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Dual coil cylinders


 
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Big G

from United Kingdom

Joined: 23 Jan 2006
Posts: 85
Location: Yorkshire,
United Kingdom

PostPosted: Thu Jul 27, 2006 12:33 pm Reply with quote

The hot water heating part of our gas central heating in our house is rubbish. Itís 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, itís 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 donít think Iíll 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 Iíll cut off next to the tee).

Replace the current cylinder with a dual coil one. Both coils would initially be unconnected. Iíd 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, Iíd rather use an indirect method so that I can put anti-freeze in it for over winter.

My plan currently has a big flaw. Iíve 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
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Big G

from United Kingdom

Joined: 23 Jan 2006
Posts: 85
Location: Yorkshire,
United Kingdom

PostPosted: Thu Jul 27, 2006 12:55 pm Reply with quote

Finally found a couple, this is the cheaper

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

Almost £300 (& VAT??) for a cylinder Ė blooming heck, Iíll 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
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doitall

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Joined: 08 Jan 2005
Posts: 18839
Location: Bath,
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PostPosted: Thu Jul 27, 2006 6:42 pm Reply with quote

Sounds like you haven't thought this out very well icon_eek.gif

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

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PostPosted: Thu Jul 27, 2006 8:55 pm Reply with quote

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
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Big G

from United Kingdom

Joined: 23 Jan 2006
Posts: 85
Location: Yorkshire,
United Kingdom

PostPosted: Fri Jul 28, 2006 8:25 am Reply with quote

Ah yes, vents Ė that little nutmeg.

Once Iíd drawn my plans onto paper, I would have noticed that the vent and feed were missing. If I didnít, by the time Iíd got my pipe cutter out in the airing cupboard and thought, whatíre these pipes here then, Iíd 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). icon_redface.gif

Iíll 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 ĎYí 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 Ė wrong!!! Also, having looked at the price of solar panels Ė Iíll probably need the more expensive evacuated tube ones as the apex of our roof runs NNE Ė 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 thatís been replaced by) grant. Alternatively, If I do it myself (getting someone in to go onto the roof Ďcos I wonít do that), Iíve to pay full whack.

Basically, Iíll forget about solar water heating for now. icon_sad.gif

Thanks for the answers.

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


Many thanks

G
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htgeng

from United Kingdom

Joined: 01 Jun 2004
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Location: Lancashire,
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PostPosted: Fri Jul 28, 2006 1:57 pm Reply with quote

Big G wrote:

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


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

from United Kingdom

Joined: 02 Jan 2006
Posts: 197
Location: Essex,
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PostPosted: Fri Jul 28, 2006 9:49 pm Reply with quote

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