My heat exchanger has had a design flaw since I made it. Basically the inlet and outlet to the heat exchanger came in through the top of the vessel. This meant on draining down there would always be some residual fluid left in the the copper pipe. It also meant an liquid lock could form which made it hard to prime my recirc pump.
I've taken it apart and corrected the flaw with the inlet coming up through the bottom of the vessel and the outlet through the top.
I never covered making this initially so I though it may be of interest to some of you guys
The bits
These consist of:-
A stainless steel pasta jar which I bought from Debenhams in the sales for £4 (I think...long time ago now
)1 x kettle element
1 x 1/2" male to 10mm compression fitting
1 x anode (new addition)
1 x roll of 10mm copper tube
2 x 10mm elbows
Tools required,
A drill, a dremmel, 20 & 40mm hole saw bits, a 10mm hss bit,
a file, a hack saw, a blow tourch, solder and wire wool.
The heat exchanger coil is 10mm copper pipe which was wound around a fire extinguisher to get a coil of copper small enough to fit inside the stainless vessel. I took the outlet feed off at a right angle, by soldering a elbow onto one end of the coil along with a small piece of copper pipe which exits through a 10mm hole at the top left hand side of the vessel.
At the other end of the copper coil I soldered another elbow to make the inlet feed vertical, again with a small piece of copper pipe
The first thing to do was to make a 40mm hole dead center in the base of the vessel wall, where the element would be mounted.
To the outside of this I drilled a 20mm hole for the inlet fitting, being careful to allow room for the lock nut of the element, and the fitting.
I used a constant supply of cold water to cool the hole saw bit and vessel whilst drilling. Then I filed the burrs off which were left after drilling the holes, with a dremmel.
Next I had to prepare the brass fitting for the inlet.
The 1/2" male to 10mm compression fitting, has a collar inside it that prevents 10mm tube from going all the way through it.
To get the 10mm copper tube to pass through the fitting, I used a 10mm titanium drill bit to drill through the collar, thus removing it, using a vice to secure the fitting whilst drilling.
I then screwed the fitting into the 20mm hole in the vessel, from the outside, applying some JB Weld to make sure it sealed water tight.
Now it was time to insert the copper coil.
Before doing this I offered the copper coil to the vessel to see roughly where the outlet would be. I marked this position, then drilled a 10mm hole through the vessel wall, at this point.
The inlet tube of the copper coil passes through the brass fitting in the base of the vessel. Then I attached the 10mm olive and nut, and tightened. I coaxed the outlet tube through the hole at the top of the vessel and then fitted the element securing it with the lock nut
I haven't fitted the anode yet.
The reason for not sealing the area around where the outlet exits the vessel, is to allow any pressure generated by the heated water to escape, as the lid is fitted with a seal.
EDIT
I had to cut some copper tube away from the coil to make my mods and thought it would be a good time to check for verdigris. I cut the removed sections of copper pipe in half. length ways, and was please to find spotless copper staring back at me
