Solarimmersion installed - Really need some help installing a de strat pump

[j2d]

I used a 64mm holesaw Toolstation > Power Tool Accessories > Holesaws > Bi Metal Holesaw
I already had the arbour to fit it to. The 64mm cutter will cut the hole slightly undersize. I then used a rotary file in a cordless drill to ease the hole out until the threads of the flange just passed through. The hole is then opened out further at the 3 and 9 oclock positions until the flange can be just pushed through and into the tank. Go steady because if the hole ends up being a slack fit it won't seal. The flange is pulled back so the threaded boss sticks out through the hole and then rotated 90deg so the wider part of the flange sits behind the wider part of the hole and the gasket and included locknut is fitted outside and tightened. The curvature of the tank will be flattened out locally as you tighten the flange.
The flanged part that fits inside the tank is circular with two sides cut off so its more of an oblong shape in plan view.
Its difficult to explain but once you see the flange it will become obvious.

Brilliant! I have a 64mm hole cutter (a common size for cutting downlights out) Just about to order the flange now. Thanks for the advice on having a big enough spanner, going to order a stillson 13.5" with a 70mm jaw, will that be big enough?

When you did this can you remember roughly how far apart the internal coils were spaced apart?

I think i'm going to have to remove the immersion heater so I can look into the tank to give me an idea this gap between the coils.

I can obviously see where the pipes enter the top and bottom of the internal coil, so have a rough idea, but am very worried about drilling the pilot right in line with one.

John

 

[j2d]

Edited

 

[Digon]

I used 'Record 14" stillsons' and they where only just wide enough. They where right on the last part of the last thread. I just measured the jaw spacing and it was on 70mm.

The bottom of the immersion hole on mine ended up about 25mm above the bottom circumferential seam. Don't forget the tank bottoms are concave so you can't go too low or the immersion will touch the tank bottom in the middle.
When drilling the pilot make sure you only just break through then have a probe about with a thin screwdriver to locate the coils. The bottom coil on mine was 1-2mm off the tank bottom therefore could not be pushed downwards. There was a ca.13mm gap to the 2nd coil but this could be lifted with the fingers (just) once the 64mm hole was done.
I don't know for sure if it matters if the coils are touching the immersion once it's all done up but I didn't want to risk the possibility of creating a galvanic hot spot which could cause localised corrosion through the coil. If you can, make sure there is a gap between the immersion and the coils because over the course of the next twenty or so years you could end up with a punctured coil.
This is not an easy project so think twice before drilling the tank and also it may be a good idea to have a contingency plan for if it goes wrong.

Dave

 

[j2d]

I used 'Record 14" stillsons' and they where only just wide enough. They where right on the last part of the last thread. I just measured the jaw spacing and it was on 70mm.

The bottom of the immersion hole on mine ended up about 25mm above the bottom circumferential seam. Don't forget the tank bottoms are concave so you can't go too low or the immersion will touch the tank bottom in the middle.
When drilling the pilot make sure you only just break through then have a probe about with a thin screwdriver to locate the coils. The bottom coil on mine was 1-2mm off the tank bottom therefore could not be pushed downwards. There was a ca.13mm gap to the 2nd coil but this could be lifted with the fingers (just) once the 64mm hole was done.
I don't know for sure if it matters if the coils are touching the immersion once it's all done up but I didn't want to risk the possibility of creating a galvanic hot spot which could cause localised corrosion through the coil. If you can, make sure there is a gap between the immersion and the coils because over the course of the next twenty or so years you could end up with a punctured coil.
This is not an easy project so think twice before drilling the tank and also it may be a good idea to have a contingency plan for if it goes wrong.

Dave

If it does go wrong i.e I drill the hole in the wrong place, what are my options? can a hole be 'repaired'

John

 

[Digon]

Just remembered something else... after drilling the initial pilot hole I lifted the hole sufficiently so the bottom of the immersion would end up clear of the bottom coil. This meant the second pilot hole was nearly in line with the second coil so I shortened the pilot drill so it was only protruding 1-2 mm in front of the 64mm cutter. Obviously you can only lift the pilot hole a limited distance so the original hole stays within the finished 64mm hole.

 

[Digon]

If it does go wrong i.e I drill the hole in the wrong place, what are my options? can a hole be 'repaired'

John

Patching the tank should be straightforward enough but it depends on your soldering/ brazing skills whether you will need to get someone in to sort it, but if you nick the coil you will have big problems which need to be considered beforehand. I'm not trying to put you off, just thought I'd better warn you, and others contemplating this, just in case.

 

[j2d]

Ok, thanks, i'll let you know how it all goes

John

 

[j2d]

Patching the tank should be straightforward enough but it depends on your soldering/ brazing skills whether you will need to get someone in to sort it, but if you nick the coil you will have big problems which need to be considered beforehand. I'm not trying to put you off, just thought I'd better warn you, and others contemplating this, just in case.

Installed a bottom entry immersion heater into the Cylinder tank yesterday, definitely not an easy job! But thanks to all the helpful advice and links to the bits I needed I got the job done! After a perfect day of sunshine today, I had a FULL tank of hot water in no time with no need for a de-stratification pump!

A massive thank you to Digon for all your help mate - Legend!

John

 

[Digon]

Installed a bottom entry immersion heater into the Cylinder tank yesterday, definitely not an easy job! But thanks to all the helpful advice and links to the bits I needed I got the job done! After a perfect day of sunshine today, I had a FULL tank of hot water in no time with no need for a de-stratification pump!

John

Glad it went ok for you.
Although not easy it's well worth the effort.

Dave