Discuss Would you expect an electric shower to draw amps in this way? in the Electrical Forum area at ElectriciansForums.net

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I just went to replace a 45A pullcord for someone as it had stopped working. It's only been in a year so I assume it must have been a loose connection during installation as a couple of the connections, particularly neutrals, were very loose in the switch but fine at the board and in the shower itself.

Anyway out of curiosity I ran the shower which is 8.7kw, wired in 6mm and it draws 35 amps. So low or 'cold' - 35 amps, turn it up to the max - 35 amps. Now it's an old shower, must be going on 25 or more years old.

My question is would a modern shower behave like this i.e. constant draw or would it be lower draw on lower settings? I've never put the amp meter on one apart from this so I don't know. They only run it on medium heat so it seems mad it's drawing max amps to heat the water but like I said I've never tested it on a different shower. I'm just thinking is it worth telling them to upgrade to a modern unit as this constant draw is going to tax any isolators, connections and the cable more or is that just pure waffle?
 
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your assuming there's more than one tap off from the element to give those different readings but water temp may be controlled by just the flow rate on that particular unit. I always tell the customer not to keep using the isolator as a switch and just turn the shower off at the shower control only. that's one of the reasons these pull switches fail prematurely. Even known people to pull the cord whilst the showers running under load. ?
 

Lucien Nunes

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is that just pure waffle

Actually, yes. The dial of a conventional shower or instantaneous water heater adjusts the temperature of the water, but it works by altering the flow rate. Regardless of whether you have high flow at low temperature or low flow at high temperature, the total heat input is constant hence the constant current load.

First, at average temperatures, 8-10kW is only just enough for a shower unless the incoming water is quite warm. It's a compromise between unmanageable load and inadequate heat output. Given that limitation, the dial makes a reasonable trade-off between flow and temperature. The summer setting cuts out part of the element and just scales the whole temperature / flow rate compromise down.

Second, it's much cheaper to control the water flow with a valve than to control the current with a thyristor.
 

brianmoooore

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I've never used a pull cord switch on an electric shower unless there was absolutely no alternative, and even then, it would be the type without a neon indicator.
My isolator of choice is a 50A 2G sized DP switch, mounted at door top level immediately outside the shower room door.
 

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