I am not a plumber nor experienced diyer and have some questions about ladder dual fuel radiators. The WWW seems to be a bit lacking.. :)
1) I was wondering how you choose your element wattage? Is it based on rad height vs element length or rad wattage vs element wattage?
2) there is discussion about how to switch between gch and electric use that tells you to switch off flow for electric and switch on for gch.
There seems to contention between advice what to do with the return valve ranging from keeping it full or slightly open to relieve pressure build up. One site even said just open the bleed valve slightly to relieve pressure instead.
I was wondering what you would advise here and is the advice the same for a rad fitted with a TRV and lock shield?
3) what are the practical and safety implications of not doing the switch correctly resulting in the following scenarios?
a. If you run the element with the flow open and the gch isn't on.
B. If you run the element with the flow open and the gch is on
C. If you run the gch having forgot to open the flow?
Hi n99 the element must be rated at less than the radiator wattage. In most cases the length wont be a problem. It seems that you've been reading some very odd advice ! With a correctly installed system, there should not be any concern as to how to switch over, the system will take up the water expansion. You really do not have to do anything other than switch on, as long as the pump is not running there will be no circulation, and the towel rail only will be heated. There should be no need to turn off the rad valve or TRV. Under no circumstances must both the control, and lockshield valves both be turned off.
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