I can't believe that I started this thread back in March
and have only now got around to actually drilling holes in the Thermoboxes. Anyway the first task was to fit this 3KW Swan boiler element (15 quid from a Blackpool based eBay seller - No longer registered) into the base of the thermobox (38.5L From Nordic Optical)
The first step was to measure the distance from the inner wall to where I wanted the element to fit . . . which was deliberately off centre to try and encourage currents to form. After adding the thickness of the wall it was time to measure and drill a 6mm pilot hole.
Oh and can I say if you are drilling holes in stainless go out and buy yourselves some cobalt drill bits . . . I use the
eBay Seller UK Drills, and it is difficult to beat the Bosch Cobalt Hole saws from
eBay Seller Hendroid
After drilling a 6mm pilot hole all the way through the outer and inner skins of the thermobox . . . time to break out the hole saws.
On the outer skin I needed some room to work so decided to break out the big 64mm hole saw. Despite taking it slowly, using cutting/broaching oil, and using a lot of pressure, I still managed to work harden the stainless . . . and burn out my old black and decker drill (which I'd had for 21 years!! . . . excuse to buy a new one :party: ) . . .and decided to resort to my new Makita Cordless . . . Which quite surprisingly made short work of the rest of the drilling.
And the thing cleaned up really easily . . I cut out the foam with an xacto knife, to remove it
For neatness I prefer to use Q Max punches to make bigger holes (
From Rapidonline), here I am using a 16mm punch to make a larger hole for the bolt for the 40mm punch I need to pass the element bits through . . . Oh and a simple piece of advice . . . get the thrust race for the larger punches it makes life so much easier.
The element is held in place by five metal studs spaced around the circumference of the main hole (This also secures a rubber washer to make the thing waterproof.) After hearing about all the problems Vossy had when he was drilling this sort of hole for the drain in his mash tun I was somewhat apprehensive . . . still
Fors juvat audentes
I had marked the position of the holes using the rubber washer, punched them with a centre punch and then drilled them using the 4mm cobalt drills . . . hot knife . . . butter, and here is the element fitted into place.
Still it is a tight fit to the connections in there . . . :hmm: do I want to use the boil dry cut out :hmm: Of course I do, so fitted the straddle wire between one terminal of the element and the live of the cut out.
And then made all the connections . . . The cable comes in from the side, via a cable gland, which stops a lot of water ingress, and is 2.5mm cable rated for 'hot' environments . . . I would suggest rubber cored instead of plastic, if you can get it use immersion element cable.
I will once full testing has been completed be securing a stainless plate over this hole probably with pop rivets, and a silicone sealant as a gasket . . . for the time being it is left exposed. I mentioned earlier in the thread that I had obtained some PT 100 sensors and glands from the sadly no longer with us Watch hill, and these were the next thing to be fitted.
After drilling a 6mm pilot hole about a third of the way up from the base of the inner skin . . .I then switched to a 25mm cobalt hole saw and made a working hole in the outer skin.
ANd again quick work with the xacto knife soon had the inner skin revealed . . . where I had to drill a 10mm hole for the thread of the gland
And with a short bit of filing to clean up rough edges here it is.
I have a sight gauge to fit, but that shouldn't be too hard . . . and a tap to do . . . but a test using the original tap at least proved that the element worked :lol: and the seal around the element didn't leak . . . . The same couldn't be said for the stainless gland, But I had cut the O ring doing the securing nut up too tight . . . I'll add an M10 stainless washer on the inside with a smear of food grade silicone sealant, and will then not need to do it up as tightly.
Next up a 38.5L thermobox boiler