Central Heating circulation issue

John.g said:

You have a combined Vent and cold feed, one vertical pipe in effect, it should connect into the system on the suction side of the pump, reason is, when connected to the suction side, the pump suction will be at the elevation head (height) from the F&E tank surface to the pump suction, say 1.5M or whatever, the pump discharge head will then be pump head + the elevation head, a pump head of say 3.5M+1.5M=5M, all the system at positive pressure. If connected at the pump discharge the pump discharge head will be 1.5M and the pump suction, 1.5M - 3.5M, a negative head of 2M, most of the system under nrgative pressure.
So if you go for the first option you just move this vertical pipe to the left of the pump after also moving the pump as per your own post #40 and thats it. If you go for option 2, my post #43, then the vertical pipe is already to the pump suction and you run the pipe as shown to the cylinder HW inlet.

There is a plasic 1/2" pipe above the combined vent&cold feed, where does that go to? or is it removed and capped somewhere below?. Or ist blanked off and removed at the tank?.


You don't have to but its better to do so and replace it with a gate valve for balancing purposes and before you install (if) a motorized valve you can simply use the gate valve as a cylinder temperature control, on/off or whatever.

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John.g said:

A gate valve is simply a shut off valve with a hand wheel on top to open/shut.
View attachment 78401

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John.g said:

If you have all the rads on and the HW cylinder then the cylinder coil which is effectively a 3/4 ins by pass can rob the CH side so that is used and maybe opened a 1/2 turn or so to reduce the flow through the coil and give more to the rads. I think its installation is frowned on now by the powers that be, I never had one on mine but I have a motorized valve and i generally programme that to come on for a hour or two before the CH so no problem but I don't notice in reduction in the rad outputs even with both on.
As I said you can use it temporarily until you install a motorized valve but you don't have to, its up to yourself.

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