Working a Coal Furnace


Tuesday 20 January, 2015 by Uncle Spike

Unless the family is at home all day and/or it’s also darned cold outside, the heating is only run at night, on low, keeping costs manageable. So each morning I turn the coal feed off (auger fed delivery from the attached coal hopper) and let the coal burn off for another couple of hours.

In the afternoon, I remove all the spent coal from the burner itself, but thankfully no ‘cleaning’ is required. The spent coal that gathers on the floor of the burn chamber gets cleared out every three days or so, but usually I only have to repeat the long cleaning job once a month. As for lighting the beast, here’s what happens…

Step one

Fill her up….  The hopper takes up to 200 kilos (440 lbs) of small sized coal. That’s eight sacks that need to be hefted from the store area around to the hopper – another good keep-fit exercise, but done rather slower this month a the rib doesn’t like me playing with coal sacks 🙂



Step two

The bags are split open and the hopper gradually filled up.







Step three

The auger drive is turned on manually in order to deliver fresh coal into The newly cleaned out burn chamber. The coal needs to be about 3-4cm (1.5″) above the burner, thereby covering the multi-jet air holes (as shown by the arrow) that drive the fire once it is lit.



The coal we use is locally produced and burns fairly clean compared to the ‘better quality’ imported coal – which is very black and dirty to handle and clean out afterwards. However, the local stuff, whilst good enough to burn, doesn’t light that well, so I add a scoop of Siberian coal on top to aid the lighting of the fire. It’s much more costly to buy (and dirtier as I said), but saving me numerous failed attempts at getting the boiler lit each night.



Our local coal has a Thermochemical burn value of 4,800 kilo-calories per kilogam of coal (or 20,000 kiloJoules) – in the US, this may be better known as ‘Sub-bituminous C’ with a BTU/lb rating of 8,580. This is compared to the Siberian import, which runs at a higher calorific burn value of 6,400 kCal/kg (or 26,700 kiloJoules) – again, in the US, this may be better known as ‘High-volatile bituminous B’ with a BTU/lb rating of 11,450.


Step four

Whilst newspaper burns well, it tends to flash burn too quickly, not igniting any useful fire, and the uniform ash it produces also tends to smother any weak flame. I therefore use just a single sheet, moulded loosely into a sort of boat, add a few pieces of Siberian import coal and a dry pine cone as my base for lighting. 



Step five

In good old boy scout fashion, a wigwam is made of dry sticks cut last spring, and left to dry over the summer. It took some practise originally, but 9 out of 10 days I can strike a match and it’s a GO, successfully lighting on the first attempt.  



Step six

As the small wood fire starts to take hold, the fan can be started, albeit turned down a fair bit. I have to revisit the furnace two or three more times to make adjustments before the fire is well and truly burning the coal (see the picture below).



Step seven

After perhaps 20 minutes more, the fan is turned up to 40%, and the auto-feed from hopper to burn chamber is turned on. Generally I run the mechanism on a 2-second feed with a repeat delay of 120-seconds, subject to a thermo-switch that turns off both the fan and the feeder delay when the desired outgoing water temperature has been reached.



Step eight

Half an hour later I will recheck progress one final time. The water temperature should then be over the 36C (97F) mark, which sets the water pump into play and the system is then operational.

It takes a bit of adjusting to get the desired result, with variables of maximum water temperature, which floors of the house (and thereby, radiator panels) to feed, fan speed level, coal delivery amount, delivery frequency delay, and of course air temperature.

This is the control panel below. The null value pressure gauge has been bypassed; I use an external gauge which is more reliable, as I need to maintain an operating pressure of between 0.8-1.1 bar (11.6-16.9 lbs per square inch), with a corresponding non-operational pressure of 0.4-0.6 bar (5.8-8.7 lbs per square inch).



These are some of the valves I get to play in order to send the heated water to where it’s needed, and to prime/add water to maintain the desired pressure reading.




And there you have it; that’s how we heat our home, from maintenance cleaning to daily operation – good old Terrance 🙂


17 thoughts on “Working a Coal Furnace

  1. writeknit says:

    It reminds me a bit of the Overlook Hotel! Hope you don’t find an old scrapbook down there… 🙂

    Liked by 1 person

  2. Yvonne says:

    I dips me lid to you, young fella!


  3. Omg all I have to do is press a button and if I am upstairs I refuse to get out of my warm blanket for even that! I tell the kids to go turn the heat on, counting my blessings!

    Liked by 1 person

  4. Our boiler is broken at the moment and there’s snow on the ground outside, so this information should come in useful, Spike!
    Seriously, we take so much for granted in the UK, and your post puts things in perspective.
    We are lucky in our house to have two fireplaces for alternative heating if the boiler stays broken, although the chimneys need cleaning. Then it’s off to the woods to collect sticks, methinks.


  5. dayphoto says:

    It seems like a simple life even has it’s major jobs that help keep it simple, doesn’t it?

    This is a really well done series…Thank you!


    Liked by 1 person

  6. cabbagetalk says:

    Very interesting. I just turn the thermostat on my living room wall and bobs ya uncle the house warms up. Never thought of how much I take for granted. My heating is so simple compared to yours 😉

    Liked by 1 person

  7. Love all of those technical details Spike!

    Liked by 2 people

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