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Changing an immersion heater element


Slim

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I've used search and read a number of posts around changing an immersion element. Grasping at straws I'm hoping someone can suggest something else.

The calorifier is a horizontal one measuring about 36" x !8". I use imperial measurements as it at least 20 years old.?. It is installed under the rear fixed steps and  sideways beyond the steps and under cupboards both sides. The element itself is at one end of the tank under the main electrical cupboard that houses almost every switch, fuse , combi etc etc. I have both a flat spanner (which just won't fit) and a Sivilerline box spanner which fits fine but because of the domed tank top it keeps slipping off if I use a decent sized tommy bar. I can only apply effort to this bar on one side. I've used PlusGas over the last week. I THINK when I installed it I used silicone gasket (don't remember if I used a fibre washer) I imagine I did. I tried to heat it up by running the engine (stationary) with little effect . I intend to take the boat for a short run tomorrow but I don't hold out too much hope of getting significant heat into the tank.. Has anyone experience of cutting one out, Drilling, cutting through the male thread or something else? If I fail to get the old one out the only option I can see is to butcher the existing tank and surrounding woodwork and fit a new one (maybe custom made ££££££££££££. Whatever I do it's not going to be easy in the present situation.

 

Sorry , no photographs

 

Many thanks

 

Frank

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8 minutes ago, Slim said:

Sorry , no photographs

 

Hard to advise without seeing it. 

 

But here goes in general. I've changed thousands of immersion heaters in domestic house cylinders, and those sealed in with silicone tend to come loose quite easily. My advice is to put considerable time and effort into finding a flat ring spanner that will fit the octagon properly. Then, with the tank FULL of hot water, give the handle of the spanner a sharp hefty blow with a club hammer. The water in the tank will damp down the shock to the copper of the tank, and the plan is the shock breaks something, specifically the threaded seal. If the seal is so strong that the copper ruptures (almost unheard of in my own personal experience) then you were never gonna get it out anyway so a new calorifier is needed anyway.

 

 

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13 minutes ago, Mike the Boilerman said:

 

Hard to advise without seeing it. 

 

But here goes in general. I've changed thousands of immersion heaters in domestic house cylinders, and those sealed in with silicone tend to come loose quite easily. My advice is to put considerable time and effort into finding a flat ring spanner that will fit the octagon properly. Then, with the tank FULL of hot water, give the handle of the spanner a sharp hefty blow with a club hammer. The water in the tank will damp down the shock to the copper of the tank, and the plan is the shock breaks something, specifically the threaded seal. If the seal is so strong that the copper ruptures (almost unheard of in my own personal experience) then you were never gonna get it out anyway so a new calorifier is needed anyway.

 

 

Mike, thanks for coming back so quickly. Prehaps I didn't explain clearly, the flat spanner won't fit because the handle doesn't have anywhere near enough clearance. Even if it did there's not enough room to swing a hammer. Making room would involve demolishing half of the back cabin. An absolute nightmare.

 

1 minute ago, WotEver said:

If you find water all over the floor then it was the wrong thing...

At least I do have 2 wet and drys on board.

Where's the scotch. ? 

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Sitting here thinking and building on what Mike said earlier about shocking it how about this for an idea. Take the box spanner and across the top weld a bit of flat plate. On the plate weld a 17 or 19mm nut. Go home for my 400? nm? impact hammer and suitable impact socket (a mere 180 mile drive) then see if can shock the thing loose. If he's there Richard on Cropredy slip could do the welding in a few minutes (I don't trust my dog poo welding). I'll try him tomorrow

What does anyone think , views welcome. 

 

 

Frank 

Edited by Slim
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6 minutes ago, Captain Fizz said:

What MTB said is about your only hope. Can you take a photo or two?

Whereabouts are you?

 

See my comment re impact driver. As for a photo, taking it is no problem . Samsung tablet or Samsung phone. As for uploading it I would need guidance at a Janet and John level.

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1 hour ago, Oldman said:

I know it sounds crazy but try and tighten first. This sometimes breaks the seal and then lets you undo it.

 

It IS crazy! 

 

The seal has the same strength whichever direction you are turning it, but if you break it by tightening, you now have a thread tighter than when you started which could otherwise have been a little looser. 

 

 

 

Edited by Mike the Boilerman
Moderate my unnecessarily blunt condemnation of an apparently good idea.
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6 minutes ago, ditchcrawler said:

It works on nuts and bolts

 

There is no technical rationalisation of why it should work better than turning in the loosening direction. So frankly, if it worked tightening, it would have worked better loosening. 

 

Or IS there an explanation?!

 

 

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1 minute ago, Mike the Boilerman said:

 

There is no technical rationalisation of why it should work better than turning in the loosening direction. So frankly, if it worked tightening, it would have worked better loosening. 

 

Or IS there an explanation?!

 

 

Possibly the threads when tightening are in better nick with the exposed thread being fouled.

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But it didn’t I tried for an hour to remove an immersion heater using different techniques. I then remembered when I was an apprentice one of the fitters telling me that to undo a seized nut give it a tighten first and then try and undo it. And it worked so I can say no more than I think it might be worth a try.

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Well, in the absence of my Idea being dismissed out of hand I'm minded to give it a shot. Whatever Richard charges, 4 gallons of diesel and a day of my time is better than the eyewatering prices I've seen for calorifiers. Change out of £1000 (diy prices) just wouldn't happen.

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2 hours ago, Oldman said:

But it didn’t I tried for an hour to remove an immersion heater using different techniques. I then remembered when I was an apprentice one of the fitters telling me that to undo a seized nut give it a tighten first and then try and undo it. And it worked so I can say no more than I think it might be worth a try.

There is also the possibility that it is limescale that has built up on the exposed end. A slight tightening can break that seal and allow the unit to be unscrewed. I've seen it work.

And as has already been said, if all else fails, then what have you got to lose?

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Not tried it on an immersion heater but tightening first certainly works sometimes on nuts and bolts, and with woodscrews. Once you have even a little movement, repeated tightening and loosening usually gives increased movement each time, until you can actually unscrew the thing. A bit of a pain though when access is difficult and you have to reposition the spanner between each tightening and loosening.

 

 

 

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One thing that worked when I had this problem recently was:

 

1. Drain the calorifier

2. Remove the thermostat & anything else loose on the immersion heater

3. Trim back the foam spray round the boss, how far you go depends on how well ventilated the space is

4. Get as much if the foam off the copper in the trimmed back area as you can. This isn't going to be pleasant if you don't

5. Play a blowlamp around the boss for about thirty seconds

6. Put the box spanner on and turn it. The one I did this to came out by hand on the spanner without using the tommy bar

7. When you have fitted the new heater get a can of squirty foam and restore the insulation round the boss

 

Depends what access is like of course. Mine was under a cruiser stern on a widebeam in a space where social distancing would be possible, side mounted on a vertical calorifier.

 

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13 hours ago, Slim said:

Well, in the absence of my Idea being dismissed out of hand I'm minded to give it a shot. Whatever Richard charges, 4 gallons of diesel and a day of my time is better than the eyewatering prices I've seen for calorifiers. Change out of £1000 (diy prices) just wouldn't happen.

Well, I've taken the spanner to Richard and it will be done tomorrow. He apologized that he couldn't do it today, Sunday !!!!!!He's going to weld an old 1/2" drive socket on to directly accept my impact wrench. 

Meanwhile, I'll enjoy the sunshine. Perfect day for going to the pub.....I wish.? 

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25 minutes ago, Slim said:

Well, I've taken the spanner to Richard and it will be done tomorrow. He apologized that he couldn't do it today, Sunday !!!!!!He's going to weld an old 1/2" drive socket on to directly accept my impact wrench. 

Meanwhile, I'll enjoy the sunshine. Perfect day for going to the pub.....I wish.? 

Ensure you do it 'hot' and with the tank FULL of water.

The copper is so thin that without the support of the water it will twist and burst.

The heat will allow expansion of the tank, and it will be greater than the expansion of the element which will help to free-it-off.

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