Hi, I'm about to pipe up my bungalow for the rads & will be using a Glow-worm 30 SXI sealed system boiler with built in pump & expansion vestal. Will be pipping for 2 rad circuits & 1 hot water via 3 motorized valves. Not having done plumbing for a wile, i remember that most central heating engineers used to at least put 1 rad on open circuit (IE a towel rail) to dissipate the heat for the pump over-run. Do boilers not require this any more as i cant see anything in the literature recommending this.
Some new boilers have internal bypasses but I am not sure if yours is one of them. Normally the instructions specify what is required.
If there is a chance the flow can be stopped, then a bypass of sorts will be needed. It is unusual on a modern system to see a dedicated bypass because the radiator which is in the same room as the thermostat will not have thermostatic valves so can act as a bypass.
What you need to be careful of is modern boilers have pump over runs so even if there is no demand for heat and the MV's are shut the boiler might still need to circulate the water to dissipate heat from the heat exchanger.
Thanks for getting back, must admit that i cant see anything in the literature, but i am fitting a large towel rail very near to the boiler, so i think i will use this with a couple of locksheild valves as a bye-pass.
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