a bit technical regarding KW Usage please

i have been called out to a pulsacoil 2000 which has trouble getting and keeping hot water for taps.

going to check the header tank tomorrow but when i went today the timer that was installed had blown up, as in it was used to time for switching on the first heater with a 24hr clock, and build into the timer had a push button booster which was variable from 5 - 20 mins boost which allowed power to the second heater.

the relay inside this timer on the booster side was black as, well burnt out.
so in order for them to still have hot water i over rided the timer and allowed them to get hot water by means of switching on the fsu for he first waer heater. after nearly half an hour still no hot water so i thought i would allow both heaters and asked them to only switch on a few mins before they needed hot water and hen turn off,

after 5 mins it tripped the 16A mcb so i put it back to one heater for now.

just wanted to clear up does the power to the heaters alternate so both heaters are not on at the same time? why would it allow boost for all this time yet hard wired trips the mcb? or is the timer set normally so that it's heater 1 or 2 and not both at the same time?

any other info you can provide for me to best take a look at when i am back there i would really appreciate.

Thanks

Phil Reed.

each element should be wired to its own spur point. 1 which is a boost facillity [usually on peak rate juice ] and 2 running on economy 7 /or 10 usually to the lower immersion heater which should kick in between midnight and go off around 7am.
if the relay is burnt out and unit is tripping the 16amp i would check the heater elements for signs of leaks as this is a very common problem.
hope this helps
mark.
www.gledhill-repair.co.uk

Mark is correct in saying each element required its own spur & furthermore the spurs should be on individual mcb if the rating is 16amps. This may not be the case if you have a Horstmann Electronic 7 timer. If both elements are on the same circuit, this would explain the overloading situation you are experiencing. If would also recommend you inspect the elements for leaks and carry out an insulation resistance test on each one.