Horstmann Electronic 7 - Boost not working

[meezrob]

Hi all,

As an electrically illiterate person I've found a lot of the posts on this forum helpful when fixing things round the house. I was hoping I might get some guidance on any next steps before calling someone in about our immersion heater.

Context: we recently switched to a smartmeter for electric and realised our boiler was on all day unnecessarily! As such I did some digging, and reset our timings to economy 7 friendly times, which was easy and has been fine. we have hot water in the mornings no trouble, but once it's gone it's gone.

However, I am about to have a baby and would like to be able to boost this as and when needed (you can never be too prepared for poonamis). According to the manual, pressing 'boost' button should give an hour boost, but this isn't working at all. it just doesn't kick in. I've also tried setting a timed boost, and it just never turns on.

As a test, I set my off peak timer to have 1 time in the middle of the day, and this works fine, but I don't need a full tank of water and also don't want to pay through the nose to have this setting on all the time.

Troubleshooting tried thus far:

• resetting to preset timings by pressing boost, select, plus and minus buttons.
• switching the wall switch off and on again (classic)

• switching the big switch from timed to off and back again
• pressing 'select' so that a black box appears next to 'timed boost' - and trying it without too.
• manually filling up the overflow tank in case it was that.

is there anything I've missed or I should try? I'm genuinely at a loss of what to do next, and baby is coming soon!

 

[Avo Mk8]

Could you confirm you have two immersion heaters in your hot water tank, and that they are both wired up to the Horstman timer? Normally the lower immersion does the timed hot water, and the upper one does the boost.

 

[snowhead]

And the model number or picture / link of the timer as there are a few

 

[meezrob]

Could you confirm you have two immersion heaters in your hot water tank, and that they are both wired up to the Horstman timer? Normally the lower immersion does the timed hot water, and the upper one does the boost.

Thanks so much for your response! as a layperson I'm not sure how I would check this from the outside, but I have attached a diagram of the picture that was left by the installers, if this helps? to me it looks like there might just be one?

 

[Avo Mk8]

Could you confirm you have two immersion heaters in your hot water tank, and that they are both wired up to the Horstman timer? Normally the lower immersion does the timed hot water, and the upper one does the boost.

Sorry I described how ours was wired!!
I see it is possible to wire them for one immersion heater, so it might be the necessary link is not in place.
Need a competent person to look inside to check the wiring.

 

[meezrob]

And the model number or picture / link of the timer as there are a few

thanks, a picture attached for you!

 

[Avo Mk8]

Thanks so much for your response! as a layperson I'm not sure how I would check this from the outside, but I have attached a diagram of the picture that was left by the installers, if this helps? to me it looks like there might just be one?

Thanks for the diagram of the heat store.
it does show two immersions can be fitted.
If you look at your thermal store, can you identify where the two immersions would be fitted, and whether there are actually two there, or just the lower one. Or is the thermal store cladded so you can't see any of the 'insides'?
I would expect a white flex to be coming out of each immersion, each going to the Horstmann timer.

Is your timer in the vicinity of the tank, so you can trace the wire or wires, or is it further away so that would be more difficult?

 

[meezrob]

Thanks for the diagram of the heat store.
it does show two immersions can be fitted.
If you look at your thermal store, can you identify where the two immersions would be fitted, and whether there are actually two there, or just the lower one. Or is the thermal store cladded so you can't see any of the 'insides'?
I would expect a white flex to be coming out of each immersion, each going to the Horstmann timer.

Is your timer in the vicinity of the tank, so you can trace the wire or wires, or is it further away so that would be more difficult?

Thanks for confirming! all the wires to the timer go through the back of the wall for this one, but there's 2 wires coming out of the front which I can now see are for the 2 heaters. pic attached. sounds to me that if both heaters are wired yp, the boost should theoretically be working, and I should get someone to come and check the wiring?

 

[Avo Mk8]

Thanks for confirming! all the wires to the timer go through the back of the wall for this one, but there's 2 wires coming out of the front which I can now see are for the 2 heaters. pic attached. sounds to me that if both heaters are wired yp, the boost should theoretically be working, and I should get someone to come and check the wiring?

OK. So your boost button ought to be turning on the upper immersion.
Really you need someone competent with a tester to ensure mains is getting to the immersion, and to check the immersion element and the thermostat.
It's more usual for the bottom heater element to fail as it's on for a lot longer than the boost one.
You might have a connection problem, or at worst the immersion heater itself might have to be replaced.

Or a less elegant solution, if the upper immersion is duff, could be for an electrician to add the link to the timer so that the lower immersion does the boost function as well. A downside could be this provides a less cost effective boost.

 

[meezrob]

OK. So your boost button ought to be turning on the upper immersion.
Really you need someone competent with a tester to ensure mains is getting to the immersion, and to check the immersion element and the thermostat.
It's more usual for the bottom heater element to fail as it's on for a lot longer than the boost one.
You might have a connection problem, or at worst the immersion heater itself might have to be replaced.

Amazing, thanks so much for your help, really reassuring to know there's not a super obvious fix that we missed before calling in the experts!

 

[brianmoooore]

The display on the controller should indicate when boost is being used. Does the display show this and the water doesn't heat, or does the boost button do nothing?

 

[meezrob]

The display on the controller should indicate when boost is being used. Does the display show this and the water doesn't heat, or does the boost button do nothing?

the boost button lights up if I touch it once, and turns off if I touch it twice. either way, no hot water is produced

 

[brianmoooore]

In that case, it's likely that the upper immersion heater has failed in some way. For several years, immersion heaters have been required to have a thermal cut out in them to prevent the water boiling if the thermostat fails in the 'on' position. Most, but not all, of these cut outs are resettable by pushing a small button, and your problem may be that this has tripped.
The reset button is invariably close to live terminals, so ensure that the power is totally disconnected before checking.

 

[telectrix]

watching this may be useful.

fast forward to 6.56 min. you can see the reset button on the thermostat. if it clicks when pressed with the tip of a Biro, it has tripped.