Advice on Hot water Tank & iboost (or similar)

LB?

Please excuse my lack of technical knowledge, but I think I know what I'd like to achieve and would like some simple advice on how to get there.

I have had a Solar PV installation for 3 years and would like to use the excess electricity that is currently being sent to "the Grid" to heat our hot water. I've read about the iboost and immersun devices and on the face of it they appear to be what I would need, but.... having examined my hot water tank it appears that it is purely heated by the gas boiler, and it does not appear to have an element in it. The few people I've spoken to about this say it's unusual - gas heated water tanks usually have an electric "back-up" - but I'm pretty certain this one doesn't!

Anyway, what would you advise to put myself in a situation to fit an iboost? Is it a new tank with an element? Can an element be fitted to my existing tank? What sort of costs do you think I'd be looking at?

Any advice would be appreciated

EricMears

LB? wrote: »

.... having examined my hot water tank it appears that it is purely heated by the gas boiler, and it does not appear to have an element in it. The few people I've spoken to about this say it's unusual - gas heated water tanks usually have an electric "back-up" - but I'm pretty certain this one doesn't!

Anyway, what would you advise to put myself in a situation to fit an iboost? Is it a new tank with an element? Can an element be fitted to my existing tank? What sort of costs do you think I'd be looking at?

First of all you need to examine your existing hot water tank (again ?) really carefully to see if it's got a large (two and a quarter inch diameter ?) blanking plug anywhere on it. Usual position is on the top but anywhere on the side is possible. If the tank is insulated, it may well be 'hidden' underneath the insulation (if that's been fitted afterwards - a tank with foam insulation applied at factory would have a hole left in the jacket).

If you do manage to find such a plug then fitting an immersion heater is very easy. Just drain system down, take out plug and fit immersion heater instead. When buying the heater, try and get one that will reach to bottom of tank if that's possible.

If you still can't find such a plug, then it is (theoretically) possible to remove tank completely, drill a large hole in it and fit an immersion heater to it using a 'back nut'. But that's a tedious job (and expensive if you don't DIY) and more likely than not you'd finish up with a leaky tank ! Probably just as easy to buy a new tank when you can take the opportunity to fit an even bigger one and choose whereabouts you have the immersion heater tappings fitted.

But you'd probably need to cost the project carefully as a new tank + immersion heater is going to be a significant cost. Looking at any plumbers merchant webpage should be able to give you some idea of prices e.g. :-
http://www.plumbcenter.co.uk


(incidentally, if changing tank your existing one may have a scrap value)

Oneday77

A simple idea to try and lead you in the right direction, can you see any mains cables running to the tank? If so how many and where do they finish up?
If it's an unvented tank, then I believe they much have some kind of thermostat attached, to stop your Boiler over heating the tank and it blowing up. (I nearly managed that by disconnecting mine..oops 77degrees C at the bottom wasn't a good idea.)
The thermostat is likely to be part of the immersion heater also, so tracing cables is a good start

LB?

Thanks to Oneday77 and EricMears for starting me off in the right direction.

I think I've located the blanking plug on the top - I've taken a photo of it here:
Sorry - I'm too new to add links

c2.staticflickr.com/6/5699/23057857912_58cb05eb47_b.jpg

As for the wiring, well there's wires everywhere, here's a photo:
Sorry - I'm too new to add links

c2.staticflickr.com/6/5626/23057904262_ea47587934_b.jpg



If you do want to look at the photos then if you search Flickr for User LennyBloke and the album "Hot Water Tank"

As for tracing the wiring, well.....

The grey wire coming out of the "Danger" box and heading to the right goes to the timer/controls. The white wire coming out of the "Danger" box (from the top left) goes to a 3 amp fused power switch (which powers the timer/controls). The black wire (as you may be able to work out) goes into the grey "pump" box sitting on top of the pipes (at the right). I can't trace the thick grey wire that comes out of the "Danger" box at the bottom left - it goes off to the side of the airing cupboard and them up into the roof.

...when you've finished splitting your side laughing at my detailed yet woefully inadequate descriptions, I suspect that none of these relate to an electric immersion element anyway?

EricMears

LB? wrote: »

Thanks to Oneday77 and EricMears for starting me off in the right direction.

I think I've located the blanking plug on the top - I've taken a photo of it here:
Sorry - I'm too new to add links

c2.staticflickr.com/6/5699/23057857912_58cb05eb47_b.jpg

As for the wiring, well there's wires everywhere, here's a photo:
Sorry - I'm too new to add links

c2.staticflickr.com/6/5626/23057904262_ea47587934_b.jpg

If you do want to look at the photos then if you search Flickr for User LennyBloke and the album "Hot Water Tank"

As for tracing the wiring, well.....

The grey wire coming out of the "Danger" box and heading to the right goes to the timer/controls. The white wire coming out of the "Danger" box (from the top left) goes to a 3 amp fused power switch (which powers the timer/controls). The black wire (as you may be able to work out) goes into the grey "pump" box sitting on top of the pipes (at the right). I can't trace the thick grey wire that comes out of the "Danger" box at the bottom left - it goes off to the side of the airing cupboard and them up into the roof.

...when you've finished splitting your side laughing at my detailed yet woefully inadequate descriptions, I suspect that none of these relate to an electric immersion element anyway?

Quite surprised that MSE didn't remove your link - in case they wake up and do so later, I'll repeat it here
http://c2.staticflickr.com/6/5699/23057857912_58cb05eb47_b.jpg

That does indeed look like a blanking plug for an immersion heater but I'm afraid the shot isn't quite clear enough to be certain. A blanking plug ought to have some way of turning it - else you'd never be able to unscrew it to replace it with an immersion heater ! Usual thing would be to have a raised 'square' (or even hexagon) that you could turn with a spanner but there's just not enough contrast in the picture to be able to make that out. It ought to look something like this : http://www.plumbcenter.co.uk/en/plumbing-drainage/brassware/brass-fittings/immersion-heater-plug--washer-21-4/


Assuming for the moment that there is some means of turning it then fitting an immersion would be pretty straightforward :-

You'd need to drain system down (not completely - just enough so that water doesn't spew out when plug is removed) and remove that plug. You've got an added complication in that you'd need to remove the length of pipe across the plug and replace it with one that diverts around that area.

You'd definitely need an immersion heater. One like this
http://www.plumbcenter.co.uk/en/heating-parts/domestic-boiler-parts/tesla-tih505-11-copper-immersion-heater---dual-safety-theremostat-%2820%29/ would only cost around £16 but for another £10 or so you could get one with a much longer element - for use with Immersun etc you really want one that almost touches bottom of tank.

You might even consider a twin element heater - I couldn't find one on the plumbcenter page but here's one from the backer range
http://www.advancedwater.co.uk/prod-032-255-0003.html
for around £60

That would let you connect the longer one to the Immersun and leave you the shorter one for a quick boost.

And of course having chosen and fitted an immersion heater you'd need a (new ?) wiring circuit to operate it. To stay strictly within part P of the building regs that ought to be fitted (or at least inspected) by a registered electrician.


The other picture wasn't a great deal of help - you'd have needed to find a wire that was actually connected to an immersion heater. But it's worth looking around that area to see if there's already a spur box that doesn't appear to be doing anything - if there is, DIY connecting an immersion heater to it wouldn't need Part P compliance.

LB?

Thanks for all your help. The photo is of a blanking plug - the low contrast is probably down to the thick layer of dust!

You've given me enough knowledge to be able to talk to an electrician I know without coming across as a total idiot The pipe above the the plug probably complicates it to the point of requiring a plumber (as I'm not competent enough to attempt this sort of job myself) - which is a bit of a shame.

I had been considering replacing the boiler (16 years old and parts availability now limited) - so if I end up getting a quote for the immersion element/pipe move I may also get a quote for boiler and hot water tank.

once again thanks for your help.

EricMears

LB? wrote: »

The pipe above the the plug probably complicates it to the point of requiring a plumber (as I'm not competent enough to attempt this sort of job myself) - which is a bit of a shame.

The end of that piece of pipe is almost out of the photo but it certainly looks as though it's a compression fitting. The other end is completely out of the picture of course but if it's also a compression fitting then there's no great level of plumbing skill required to replace that length of pipe with either a lot of short pieces of copper pipe joined by elbows or a single length of plastic pipe which (providing it's a suitable grade for hot water and you use pipe stiffener inserts) can use the same compression fittings as copper pipe.

That probably makes it a DIY job but if you need to employ an electrician a simple pipe replacement should be well within their capability.

If you do decide to replace the tank (and anyone offering to fit a new boiler will probably try and persuade you to rip it out altogether and fit a combi boiler instead ) then to maximise the return from an Immersun, go for the biggest one you can fit in the space and an immersion heater at bottom of the tank.

LB?

EricMears wrote: »

The end of that piece of pipe is almost out of the photo but it certainly looks as though it's a compression fitting. The other end is completely out of the picture of course but if it's also a compression fitting then there's no great level of plumbing skill required to replace that length of pipe with either a lot of short pieces of copper pipe joined by elbows or a single length of plastic pipe which (providing it's a suitable grade for hot water and you use pipe stiffener inserts) can use the same compression fittings as copper pipe.

That probably makes it a DIY job but if you need to employ an electrician a simple pipe replacement should be well within their capability.

If you do decide to replace the tank (and anyone offering to fit a new boiler will probably try and persuade you to rip it out altogether and fit a combi boiler instead ) then to maximise the return from an Immersun, go for the biggest one you can fit in the space and an immersion heater at bottom of the tank.

Again - thanks for the advice Eric!

I hadn't noted the type of fitting, so as you say - it might be simpler than I had assumed. The Electrician I use is pretty competent at most things so I'm sure he'll be fine with the Pipe if it is a compression type (it's just a nightmare to get hold of him). If this does work out then I would leave the boiler replacement until a later date.

Cheers :T

theboylard

As Eric said, don't get a combi boiler, they won't work with any diversion device as you'll lose the tank!

Depending on your needs, a competent heating engineer (I don't include British gas sales droids) can install a heat only or system boiler (they are different) without too much fuss.

If you don't have one in mind, top tip is to find your local trade only boiler spares co and ask them who they would let loose in their house!

There are a lot of engineers out there, I know some who have set fire to houses, and not just once!!

Ectophile

Just to be a wet blanket - before you dive in and get all the work done, do the sums first.

I looked at having an Immersun fitted a while back. Before I made the decision, I tried checking how much gas my boiler used to re-heat the tank every morning. To my surprise, it barely even registered on the meter, ticking up 1 or sometimes 2 units on the last digit of the display. I estimated that to be about 15 to 25p worth of gas.

In the end, I decided it wasn't worth bothering.

EricMears

Ectophile wrote: »

Just to be a wet blanket - before you dive in and get all the work done, do the sums first.

I looked at having an Immersun fitted a while back. Before I made the decision, I tried checking how much gas my boiler used to re-heat the tank every morning. To my surprise, it barely even registered on the meter, ticking up 1 or sometimes 2 units on the last digit of the display. I estimated that to be about 15 to 25p worth of gas.

In the end, I decided it wasn't worth bothering.

Couldn't agree more - if the OP already has a low cost DHW system available. However, not everyone has a mains gas supply - some of us rely on oil or LPG (both temporarily 'cheap' but usually much dearer than gas); others (not OP obviously) may be relying on an immersion heater as only DHW supply.

This is an MSE forum - it's always implied that projects need to be evaluated before commitment to them !