I've always gone to the isolation valve and yes I agree wholly with your comment about bonding, my point and biggest gripe is that the gas regs and the electrical regs are not the same. and probably never will be !
I have had this conversation with so many gas engineers and their answer is that it is no longer referred to a Thermostat its a safety interlock incase the return stat in the boiler fails it can shut down the boiler ????? -------- if you ask me but that is what they need/install to meet their...
Most Manufacturers do a single module contactor rated at 20A however they are only 230V coils so you will need a Neutral across A2 and a feed from each switch to A1 let me know if want a drawing..
You say that the shower is fed directly from the boiler so the rads will be as well so they should be at the same potential unless the however the water is plumbed in plastic and the rads in copper for arguments sake so I would check the boiler first for any issues and see if you can ascertain...
Table 4D2A says that a 2.5mm 70 degrees c, cable in a conduit buried in a thermally insulated wall will carry 18.5A
2.5mm cable 70 degrees c, enclosed in conduit or trunking ON a wall will carry 23A with a run of 5 meters VD would not come into it
If the cable run with others if so the...
Me personally i use both methods so for argument sake i would feed the lights in the hall and not the switch because you may well have 2 way up and down plus an external light so you end up with a very busy switch then into the kitchen i may feed the light switch as 3 plating down lights is a...
Good Luck! won't be back on till Monday i'll see how you get on then! just another thought is that its worth checking the voltages on the other equipment upstream from the contactor as the voltage would still be low on L1 further up stream
Definitely a fault on L1 I would check what James has listed It may well be an isolator or supply cable upstream feeding the DOL that is failing causing a high resistive joint looking at the current readings
The intention os good, however is drive by dave prepared to be fined or imprisoned for false reporting until that happens they will not be worth the paper that they are written on, only when this happens will people sit up and realize that it is there for their protection not a financial gain...
What you might find is the bearings in the motor at starting to seize or the gear box that the motor is driving has become warn out, you could do with a clamp meter on it and if you adjust the overload up you can see the current rise you might find due to its age that another amp makes the motor...
Personally i would go with your own risk assessment and that should be based upon location, height, access available, time that you need to be up there and personal safety.
Good Luck
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