Stoker Boiler questions

Ok, after much digging, thinking and asking around I've decided that what I need to do is replace my old (and not currently used) oil fired boiler with a stoker boiler. Found what seems to be a great deal on a Keystoker K6 but my question is what's the best way to determine what size boiler I should get? We've got a bunch of radiators in the house, not sure if that's how boilers are rated or if it's by sq foot like a normal furnace.

Also does anybody have any experience with the K6? I'll keep my hand fired furnace as a back up and supplemental heat source but really want to use the hot water rads since they're in every room (some rooms have several)

I'll check the size of the oiler but to be honest I've never used it. We bought this house last spring and with the cost of fuel oil I figured that I would heat with wood this winter to see how I liked it. The house also came with a Brunco 150, once I discovered the joys of burning coal the wood idea went right out the window.

The previous owner used both the Brunco burning wood and the oil boiler along with a fireplace insert so I don't know if he was trying to save money, produce enough heat or some of both. I do know that when we started the buying process last Jan/Feb they always had the house WARM but then again our winter last year was really really mild (we were painting the outside of the house in late Feb).

rick is right, if the oil boiler did a good job, keep it the same size. also, you can add up the btu out put of all your radiators to confirm your making the right decision. i run a ka-6 and love it, easy set up, clips away great with very little attention. just empty ashes and top off the hopper every other day. really same with any stoker boiler.

I'll call the PO tonight or tomorrow to see what they thought of the heat output of the oiler, it's a great starting point I agree. Not sure how to figure out BTUs per radiator, the house was built in the 30s, only has one cast iron rad in the garage, the rest of them are steel ones set into the walls with covers.

Looking forward to a stoker, thought that I would have to go hand fed for a boiler because of the cost but I'm finding some seemingly good deals on used boilers, only a couple of used stokers now but if I can get hooked up with this KA6 for 1100 bucks I'll be a happy camper.

you never ASSume - OLD appliance installs were almost NEVER sized for the load - they were sized by what was available - what the installer could make money on - and big enough so he never got called back

You want to know?
you do your own --- wait of it

HEAT LOSS CALCULATION

First off, you are smart to take advantage of the radiation in your house and distribute the heat where you want it. A stoker boiler will be a great upgrade for your home.

Hot water boilers are rated by the sq. feet of radiation they can serve, and with a btu/hr figure. A KA-6 has a "recommended load" of 675 square feet of hot water radiation, and 122,000 btu's per hour of Net output. If you want to know how to measure the radiators, read this guide: http://www.columbiaheatingsupply.com/pa ... 0Guide.pdf

If you were building a new house, a heat loss calculation would be done to see how many feet of radiation you need in each room, and how large of a boiler you need to heat the house. You have an older home with unknown R values and air exchange rates, so without spending a lot of $ on some fancy thermal analysis and blower door test...you will have to estimate those things if you want to do a heat loss calculation.

I have done it both ways, and when it comes to an older house...I like to do a "short hand" version of a heatloss calculation to get a general idea of the total load, and also do an analysis of the existing system (rating, run-time, and fuel consumption). In your case, you don't know how much fuel the existing system used, or how well it worked...so all you can do is see if the radiation is capable of meeting or exceeding the heat loss, and then picking a boiler that can meet that load.

The reason I recommend doing a heat loss AND measuring the radiation is that many older houses were over-radiated. If the heat-loss works out to 100k btus/hr at 0 degrees, but there is enough radiation in the system to spec a 200k btu/hr boiler...you may decide to pick a boiler that can comfortably run 150k btus/hr (just an example).

I recommend you take the time to measure the radiators in each room, and do a heat loss calculation using free software. Slant-fin has a free program that is easy to use...maybe someone can post a link to it.

Now, about the Keystoker KA-6...do you have access to buck size coal? A friend of mine has been struggling with a Ka-6 for a week, it has been running hard to heat his house and creating clinkers in the stoker that sometimes stop the flow of coal. I gave him some buck to mix in with the rice, and now it runs great with no clinkers. If your heat load comes in on the high side of the KA-6 capability, I would plan on running buck or getting a bigger boiler.

What was said already plus it would be important to take a peek at the chimney size and condition while you are at it,to be sure what you are working with. If you have to go much past a K6 some of the boiler breechings can get "biggity". Mike

For reasons covered in detail in other threads, I definitely would not limit the size of the boiler to correspond to what some computer program says is your heat loss. The assumptions typically don't correspond to the conditions you are likely to experience, and especially in an older house factors like air infiltration that are hard to measure are very significant. Even a unit that theoretically could meet the actual heating load may come up short due to ash buildup, coal quality issues, DHW load, imperfect fuel/air mixture, etc.. I think there are legitimate reasons why the original installers of coal-fired equipment used generous sizing, and would caution against spending money to create an underpowered system.

Mike

Pacowy wrote:The assumptions typically don't correspond to the conditions you are likely to experience, and especially in an older house factors like air infiltration that are hard to measure are very significant.

It was easy to assess the impact of "infiltration" last night when our house was hit with 20 mph winds at -2 on the thermometer...my boiler ran without stopping for 2 hours. It maintained our desired interior temperature, so there was no need to adjust the stoker to a higher output...but it was sure nice to have the option. I did a mid-season cleaning two weeks ago, and my current supply of coal is very good...if the boiler was due for a cleaning, or the coal was "fair", the "reserve" stoker capacity would have been called into action.

How wide is the basement door? Sometimes that is the limiting factor on boiler choice...

Rob R. wrote:

Pacowy wrote:The assumptions typically don't correspond to the conditions you are likely to experience, and especially in an older house factors like air infiltration that are hard to measure are very significant.

It was easy to assess the impact of "infiltration" last night when our house was hit with 20 mph winds at -2 on the thermometer...my boiler ran without stopping for 2 hours. It maintained our desired interior temperature, so there was no need to adjust the stoker to a higher output...but it was sure nice to have the option. I did a mid-season cleaning two weeks ago, and my current supply of coal is very good...if the boiler was due for a cleaning, or the coal was "fair", the "reserve" stoker capacity would have been called into action.

How wide is the basement door? Sometimes that is the limiting factor on boiler choice...

My thoughts exactly Rob. Same temps as you. Same winds, if not stronger. The little Kaa-2 ran quite often. One zone would be on. Another would come on. One would go off. Another would come on. Sometimes all three would be on, which drew the boiler temp down to 160*. Then one would go off. Then the other two go off. Then a short break, and it starts all over again. In other words, lots of activity. The Kaa-2 maintained thermostat settings of 74* throughout the entire house. I too could have turned up the feed another full turn, which would put fire all the way to the edge of grate...........But Why???

Wow , all a little overwhelming , been using a 90 btu wood boiler and ready for coal . Really cold nights in Maine drag it down when garage radiant comes on , then hot water , then bedrooms . been looking at ka -6 from keystoker wondering if its too big . I think my plumber rated the house heat loss arond 69,00 0 ?
house is 1500' garage (radiant) 900' basement (radiant ) 800' . New modular home heats well above 0 but man you can't lug enough wood when it's below 0 . My oil is 100,00 will keep up but sure runs alot . My concern is too much overboil if ka-6 is too big . I probably will only use for winter season