Cylinder Immersion Heater Install

[Monkey Wrench]

I have today tried to replace the bottom immersion heater on an Economy 7 direct hot water cylinder but ended up with a major problem.
The heater element came out relatively easily part from being quite stiff to undo which I put down to the age of the cylinder.
I removed the old heater element, cleaned the thread and removed all the gunk/dirt from the mating surface for the new immersion.
I then tried the new immersion in the thread, gave it about half a turn without any problem then removed it to apply the gasket and some
FERNOX LX to the mating surfaces for good measure.

However, I then tried to put the new immersion back into the cylinder but could not locate it on the thread to get it going.
After several attempts, it went into the thread but would only go about 1 1/2 turns and then binded
with still along way to go before it would have been water tight. I struggled with it for about 10 minutes, removed it and tried the old element which
went in about 2 1/2 turns before again binding well before the fibre washer was touching the cylinder.
After about an hour and a half (should be a 15 minute job max) of trying the get the new immersion into the thread I gave up.

The new immersion will just not turn fully into the thread not matter how many times I try and neither will the old one. The thread looks fine with
no obvious signs of cross threading but even an immersion blank plate wouldn't go fully into the thread either.

Does anyone please have any suggestions how I can resolve this ?

Thank you

 

[scotty plumber]

Hi, If the old immersion came out fine then the old immersion will not go back in fine after attempting to put the new one in it sounds like you have damaged the threads on the cylinder, you should have managed to get the new one in most of the way with just your hands or did you use your key straight away??

 

[mcniven]

New cylinder reqd done this before :-(

 

[mikegas]

try some lubricant on the threads, does sound like the threads are crossed though

 

[scotty plumber]

A little perseverance can sometimes fix this

 

[Monkey Wrench]

Thank you for the prompt responses.

Once I'd got the new immersion on the thread I turned it by hand about 2 turns before it started to bind, assuming that it was just a bit of dirt on the thread,
I then used the key for about another half a turn before it wouldn't turn anymore without a lot of pressure and thats when i backed off.

I guess the thread might be crossed but there's no visible sign of it. If it is, is there anyway of getting it back again either by re-cutting/threading it or another
simpler solution. The theads look sound without any visible damage but after 2 1/2 turns the immersion doesn't sit square in the thread but at a slight angle.

This is the first time I've evr had this problem changing an immersion element !

 

[PlumbBobBob]

when you offer the immersion up turn it the wrong way slowly until you feel the thread click you may even hear it. then turn it the right way and it should go in properly. when the thread clicks it is just finding the start of the thread.

 

[Billy Bob Bob]

Thank you for the prompt responses.

Once I'd got the new immersion on the thread I turned it by hand about 2 turns before it started to bind, assuming that it was just a bit of dirt on the thread,
I then used the key for about another half a turn before it wouldn't turn anymore without a lot of pressure and thats when i backed off.

I guess the thread might be crossed but there's no visible sign of it. If it is, is there anyway of getting it back again either by re-cutting/threading it or another
simpler solution. The theads look sound without any visible damage but after 2 1/2 turns the immersion doesn't sit square in the thread but at a slight angle.

This is the first time I've evr had this problem changing an immersion element !

it can sometimes be difficult to start off being a economy 7 cylinder i presume the immersion is on the side sometimes as hard as you try the weight of the element stops you putting it in strait just make sure you correct this as you start the thread off steves tip also works

 

[tamz]

You are not the first person to do this and won't be the last. Your best bet of fixing this is to remove the cylinder and lay it on its side where you can see the threads properly. Try using the edge of a small screwdriver and run it around the threads from inside out. This may uncross it enough to get it started again with a bit perseverance. When screwing the new one in keep the cover on it. It makes it easier to hold and judge if it is straight.
If that doesn't work it is new cylinder time unless you know how to solder one in or can be bothered to cut in an essex flange.

 

[kay-jay]

You are not the first person to do this and won't be the last. Your best bet of fixing this is to remove the cylinder and lay it on its side where you can see the threads properly. Try using the edge of a small screwdriver and run it around the threads from inside out. This may uncross it enough to get it started again with a bit perseverance. When screwing the new one in keep the cover on it. It makes it easier to hold and judge if it is straight.
If that doesn't work it is new cylinder time unless you know how to solder one in or can be bothered to cut in an essex flange.

im damn sure i'd give a flange a go before shelling out for a new cylinder if it was me!

 

[quality]

A local engineering machine shop would have a tap that you could try to clean the thread out

 

[Monkey Wrench]

Thank you all the help and advice.

when you offer the immersion up turn it the wrong way slowly until you feel the thread click you may even hear it. then turn it the right way and it should go in properly. when the thread clicks it is just finding the start of the thread.

Thanks for the tip. I've not had a chance to look at the cylinder today but will give it a try tomorrow.

it can sometimes be difficult to start off being a economy 7 cylinder i presume the immersion is on the side sometimes as hard as you try the weight of the element stops you putting it in strait just make sure you correct this as you start the thread off steves tip also works

The cylinder has two immersions and both are on the side. The blown element was the Economy 7 immersion and is located about 5 inches from the bottom of the cylinder making the job even more of a hassle as the drain-off had been installed above the centre line of the immersion heater.

You are not the first person to do this and won't be the last. Your best bet of fixing this is to remove the cylinder and lay it on its side where you can see the threads properly. Try using the edge of a small screwdriver and run it around the threads from inside out. This may uncross it enough to get it started again with a bit perseverance. When screwing the new one in keep the cover on it. It makes it easier to hold and judge if it is straight.
If that doesn't work it is new cylinder time unless you know how to solder one in or can be bothered to cut in an essex flange.

Ive taken the cylinder out and its currently in the garage awaiting my attention. I will certainly try running a screwdriver around the threads but, having had a quick look earlier, I noticed that the second thread in from the outside of the cylinder seems to be slightly flattened so maybe thats causing the problem ! If I can get the new element in square would that cut another edge or am I being too optimistic ?

I've cut-in Essex flanges before but not 2 1/2 inch in diameter ! Do they even exist ? The other thing is how would I blank/seal the gaping hole left by the immersion (or am I missing something) ?

A local engineering machine shop would have a tap that you could try to clean the thread out

I will certainly give that a go if nothing else works.


Thanks again

 

[PlumbBobBob]

one thing i would say is be careful that you don't rip the copper when you tighten the immo up. i would wait until the cyl is back in place until you finally tighten it up when it is full of water to help support the sides.

 

[Monkey Wrench]

one thing i would say is be careful that you don't rip the copper when you tighten the immo up. i would wait until the cyl is back in place until you finally tighten it up when it is full of water to help support the sides.

Thanks for that SteveB.

The only problem is that the immersion is at the bottom of the cylinder and so surely I'd need to tighten it before filling with water to prevent leaks.
I didn't try loosening it (for removal) until after completely draining the cylinder for this very reason and, because the drain-off was the same height
as the immersion, I had to remove the hot water outlet in order to put in a hose to siphon the water out.

Thanks again.

 

[heatybob]

this happened to me,what worked for me was i ran in a 2 1/2" mild steel nipple which basicaly recut the brass thread,ithen took more care with the new immersion:sweatdrop: best of luck mate

 

[Monkey Wrench]

this happened to me,what worked for me was i ran in a 2 1/2" mild steel nipple which basicaly recut the brass thread,ithen took more care with the new immersion:sweatdrop: best of luck mate

Thanks for that Heatybob.

Where did you get a 2 1/2 inch mild steel nipple from ?

 

[REDSAW]

try a thread file on it?.

 

[quality]

Crosslings, pirtek or any hydraulics outlet would have nipple that size

 

[heatybob]

as above,bss pipeline center etc,maybe worth a try for a couple of quid,it worked for me

 

[PlumbBobBob]

just a thought if it's a normal cylinder and not a combination one you could put a new drain in while it is out. just put a tee into the cold feed at the bottom and bring a drain to the front where you can get to it at the base.

 

[heatybob]

just as an add on,and this may sound silly but just to let you know that for some reason different manufacturers have differant size threads in so much that GF fittings as stocked by bss are a lot smaller than say Crane(pipeline)this applies to all sizes,dont know why 2" is 2". 1" is 1" to me(nobody ever been able to answer that one)off topic i know but can be a pain if your using fittings from both mans. keep altering the threads etc

 

[kay-jay]

This is why i hate immersions . I always try a stat change first cos most of the time its not actually the element........hopefully the op hasn't ended up in a pickle unnecessarily

Sent from my GT-I9100 using Tapatalk

 

[Monkey Wrench]

Thanks for the posts.

try a thread file on it?.

Do you have idea what the pitch of the threads are so I could get the right size thread !

Crosslings, pirtek or any hydraulics outlet would have nipple that size

as above,bss pipeline center etc,maybe worth a try for a couple of quid,it worked for me

Do I actually ask for a "mild steel nipple" or is it called something else ?

just a thought if it's a normal cylinder and not a combination one you could put a new drain in while it is out. just put a tee into the cold feed at the bottom and bring a drain to the front where you can get to it at the base.

The centre line of the cold feed is exactly the same height as the centre line of the immersion heater and so any drain-off would still leave about an inch of water in the cylinder. Unbelievable IMO !

This is why I hate immersions . I always try a stat change first cos most of the time its not actually the element........hopefully the op hasn't ended up in a pickle unnecessarily

Sent from my GT-I9100 using Tapatalk

The first thing I checked was the stat which worked perfectly (live both sides) and I can confirm that the element has a split in the side.


Thanks again for all the excellent help and advice.

 

[WHPES]

If the old one goes in and out OK still, the threads are probably tight on the new one. Try a different make of element

 

[REDSAW]

dont you have a thread gauge?. get them from machine mart, toolstation etc. then file out thread.