reduced supply voltage

[the pict]

just back from a call out no hot water in a hotel, plumbers been and he changed element and stat, voltage at board incomer 220v the other two boards are at 242V will this 20v differance have an affect on this water heater, it's a 4K element so 16.6A so I take it the resitance is pushing back 2 and a bit amps but will this stop it or just make it abit slower in heating a tank of water.
Pict

 

[telectrix]

should make hardly any difference. what voltage have you got at the heater with it switched on? clamp meter the phase conductor. is it drawing current?

 

[nickblake]

single or three phase .. thats a hell of a voltage drop if its single phase id check the connections as some thing could be amiss

 

[the pict]

I checked back at the board supplying this and whipped the covers of the other two all incomer tails are tight as are the busbar and N terminations same with the breaker didn't have my clamp with me but the voltage at the element is a couple of volts lees that at the breaker luckily I might run into the area DNO engineer over the w-end and get him to have look monday
Pict

 

[IQ Electrical]

What is the supply type?

 

[james king]

we have had that once on a farm house the voltage dropped by 80v on single phase, it was the DNO in the street up the road

 

[nickblake]

Thats a very low voltage almost to the max permited allowing for diversity of the supply if the board is comming directly from the supply then there could be a supply fault im assuming its three phases and 1 phase the volatge is low ,could be an idea as you have said to contact the DNO as IQ has said what is the supply type

 

[the pict]

It's PME done about six years ago by the guy who is now the area engineer,

 

[IQ Electrical]

Is it 3-phase, a phase per board?

 

[the pict]

phase per board

 

[nmaverick]

Voltage Drop would increase the current,but it should not change the heating rate,as the power fed would be constant

 

[MarkieSparkie]

NO!, NO!, NO!, nmaverick you are wrong. The water heater element is purely resistive, the resistance does not change and the current is inversely proportional to the resistance (ohms law) so the only variable is the voltage (which in this case is reduced), therefore the power consumed by the element is REDUCED in proportion to the voltage and not constant as you stated.