Help - side entry immersion element-bottom of hot water tank

[rikkiokbye]

Hi all

I currently have a top entry 27" immersion element but this is in the context of a 5ft hot water tank. I want to have a side entry immersion element fitted at the bottom of the tank so that ALL the water is heated.

The reason I want this is because I have 4 Kw solar PV fitted and during the day we are generating 20+Kw. I would like to use this to heat the hot water. I have recently spent £350 on the Solar-i-Boost from Malek - it intelligently feeds excess solar energy to the hot water immersion - from as little as 100w upwards. The problem is that the 27" immersion heats the top of the tank then the thermostat (at max) of the immersion kicks in. Hence in a day I am using 3Kw of the 20Kw to heat water.

Therefore, if I had a bottom side entry element I am thinking more of the water gets heated and thus less work for my boiler to do if it is required to raise the temperature further. We are a family of four and thus need a large amount of hot water each and every day.

So to summarise, I want to disconnect the top immersion and fit a new bottom side entry 3kw immersion on the existing tank - can this be done and how much am I looking at - ball park?

Any help/advice and links to elements etc will be much appreciated.

Many thanks in advance

Rikki

 

[45yearsagasman]

http://www.bes.co.uk/products/107a.asp

These sell the gear you require. The only problematic bit is to cut the cylinder wall to fit the new flange.
Drain down, cut and fit new flange, fit heater and connect and refill and test. I reckon 3 hrs work + parts. £200+. You could save yourself a bit by draining down prior to fitting. Can't be more precise than that without seeing job, but it's a start.

 

[Agile]

If its an open vented copper tank then an immersion boss can be soldered/brazed into place.

But that requires some experience and few people are likely to have that or to be willing to take the risk of being held responsible if it sunsequently failed.

The tank has to be emptied first an that can take about an hour before the cutting/soldering starts. So all together a 2-3 hour job.

So a cost of perhaps £200 if you can find someone willing to do it assuming first the cylinder is suitable.

But I thought that you can sell your PV power for 34p a unit and then buy back power from the mains later at 12p a unit???

Tony

 

[JohnD]

If it was me, I would certainly be thinkng of a new cylinder with the fittings you need, as big as I could find, rather than hacking about the old one.

it might cost more but would be far less likely to go wrong.

There are a lot of stainless cylinders coming onto the market now at similar prices to copper,double-skinned with factory insulation, some of them pressurised to give better flow for a powerful shower . I would hope they'll have a long life and not be as easily damaged as copper ones.

Some photos of your existing cylinder would be nice.

 

[Jackrae]

A 2 1/4" Essex flange will be a b*gger to fit and guaranteed to seal properly - not a job for an amateur - especially on a cylindrical tank.

A lot less expensive and a lot easier to do - if you have the head room for access - is to fit a 4'6" accelerator tube to form a jacket around your 27" immersion element. Basically it consists of a 2" OD thin wall tube - ideally copper to prevent electrolytic corrosion - which is loosely fitted around the immersion element. Before you fit it make some very large cut outs in both top and bottom of the tube.

When the immersion is energised it heats the water in the tube (jacket) which then rises up to the top of the tube and flows out of the large cut outs you previously made. This draws in cold water from the bottom of the tube (ie bottom of cylinder) to be heated which then flows out the top. Process continues until complete tank is hot

It doesn't matter if the jacket is a fairly tight fit or contacts the element walls of the element since the whole thing is immersed in water so conduction carries away any potential for localised heating effect.

QED

 

[Agile]

It is a simple solution but I have never come across an installation using that so conclude its not often done!

But I am still waiting for the OP to explain why he cannot profit from the absurd subsidy on PV supplies!

Tony

 

[rikkiokbye]

Hi all,

Thanks for all the replies.

I do NOT own the PV panels - 3rd party owned - hence I only benefit from the free energy I can use.

I shall speak with my plumber to see what the best way forward is.

Thanks again!

Rikki

 

[Jackrae]

An alternative, and perhaps easier solution for you would be to get hold of a small Ch circulation pump. Take a tapping off the cylinder outflow connection (the top one on the cylinder, feed it to the pump inlet. Then connect the outlet of the pump to the infeed connection on the cylinder, the bottom one. Wire up the pump so that it runs when the sun shines. This will then "mix" the water in the tank and permit the immersion to heat the full tank.

 

[rikkiokbye]

Hi Jackrae

I have just tried searching for an acceleration tube but no luck - any chance you can send me a link please?

Thanks

Rikki

 

[Dan Robinson]

An alternative, and perhaps easier solution for you would be to get hold of a small Ch circulation pump. Take a tapping off the cylinder outflow connection (the top one on the cylinder, feed it to the pump inlet. Then connect the outlet of the pump to the infeed connection on the cylinder, the bottom one. Wire up the pump so that it runs when the sun shines. This will then "mix" the water in the tank and permit the immersion to heat the full tank.

That would be called a destratification pump and would require some basic electronics with a pipe thermostat and some non return valves.

 

[Charnwood]

These sell the gear you require.

Not according to the page linked to. It only shows two 21/4" essex flanges; flat (E1/R) and domed (E3/R).

For the side of a cylinder you will need the curved E2/R to get the best seal possible. It won't deform the curved surface. They are, as previously stated, a b'stard to fit.

 

[Jackrae]

Have never seen an accelerator for sale as a separate item. Once had one on a commercially supplied immersion and it's not exactly rocket science to make your own.

Destratification is exactly what the OP is seeking so a pump is simply one of the means of achieving it using his top mounted immersion. cannot see the need for non-return valves since any tendency to flow from the hot taps will preferentially come from the top connection (due to, amongst other things, the resistance of the rotor labyrinth within the pump)