Hot Water in boiler not going to hot taps

E

eggerb

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Any advice much appreciated!

I have a gas boiler which heats my rads and hot water. When I turn the gas boiler on, I previously had hot water from the taps and hot rads. Now, I just have hot rads unless I turn on the immersion in which case I get hot water as well. Therefore, the problem seems to be that the hot water from the boiler isn't getting to the cylinder. (When I heat the water in the cylinder via the immersion, I have no problem!)

Working on the picture below,

2804ep0.jpg



the two pipes at the top are (I think ) hot out. These are cold.

The pipe at the bottom (with a drain valve), I'm not too sure about.

The pipe in the middle and second from the bottom are hot in (I think). They are both very hot right up to the cylinder (pass the valves) when the gas is on but it is as if the water doesn't get into the cylinder.

I'm not exactly sure why there is to hots in (or two outs) but they seem to be joined by a pipe (not sure if the valve should be open or closed) and one of them has a thermostat (again not sure the purpose of this).

Any thoughts much appreciated.
 
Great photo.

The two pipes that enter the cylinder are the flow (top) and return (bottom). Check that the valve on the return is on. Turn it the same way you would if it was a tap I.E lefty loosey, righty tighty!

I suspect if is the thermostatic valve(white, top pipe) on the flow. This white head can be screwed off the valve (without water leaking everywhere) and you will then see a steel pin. Grab the steel pin with a pliers etc and gentely pull on it. These sometimes get stuck. My money is on that.
 
Thanks v much DJ. The 'righty tighty' rhyme is worth remembering!

I removed the thermostatic valve altogether and it is definitely letting hot water through as it is very hot on both sides. Also, the return seems to be very hot too so I'm thinking that the coil is filling with water but I'm still left with cold water from the hot taps unless I use the immersion!

Is there any chance that the coil is not filling with water? (Oh, I closed the connection pipe between the flow and the return as this sort of made sense as the hot water needs to go through the coil. Thanks again.
 
Some success- two hours later the water from the hot taps seems to be getting hot! Its not really that hot though - nothing like as hot as the pipes going into the cylinder. Do I just have to have a bit of patience. Normally, a half an hour gives us enough water for two longish hot showers. As this rate, I'd be a thousand times better off using the immersion. I wonder has my problem anything to do with me not using the gas boiler for two weeks as I was on hols?
 
something is restricting the flow through the cylinder, I would replace the whole thermostatic valve as I have seen these fail more then once. Before you change the valve drain down heating system disconnect pipes from coil in cylinder and ensure it isn't blocked with something. It happens. once you have drained down you should spot the problem I.E blow through an opened valve to see is it letting by etc.

As for the 1/2inch pipe between the flow and return, this is a pump by-pass. It is unfavourable to have your pump pumping against a stopped circuit/zone. I.E thermostat on cylinder is hot enough, (zone closed) downstairs, hot enough (zone closed)Upstairs (zone closed) etc. This ensures the pump will still circulate water when all zones are satisfied. so the 1/2 gate valve should be left sightly open (about 4 full turns)
 
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