looking for some help/advice

Totally new to all this and need some advice,
Hello, I have a Harmon 260 boiler that I just got connected to my oil boiler. My home is not large with baseboard heat and a thermal store for hot water use. The boiler was from a neighbor and over 10 years old.
I have a circulating pump on my coal boiler that I have set to 140 to start between the two boilers. Other pumps on the oil boiler take care of the house and thermal store. The draft control on my coal burner closes at about 160-170. I have a switch on the oil burner so I can shut it off and still use the house thermostat to control the house temperature. I have been waiting for the weather here in upstate NY to get cold enough to get my coal boiler going. So I started it for the second time and have failed MISERABLY !! A couple of details, I am using Blaschak nut coal. Started with wood and added coal slowly and got a bed started HOWEVER the old manual I had said to go up to about 10 inches deep I didn't even go half that much.
The boiler came up to temp and the pump started circulating between the boilers. I set the draft door(works on water temperature not electric) to close at about 170 can't be any more precise than that. The small vent on the draft door is set at half open to keep a little air to the coal bed.
Then I fail! The house didn't call for heat soon enough and I lose my coal boiler fire. I can't just open the coal boiler fire any more or the temps and pressure would climb too high.
I am new to all this and any advice would be very much appreciated!!!
Thank you for looking at this.

You might have to make your fire box smaller. Block off half the bed/grates so your fire isn’t so big. Your boiler is meant for a larger house.

Your coal bed is too shallow. A nut coal fire less than 5" thick or so won't sustain itself very well at all.

You already know how to get the fire started, which is the hardest part. The next time you try it, once you have a few inches of coal burning well, keep adding coal (add a layer, let it catch, repeat), until the firebox is full.

It might be helpful to open some windows while you do this to keep a load on tbr boiler. Once you have a good fire established you should be able to tend the boiler 2x per day.

Rob R. wrote: ↑

Tue. Jan. 12, 2021 7:58 pm

until the firebox is full.

Meaning to the top of the fire brick or 9-10 inches deep minimum all the way across.

Like Rob said you will need more depth in your coal bed to sustain a fire. You should also try reducing the amount of air entering from under the coal bed as well. That will help keep temps down once the fire is established. If you are not calling for heat very often you may be able to close the lower damper completely.

Something I and a couple friends have found that works to help keep the fire going is using stove coal instead of nut. It seems to burn up more completely and keeps a fire easier.

welcome to the world of coal boilers! I had a oil fired boiler and coal hand fired SF260 hooked together. Had it working good after a year of researching how to make them work together. SF260 came with Johnson Control boxes...... they worked very well. Yet to open loop in to existing manifolds i didn't grasp. I called RIB relay company talked to a tech there, they brought all in concept i could grasp. First thing getting additional control head on coal boiler that will give high/low shut offs, and how to switch to back-up heat source. RIB relays explained it to me how 12v/120V relays worked but still isolated. took me 2 months to to understand it, but i wired in, with an additional JC controller. Its not simple electrical wiring to do so is intensive, but it does work. I used taco pumps with check valves, ideally you should use shut off valves between units. I will explain it to you, and if i can find wiring schematics will share. There is a point to water circulation from what boiler, Coal boilers don't turn off off always are burning are making heat . the third JC head is what controlled which boiler water Hot circulating water was coming from. what looked like elecrically when wired

Thanks so much for the responses. I didn't know about the depth and will give this a try after this weekend, supposed to get to 40 degrees. I purchased some firebrick and going to attempt to make the firebox smaller. I am hoping that this might work. If I still don't get it right I am hoping to put some photos on this forum an maybe someone might see something obvious that I don't have any idea about. The photos will show the pumps and controls perhaps like one of the posts suggested that there might be more work to do.
Thank you all for responding good to know there is some help out there!!!!

I cut the firebox down to 14" =/-. The temperature was in the 20s today and starting cold it took about 5 hours before the house got to temperature to turn off the baseboard circulating pumps. I am not sure the SAMSON draft control is working 100%. Does anyone out there know if they are still available, I have seen electric kits for my Harman.
Here are some pics, I hope.
Thanks for all the help!
download/file.php?mode=view&id=107497
download/file.php?mode=view&id=107498
download/file.php?mode=view&id=107499
download/file.php?mode=view&id=107500

They are still available...DS Stove uses them on some of their models.

So is the fire easier to tend now? Are you able to maintain the fire?

I had a good stable fire. I had started the coal boiler without having the oil boiler on, so the baseboards were cold and the oil boiler was only about 70 degrees because it only comes on when the house calls for heat. So it took hours for the system to come up entirely and get the two boilers balanced at about 160 degrees. I thought it was going to work well but then it got up to about 36 degrees outside the house didn't call for heat and coil boiler just kept circulating between the two boilers with the draft on the coal boiler not opening, like it should. I had my small circle vents on the draft door open about half way. The pressure on the boiler went up from 17 psi cold to about 23 psi at 160 degrees when just the circulating pump between the boilers running and the house not calling for heat. I kept checking on it every 10 minutes because I was nervous about heat/pressure. I ended up letting it die by closing the vent entirely and went back on the oil boiler about 10PM.
This weekend now it is supposed to be cold in the teens with lots of wind. So I am going to try again but this time leaving the oil on until the coal boiler is up to temp (starts continually circulation between the boilers at 140 degrees) then I am going to shut down the oil boiler and see how it goes. I am hoping with the colder weather it will work better.
My only other thought is putting a Modine heater in the garage to help putting an additional load on the coal boiler.
Any thoughts of suggestions are MOST APPRECIATED that I might try.
Sorry so long winded but lots to explain.

Water pressure need only be high enough to reach the highest radiator or baseboard in the house. Why was it 17 pounds? What do you have to absorb the water expansion as it heats?

Yeah, proper sized expansion makes for zero pressure change for either hot or cold.

I have an expansion tank on my oil burner. You can see the bottom of it in one of the pictures(the oil boiler). I do not have one on the coal boiler. I thought since the two are connected with the 2" copper pipe it would all equalize but reading your posts I am guessing that was wrong. Is another tank required on the coal boiler also?
Thanks,
Paul