Downstairs rads cold when hot water on.

[JohnD]

I found reference to "old" cylinders sometimes having a 5kW coil, and modern unvented cylinders mostly in the 12kW to 24kW range.

I have a modern blue vented cylinder, don't know its figure (but I see a similar one advertised as 16.5kW)

A 3kW immersion heats water at about 1 litre per minute.

 

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Thanks, so a new cylinder "should" heat the water up in about half the time. Which would make sense with my old house heating the newer blue vented cylinder in about 40 mins instead of 90 minutes. The insulation on the cylinder isn't very thick either, although I do have an old jacket to put on which will help for now. It seems a new cylinder is on the cards, then I should be able to balance the heating and hot water better so I don't lose heat downstairs. When i get the boiler serviced I will see what they say also. Many thanks.