Hot Water Cylinder

6 Nov 2007
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United Kingdom
I want to replace our hot water cylinder for a larger one on a vented, indirect, 2 motorised system.

I'm confused as it appears the boiler flow enters the cylinder at the bottom in 22mm pipe since it has a motorised valve on the pipe before it enters the cylinder. The pipe above it in 15mm appears to be the boiler return.

Is this correct, should the new cylinder have the flow above the return pipe. There is a pump which tees off to both valves if that makes a difference.
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Flow should be to the top. Although the existing valve is on the bottom one it just means it's on the return.
Is there an arrow on the existing motorised valve? This will confirm the flow direction.
You're right the arrow indicates this so the flow is fixed to the bottom. When I replace is it advisable to swap the pipework around so the flow is at the top?

Also, should I replace the 15mm with 22mm for the return.
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Flow in at the top promotes stratification, which is generally what you want.
Flow in at the bottom transfers energy into the water quicker, and gives a more even tank temperature.
It doesn't make a whole lot of difference really.

If the coil on your new cylinder is capable of dissipating more than half a dozen kW, then yes, it would be a bit quicker to reheat with 22mm pipes - but not vastly. Depends on the distance.

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