15 full cords of hedge a year. I ran year around as I heated my domestic water with it also. Gary from Switzer won't be a t Louisville next week. He's not a big factory. Just him and either a son or son in law. Give him a call he loves to talk burning wood to make heat. Very smart guy. In todays age its going to be min $15-$20K. Once in while a use one of his comes up for sale. The nice thing with his close system is no chemicals to buy or check.

 

[RufusToad]

Wow, 2,000 gallons sounds like a lot. I’ve seen people recommend keeping the water temp around 200°F, but that feels a bit high for PEX over long periods—though to be fair, they say not to use PEX for air lines and my whole shop has been plumbed in PEX for years without a hiccup.


How long does it usually take to relight the fire and bring the water temp back up? And am I right in assuming the big difference between this setup and other gassers is mainly the size of the water tank—basically just extra storage?


My house is set up almost exactly like yours, Tonti, except I’m running an electric furnace. I use two thermostats: the main one is set about 20° lower than the secondary, so if anything goes wrong the electric kicks on automatically. I also work for a hydronic heating company that builds diesel-fired heaters, so I keep a 100k BTU unit tied into the furnace as backup. That was a big motivator for building my own stove—I could integrate the diesel heater right into the firebox. But like I mentioned before, I could also just plumb the return through it first on a purchased furnace. Lots to think through, especially when it comes to cost and space.


I emailed Switzer early this morning, but I may give them a call next week. I don’t mind learing from folks who are a lot smarter than me.

 

[Tonty]

You’ll be better off calling Switzer, I think.
Gary actually recommends heating to 220*, but I try to keep it to 200-215. Most of my piping before my mixing valves is copper, but for some reason I did put in about 8’ of pex. That’s why I don’t go higher than I do. My in floor hydronic heat is pex, of course, but it has a mixing valve on it because it’s not a good idea to dump 215* water in a concrete floor. I have the mixing valve for my house floor set at 100* and the garage floor set at 70-80*. I only run the garage when it gets down to 20 at lower. The water running through my furnace coil is not tempered.
It takes me about 20 minutes from start to finish to light it. That’s mainly a personal choice, as actually loading and lighting the fire only takes about 5-10. I like to see my flue temp hit 250-260 before I leave my boiler room, but there’s really no solid reason for that. I cheat and use a MAP gas torch to light, so I don’t even use any kindling or anything like that. If I’m burning twice a day, often there are a few coals that will light the wood once you kick the inducer fan on. It moves a lot of air.