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So it’s wired --- over t!t, then?
Sort of. The tank elements only have one shared feed using one 2.5mm2 cable off a B20A on the peak busbar. I have advised Megan only to use one element at a time. Something has happened in the past to make this so and to change the pattern/brands of the IH iso switches.
 
The extreme RH MCB position on the CU is blanked off and marked spare, but was originally labelled 'immersion'. Is there any evidence inside as to what this might have been about?
You say both switched cable outlets for the immersion heaters are connected back to the CU by a single 2.5mm2 T&E. Does the feed go to one and then spur on to the other? If so, does this look original?
 
The extreme RH MCB position on the CU is blanked off and marked spare, but was originally labelled 'immersion'. Is there any evidence inside as to what this might have been about?
You say both switched cable outlets for the immersion heaters are connected back to the CU by a single 2.5mm2 T&E. Does the feed go to one and then spur on to the other? If so, does this look original?
1. Theis new MK CU was installed when Megan moved in.

2. I suspect strongly that the RH mcb position you mentioned was for the off peak IH element. It is now fitted second right to off peak MS but does not power anything. I reckon one of the original three B20A rcbos (two for SHs and one for off peak IH) on the right of the off peak mainswitch has been moved to the right of the far left peak main switch to supply the hall dimplex.

3. After Megan bought the flat but before she moved in the electric space heating was renewed in toto.

3. The original red black 2.5 mm2 feed from peak side B20A marked IH arrives at top IH iso. Spurred off it in brown blue is a drop to the lower IH iso. Spurred off lower IH iso is a drop to the new 13A socket for the water pump.
 
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So it's looking likely that the conclusions that timhoward and I came to at exactly the same time, in posts 31 and 32, that there was a fault with the off peak supply to the lower immersion are correct? This was then bodged to get the lower immersion working again, most likely without telling the customer that the cost of water heating would be doubled.
 
The single feed to the immersions could perhaps be used as is by installing a Horstmann Economy 7 type controller, fed from one of the existing FCU's, which could output to the two immersions, as it ensures only one can be powered at any one time. So setting the timeclock to E10 periods would power the bottom immersion on cheap rate, and the rest of the time the boost button would be available for a top-up, on peak rate of course.
But does the pump draw too much to be left on that citcuit as well, I guess it doesn't consume much?
 
So it's looking likely that the conclusions that timhoward and I came to at exactly the same time, in posts 31 and 32, that there was a fault with the off peak supply to the lower immersion are correct? This was then bodged to get the lower immersion working again, most likely without telling the customer that the cost of water heating would be doubled.
Yeah -we did ok!
But I can't get my head around someone's decision making process. I'd have thought the choices (most preferable first would be)
1) Actually fix it and sort out the off peak supply
2) leave lower IH connected to peak supply and fit a ?radio time switch. Customer has control over when there is hot water and can heat it up overnight.
3) leave lower IH connected to off-peak supply - Tank heats overnight at cheap rate, customer has hot water at better price for some of the day
4) leave peak connected to both IH's. Overload the circuit 24/7 and pay through the nose for perpetual heating of water.

Only a right muppet, or someone completely ignorant about how it worked would choose option 4.
 
The single feed to the immersions could perhaps be used as is by installing a Horstmann Economy 7 type controller, fed from one of the existing FCU's, which could output to the two immersions, as it ensures only one can be powered at any one time. So setting the timeclock to E10 periods would power the bottom immersion on cheap rate, and the rest of the time the boost button would be available for a top-up, on peak rate of course.
But would the pump draw too much to be left on that citcuit as well?
Your idea should be option 1a in my list. Nice!
 
I think the problem with the peak/off peak was suggested way before #31 and 32.
It was only in post 30 that is was determined that there was no Horstmann E7 or similar controller fitted anywhere, which would have only required a single 24 hour supply.
There are efficiency advantages to be had by using a controller in preference to the supplier's off peak switching - the off peak supply starts heating the water at a time of day when there is likely to be little demand for hot water, finishes heating it after three hours or so, then spends the rest of the night bouncing off of the thermostat, as heat leaks from the cylinder.
Ideally, you want the cylinder to finish heating just before the end of the off peak period.
 
Yeah... im going to be pedantic.... 🙂

I think you'll find that back at #8, there was mention of a Quartz E7 controller or similar..... i believe that trumps your #30

😛
 
I left Megan saying I would consult the contributors to her post and seek their recommended solution. She’d like it done during one visit by a recommended electrician - baldelectrician’s ex apprentice perhaps?

With the new expenses of a new baby to look after something economical yet allows best employment of E10 tariff please. Near M25 junction 26.
 

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That is exactly what I have in mind, and the cheapest complete solution. No experience of the Sangamo, but from the link it seems to do exactly what the Horstmann does. Don't know why it's described as an 'upgrade' to the Horstmann?
Don't forget that the 'stats need changing as well.
 
The issue of safety overheat devices in immersion heater thermostats is becoming less and less important, as more properties and new builds use direct mains feeds to the hot water cylinders, or even utilise one of those horrible combi boilers.
The safety issue only really arises if there is a loft mounted plastic feed tank. Something which DOES very likely apply to this property.
 
Hi all
Touching base
I can’t thank you all enough for all your help - I am unsure how I will ever repay you all!!
I am keeping in touch with @marconi now re all of the solutions/someone to sort, which again I am so eternally grateful for as I wouldn’t know where to start with finding someone able to carry out the works from his diagnostics.
Very grateful you all found my post when you did.
I really like the idea of the Sangamo, looks much more user (average Joe!) friendly
 
The issue of safety overheat devices in immersion heater thermostats is becoming less and less important, as more properties and new builds use direct mains feeds to the hot water cylinders, or even utilise one of those horrible combi boilers.
The safety issue only really arises if there is a loft mounted plastic feed tank. Something which DOES very likely apply to this property.
Yes plastic tanks are there above hot water tank. We will fit safety 'stats.
 
Fellow electricians - an update.

First a big thank you to baldelectrician for the excellent recommendation. Mr K ON was spot on and Megan has kept his contact details should she require any further electrical work. You trained him well in theory, craft and safety and importantly how to comport himself in a stranger's home. He was quick on the uptake of my on-site brief.

The electric water heating is now under off peak control with manual boost and wired as in my #55. Over the next few days we just need to confirm the timings for the three on/off periods of E10 to ensure the Sangamo off peak timer is in sync - there are four E10 programmes which can be viewed at the link below second page bottom right.. I will pop back to adjust if needs be. See:

https://cdn.shopify.com/s/files/1/1...xi_User_Instructions.pdf?14510365057969918178

There was indeed a 2.5mm2 T/E feed in red/black to the bottom IH isolator. It was simply cut back and tucked out of the way. There was no continuity between this point and the 2.5mm2 T/E in red black wired into the far right rcbo (marked inside IMM) of the CU on the off peak busbars. All nicely isolated both ends now in wagos.

Regards

M
 
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