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Ontheball
Hi folks. First post on this forum. I'm a gas safe plumber/engineer and came across a hot water problem in a property with a type of direct hot water cylinder I've not encountered before. I know someone on here is going to wonder what type of plumber i am for not understanding this system, but there's always something you haven't come across.
Anyway, to explain the system, there's a cube shaped, insulated hot water cylinder with 2 side entry immersion heaters and a header tank. The header tank is all within the cube shaped cylinder body. It seems to hold approximately 5 litres of water and has the normal side entry inlet with float valve and a bottom entry outlet, as well as an overflow that leaves the cylinder body and then runs out of the property. The header tank also has what looks like a vent entering it, which is coming from within the main compartment of the cylinder.
The cold water mains enters at two points at the top of the square cylinder body in 15mm pipe. One to feed the header tank, and one for something else (in the case that the header tank is not supplying the water to be drawn at the taps, then I presume this second cold supply entering the cylinder is the water to be heated and drawn at the taps).
There are also two hot water pipes exiting the top of the cylinder body, also in 15mm pipe, which connect together and then T off into the hot inlet of a thermostatic mixing valve (the cold side of this mixing valve is supplied from the same cold water mains pipe that supplies the cylinder). The outlet of the mixing valve then obviously supplies the hot water to the property.
As for the immersion heaters, one is labelled "mains" and is constantly live, which means this is not an economy 7 system. And the other is labelled "boost" and it has a timer wired between its power switch and the immersion heater.
Now for my 2 questions (if you're still reading. Lol). Firstly, can someone please explain what type of system this is? Because i don't know why there is a header tank as well as another cold water feed entering the top of the cylinder body, plus i don't understand why there are two hot water pipes leaving the top of the cylinder body (even though they're connected together and then T'd off)....I've tried googling this, by the way.
And secondly if, when I open the hot water tap, i get hot water for 10-15 seconds before it goes cold again (although not as cold as the cold water mains, so there is still a little hot water coming through), and I've tried adjusting the thermostatic mixing valve, am I Still looking at the obvious diagnosis of a dodgy mixing valve? I ask this just to be certain before changing anything, since I don't fully understand the whole system...better to be in the know....cos you never know.
Many thanks if you read all of that and much appreesh for any helpful responses.
Cheers, Baz.
Anyway, to explain the system, there's a cube shaped, insulated hot water cylinder with 2 side entry immersion heaters and a header tank. The header tank is all within the cube shaped cylinder body. It seems to hold approximately 5 litres of water and has the normal side entry inlet with float valve and a bottom entry outlet, as well as an overflow that leaves the cylinder body and then runs out of the property. The header tank also has what looks like a vent entering it, which is coming from within the main compartment of the cylinder.
The cold water mains enters at two points at the top of the square cylinder body in 15mm pipe. One to feed the header tank, and one for something else (in the case that the header tank is not supplying the water to be drawn at the taps, then I presume this second cold supply entering the cylinder is the water to be heated and drawn at the taps).
There are also two hot water pipes exiting the top of the cylinder body, also in 15mm pipe, which connect together and then T off into the hot inlet of a thermostatic mixing valve (the cold side of this mixing valve is supplied from the same cold water mains pipe that supplies the cylinder). The outlet of the mixing valve then obviously supplies the hot water to the property.
As for the immersion heaters, one is labelled "mains" and is constantly live, which means this is not an economy 7 system. And the other is labelled "boost" and it has a timer wired between its power switch and the immersion heater.
Now for my 2 questions (if you're still reading. Lol). Firstly, can someone please explain what type of system this is? Because i don't know why there is a header tank as well as another cold water feed entering the top of the cylinder body, plus i don't understand why there are two hot water pipes leaving the top of the cylinder body (even though they're connected together and then T'd off)....I've tried googling this, by the way.
And secondly if, when I open the hot water tap, i get hot water for 10-15 seconds before it goes cold again (although not as cold as the cold water mains, so there is still a little hot water coming through), and I've tried adjusting the thermostatic mixing valve, am I Still looking at the obvious diagnosis of a dodgy mixing valve? I ask this just to be certain before changing anything, since I don't fully understand the whole system...better to be in the know....cos you never know.
Many thanks if you read all of that and much appreesh for any helpful responses.
Cheers, Baz.
