I'd expect a three port motorised valve to be fitted adjacent to your hot water cylinder. It directs heated water from the boiler to the coil in the cylinder when the cylinder stat calls for heat and to the floww for the CH system when the room stat calls for heat. This is known as a Y plan system and you can find a diagram at "ultimatehandyman.co.uk/y_plan.pdf"
No your system will not definitely have a 3 port valve. You MAY have two valves which will be two port zone valves. One for the heating circuit and one for the HW circuit. This is known as an S plan system and you can find a diagram at "ultimatehandyman.co.uk/s_plan.pdf
i still cannot find this valve and ive looked every where :oops:
looking at my boiler again closer (glow warm space saver 38) i can seee that there are 4 pipes in total running to and from the boiler. i can set there is a central heating inlet and outlet which get hot when the ceentral heating is on but the other 2 which im sure is the hot water inlet and outlet are cold.
i guess this means my system wont have a three port valve or am i wrong??
the inlet and outlet pipes get warm close to the boiler when the hot water is turned on, but the rest of the pipes is stone cold. i guess this is just residual heat from the boiler when the central heating is on.
does this boiler use some kind of pump to push the hot water through the coil in the cylinder???
i looked at that diagram and it is similar to that except the water that is heated for the central heating is not used to heat the heat exchanger in the cylinder.
this glow warm boiler has an inlet and out let for the central heating which has a grunfos pump on the line. The pump kicks in when the heating is switched on. There is no problems with this side.
but the boiler also has also 2 other pipes. one an inlet and one an out let. this. This is like a ring main. for HW, the boiler heats the water in this 'ring main' it flows through the heat exchanger in the cylinder and returns back to the boiler.
what i cant figure out is how the water is pumped from the boiler, through the heat exchaanger and then back to the boiler. i cant find/see and pump anywhere on this line.
If it looks like that then you DO have a gravity HW system. The HW system is NOT pumped and there is NO 3 port valve.
You have a blockage in your primaries. Its either scale or its air.
Trouble is with a gravity system just adding descaler won't help 'cos it doesn't get pushed round the HW circuit by a pump. Trace the blockage with your hand on the pipework. Where it suddenly goes cold its there!
If its air then the quick way is to boil it out but don't attempt this yourself. Get an RGI in as although its not a gas related problem he will know the limits of how far he can push this boiler / cylinder to do that.
Methinks you may also have reached the time where, medium term, you need to be considering a boiler replacement. As I said this one is over 30 years old!
i understand that i should get a new boiler but im thinking of putting an extension on the side of my house. it will be quite a big extesion. this means that i will want the boiler in the new extension
i dont want to have a new boiler installed, only to have it moved in 12 months time.
i would prefer if i could get the existing boiler to run another 12 months
Hi, you def have a gravity hot water system and pumped heating, first thing to check is the expansion tank (the small tank in loft) has it got water in it or is ball valve stuck? iif so free ball valve end of problem, if not could be blocked cold feed as already suggested or air, would not advise removal of boiler thermostat yourself to boil the primaries however if you find a drain point fill it up off the mains water pipe, this will take push the water through system and up into expansion tank, if tank fills first then overflows cold feed to system is probably fine and it is air which should now have been pushed out, if water comes through vent pipe over tank first cold feed is probably blocked, you could combine the two in the loft and see if that works otherwise cold feed should be the smaller pipe (15mm) going into the 1" primary return off the cylinder good luck Paul
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