Immersion Heater - Element Length

Can't you just measure the depth of the tank and buy one to fit ,like a 24 " one for example. I'm assuming there is enough room above the tank to let you get a longer one in .

I was working on that theory.... I should be able to get a 36" element in. I was just wondering if there were any guidelines regarding length of element/proximity to side of tank etc.

Andy

I'm assuming that the immerser fits straight down the middle ( or does it?) .If so then it won't be any nearer the sides than the old one . I know that some fit in sideways and some ( I think) are at an angle . You still have 12" between the end and the foot of the tank ( less an amount for any concave in the bottom of the tank which you won't be able to see unless you remove the tank )and allowing for any sludge at the foot of the tank . Does this help...it suggests 27" is the most common size

One thing is certain - any water *below* the element won't get heated significantly by it.

If it goes in horizontally near the bottom of the cylinder, length doesn't matter too much - but it makes sense to get one whose length is just short of the cylinder diameter.

If it goes in (near) vertically from the top, you need one which extends as far down as you can get. I doubt whether you can get one that's anywhere near 4' long.

I assume that the immersion heater isn't your *only* way of heating the water, and that the cylinder also has an internal coil carrying hot water from a gas boiler boiler or somesuch as the principal means of heating the DHW?

Our (non-std size) direct cylinder was heated for years with an 11" 3kW heater but it was fitted at the bottom of the tank so could heat the whole contents. When I fitted a new indirect cylinder last year (standard 900 x 450mm B&Q type) I also fitted a 27in immersion heater at the top. I have posted a graph showing the temperatue at the top of the tank and at about

Geo

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Andy Kirkland saying something like:

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Geo saying something like:

They're designed not too - although you wouldn't believe that from the struggle you sometimes have to get the bloody thing in past the coil.

Before I got a new boiler I had a Primatic and when the immerser failed it was a bit of a struggle to get it out and the new one in ,not helped by the lack of space immediately above the tank between it and floor of the flat above .

It sounds like you have done one before, so how did you get the old one out? I tried to get my mates out, but it wouldnt budge. Alan.

Black art and luck. Don't drain the system until it starts to budge - modern tanks have very little strength when full and none at all when empty. Local heating, Plus-Gas, sacrifice, prayer, incantations and the preparedness to buy a new tank are essential.

Thanks everyone for the info - will go for a 27" or 36" one.

Now to the task of removing the old one..... penetrating oil, wait, more oil, wait, tap gently, more oil, wait, attach spanner, pray!

Cheers

Andy

Hope you'll be pleasantly surprised .Mine unscrewed quite easily altho' it had been in years

AIUI the 24"/27" does the heavy lifting & the 11" is just a top up. The 11" one won't heat enough water fast enough for most domestic applications.

The ring type flat spanners are all but useless. The box spanner type is much better.

They are all around 3Kw, so because the 11" ois only able to heat the upper water levels, it would in fact heat it up much quicker than a longer element. As hot water rises, the hot water produced would stay at the top of the tank.

On Fri, 07 Nov 2008 18:03:20 GMT someone who may be "The Medway Handyman" wrote this:-

Other than a bath, and perhaps a power shower, a short immersion heater is fine for normal domestic use. It will heat up the top of the cylinder rapidly enough to cope with demand.

Those who want deep baths, or are heating water overnight for storage in a properly insulated cylinder, will consider a longer heater.

If one wants both the whole cylinder and the top part to be heated in different circumstances extra bosses can be fitted. I also have a vague recollection of dual element immersion heaters which fit in one boss, though I have never encountered one that I can remember.

I replaced my immersion heater once, using a lever with a piece of chain attached to it.

Some 10-15 years later I removed the tank. It was impossible to get the element out of the tank without damaging the tank.

There are still RedHeat Dual elements on sale. They have a long and short element. The long one used to heat the whole tank on the over night tariff and a small one for boost during the day. But they are usually fitted on cylinders that have 4 inches of soft insulation around them. It is the only way to make them economical enough to use.

Hitting the spanner with a hammer is less likely to crumple the tank than applying high sustained force IME... Good luck!