Dual-fuel boiler

Mike4484

Hi my name is Mike. A few years ago I bought an old twin farm house. I have been working on renovating the larger side since I bought it and am finally seeing light at the end of the tunnel. I have installed all of the piping for my new boiler system and I had bought a used H.S Tarm tri-fuel boiler (wood, oil, coal) not long after I purchased the house. I recently had a contractor come take a look at my boiler and he said that he would recommend installing a new boiler because he couldn't guarantee how long or if the used one would work once installed.

I wanted to see if anyone has experience with maintenance on H.S. Tarm boilers, or recommendation for a new dual-fuel (wood/oil) boiler? I have a near endless supply of oak lagging boards from work so that is why I want to stick to a wood burning option, but I also need for it to switch to oil if I am not home to load the wood because I don't foresee my wife wanting to do that. The house is roughly 2300sf, uninsulated one foot thick masonry walls, with newer (maybe 15yo) windows. I will be using wall mount ecostyle steel radiators to provide the heat.

Thanks,

Mike

EdTheHeaterMan

How old is the used boiler?

How long has the boiler been operational?

How long has the boiler been disconnected?

Most of the old wood/oil boiler manufacturers built their steel heat exchangers with thicker sheets of metal than those made for oil or gas only operation. So chances are that a 10 or 15 year old boiler has years of life left in them. If the boiler is over 40 years old, then I'm not so sure that is a good investment, especially if the boiler is the only source of heart for the structure.

hot_rod

A lot depends on how well that boiler was treated in its former life.

Overheated? Long cold run cycles?, water quality or fresh water added often, fire tubes cleaned regularly, green or wet wood burned in it?

Solid fueled boilers require more maintenance, every two weeks or so I did a deep clean on my wood fired boiler, and I burned seasoned hardwoods all the time, coal occasionally.

Knowing the former owners burn habits would tell a lot about the boiler.

A multi fueled boiler is a bit of a compromise, between boilers built to a specific fuel use.

psb75

Make sure you plan for plenty of heat-storage—hundreds of gallons of water in tank(s). This is so that you can charge your wood boiler with good, dry fuel and burn it up…hot and efficiently…with most of the heat going to storage. Good burning will allow for less cleaning of the boiler. H.S. Tarm boilers were made with plate steel. They were good boilers. Usually a dual-(tri)-fuel boiler is a compromise. A modern wood gasification (down-draft) boiler would be a better choice—even if you put it in after trying the H.S. Tarm for a while.

leonz

https://forum.heatinghelp.com/discussion/197367/dual-fuel-boiler

You have to be diligent about cleaning the HS Tarm OT model boiler as it has a multiple smoke passage design.

I have attached the installation manual in a separate file as well as an image of the exposed side view of the OT model from Popular Mechanics showing the smoke passages for the oil burner and the boiler vessel water baffles in the fire box.

The Internal domestic coil is fully inmmersed in the boilers water chest and can be replaced by removing the dome covering part of the vessel.

When you get around to pressure testing the boiler you should remove the top cover to check for a gasket leak at the same time you pressurize the boiler to 60 PSIG

HSTARMpm1979.jpg

ot_28.pdf

HSTARM OT-Brochure.pdf

I used my switzer wood and coal boiler for 33 years before I switched to a keystoker coal stoker in 2015. The stoker boiler works well but keystokers service/help is/was worthless.

Your plumber is correct and honest about this in his thinking in discussing this with you. The HS Tarm wood and coal boilers were excellent boilers. I would have purchased one but I could not afford the purchase cost.

You need to put 60 pounds of water pressure in the boiler vessel and see if it holds 60 PSIG for 12 hours just to be sure.

You will need to plug or cap all the exposed tapping's and use a jet pump to pump water into the boiler drain as you use a ball valve in a top tapping to vent the trapped air as you fill it.

You should have a second ball valve installed in the tapping where the jet pump is pushing water into the boiler vessel also to seal the boiler for the pressure test.

Anytime you intend to switch to oil you will have to reinstall the oil burner in the oil burner mounting flange weldment.

The only boiler I would recommend as a dual fuel unit to burn hand fed wood and oil is from Alternate Heating Systems. This boiler model is the E140 employs an induced draft combustion system creating gasification using a 2 pass system.

The boiler E140 boiler has a refractory lining, swirl chamber, cyclone ash collector and an oil burner chamber that is separate from the wood burning chamber and the heat and oil flue gasses also pass through the swirl chamber before it exists out the flue pipe. The unit also has a domestic hot water coil as well.

You should select only carbon steel for the boiler vessel as the steel preference.

Mike4484

Thanks for all of the information. Can I pressure test the boiler with air? I don't have a hydrostatic test pump. If it holds pressure cold is it possible that it could crack when heated or is that unlikely? The guy who came out said that it is 40 years old, and it has been sitting unused since I bought it 7 years ago. I would like to use it for a year or two while I save some cash to buy a new one, but if you guys think that it is unlikely to work maybe I will have to bite the bullet now.

leonz

Hello and good morning Mike4484.

No, you should not pressure test the boiler with air!!!

When the boiler was purchased were the pipe tappings capped or plugged when you bought it??? This question has to be answered first, If, it has been left open and exposed to the elements it will have rust in the water vessel and other members of the forum can answer this question better than I can as a cleaning product used to clean steam chests may be able to take care of this for you.

Is there any reason you cannot use household water pressure temporarily by raising the cut out pressure to 65 PSIG temporarily and pressurizing the boiler and then closing the ball valve?

If the water vessel has been sealed during the last seven years it would not hurt to see about renting a dry ice sand blasting unit for a day or two or hiring a painter that has one to sandblast the fireboxes of the boiler as using dry ice blasting does not damage the surface it cleans and leaves only the built up material that was in the fire box as residue.

PRR

Can I pressure test the boiler with air?

Water does not compress; so it won't expand. (not enuff to hurt) You hear a TUNK as the steel rips, then a spray, but it won't fill the room for a while.

Steam expands ~~~ a thousand times; a steam boiler explosion typically tears the roof off.

Air is in the middle, it may only tear your face off. (If you know retired truckers: the old several-piece wheel rims could let-go violently and sometimes fatally. https://www.youtube.com/watch?v=eFXVOa44oSE )

Over-pressuring boilers with water is a very old technique, used to certify steamships for insurance.

Robert_25

https://forum.heatinghelp.com/discussion/197367/dual-fuel-boiler

Those Tarm boilers are very rugged - if it doesn’t have obvious corrosion issues and passes a pressure test with water it should be good to use. With that said, there are better options for burning wood. A gasification boiler like a Wood Gun will burn much cleaner and use less wood.