another E7 / immersion problem

13 Mar 2006
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United Kingdom

I have recently changed a Economy 7 immersion control box as I believed the last one had failed. However, the new one (Horstmann BX2000) is still showing the same problems as the old one.

Basically, the immersion works when the 'boost' is manually activated, but fails to operate during the E7 hours. During the E7 hours the 'off-peak' LED on the box illuminates, but the immersion still fails to operate. I have double-checked this with a multimeter and there is 248V going into the control box from the E7 supply, but 0V at the output to the immersion. (this was exactly the same scenario with the old control box - so perhaps it was not at fault after all). Also, I can hear the relay in the box switching when the E7 supply is activated, so to me the control box seems to be doing its job.

I have ruled out there is a problem with the immersion element as it works 100% of the time on boost, but to date has not worked through the E7 supply. The control box is fed by two consumer units (one for the 24hr supply and one for the E7 supply). Also, it is a single element hot water tank. (Sorry for the poor circuit diagram!)

Control Box------------24 hr CU
isolating switch
immersion element

I have checked all connections and continuity (all seem ok) but now I am stuck for ideas. Any ideas would be most welcome…

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Hi again, thanks for the reply

Yes, it is wired as per the instuctions on the bottom page 2 (for use with a single immersion element) I have triple checked this to make sure.

The old control box was similar but an older design (type Pactrol WHB2). occasionally the E7 would kick in the immersion on the odd night (rarely though), so I thought it could be a loose connection - but after checking I found this was not the case. I bought the new box assuming the old box was faulty.

The E7 supply is getting to the new Horstmann box (checked during E7 hrs with a multimeter), but for some reason no power is coming out at the other side.
Can you check the E7 supply with test lamps between L&N when the supply is on, clutching at straws but could be a dodgy neutral on the E7 side? If this is OK then its looking more like a dodgy controller, worth waiting for a 2nd opinion though.
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I have exactly the same problem: Horstmann E7 controller and the boost works all the time but the E7 timer will not switch the heaters on. The onlt difference is that the LED will not come on no matter how I turn the timer switch.

I've checked all fuses back and all are ok.

Any ideas/solutions much appreciated!
Have I been here this long :eek:

Best to start by checking you have 240v input between L&N on the off peak supply control box when the E7 supply is active.

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