Advice before I buy a boiler

[JohnB]

I am considering purchasing a Tarm ad-on interior wood boiler. I need some advice from people who have experience with them rather than just from the dealer, to make a decision to buy one or not. So... here are a few questions I have been pondering before I decide to purchase:

How do you dissipate the excess heat these units do, or may, generate?

A plumber/heating guy told me that many of the boilers generate allot of excess heat and the a unit sized for my house may provide much more heat than I will actually need and suggested purchasing a slightly smaller unit than recommended for my square footage. The house is new and well insulated???

How hard is it to manage the fire in the boiler? Can I fill the fire box, set the vents and damper and leave the unit for some time, or do you have to attend to the unit every hour or so?. You must be able to leave the boiler going when away from the house?


Should I be concerned with getting smoke in the house during loading the boiler?

Are there any explosion hazards with these boilers?


I appreciate any advice on the operation of a boiler and whether I should purchase one.

 

[Bills330i]

I would like to ask a couple additional questions as i am also considering swapping out my oil boiler for a wood/oil combo.

What are the top 3 wood /oil boiler manufacturers?
Approximate cost including installation?
Do you need 2 flus or can the wood and oil use the same flu?

 

[Nofossil]

Most boilers (you didn't identify a model number) will idle when there's no heat demand. That's very inefficient, so you want to minimize idling. A smaller unit will idle less and therefore be more efficient. Storage is another way to minimize idling - plenty of threads that discuss that. Most HVAC folks who are used to fossil boilers will oversize. You may be surprised at how small a boiler you actually need.

Most boilers can be loaded and left to themselves once they're running. Mine requires tending every 4-6 hours.

Smoke depends on how much draft you have, whether you have adequate makeup air supply to your boiler room, and whether you mess with it when it's running at full blast. I add wood to mine only when it's burned down to a coal bed.

Gasifiers can present a 'puff-back' hazard if improperly operated. They build up a big charge of combustible gas which will ignite if fresh air is mixed in.

Many (myself included) recommend against combination units. I think its better to have two separate units so that either one can fail, be serviced, or be replaced without affecting the other. I think separate units are also more efficient.

I'm currently a fan of a wood boiler backed up by a propane / natural gas tankless DHW heater.

 

[DaveBP]

In addition to the points that nofossil makes, when I was doing this same research for myself I compared the price difference between the combo boiler and the same size wood-only boiler. That difference more than paid for a very high efficiency direct-vented fossil fuel backup boiler and the additional plumbing it would entail. Direct-venting means you only need the one chimney flue for the wood boiler. That was the case with the brand I was considering, at least.

 

[Reggie Dunlap]

I bought my Tarm directly from the Nichols family in Lyme NH. After installing it their technical guys were very helpful every time I called with questions.

If you are going to hire someone to install the boiler I'd buy it from the installer, that way you only have one guy to deal with if there are any issues.

 

[jebatty]

How hard is it to manage the fire in the boiler?

For me the initial firing from a cold boiler takes 5-15 minutes; then full load, walk away, and no further effort until it needs reloading. As nofo says, let it burn down to low coals before reloading. Most winter days (15 to 25F) takes one firing per day (1000 gal storage); coldest winter days (-30 to 15F) initial firing plus one reload as needed. I have radiant heat so storage does not have to be really hot all the time for effective heating.