Trouble getting enough heat from coal boiler

I have a Jensen 30B coal boiler. It is connected in series with my oil boiler. Trouble is that I do not seem to be getting enough heat from the coal to keep the house at 70. The unit has a blazing fire inside but that doesn't seem to be transferring to the water. As a test I've closed the shut-offs to the coal and it still takes about 10 minutes for the water temp. to rise 5 degrees.

Any suggestions on what is wrong?

circulating too much? can you change your pump setpoints or slow down the flow with a valve, so it stay in the boiler longer? You could be loosing heat in your oil boiler tank when it circulate thru.

If it takes 10 mins to rise 5 degrees, sounds pretty good recovery. It's depends on the volume of your system, your setpoints for the aquastats, etc.....A little more info on your system, zones, setpoints, house size, etc...

I don't believe it is circulating too much because it doesn't heat quickly even when I've closed the shut-offs so the same water is trapped in the boiler. I've set the circulator's setpoint at 170 degrees but then the house is cooling off faster than the unit can recover. I've tried partly closing the shutoffs to limit the flow rate of the water but that was unsuccessful as well.

The hot water from the coal does not go through the oil so it isn't loosing heat to the oil boiler.

The house is about 2,400 sq. ft. with old cast iron radiators so I'm sure that there is a large volume of water in the system. The whole house is setup as 1 zone. The radiators closest to the system get warm but the farther away radiators are not warm which is where the thermostat is located.

I've tried heating the house on oil in the morning to help the coal system along and it holds the temperature for quite a while but over the course of 7 hours the temperature drops from 69 to 63 so the coal isn't able to maintain that temperature.

Barometric damper?
Coal to the top of the fire brick?
Picture of your setup?
Sounds like the heat is getting sucked up the chimney.

It seems, as you say that the house is losing heat faster than the coal boiler can replace it.

When you used the oil boiler alone how much oil did you use? What is the firing rate and Btu rating of the oil boiler and did it heat the house well? Did it run constantly in cold weather?

What is the Btu rating of the coal boiler? To achieve that rate you need to burn about one pound of coal for each 10,000 Btu of its rated capacity. How much coal are you burning? What is the stack temperature?

What you set the cut in point for the circulator is irrelevant if the boiler can't keep up.

Just trying to get a feel for your system to suggest answers.

Richard

I have a a draft damper installed close to the back of the boiler and then a barometric damper further along the flue pipe. I been able to close the draft damper almost all the way and the fire doesn't slow at all. I usually keep the draft damper closed about 75% of the way.

I load the coal all of the way to the door and bank it to the rear. If I load any more it will fall out the door.

The oil is able to keep the house up to temperature. Firing rate says .75 1.05 It has either a 107 or 123 Btu rating (Can't determine which is supposed to be the right Btu rating).

I'm guessing I've burned about 1/2 ton of coal so far this season. I haven't really determined how much per day. I don't have a thermometer on the stack to determine the temperature. I was thinking about getting one though.

It seems to be catching up now after all day of falling behind. I've shake it and then poke it around from the top to push the coal down to the shaker grates and to make sure all of the coals are lit. Doing that seems to be helping it. It has a very huge fire in it though. I don't feel like it should need to be filled to capacity to get the house up to temperature.

Not sure if that helps to figure out what's going on. I can always take pictures to show the plumbing if that helps.

What is the Jensen 30B rated BTU output? It sounds like you just don't have enough BTUs from the coal boiler.


Greg L

I don't know the Btu rating of the Jensen. The pamphlet I have doesn't say and I haven't been able to find any info online.

OK, how big is the fire..? not the depth of the fire, but the width and length.. the square feet of burning coal.. we can compare to other boilers with known BTU ratings..

Greg L

Sounds like the coal may be bridging/fusing from running too hot and not dropping down like it should.
Can you take some pictures of the boiler and the fire?

The inside dimensions of the box are 28 deep by 13 wide.

The pictures of the fire don't show it but the whole box was on fire before. I've been letting it die down to see how the temperature in the house responds.

Jensen furnaces - (renamed ASHLEY - a US Stove product )- are popular and economical
http://www.prestontradingpost.com/furnaces.htm
http://www.prestontradingpost.com/jensen_24aj.htm
Love that Internet
http://www.usstove.com/Downloads/Owners%20Manuals/24AFMANUAL.pdf
Sure it is a furnace not a boiler but it may provide some help.
So is it a 'Vee' bottom or flat bottom?
Forced draft or natural?

My model is V bottom and forced draft

Ah-ha!
Your boiler is designed to burn wood better than coal.
You really need a vertical sided firebox to burn coal properly.
You would be better off replacing the boiler with a designed for coal boiler.

I think your heat is going up the chimney. Get proper gauges to see draft & stack temps.