On Sun, 16 Dec 2018 00:10:06 -0000, trader_4 wrote:

On Saturday, December 15, 2018 at 6:48:12 PM UTC-5, Kristy Ogilvie wrote:
On Sat, 15 Dec 2018 23:14:13 -0000, trader_4 wrote:

On Saturday, December 15, 2018 at 12:25:03 PM UTC-5, Kristy Ogilvie wrote:
On Sat, 15 Dec 2018 17:04:34 -0000, trader_4 wrote:

On Saturday, December 15, 2018 at 12:03:16 PM UTC-5, trader_4 wrote:
The point is, if it overheats something is wrong. Your statement above
suggests that overheating it is frequent? For example, I had one
of those instant hot water dispensers for the kitchen sink. It quit and
it turned out the thermal fuse had blown out. But there was no reason,
it had not gone empty, etc. The new part was a different design. Which
lead me to believe they had a problem, the original ones were set too
low or failed for another reason. But that's how it worked. Thermostat
for normal operation, thermal fuse for when things go wrong. Had an
electric kettle, same kind of design.

Forgot to add, if you really want to know and have easy access to it,
put a volt meter on the thermostats and watch what happens vs water
temp.

Good idea. Tested. They switch as I thought. Both elements stay on permanently unless I turn it to an uncomfortably high temperature, then one cuts out for several seconds. I couldn't get the other to cut out, that's probably if the mains pressure drops lower.

Uncomfortably hot 105c

But as you've said, it doesn't have to be 105C, and it isn't. It cuts out at about the temperature I'd consider my skin about to be damaged,.

If it cycled all the time it would be annoying, as incandescent lights would dim and brighten each time it switched it

Any heater like that is going to cycle

Yet it doesn't, as the temperature is fine tuned by pressure. The heater is either off, 4kW, or 8kW, and remains that way or the whole showering session.

Wtf? The shower changes it's flow rate instead of the obvious, ie the thermostat cycling? That's one of the dumbest things I've seen here in a long time. And it's flow rate that would have to change, not pressure.

You seem confused. When I take a shower, I select 4kW or 8kW, then adkjust the pressure valve until it's precisely the temperature I want. That temperature stays constant. Next time I take a shower it will be left set the same.

and FF it causes your lights to dim, you have bad wiring.

It doesn't take much of a voltage drop for you to see lights dimming, only a couple of volts. And drawing over 30A on a 100A system tends to do that.

Well 100a service, you couldn't get that installed here today. It's circa wwii. I

You're forgetting we have a decent voltage in the UK. Call it 200A for your piddly little 110V service.

- in fact I remember as a kid my parents' shower did the same as mine but much faster - it only had one heating element, 7kW, but the switching was for 1 second, as the lights would dim and brighten quite often when you turned it too high. It's basically just an anti-scold (or damage to the heater perhaps) feature to protect against water pressure dropping, or you turning the dial too high.

I have 200a service, 3 ton ac, double ovens, electric dryer, no lights dim, ever.

No point in wasting money on thicker wiring just to stop lights dimming. And they don't with LED lighting anyway.