surprised at some of the replies to this thread.
This sort of system was very common years ago but thankfully rare now. A solid fuel boiler cannot be switched off like gas or oil,as long as it is lit it will continue to heat. For this reason it must be connected to an unrestricted gravity loop which must be vented. The loop generally is the indirect coil in the HW cylinder. A solid fuel boiler in full flight will heat a hot tank in no time,if no water is being drawn off it will heat to the point where it will boil. This is normal and the expanding water and steam simply vents out into the cold header tank in the loft. The heating is simply a pumped flow and return. The purpose of the low limit stat is to prevent the pump running if the pipe temperature is too low and pumping cold water around the system. The high limit stat is vital, remember there is nothing to prevent boiler water temperature reaching boiling point,if this was pumped round the heating circuit radiators would reach a dangerous temperature, the high limit stat is there to switch off the pump if the flow temp becomes dangerously high.
The obvious problem with the system is the danger of unrestricted rise in water temp which can result in boiling water from the taps....not good with kids and elderly,or anyone for that matter. Which is why you don't see them much these days.
...At last...well said.
We do not know what system this is,or how it is or should be functioning,but it strikes me it does not have any fail-safe design.
You cannot have pumps and stats controlling possible uncontrolled or unwanted build up of heat.
This should be "designed in",BEFORE any additional features. Even with the gradual acceptance of functions such as dumping and quenching,as extra fail-safes,they never trump sound, basic hydrodynamics.
I have come across many systems,where pumps have been flung in,due to the lack of knowledge,willingness and money,to fit pipework to falls,etc.
Usually,it is Tarquin's mother and father,who see a splendid AGA at the Ideal Home Expo,and they brow-beat the 3rd plumber along,to vascular surgeon it to the same pipework the Glow-worm used, for the last thirty years...then wonder why nobody can make it reliable.
True story...two years back,a good mate of mine,and a quality gas engineer,got involved with a couple similar to ^,asked me to bob down to view their Rayburn boiler set-up,two heads being better than one,even if they are sheeps' heads...gave him the bad news...he passed it on...customer said "can't be true...we have spent £8000..." Nowt came of it.
One year later,another pal got a call,to install a posh feature wood-stove,in a conservatory,at the same property,got asked about wet systems,and said he knew someone...so,back i went...
Lady of the house arrived back,an hour into my investigation,which was 55 minutes after noticing that nothing had changed,she asked me what i was there for...i told her "Getting paid twice,for the same thing..."
I have yet to receive, one single Christmas card from her...
