Water to Hot

blackhawk7

a family member is living in an old house with an ancient plumbing set up. there is a solid fuel Rayburn no.2/3 with a boiler, no central heating. problem is, the water gets crazy hot, you could make tae with it. eventually the water from the boiler will travel up the expansion pipe to the attic,2 storey house,and into the supply tank (not the header tank). once it starts running it wont stop and continues to run until all hot water (boiler and hot tank) goes cold.the hot water from the boiler is going into the top of the coil in the hot tank also the boiler circuit doesnt have a circulation pump on it,should it?

sky6

If it's heating the water on Gravity as is then it doesn't need a pump. You could install a bigger Cylinder or try running a Radiator off the circuit to room close by.

blackhawk7

i suppose the boiler is just able to heat more water than is being used.i kept a close eye on it today and used up all the hot water,keeping the hot cylinder cold.the pipe going into the coil was scalding and overflowing up the expansion pipe on and off all day but the pipe coming out of the hot cylinder was cold.

braddun

turn down thermostat

blackhawk7

there isnt a thermostat,it is an old house with a solid fuel cooker/boiler without central heating

Dtp1979

blackhawk7 wrote: »

there isnt a thermostat,it is an old house with a solid fuel cooker/boiler without central heating

I'd put a rad and pump off it and maybe a mixing valve on the hots to the house. That way if the water in the cylinder is 70, you'll only be getting maybe 40 at the taps

blackhawk7

just another question on this,when a good fire is going,the pipes bang like crazy.is this because of air in system or something else?

Dtp1979

blackhawk7 wrote: »

just another question on this,when a good fire is going,the pipes bang like crazy.is this because of air in system or something else?

No it means the water is basically overheating. That's why you need to dump heat to a radiator

RJF

This is a circulation problem. The solid fuel heats the water in the boiler which rises to the copper cylinder where it cools and drops back to the boiler via the return pipe. This is a gravity convection circuit. Some older systems may have a direct cylinder (no coil). You said yours has a coil. Over the years there may have been a build up of sludge/scale. This may be in the pipework, boiler and cylinder. From your description you are getting flow as far as the cylinder but it is being restricted from circulating back down the return leg and thus venting up the expansion pipe. Also a leak in the coil inside the cylinder may be the problem. The solution is to first make sure the balancing valve (if there is one) is open (turn anticlockwise). Second pressure test the coil to ensure no leaks in the cylinder, check for blockage at connections to coil. Third - clean the circuit using descaler/cleaner and flushing. Also the cylinder would often be uninsulated in these old systems. Has the cylinder been changed from an old direct to an insulated indirect at some point? As there is no control on this system if the boiler is heated long enough with no draw off on the hot water it can get very hot and even overheat. The expansion/vent pipe is there for this reason but it should not vent into the supply tank (to DHW) which may be a more recent addition. Is either tank an old galvanized one?

Dtp1979

RJF wrote: »

This is a circulation problem. The solid fuel heats the water in the boiler which rises to the copper cylinder where it cools and drops back to the boiler via the return pipe. This is a gravity convection circuit. Some older systems may have a direct cylinder (no coil). You said yours has a coil. Over the years there may have been a build up of sludge/scale. This may be in the pipework, boiler and cylinder. From your description you are getting flow as far as the cylinder but it is being restricted from circulating back down the return leg and thus venting up the expansion pipe. Also a leak in the coil inside the cylinder may be the problem. The solution is to first make sure the balancing valve (if there is one) is open (turn anticlockwise). Second pressure test the coil to ensure no leaks in the cylinder, check for blockage at connections to coil. Third - clean the circuit using descaler/cleaner and flushing. Also the cylinder would often be uninsulated in these old systems. Has the cylinder been changed from an old direct to an insulated indirect at some point? As there is no control on this system if the boiler is heated long enough with no draw off on the hot water it can get very hot and even overheat. The expansion/vent pipe is there for this reason but it should not vent into the supply tank (to DHW) which may be a more recent addition. Is either tank an old galvanized one?

Why would there be a balance valve on a gravity circuit of a solid fuel boiler?

SpaceTime

Those old gravity systems often don't have any coil, they'll just direct heat the water.

Be very careful with it as they can produce domestic hot water at close to 100ºC and boil the immersion tank.

If you've heard water boiling in the tank at any stage, it's not heating it with a coil.

Dtp1979

SpaceTime wrote: »

Those old gravity systems often don't have any coil, they'll just direct heat the water.

Be very careful with it as they can produce domestic hot water at close to 100ºC and boil the immersion tank.

If you've heard water boiling in the tank at any stage, it's not heating it with a coil.

Well spotted. I'd say there isn't a coil on this cylinder.

SpaceTime

They're fairly dangerous systems as they can cause very serious scalds and would usually predate any modern safety regulations.

There was one in my grandmother's house and it would get so hot that steam and no water would come out of the taps!

Basically all you've got is a solid fuel fire heating a simple boiler. Water rises when it gets hot so it will go up to the tank and cold water falls and goes back into the boiler. This just circulates by gravity.

The problem is that there's no regulation on the heat input as it's just burning solid fuel and it will just get hotter and hotter. The only way to control them is by putting less fuel in the fire.

Dtp1979

SpaceTime wrote: »

They're fairly dangerous systems as they can cause very serious scalds and would usually predate any modern safety regulations.

There was one in my grandmother's house and it would get so hot that steam and no water would come out of the taps!

Basically all you've got is a solid fuel fire heating a simple boiler. Water rises when it gets hot so it will go up to the tank and cold water falls and goes back into the boiler. This just circulates by gravity.

The problem is that there's no regulation on the heat input as it's just burning solid fuel and it will just get hotter and hotter. The only way to control them is by putting less fuel in the fire.

Or running the hot tap in the bath

RJF

Hi DPT1979 and Spacetime. As I said in my post these older systems often had a direct cylinder with no coil and worked on gravity circulation with no control. The reason I said there might be a balancing valve is that someone might have replaced the original direct cylinder with an indirect one and may have also put in a balancing valve. The original post from Blackhawk 7 said there was a coil. There may not be one but he would find this out if he followed the steps I suggested. This is also why I asked about the insulation and the old galv. tank. Someone may have changed the original system.

Dtp1979

RJF wrote: »

Hi DPT1979 and Spacetime. As I said in my post these older systems often had a direct cylinder with no coil and worked on gravity circulation with no control. The reason I said there might be a balancing valve is that someone might have replaced the original direct cylinder with an indirect one and may have also put in a balancing valve. The original post from Blackhawk 7 said there was a coil. There may not be one but he would find this out if he followed the steps I suggested. This is also why I asked about the insulation and the old galv. tank. Someone may have changed the original system.

Yes but even if there was a coil, why would there be a balancing valve?

blackhawk7

a circulation problem is what i thought from the outset and was wondering if a pump would be of any benefit or would that just heat the water even more.
most if not all of the pipe work was replaced about 20 years ago when the cooker/boiler was replaced along with the cylinder and tanks in the attic,now plastic.unfortunately everything was just replaced like for like and there was no improvements made on a pretty basic system.the overheating problem was there from day one but because there was a whole family living there,hot water was always being used up.now there is just one elderly person living there with very little usage.the cylinder definitely has a coil as it was replaced about 10 years ago after the old one leaked.
the person living in the house is reluctant to spend anything as they are adamant that the whole house will be refurbished this year,but im listening to this for a long time.they wondered if the back of the cooker was built up with firebricks,would this direct some of the heat away from the boiler

Dtp1979

blackhawk7 wrote: »

a circulation problem is what i thought from the outset and was wondering if a pump would be of any benefit or would that just heat the water even more.
most if not all of the pipe work was replaced about 20 years ago when the cooker/boiler was replaced along with the cylinder and tanks in the attic,now plastic.unfortunately everything was just replaced like for like and there was no improvements made on a pretty basic system.the overheating problem was there from day one but because there was a whole family living there,hot water was always being used up.now there is just one elderly person living there with very little usage.the cylinder definitely has a coil as it was replaced about 10 years ago after the old one leaked.
the person living in the house is reluctant to spend anything as they are adamant that the whole house will be refurbished this year,but im listening to this for a long time.they wondered if the back of the cooker was built up with firebricks,would this direct some of the heat away from the boiler

You can get some heat shields for cooker boilers. Stanley do them and I think they own Rayburn now

RJF

I did not say there should be a balancing valve, I just wanted to eliminate the possibility that there might be due to possible DIY install or WTF. I still don't know. "With normal usage the Rayburn no 2 has an output of approx 100,000 BTU in 24 hours of continuous burning, sufficient for 2/3 hot baths and normal usage. This is provided that cylinder (direct or indirect) is laggged, fixed vertically and < 35 gallons. 1" flow and return pipes should not exceed 30 feet and should be lagged if exceeding 15 feet. The draw off pipes to the taps should be a dead leg connection from the expansion pipe. There should be no towel rail, radiator or secondary circulation. To obtain the above output the fire needs to be left in overnight". This is according to the manual for the no. 2. If the circulation circuit is cleaned to operate properly and the pipework is properly sized (min 1") and the cooker is properly serviced and in good condition ( No broken or unsealed fire bricks, no blocked airways, ropes in good condition etc.) I see no reason this system cannot operate without overheating. Also another possibility is that overtightened connections to the coil can sometimes cause a twist in the coil which restricts circulation.