Boiler without storage sizing

[NCPABill]

First post (after much lurking). I've read (almost to the point of divorce!), but wanted to see if I could get some direct answers.

I am using a 1978 Tarm wood boiler in my basement. I cut and season one year my own wood. I would like to update by placing this unit in a shed about 100' from the house, which would allow for wood storage, etc. At this point, I would not be adding storage, and have the need to look for the longest practical burn times. I fully understand that storage is the answer, but as always, price is a concern for total dollars invested at one time. I am envisioning a straight chimney which I can clean frequently (due to the idling causing creosote).

My Btu/H for the worst case (-10 outside to 75 inside) temperature scenario is around 139,000. Would you recommend oversizing? I understand some boilers respond to room temperatures, like what is advertised by the AHS Wood Gun.

Thanks for all of the reading, past and future.

Bill

 

[flyingcow]

I've got my unit next door in the garage, works well for me.


Are you buying a new unit or moving your old one over?

 

[jebatty]

This is my 4th heating season with Solo 40, always used storage. Assuming you will be getting a new gasification boiler, no storage, I recommend using 75-80% of the rated output as the "average" usable output over a burn, full load to low coals, then reload if needed. Since these boilers are most efficient in performance when burning "full out," I also recommend sizing based on something less than your peak load. For example, where I live -30F would be peak load, we get about a month of -10 to +15F, and then the rest of the winter is probably +5 to +30 and ultimately higher. To keep cycling/idling of the boiler at a relatively low level, I would size the boiler in my case based on something like -5 peak demand, and then supplement with an alternate heat source for colder temps. This would keep the gasification boiler mostly in the range of high burn over the heating season. My suggestions would change if storage is added, and if that is in your planning, which may be a good idea, I would size the boiler differently.

 

[NCPABill]

Thanks for the posts - I appreciate your time.

flyingcow - I will be buying a new unit.

I'm hoping to get 10 hours of burn time out of the new unit, which begets the question about oversizing. I suppose I really only need a 140k btu/h unit, with a wood firebox the size of a 280k btu/h unit! I think that my temporary answer (until storage?) is a system which senses low water temp / receives signal from the cold thermostat, and fires at notice, otherwise, it idles as low as possible. I'm willing to clean chimney frequently as needed. This unit will be the only thing in the building, with a new chimney at installation.

Thanks again for your time,

Bill

 

[stee6043]

I personally would not want to spend $10k+ on a gassification boiler to have creosote dripping from every seam on day 2 of operation. To get 10 hour burns you're going to idle more than you're going to burn. With my 140k btu/hr boiler I get roughly 4 hours of full tilt burning per load of well seasoned hardwood. My last load of the night might bounce off the 195 max a few times and stretch to 5-6 hours but this would be rare. And I can always tell when this happens because my lower chamber will be a little brown the next day instead of the normal gray/white/clean.

I think you'll be much, much happier to do this thing right the first time. Either install a properly sized high efficiency boiler and plan to feed it 4+/- times per day or go with storage and an oversized boiler right off the bat and get the run times you're looking for. Ultimately I think you'll be happier.

 

[flyingcow]

My burn times are very similiar to Stee.

 

[NCPABill]

Thanks both stee6043 and flyingcow. I know I'd be happier (well....except my bank account will be negative!) I'll revise plan and budget for storage.

Thanks again,

Bill

 

[flyingcow]

You can always install storage later. Rough in for storage while doing install. Storage is a good convenience, but not necessary. But I'll give you a rough idea of my typical day burning. About 4 or 5 pm start a fire(when every just gets home). The systm is designed to heat house first, excess heat goes to storage. In about 3 to 4 hours later check storage temp. Mild winter night, thats all i need to do. Below zero, refill boiler once. That will give everyone plenty of heat for the night, plus showers for family of 5 in the morning. This keep the house warm until the following afternoon. Spring and Fall it's really nice to have storage. Let storage get down to 110 or 120, start a fire(takes maybe about 10 minutes) and that will do it for a couple of days. In the summer, one fire will give us shower water for 4 to 5 days. Thats basically how my house runs on storage. In the deep of winter, one really good cleaning of boiler, approx every 2 weeks. Storage is especially nice since my boiler is located next door in the garage. Start a fire....takes 10 minutes....and majority of the time, don't go back for at least 24 hours.