Back Boiler common in UK question

[Lloyd]

Coaly, you appear to be the main man for the Fisher wood burners.

I am helping our pub landlord with his hot water circulation problem , I think the back boiler is sludged up as the rest of the system throughout the pub looks good .

Do you have any info on grandpa bear stoves with back boilers fitted.

Here Is the link with the previous poster https://www.hearth.com/talk/threads/fisher-stoves-in-england-uk.86181/.

The unit is the one in the pub with the flooded road.

Will keep you updated on progress of the refurb.

Thanks

Lloyd

 

[coaly]

Welcome to the Forum !
Moved this question to your own thread, it may get views and answers from others familiar with the problem.

Back boilers are very common throughout Europe and when people ask how to heat more area or get more out of their stove in the US, it's usually a waste of time explaining how much heat can be extracted with water. It seems most here only use water circulation with a dedicated boiler instead of adding it on an existing stove. There was no factory hydo system here or in Canada. I believe they were fitted by the owner. Fisher did not make a boiler here like the "Wood Lord" you have available there. We call them "water jacket" or "coils" here. I personally like to use 3/4" stainless pipe as a U shape coil above or on the side of the fire to heat the water directly.
This isn't Fisher specific, but I have experience with steam boilers on locomotives and steam traction engines. Ph is tested and chemicals added to prevent this. I can tell you the copper coils do get sluged up from minerals in the water. Keeping the same material everywhere in the system helps with corrosion from dissimilar metals. A copper coil, copper or iron lines and iron radiators connects the materials together with the minerals in the water. If it has an expansion tank and air seperator, as the water heats, the oxygen in the water comes to the top and is removed. More water (and minerals) is added to keep system filled. This allows the minerals in the water to become more concentrated. With time, the more water is added and oxgen is removed, the higher the concentration of these minerals. (dissimilar to the minerals the iron and copper is made of) This cooks onto the hot heating area as a scale that can clog the system. I never tried automotive radiator flush, but running the system with it in may claen it up, then flush well with plenty of water. I don't know if the stainless doesn't allow the scale to stick, or the heat from the flame direcly on the pipe prevents it from sticking, but mine stays clean. I only have the stainless heat absorbtion area and copper radiation, so keeping dissimilar metals to a minimum may prevent it. If you do have iron and copper in the same system, boiler chemicals should be added.

 

[Lloyd]

Coaly, Thanks for the swift response and for relocating the thread.

I am cutting into the gravity feed system in the next week or so, so that I can power flush the water jacket to see what comes out .

From the input from one of the locals it appears to be a DIY after market install, but given the heat output it would be a shame not to utilise this heat for domestic hot water and 8 radiators .

Here is a typical schematic of what the hydraulic configuration looks like

 

[Lloyd]

Had ago at the back boiler which hasn't been working , cut in some flushing points and gave the system a good clean out.

It appeared to be pretty clean so when I put it all together and refilled I wasn't expecting any improvement.

The landlord had fitted a 10mm plate between the flue outlet and the main burner area,to try and hold the heat. We removed this also .

Lit the fire and In about 30 mins had heat rising to the hot water cylinder above and gravity feeding to the 3 upstairs radiators.

There is as all circulation pump in the system to feed the down stairs radiators . Switched that on and now have 6 rads getting heat , hot water and the main furnace in the bar.

Everyone happy , result