D
Dymock
Hello all,
I have a problem with the gravity circuit on a system with 16kw multi fuel burner with a back boiler. The existing plumbing is about 15 years old, roughly. House was vacant before buying and had an old inset stove that was falling apart, assume it worked fine as it was a housing association property with long-term tenants.
A plumber has installed a replacement stove, replaced the cylinder (apparently it has the wrong type of coil), added a heat leak radiator and relocated a section of 28mm pipe. Also added a control valve on the return, I think. There is also a central heating circuit with 8 rads, again prexisting.
When fired up the hot water doesn't go into the heat leak radiator or the cylinder, but vents periodically into the expansion tank in the attic then overflows out of the side of the house. This is quite a noisy process and seems to cycle as the pipes get really hot then go cold after the venting.
The plumber has checked everything he can think of and is now getting reluctant to undertake further work without something major being tried, saying we could try replacing the fire or moving the whole circuit and see if that helps. So far he has tried removing the control valve, checking the rise of the gravity circuit, "blown through" the cylinder and heatleak radiator and cut sections of pipe out to look for sludge.
The existing circuit has a short near horizontal run from the fire, then up to the ceiling and another horizontal run of about 4m to the heat leak radiator, then a couple more to the cylinder. Admittedly this doesn't sound ideal, but as the plumber noted it must have been OK before. The cylinder has a rise of a metre or so, then there is the hot water header tank above that then the expansion tank in the attic, about 4m above the heatleak.
Currently, my thoughts are (from reading around on the web) that it presumably has to be an airlock, blockage like sludge or a misconnection. The plumber says he doesn't think there is an airlock in the pipes having checked. He can't find sludge in the pipes either. Could there be a blockage in the stove? I assume it's just a simple tank, but could air or sludge cause the venting?
If the pipes are misconnected would it cause the system to purge heat like it does? Could a brand new cylinder be faulty and cause it?
Could it be simply too much resistance for the gravity circuit now we've added a heat leak radiator and put the correct type of cylinder in? Would reducing the horizontal runs fix it? I'm nervous of doing this without being fairly sure as it's expensive and not easy to do due to the layout of the house, but if this is most likely then it will need to be done I guess.
For info, the stove and heatleak radiator are 12 months old but in good condition.
Any help much appreciated as we have reached something of an impasse. Apologies for any missing detail, my plumbing knowledge is limited to simple jobs.
I have a problem with the gravity circuit on a system with 16kw multi fuel burner with a back boiler. The existing plumbing is about 15 years old, roughly. House was vacant before buying and had an old inset stove that was falling apart, assume it worked fine as it was a housing association property with long-term tenants.
A plumber has installed a replacement stove, replaced the cylinder (apparently it has the wrong type of coil), added a heat leak radiator and relocated a section of 28mm pipe. Also added a control valve on the return, I think. There is also a central heating circuit with 8 rads, again prexisting.
When fired up the hot water doesn't go into the heat leak radiator or the cylinder, but vents periodically into the expansion tank in the attic then overflows out of the side of the house. This is quite a noisy process and seems to cycle as the pipes get really hot then go cold after the venting.
The plumber has checked everything he can think of and is now getting reluctant to undertake further work without something major being tried, saying we could try replacing the fire or moving the whole circuit and see if that helps. So far he has tried removing the control valve, checking the rise of the gravity circuit, "blown through" the cylinder and heatleak radiator and cut sections of pipe out to look for sludge.
The existing circuit has a short near horizontal run from the fire, then up to the ceiling and another horizontal run of about 4m to the heat leak radiator, then a couple more to the cylinder. Admittedly this doesn't sound ideal, but as the plumber noted it must have been OK before. The cylinder has a rise of a metre or so, then there is the hot water header tank above that then the expansion tank in the attic, about 4m above the heatleak.
Currently, my thoughts are (from reading around on the web) that it presumably has to be an airlock, blockage like sludge or a misconnection. The plumber says he doesn't think there is an airlock in the pipes having checked. He can't find sludge in the pipes either. Could there be a blockage in the stove? I assume it's just a simple tank, but could air or sludge cause the venting?
If the pipes are misconnected would it cause the system to purge heat like it does? Could a brand new cylinder be faulty and cause it?
Could it be simply too much resistance for the gravity circuit now we've added a heat leak radiator and put the correct type of cylinder in? Would reducing the horizontal runs fix it? I'm nervous of doing this without being fairly sure as it's expensive and not easy to do due to the layout of the house, but if this is most likely then it will need to be done I guess.
For info, the stove and heatleak radiator are 12 months old but in good condition.
Any help much appreciated as we have reached something of an impasse. Apologies for any missing detail, my plumbing knowledge is limited to simple jobs.
