Pipe Stat on Stove Boiler - Problem!

Tester46

Hi,

I have a multi-fuel stove with a back boiler to heat hot water and rads. My plumber originally wired it with the pipe stat for the pump up at the hot water tank upstairs, not at the stove boiler downstairs. He said his reasoning was that the gravity feed would bring the hot water from the stove boiler up to the tank, the pipe stat would be triggered and the pump would kick in.

The problem is that the pipe stat never kicks in automatically. When I light a fire in the stove, it heats up and then an incredibly loud knocking and banging sound begins in the pipes as the water gets superheated. On my plumber's advice, when that happens (i.e. everytime I light the stove) I turn the stove damper down to zero and run upstairs and manually turn the pipe stat down to whatever temperature gets it going (usually about 10 degrees). The pump then stays on until the fire dies down the next morning and I manually turn the pipe stat temperature back up until it switches off.

Apart from being a pain in the ass, the system is clearly not working. What can I do? Is there any easy way to move the pipe stat downstairs to where the boiler is without having to re-wire and drill through walls and ceilings (I'm guessing no)?

DublinDilbert

Tester46 wrote: »

Hi,

I have a multi-fuel stove with a back boiler to heat hot water and rads. My plumber originally wired it with the pipe stat for the pump up at the hot water tank upstairs, not at the stove boiler downstairs. He said his reasoning was that the gravity feed would bring the hot water from the stove boiler up to the tank, the pipe stat would be triggered and the pump would kick in.

The problem is that the pipe stat never kicks in automatically. When I light a fire in the stove, it heats up and then an incredibly loud knocking and banging sound begins in the pipes as the water gets superheated. On my plumber's advice, when that happens (i.e. everytime I light the stove) I turn the stove damper down to zero and run upstairs and manually turn the pipe stat down to whatever temperature gets it going (usually about 10 degrees). The pump then stays on until the fire dies down the next morning and I manually turn the pipe stat temperature back up until it switches off.

Apart from being a pain in the ass, the system is clearly not working. What can I do? Is there any easy way to move the pipe stat downstairs to where the boiler is without having to re-wire and drill through walls and ceilings (I'm guessing no)?

Is the pipe where you pipe stat is fitted actually getting warm? I assume it is. Clearly the pipe stat is faulty or has been wired wrong. Either way its not right and your plumber should come back and change it. Failing that get another electrican/plumber to sort out the pipe stat, sounds like the plumber may have mixed up the NO and NC contacts on it.

demanufactured

You have the same setup as me , the pipe stat is upstairs in the hotpress rather than nearer to the stove.

I have my stat set for about 40 degrees and it works fine , your setup is probably different to mine though , get your plumber/electrition back to move it to the hot pipe at the stove.

shane0007

The pipe stat should be on the flow as close as possible to the stove. It will need to be moved. If you just set the temperature to a lower temperature, true it will bring on the pump earlier, however, once the fire dies down, the pump will dump the heat out of the cylinder at heat the stove until the two temperature become equal, i.e. the stat temperature.

Tester46

Thanks for the replies. I think the issue with my system is that the pipe stat never kicks in automatically. I always have to switch it on and off manually. I think that what is happening is that the water down at the stove is being superheated by the stove boiler, but that water is not moving up as far as the pipe stat upstairs at the water tank. When the banging and knocking starts, I have to manually intervene and adjust the pipe stat by hand until it kicks in. In other words, I might as well just have an on/off switch instead of the pipe stat as I end up turning it on and off by hand anyway. Once I turn it on, it stays on until the fire dies down, so I don't get the benefit of the stove boiler as the pump just pushes cold water through it and it doesn't get heated properly.

The pipe which the pipe stat is on does get warm sometimes, but only because of radiated heat from the hot water in the tank, not from hot water coming up from the stove. If the water in the tank is cold, then the pipe which the pipe stat is on is cold.

Any ideas?

freddyuk

Where is the DHW cylinder in relation to the stove? It sounds like the gravity system is not working as you may have a long horizontal run or dip in the return.
The stove will heat the water before the gravity system gets going and therefore boil the water in the stove before it gets a chance to hit the stat.
I had the same problem and re plumbed with a cylinder above the stove so now it works a treat and I can have the stove at full bore and it will not make a sound. All the heat goes straight into the cylinder. If the flow pipe into the cylinder is not getting hot then there is no gravity feed and should be easy to check.

Tester46

Thanks. The stove is downstairs at one end of the house and the DHW cylinder is upstairs in the middle of the house.

What you are saying sounds right i.e. the hot water from the stove does not seem to be moving up to the DHW cylinder and is therefore not triggering the pipe stat.

Do I need to have the entire system replumbed or do I need the pipe stat moved downstairs?

freddyuk wrote: »

Where is the DHW cylinder in relation to the stove? It sounds like the gravity system is not working as you may have a long horizontal run or dip in the return.
The stove will heat the water before the gravity system gets going and therefore boil the water in the stove before it gets a chance to hit the stat.
I had the same problem and re plumbed with a cylinder above the stove so now it works a treat and I can have the stove at full bore and it will not make a sound. All the heat goes straight into the cylinder. If the flow pipe into the cylinder is not getting hot then there is no gravity feed and should be easy to check.

freddyuk

Gravity systems will not work effectively if there are long horizontal pipe runs.
How far horizontally does it travel? Is it going up into the loft or under the first floor or where?
If you can get a hot loop working so it rises into the loft and then comes back down to the cylinder you may get some flow but I would not guarantee it. Where does the return go as it may be this is causing the flow to stop also.
Is the hot flow side insulated and the cold uninsulated?

Tester46

Hi, I don't know enough to answer all your questions! When the hot pipe goes upstairs, it had about a 20ft horizontal run to the DHW cylinder. Is that too long?

freddyuk wrote: »

Gravity systems will not work effectively if there are long horizontal pipe runs.
How far horizontally does it travel? Is it going up into the loft or under the first floor or where?
If you can get a hot loop working so it rises into the loft and then comes back down to the cylinder you may get some flow but I would not guarantee it. Where does the return go as it may be this is causing the flow to stop also.
Is the hot flow side insulated and the cold uninsulated?

shane0007

The complete run from the stove to the cylinder should be no more than approx 25ft in total. For every 90 elbow, this will be approx 20" deducted and for every sweeping bend, deduct approx 12".
There should also be no drops in the flow pipework and no rises in the return pipework.

Allysonp

Hi, apologies if I have used this site incorrectly, but on reading the post regarding multifuel boiler stoves I wondered if any members have advice. I have just recently had a plumber installed a multifuel stove dunsley and have had nothing but problems it does not seem to heat the hot water cylinder, so the plumber then installed a pump and pipe stat to help, but although there is heat going to the radiators, theres still no hot water at the cylinder, I'm thinking could the run of the pipes be problematic, the pipes from behind the stove are horizontal for a metre or so before heading up to the bedroom above then, they are horizontal again until it reaches the dunsley neutraliser? No idea what the problem could be and plumber does not seem sure either. Another problem could be that the whole system is too large for the type of stove!! I have the stove plumbed in along with oil central heating? Any advice would be welcomed. Thanks

Dtp79

Allysonp wrote: »

Hi, apologies if I have used this site incorrectly, but on reading the post regarding multifuel boiler stoves I wondered if any members have advice. I have just recently had a plumber installed a multifuel stove dunsley and have had nothing but problems it does not seem to heat the hot water cylinder, so the plumber then installed a pump and pipe stat to help, but although there is heat going to the radiators, theres still no hot water at the cylinder, I'm thinking could the run of the pipes be problematic, the pipes from behind the stove are horizontal for a metre or so before heading up to the bedroom above then, they are horizontal again until it reaches the dunsley neutraliser? No idea what the problem could be and plumber does not seem sure either. Another problem could be that the whole system is too large for the type of stove!! I have the stove plumbed in along with oil central heating? Any advice would be welcomed. Thanks

What's a dunsley neutraliser?? A few pics of the hotpress would help

shane0007

It's a UK standard installation component that would be the norm for installations combining solid fuel & other fuel sources such as oil in the UK. Never really promoted here but an excellent product all the same.
It is basically a mini buffer tank, which neutralises the various inputs so that they can operate freely together without pitching or issues that arise from combining solid fuel & other fuel sources.

To Allysonp, nobody really is going to be able to answer the issue remotely.
Your best option would be to get your plumber to contact Dunsley directly to speak to their technical department.

Robbie.G

Theres info on the neutraliser here
http://www.dunsleyheat.co.uk/LINKUP_LEAFLET.pdf
http://www.dunsleyheat.co.uk/nuetralizer.doc