Immersion Boost function not heating water

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Hello,

I have an immersion heater with a Horstmann Economy 7 controller. The immersion tank has 2 elements.

The Economy 7 function works ok (bottom element).

When I try to use the 1 hour Boost function (top element), the boost light on the Horstmann flickers on briefly but then goes out again. The timer moves round but I don't get a boost light or any hot water.

The only way I can get hot water outside of Economy 7 hours is to temporarily manually move the clock so that the system thinks it is 1 am in the morning. I'm assuming in this case the system is using the bottom element?

I've had the immersion tank drained and the top element replaced but that still didn't make any difference.

I've also swapped the top and bottom elements round and tried the reset switch on the top element but none of that makes any difference. The boost function still doesn't work.

I'm puzzled as I assume that the timer must be ok if it works in Econ 7 mode?
 
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Yes, it has been changed for a new element and I've swapped top and bottom elements around.
 
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When I try to use the 1 hour Boost function (top element), the boost light on the Horstmann flickers on briefly but then goes out again. The timer moves round but I don't get a boost light or any hot water.
Possibly a loose/burnt wire inside the Horstmann controller, more likely it's just broken.
 
It only has a 1 hour Boost option. It's one of the old style Horstmann units.

I'll take a look inside and see if I can see anything obvious. I've already spent £200 getting the tank drained and element changed so want to identify exactly what's wrong if I can before getting someone in to "fix" it again.
 
Yes.

Also, sorry I should have said I changed the thermostats around (not the elements) to check that it wasn't a thermostat problem. That didn't make any difference so I then had the tank drained and the top element replaced. It cost £200 as it took an hour to drain the tank (elements go in at the side). Still no difference.
 
Why havent you tried just supplying the immersoin with power directly? Stick a bit of flex on it with a plug on the end and make sure it works.... Would have cost you nothing and saved you the £200.

Similarly, if you have the wiring diagram for the controller, you can simply link out the feed to the immersion at the controller backplate and prove that the electrical supply is all working as it should be.
 
A quick visual check inside the unit doesn't show anything odd. I've put photos in album "Horstmann".

Unit has power coming in as the timer works ok (both for Boost and Econ 7) and I do get hot water on Econ 7, but not on Boost.

It could be something to do with the power to the Immersion Boost. I'm not an electrician so can only do basic diagnostics myself. I don;t mind calling in an electrician but just trying to be confident where the problem is so as not to waste any more money.

Thanks,
Maggie
 
Thank you Aragorn84. It hadn't occurred to me to do that but now I see that's the obvious thing to do, after all it's just a big kettle isn't it.

I have some time this weekend so will give it a try.
 

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