coal fire heating

[wayne1979]

i dont know if this is the right place to post this but here it goes,

i have a coal fire and oil heating the oil heating works fine to heat the water and rads but the fire will only heat the water and when it is lit the water is pipein hot but it wont feed the rads so i had a look and after a few hrs i found the switch which i think is connected to the pump but it wldnt work there is a thermo on the main pipe into the hw tank and from this it goes into the switch and a cable comes out of the switch and under the floor in the hot press so i took the switch apart and just wired it straight up to a plug and when i switched it on i heard the hum from what i think is the pump under the floor and the rads started to heat up they stayed hot for about 5 min the went cold again do you think its the thermo that is broke and wld this control the hot water for the rads any help wld be great

 

[dontknowitall]

Can't quite make out the system but my guess is it's the pump at fault and not throwing the water around the system. If when it's the pipe on one side is much warmer than the pipe on the other side then the pump's not working. If you undo the wide screw does water drip out reasonably quickly? If not then I'd suspect the pump.

But hang around for another thought or two.

 

[djboyd]

Wayne, I also have a coal fire linked to oil CH boiler. My system was wired similar to yours, it sounds. It could just be that the back boiler will not sustain a long period of heat before cooling off. Mine heats rads hot for perhaps 20 mins before becoming just warm. My system is now linked up using a neutraliser and connected to a pipe stat (anti boil stat) which turns the CH pump on when too much heat (ie fire is on). It used to be wired so that it would heat hot water only. A neutraliser allows use of both systems together - fire provides heat and oil boiler cuts in when it needs to. works well for me.

 

[wayne1979]

thanks for the comment dontknowitall but i think the pump is fine as all the rads in the house heated up straight away then the went cold well lukewarm the reason i was thinking the thrmo wasnt working is because i used a fasetester to check if there was power getting to it but there wasnt thats why i disconnected it and just put a plug with some flex into the mains in on the switch and the light on the switch came on and the pump started do you think the thermo will controll when the pump comes on its a danfoss at thermostat

 

[wayne1979]

djboyd how do you set up that sort of system cause that wld be great

 

[djboyd]

Wayne

Try this link

[DLMURL="http://www.dunsleyheat.co.uk/linkupsys.htm"]dunsleyheat uk manufacturers of multifuel stoves, range cookers, boilers...[/DLMURL]

A good system, but it needs some careful design - put mine in myself a good few years ago (I'm not a plumber). Basically, everything connects into the neutraliser. If you can manage some wiring too, that would help. Cost about £250 for neutraliser but you would need to factor in the rest of the system + controls (stats, etc)

 

[mrlennie]

Had a customer today solid fuel boiler pipe stat faulty. It would not operate unless the stat was SET to below 40 degrees. And then obviosly it would cut out when it reached 40 degrees. Replaced pipe stat its fine now. Dunno if that helps sounds similar. Oh one thing you can try is to take the pipe stat off and leave it dangling this makes it call for heat constantly if it is this problem.

It was the thermo that controls the pump and get this.....it was a danfoss pipe stat and get this.....it was just 30 bucks to replace from plumb center. Make sure you write a diagram of how the orignal is wired up though as it is a pigs ear believe me.

 

[tamz]

Here is a drawing of how a pipe stat "should" be wired to an open fire.


The pipe stat needs a permanent live which switches power to the pump and bypasses the pump switch. The neutrals are commoned in the pump switch (FCU). BTW if you are ever working on one of these pull the fuse on the unswitched spur.
Depending how the pipe stat is to be used,
If to prevent overheating, the stat should be fitted to the return and should be set around 60° and the heating switched on manually at the pump switch as required.
If to automatically turn the heating on, fit on flow set around 50 - 60°.
Danfoss AT are as good as any at around £25+vat


If your heating came on (het up) for a short period then quickly cooled you have too many rads for the size of boiler, are using the wrong coal or the fire is too small.
One great myth put out by all solid fuel boiler manu's is they can heat xx amount of radiators. Not in the real world they don't.
Most open fires are under 20000btu, Grant triple pass and the like are up to about 30 odds if i remember correctly. This is when you have a raging fire and are burning the correct fuel. Smaller fire, lower output.


Disregard the attatched thumbnails bit at the bottom. It is wrong and i don't know how to get it off.......Puddle or Redsaw???

 

[wayne1979]

ok people after some work i know have the pipe stat turning the pump on but it wont turn it off when the temp in the pipe drops so its allowing cold water to enter the system was thinking of changing the stat to a Salus CT100 do you think this will turn the pump on and off and allow the rads to sorta stay at a decent temp, tnks for all the input its really helping me to get this sorted and do you think if i turned some of the rads off in the rooms we dont use this wld help aswell there is 10 rads al2gether and there are three rooms we dont ever use that wld leave only 7 to be heated

 

[mrlennie]

Tamz the pipe stat I came across was on the coil connections on the hot water cylinder is this normal or should it be near the boiler?

 

[tamz]

Tamz the pipe stat I came across was on the coil connections on the hot water cylinder is this normal or should it be near the boiler?

Usually quite near the boiler but it would do the same job at the cylinder. You may need to play with it a bit to get it set right.

Wayne
It is easy to test a stat using a multimeter or even one of those cheap neon screwdrivers. If it needs replacing the Salus one would do.
The difference between heating with oil or gas is you have a constant output usually 2-3 times greater than what an open fire can provide at full pelt so if you try heating the system with the coal fire it is never going to make it.
On a system as big as yours (4 bed house?) a roomheater would struggle to make it. The only coal boiler that would is a gravity fed so don't expect an open fire to. You will just have to compromise or use your oil.
Depending on how your system has been linked it should be possible to use the open fire to "add" to the system alongside the oil.

I served my time fitting coal heating in the 70's and even then 5 -6 single panel rads with a total output of about 15'000btu's (sometimes fed from 6mm pipes!) would only be lukewarm (probably around 40°) most of the time.
People had never had any form of heating before so a lukewarm radiator was a major improvement on nothing.
When the pits shut in the 80's and everyone was converting to gas the favourite one we would hear was of how good the coal had been and gas would never beat it. Until you switched it on!!! when they realised what they had been missing.