Drilling a hole in an immersion tank.

[Stevex]

I checked where to fit my essex flanges for the recirc pump after looking into the water tank.
The hole cutter I have is in the pic. Are the teeth too coarse for thin copper?
Anyone cut into a hot water copper tank? What sort of hole cutter did you use?
Thanks.

 

[exedon2]

I would personally use one with smaller teeth probably a starrett.

 

[snowhead]

If you've never used a hole saw before, then practice on some scrap first and use the drill on a low speed.
If you've never used a hole saw to cut very thin metal, then practice, practice, practice, on some scrap first.
If you've never used a hole saw to cut very thin metal that's curved, like the side / top of a cylinder, then practice, practice, practice, on a tin can or other curved metal suface.

As you'll see if you practice, the teeth can gab and rip thin metal to shreds, not what you want with a cylinder that'll then need replacing.

And as above a cutter with more teeth would be preferable.

This was the original tool of choice for holes in cylinders or tanks, using a carpenters wheel brace.
Still got mine somewhere.

 

[Stevex]

Thx for the replies. I'm going to use a small hole cutter just big enough to get a rotary grinder in.
Just bought one of these.

 

[Ben-gee]

Get someone to hold a vacuum nearby to try and minimise the filings going into the cylinder

 

[ShaunCorbs]

I wouldn’t recommend one of them be better with your hole saw run in reverse before you use a carbide burr

 

[PETE 123]

Could you use a surrey flange instead.

 

[Stevex]

Finally got round to fitting the pump.
Practiced the hole cutting on some thin gauge aluminium sheet I had and then onto the copper tank. To be honest the hole cutter mentioned previously worked a treat with no problems. The Essex fl@nges went in easily. Wired it up this morning and ran the pump for half an hour but it doesn't appear to be working!!. Top pipe out of the tank is hot and the pipe below the pump is lukewarm and doesn't get hot; the pump makes a pulsing noise. Also the temp gauges I've got at the top and bottom of the tank don't change. Fired an email off to Wilo, but I can only presume they'll ask for it back to check it out.

 

[ShaunCorbs]

Does the pump have non return valves in ?

 

[Stevex]

Yes, NRV fitted in the discharge side.

 

[snowhead]

Is the ball valve on the inlet to the pump open?
And have you tried the Wilo instruction if airlocked of On/Off for 30secs 5 times?

 

[Stevex]

Is the ball valve on the inlet to the pump open?
And have you tried the Wilo instruction if airlocked of On/Off for 30secs 5 times?

Yes to both; weirdly enough I turned the pump off earlier and went back to it a few hours later and turned it on. The lower pipe started to get as hot as the top pipe, but within 5 minutes back to square one with same symptoms...weird.

Hopefully this video uploads, this is what it sounds like.

 

[ShaunCorbs]

Would try removing the nrv if you can

 

[Stevex]

Would try removing the nrv if you can

The NRV is built into the pump and that component is torqued on fit at the factory.
I did wonder if the NRV might not be opening, but I don't want to disassemble the pump until I've had a reply from Wilo in case it invalidates the warranty.

 

[snowhead]

Close both lever valves on the new pump circuit.
Crack the lower compression nut on the pump.
Open the top lever valve slightly and see if water is getting through the pump and NRV.
If it does, close the top lever and open the bottom lever slightly to see if the lower section of pipe is airlocked.

 

[Stevex]

Close both lever valves on the new pump circuit.
Crack the lower compression nut on the pump.
Open the top lever valve slightly and see if water is getting through the pump and NRV.
If it does, close the top lever and open the bottom lever slightly to see if the lower section of pipe is airlocked.

I took the pump out and blew through it to confirm the NRV works, which it does, it opens with very little pressure required. It also blocks with opposite flow. I removed the pump head and ran the motor to check the impeller was working and for any obstructions, all normal.
Refitted the pump and now when it runs it doesn't pulse and has that normal pump running sound.
Just waiting for the solar to heat the top half of the tank and then will see what the pump does.

Edit: After letting the upper tank temp rise with solar power to about 35°C with the lower temp sensor indicating 24°C, I turned the pump on. After about half an hour re checked and the 2 temp sensors are now within 1°C of each other.
So finally the pump seems to be working, although I've no idea what the original fault was.