how immersion heaters work.

just want to check i ve got something right,

if theres an immersion element in to the top of the tank, ie off centre at an angle, does it just heat the top half of the tank? for the full tank to be heated does it need to located at the bottom of the tank?

cheers wayne

how long is it?

Top mounted immersions are usually quite long so they reach nearly to the bottom of the tank. That's if they have fitted the right one.

You could also get them with a long and a short element, so you could heat just the top of the tank more quicky.

not sure mate, customer complaining about hardly having any hot water. theres just the element in top of tank that comes on with economy 7, no boost or anything. i suggested its because the tank not getting fully heating.

If it says 3kw then the only sure way is to remove the element and see if its the correct one for the cylinder.

Tank full of limescale? It must be a pretty old tank, so I would advise replacing the tank for a new one with two elements, the bottom one for overnight E7, and the top one for a daytime boost if needed.

1/ Take the cover off & pull the thermostat out..

that will tell you how long it is..

2/ Is the thermostat tripping off too soon?

Adjust it try it hotter.. or stick a new one in..

3/ Is the circuit RCD protected..

i.e. could the element be shot and current flowing back through earth via the water?

4/ Measure the resistance of the element..

230v2/3000w = should be around 18ohms - 20ohms ish

5/ By pass the timer switch, connect it direct measure how much current it is drawing

3000w/230v = should be around 12A - 13A ish...

various combinations of all or some of the above should answer your problem...

Guinness

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6/ It should be a 27'' not an 11''

e.g. this

Immersion Heater Copper Element 27" | Screwfix.com

not this

Immersion Heater Copper Element 11" | Screwfix.com

take one of these with you as a test..

Dual Safety Thermostat 18" | Screwfix.com

GuinnessGuinness

The thermostat length has no baring on the immersion heater length. If its a 3kw heater the resistance will be the same whatever the length so the only way to be sure is to remove the element. Have you checked the thermostat is operating correctly

Wellllll, it sort of does.

They don`t usually have 2`3" thermostats on 11" immersions :slap

When fitting the new one, check that

there is a stat in the head that needs

manual reset if it operates.

ive not been back yet so not got any info on length. the problem has been like this for nearly 15 years, the water is heating up and is hot but theres never enough to have a bath or a couple of showers. i suspected the length of the immersion, didnt realise there was a really long one. the plumbers hasnt really got a clue and passed it on to me. over the years the owner has had many electricians and plumbers round but they either dont know or never come back. the heater is only powered by eco 7 which seems to be working as it should ie customer notices neon working in the night.

ive not been back yet so not got any info on length. the problem has been like this for nearly 15 years, the water is heating up and is hot but theres never enough to have a bath or a couple of showers. i suspected the length of the immersion, didnt realise there was a really long one. the plumbers hasnt really got a clue and passed it on to me. over the years the owner has had many electricians and plumbers round but they either dont know or never come back. the heater is only powered by eco 7 which seems to be working as it should ie customer notices neon working in the night.

Click to expand...

If there's only one heater, fit the OLD style Horstman boost controller, the one with the clockwork timer for the boost peoriod. I'm not sure if you can still buy them new, but if not I probably have a used one in the garage.

With that, it will power the one heater overnight from the off peak supply, and will energise the same heater in the daytime for a boost if needed.

You really need to take the element out for a look. That will show you if it's long or short, and give you an idea of the tank is okay, or full up with limescale. It's a grey area if that's a plumber or electricians job, but like many electricians I have an immersion heater spanner and will change an immersion heater.

However in the long run, I do suggest you consider a new tank. Especially if the existing one is really old and not even foam lagged.

Ive got a few of those kicking around too Dave, brand new,

Im fairly certain you can still buy them.

I bought one recently, not cheap !

you're right

timer

ive not been back yet so not got any info on length. the problem has been like this for nearly 15 years, the water is heating up and is hot but theres never enough to have a bath or a couple of showers. i suspected the length of the immersion, didnt realise there was 'a really long one'. the plumbers hasnt really got a clue and passed it on to me. over the years the owner has had many electricians and plumbers round but they either dont know or never come back. the heater is only powered by eco 7 which seems to be working as it should ie customer notices neon working in the night.

Click to expand...

It isn't a 'really long immersion heater', it is a standard length, or a shorter length. On the balance of probability almost all plumbers would have been likely to have fitted the standard (long) element anyway when the cylinder was initially installed.. It sounds to me that it just needs to be left turned on for longer periods, possibly with a higher temperature setting on the thermostat and maybe some improved lagging on the cylinder. Irrespective of the length if it is still a 3kW element it will still heat up the water. But as with a large pan of water on a small gas ring, it takes longer to heat up, and if you turn the fuel off too soon the water wont be getting as hot. I cannot believe no one has been able to address the problem in 15 years. a few simple tests narrow down the cause quite quickly. Assuming the element is not faulty.

Doc H.

Had this problem recently - temporary connection to top immeresion on twin immersion tank. The hot water doesn't tend to circulate so trips out thermostat before heating whole tank so you only get small amount of hot water.

Have you seen this thread http://www.talk.electricianforum.co.uk/central-heating-forum-storage-heaters-forums-forum-including-electrical/15968-immersion-heater-stat-keeps-tripping.html

If its been like it for 15 years I'd say it was a short (11") element TBH . Have you had the ammeter on it ? And if the bottom of the tank is cold that pretty well answers the question .

I have a twin immersion system. The bottom element is knackered it has a short circuit on it and plumber could not get it out. I have wired top tank now to E7.

My question is this I assume both tanks have a cold water inlet, how does the hot water just flow from one tank but not into the other? Is there some valve on each tank?