Dual coil cylinders

The hot water heating part of our gas central heating in our house is rubbish. It’s gravity fed, piped up in too small a diameter pipe and the cylinder is a substantial distance horizontally from the boiler. The result is that, even in summer, in order to heat up sufficient water for a 4 inch deep bath each evening for the kiddies, it’s costing £40 a month. This is in the summer!

The cylinder that we have is an old looking thing and does have an immersion heater in it. My plan is to use electric to heat the water instead of gas. The immersion that is in the cylinder looks a bit dodgy so I was going to replace it. However, looking at the cylinder, I don’t think I’ll be able to get it out without distorting the cylinder (or worse).

My plan, therefore, is as follows. Cap off the primaries for the current cylinder (the bathroom radiator is heated by gravity so I’ll cut off next to the tee).

Replace the current cylinder with a dual coil one. Both coils would initially be unconnected. I’d connect the upper coil either if I can be bothered to convert the current system to fully pumped or when the heating system gets replaced at some point in the future. The lower coil would be used when, at a future date, I put a solar panel on the roof. Rather than connecting the panel directly, I’d rather use an indirect method so that I can put anti-freeze in it for over winter.

My plan currently has a big flaw. I’ve searched the Internet and cannot find dual coil cylinders. Plenty of reference to them but no suppliers.

Anyone any ideas, or thoughts on my above plan?


Cheers

G

Finally found a couple, this is the cheaper

http://www.solarsuppliesuk.co.uk/index_files/Page1284.htm

Almost £300 (& VAT??) for a cylinder – blooming heck, I’ll just keep burning fossil fuels me-thinks. A 120 litre cylinder in Wickes is about £120. How can a dual coil one be two and a half times that price?

May just fit two cylinders. Insulate them really well and fit them in line. The first one is connected to a solar panel, the second one to the heating. The first one is fed from the header tank and the second from the first. Would save me money but not space.


G

Sounds like you haven't thought this out very well

How about open vents etc for the boiler, when the primary pipes are capped off for starters.

Megaflo, Oso, range, Vaillant to name but a few all do dual coil cylinders. What you should look for are cylinders with sensor pockets suitable for the thermistors used on a solar system. Dual coil system saves less room than having 2 single coil cylinders, if using this method dont forget to vent the first cylinder as well as this will be the main safety feature for the solar system. Cylinder sizing should be a min of 35litres per person in the house but is usually calculated at 50litres and then this is multiplied by 1.5-2. therefore an ordinary cylinder that is 120 litres would need to be increased to 170litres minimum for a twin coil.
Any insulation needs to withstand temps of 150 degrees and normally armaflex is used. Hard solder on joints as well.
Lee

Ah yes, vents – that little nutmeg.

Once I’d drawn my plans onto paper, I would have noticed that the vent and feed were missing. If I didn’t, by the time I’d got my pipe cutter out in the airing cupboard and thought, what’re these pipes here then, I’d have noticed. And if all else had failed, trying to fill up the system may have been a tad difficult without a feed so I just might have noticed by then. (I hope).

I’ll have a look at the system tonight and do a drawing to see just how difficult it would be to convert to fully pumped. A ‘Y’ plan pack is quite reasonable in Screwfix. Does wiring up an actuator head, cylinder stat, pump, etc come under Part P?

Regarding solar, I was just thinking that if I was to go down the solar route in the future, I might as well plan for that now. Seeing that a normal indirect cylinder costs in the region of £120, I thought that a dual coil would be maybe £50 more expensive – wrong!!! Also, having looked at the price of solar panels – I’ll probably need the more expensive evacuated tube ones as the apex of our roof runs NNE – SSW so the panel would be pointing WSW.

As I see it, I may as well wait until I actually have the money available to get a solar hot water system installed. If I use an approved installer, I should get a clear skies (or whatever that’s been replaced by) grant. Alternatively, If I do it myself (getting someone in to go onto the roof ‘cos I won’t do that), I’ve to pay full whack.

Basically, I’ll forget about solar water heating for now.

Thanks for the answers.

One question though – in the past when I’ve done small plumbing jobs, I’ve used compression fittings. Larger jobs such as when I installed central heating in a house (the gas boiler was already in) I’ve used pre-soldered fittings. What is hard solder?


Many thanks

G

Big G said:

Seeing that a normal indirect cylinder costs in the region of £120, I thought that a dual coil would be maybe £50 more expensive – wrong!!! G

Click to expand...

Look again. you can be looking at best part of £2000 for a decent sized unvented solar cylinder.

Sonnenkraft solar cylinder is about £800 for a 300litre. But they are the dogs privates. Ceramic linned. which is nice.