Solar Coil to Existing Copper Cylinder

nophd08

Hi, Has anyone had this done to a vented cylinder? Apparently a coil can be retrofitted to your HW cylinder via the immersion outlet or inlet, cuts on initial costs. Ok so it wont be as good as the proper insulated set up but end product has to be the same, ie hot water,.
Any feedback welcome.

bertie1

You could also use a heat exchanger

Iwannahurl

Good question.

I have no expertise in this area, but the concept always made intuitive sense to me. I asked several retailers/installers of solar water heating systems to explain to me why solar cannot simply be grafted onto an existing vented set-up. Nobody gave me a satisfactory answer.

It seems unnecessarily complicated, expensive and wasteful to throw out what is already there in order to install a new cylinder along with the solar collector and associated plumbing etc.

AFAIK there is such a system in existence. It's available in the UK, but has not been approved here. I can't think of its name just now, but if I remember it later I'll post it here. IIRC it uses a solar pump to force the heated water into the cylinder.

DoneDL

just google solar immersion coil.

ccsolar

Hi
The solar plug is readily available on the Irish Market there is also another system manufactured in Antrim for a company called Willis which works off the cold inlet and hot outlets on the tank.
The main reason for not fitting the solar plug is that the cylinder is old and poorly insulated if insulated at all, the capacity of the cylinder is insufficient for the occupancy of the house and inorder to get the maximum performance from your solar system a bigger capacity cylinder is needed.
We fit the solar plug regularly in houses where the occupancy is only 2 people, (eg: retired couple) or in rental properties where the landlord wants to attract tenants.
The cost of the solar plug is around €250 where as a 200 Ltr S/S cylinder is €550 +Vat.
The maximum solar collector size to be fitted with the solar plug is 20 tubes or 2.5Sqm, there are 3 different sizes of solar plugs but this only relates to the height,capacity of the existing copper cylinder.
It is also advisable to agree a price for replacing the cylinder before any work starts as some times when the old copper cylinder is inspected it has reached it's term, always fit a heat dump with any solar system.
Hope this helps.
Cc

Iwannahurl

Very helpful info re SolaPlug and Willis. Thanks.

Just spotted some potential issues.

1. How difficult/disruptive is it to get the solar heated water to the SolaPlug heat exchanger in the cylinder? I'm wondering whether a lot of gouging would be needed, and I'm not overly keen on that as we recently had the attic converted.

2. The SolaPlug documentation states that the existing boiler should have separate central heating and water heating controls. The typical Irish installation is more primitive than that, and ours is no exception. In other words, it just has the usual bog-standard HW/HW-CH switch plus a single timer. What are the implications?

nophd08

Meeting a solar co. midweek to discuss above set up. Apparently, no rocket science needed, once you have a large insulated cylinder and its sized properly and a heat dump connected. Sounds simple, I'll post back when I've more info.
Any other technical queries I should quiz them on.

Iwannahurl

Great.

1. Is there a maximum size of cylinder?

2. Is it compatible with a pumped shower (Aqualisa)?

nophd08

Iwannahurl wrote: »

Great.

1. Is there a maximum size of cylinder?

2. Is it compatible with a pumped shower (Aqualisa)?

You're Aqualisa wont care where the hot water comes from, (as long as there is plenty of it) :D

quentingargan

The restriction with the Sola Plug device is its surface area, which is small compared to the coil of a proper solar cylinder. So it works fine with 2, or at a stretch 3 square metres of solar panel, but it will struggle to transfer the heat of anything but the smallest solar panel.

The main saving is in the cost of labour for changing the cylinder, especially if you have a very well insulated cylinder, and no gouging is requires. But it is a compromise system to some extent, particularly restricting the size of panel you can use. As Csolar says, fine for a retured couple with a 120L cylinder and happy to have a small panel, to make a low cost installation.

The Wilis syphon system has a different compromise, in that it only transfers heat when the solar panel is hotter than the top of the cylinder. I wouldn't persoanlly use it with flatplates, because the heat loss of keeping your panels at over 65 degrees all day long is too high, but people report that it works OK with tubes.

Iwannahurl

It's the 'plenty of hot water' aspect that I am most concerned about.

Clearly I have a lot to learn about solar installations. Normally I like to research the technologies and the various options before deciding anything, but in this case I'm a bit clueless.

It does seem as if the SolaPlug might not be sufficient for my needs, though.

It would have to generate a significant saving in order to justify the expense and hassle of installation. Our situation -- eg pumped shower, two kids and frequent guests -- would be beyond its capabilities I reckon.

Is there a way of calculating these equations, rather than relying on rule-of-thumb?

quentingargan

Iwannahurl wrote: »

It does seem as if the SolaPlug might not be sufficient for my needs, though.

It would have to generate a significant saving in order to justify the expense and hassle of installation. Our situation -- eg pumped shower, two kids and frequent guests -- would be beyond its capabilities I reckon.

Is there a way of calculating these equations, rather than relying on rule-of-thumb?

The Solarplug website claims that the device is suitable for up to 5 sq m of solar panels, but the surface area of the coils is just 0.5 sq m. The norm is to have at least 0.2 to 0.25 sq m of surface area on the coils per sq m of solar panel.

If you don't observe this, then the temperature difference between the panel and the fluid in the cylinder will have to rise. This makes the panels less efficient.

The temperature difference in practice varies from installation to installation, depending on pipe length, panels, cylinder and sunshine at a particular time. Many systems I have seen would operate at a temperature difference of about 10 to degrees during sunshine. If you put 5 sq m of panels into a solaplug with 1/3rd of the surface area, I expect you would get a difference of about 25 to 30 degrees. However, localised heating and speed of convection might rise this somewhat. The easiest way to find out it to look for someone who has such a system. A difference of 30 degrees would be substantial in a flatplate, and less so in a vacuum tube system.

There are also other issues in that the coil often enters at the top of the cylinder, and although the coil is at the bottom, there will be heat transfer back into the return from the temperate at the top of the cylinder.

Personally, I think that for your household uses, you probably want a 6 sq m system with 300L cylinder. What you are looking at in this system is a compromise, which is probably half the price, and slightly more than half as effective, but unbiased and specific research isn't available to be more specific than that AFAIK...

championc

Personally, I was looking to break even over 10 or so years. As Quentin says, a system of this kind may well not work at it's optimumand therefore, end up taking well over 10 years to pay for itself. So while it's annoying to add or replace more pipework or a cylinder, it sounds like the extra expense is money well spent and far more quickly repaid.

In addition, I think it's possible that your current copper cylinder won't be anywhere near as well insulated at a proper "Solar" cylinder. Mine loses only 1 deg C every 2 - 3 hours. I'm sure someone on here should be able to confirm the aproximate loss from a standard copper cylinder which is foam (or whatever you call that stuff) covered


C