Brand new electric shower

Good it gets hot, even if briefly, that says  the element has not been blown by dry running, which is what the commissioning tests are all about.

I wonder if you do not have enough water pressure for some reason - we have a marginal system at home where the water is incapable of filling the tanks in the loft if the loo is flushed for example, and the shower only works if we are not using water and neither are the neighbours.  (leading to a lot of shouting from the bathroom if someone forgets and goes to fill the kettle or something).

At least in ours the switch is a simple pressure device, and has a bit if a hysteresis to give it a snap action, so you can have a situation where it is fine on a 'hot' settiing (low water current) and then  snaps off after a bit if you try and run with a cooler setting, as that needs more flow, and the pressure droops below the critical value after a short delay. Then you have to shut the flow off to restart.

Has the cold water pressure been checked both on and off load - that is to say with water running does the pressure droop ,  are all stop valves in the line to the shower opened properly, all filters free of crud and that kind of thing ?

It may not  be that at all, but it may be worth a check.

(or do as I do and have a bath, it is Mrs MAPJ1 who uses the shower, and she get up for a shower before next door are using a lot of water.) I did install a proper mixing shower from the stored hot water downstairs that has a decent flow rate, but that  is not popular, as it is downstairs, so we have a cat litter tray in it instead.  However, to be honest, based on experience I can not particularly  recommend that, unless of course you have a cat and never use the shower.


M.

Good it gets hot, even if briefly, that says  the element has not been blown by dry running, which is what the commissioning tests are all about.

I wonder if you do not have enough water pressure for some reason - we have a marginal system at home where the water is incapable of filling the tanks in the loft if the loo is flushed for example, and the shower only works if we are not using water and neither are the neighbours.  (leading to a lot of shouting from the bathroom if someone forgets and goes to fill the kettle or something).

At least in ours the switch is a simple pressure device, and has a bit if a hysteresis to give it a snap action, so you can have a situation where it is fine on a 'hot' settiing (low water current) and then  snaps off after a bit if you try and run with a cooler setting, as that needs more flow, and the pressure droops below the critical value after a short delay. Then you have to shut the flow off to restart.

Has the cold water pressure been checked both on and off load - that is to say with water running does the pressure droop ,  are all stop valves in the line to the shower opened properly, all filters free of crud and that kind of thing ?

It may not  be that at all, but it may be worth a check.

(or do as I do and have a bath, it is Mrs MAPJ1 who uses the shower, and she get up for a shower before next door are using a lot of water.) I did install a proper mixing shower from the stored hot water downstairs that has a decent flow rate, but that  is not popular, as it is downstairs, so we have a cat litter tray in it instead.  However, to be honest, based on experience I can not particularly  recommend that, unless of course you have a cat and never use the shower.


M.