Archives for posts with tag: immersion heater

Informational content by Jamie @ Immersion Heaters UK Ltd.

Regularly our most consistent seller, but not entireley sure why this is over other power ratings, a 6kW immersion heater obviously suits many industrial applications.

The popularity could be down to the fact that, with the correct wiring, fuses, etc, you can get away with 6kW on a Single Phase feed, or as it houses three elements, it is also fine for a Three Phase feed. If the heater is wired 4 WIRE STAR, it can even be reconfigured to single phase by shifting ther busbars around, but that is clever stuff, for cleverer folks than me. If you are sufficiently intrigued, the images on this page will hopefully show this theory in practice.

It could also be down to the immersed length at 20″/500mm or below being a good fit for many liquid vessels. Some customers fit multiple 6kW heaters into a vessel as a bank of heaters, rather than fit an 18kW immersion heater, at about twice that length.

This may also effect the control side of things, with an 18kW immersion heater consisting of 3 x 6000w elements, whereas our friend the 6kW heater has 3 x 2000w elements. Some customers switch entire heaters in a bank on /off for temperature control purposes, some cleverer folks switch phases of just one heater on/off. Others use thyristor control, which basicaly varies the voltage, dialing up & down the power to fine tune temperature.

Insider Knowledge, you can put any voltage thru an element & get proportionally more or less power.

Thank you for visiting, & kudos to you for reading this far. If you have any feedback, suggestions, etc, please feel free to contact me.


Anyone limited to a 240v Single Phase supply, as most domestic situations are, must buy a Single Phase Immersion Heater. These will by necessity be limited to 3kW under normal household circumstances, or 6kW if you have 32 amp wiring, fuses, etc.* If you are reading this & are clever and wish to educate me so I am able to elaborate further, feel free on 07897 246 779 or immhtr at gmail dot com)

If you buy something on a budget, you are likely to get one element on a screwplug, thus you attatch live to one terminal, neutral to the other, and away you go (unless you have a control/cutout stat, but lets keep things simple here & now. If you want complicated, there is a wiring diagram HERE). The downside to the financially economical (cheap) option is that it is likely to have a really high watt density (explanation for normal people HERE , but if you are one of that rare & special breed, THE BREWER, click HERE).

Put simply the more heating power coming out of every square inch or cm of your hot element, the higher the sheath temperature, the more sh1t sticks (calcium & magnesium in our gloriously hard water) and the more any chemicals, acids/alkalis, etc, in your solution will attack the glowing element, and cause it to go pop, sooner rather than later. I sometimes advise customers to follow this disposable route, which is fine if you are proving an application, limited on budget, etc.

But if you want to (hopefully) fit & forget, you will have to spend a little more money on a 3 element Single Phase Immersion Heater, like our Industrial Immersion Heaters Range at 3kW or 6kW or our Brewery Immersion Heaters Range at 3kW or 6kW , or indeed any of the Oil Immersion Heaters Range. 3 element terminals will be linked with busbar to provide a common connection for the LIVE line, and similarly the other 3 terminals will be “commoned” up with busbar to provide connection for neutral. As below, in images I immediately feel the need to apologise for. Sorry.

3 elements will allow the watt density to be chopped into thirds. For example a 3kW heater with 1 x 3kW element, or a 3kW heater with 3 x 1kW elements (If the immersed length & element shape are the same. (It’ll last longer. How much longer? 3 times longer? Who knows? Certainly not me. But surely logic dictates? Only if you are a Vulcan). Which leads me on to U bent or looped elements. On a 1.5″BSP screwplug (Domestic Standard in UK) it is only possible to fit 3 U bent elements (8mm ⌀ , and a coupla stat pockets if you know an ElementJedi) whereas on a 2.25″BSP screwplug (Industrial Standard in the UK) you can fit looped elements, as below.

This enables even more element to be fitted into the space available. Which is why I often annoy customers by insisting on the “MAXIMUM immersed length”. An extra inch (Matron!) on 3 looped element is an extra 6″ of element, which is only gonna extend the working life of your heater a little bit more. So size is important, after all.

We stock the Industrial Immersion Heaters listed below for rapid delivery, but can make bespoke items to suit your specific needs if required. In BRASS that can include BSP screwplug sizes including 1″BSP, 1.25″BSP, 1.5″BSP, 1.75″BSP, 2″BSP as well as the British Industrial Standard size of 2.25″, which can be fitted with an adaptor to take it up to 2.5″BSP. In STAINLESS STEEL we can offer 2″ & 2.25″BSP screwplugs.

Bespoke items usually take a coupla weeks, but can be shuffled to the top of the pile if you are willing to pay a premium surcharge of approximately 50%. Customers only tend to do this when they are desperate, due to a production line being down & costing £££’s due to not carrying a spare. The moral of this story being, CARRY A SPARE, especially if your heaters are not standard (ie, 2.25″BSP and a multiple of 3 in terms of kW power output) and stock as listed below.

STOCK Single Phase Immersion Heater

  • 3kW, 6kW, Industrial Immersion Heater stock available for rapid delivery.
  • One cable entry M25 (two available as an option).
  • Terminal covers rotateable through 360 degrees to allow cable entry position to be chosen.
  • Alloy IP67 terminal enclosures. Measuring 120mm diameter x 105mm height.
  • Incoloy 800, “a superior stainless steel”, 8mm diameter elements.
  • Complete with SS thermowell to house our range of 11″ stats.

BESPOKE Single Phase Immersion Heater

  • Available at any kW loading from 500w up to 6kW.
  • 1.25″, 1.5″, 1.75″, 2″, 2.25″ and 2.5″ screwplug sizes are available in brass.
  • 2″ and 2.25″ BSP also available in stainless steel.
  • Available with 1 or 2 thermowells at 7, 11 or 18″ for thermostats / cutouts.
  • 1 additional M25 cable entry glands as an option.
  • Available with no thermowell if specified by the client. If you don’t need it, omit it from the build, as it is an unecessary weak point.

Call Jamie on 07897 246 779 to discus your Single Phase Immersion Heater needs.

*Fair play to you for checking out the footnote, hope it’s worth it? Having said all of the above, I have spoken to many a mad brewer, telling me they are running 12 & 15kW on a single phase, but that is mere rumour & hearsay, and my calls are not recorded for training & quality purposes). Again, if you are clever and can explain htf that is doable, please contact me, explain in small words, and if I can grasp it, we will share it with the world. I love a bit of Collaboration.

Informational content provided by Jamie at ImmersionHeaters.UK or 07897 246779.

An immersion heater is, simply put, a number of elements, usually 3, elements, a screwplug and a IP rated terminal box to protect the connections.


3 of these (preferably not chopped up) and


screwplug sizes

…one of these, drilled through, for the elements to be braised or welded into…


Terminal box

…and one of these to attatch to the screwplug, to house the terminals and wiring.

And, in the best Blue Peter traditions, here’s
one we made earlier…

 Immersion Heater

II Industrial Immersion Heater

The heater is then screwed throught the side of the tank using a weld boss…

weld boss

Mild steel weld boss

Mild steel tanks require mild steel weld bosses, and likewise, stainless steel tanks require horribly priced stainless steel weld bosses. I’ll tell you what brass bosses are used for when I find out.

Informational content provided by Jamie at ImmersionHeaters.UK or 07897 246779.

Informational content provided by Jamie at  Call on 07897 246779.

I was going to provide a link to the best definition of watts density available on the web, but they are in very short supply, so here goes.

Watts density is the amount of heating energy emanating from any given amount of surface area of the hot part of an element.

In Imperial Britain and the States, this is usually described in terms of watts per square inch, but could be expressed (to keep the Eurocrats happy) as watts per square cm, mm, or indeed, meter. But why bother?

For 8mm diameter elements, simply divide the heating power output (in watts) of the given element by the length of hot section, ie. subtracting the cold ends at either end of the element, which can be 2″, 4″, 6″ or any custom length.

So, for the benefit of a simple example, if we have a 1kW, 54″ element with 2″ cold sections, we first take 4″ (2 ends of 2″) of cold off the total length of the element to give our hot section, 50″. Then we divide the power output of 1000w by 50″ to give us a watts density of 20w/in².

Now imagine we have a 1kW, 104″ element with 2″ cold ends (c/e), giving a hot length of 100″, do the maths as above, and you should get a watts density of 10w/in². Now, picture an inch square in your mind, or draw it if you prefer. Now, fill the box with 10 or 20 little boxes, happy faces, “watt monsters”, whatever crumbles your cookie. The size of the square doesn’t change between the 2 examples, but the size of the contents do, more watts per square inch means more squashed, little watts trying to get out of the same space. Now draw a box, mentally or on paper, and squeeze 40 of your little watt icons in that box. While your at it, have think about how long a 1kW element with 2″ c/e, would need to be to give a watts density of 40w/in²?

For the less imaginative among you, somebody kind drew this –

Watt Inch

Different watts densities are requires for different applications. Some are set in stone, for obvious reasons, such as oil heaters needing to be no more than 12w/in², others are a little more flexible and open to “interpretation”. ElementYoda always told me 5w/in² for elements in still air, but as can be seen below, grill elements can work at up to 42w/in². Fortunately, we don’t supply many of them, cos there wouldn’t be much of a guarantee at that top end. We are mainly suppliers of immersion heaters for water, with soft water being fine between 50-75w/in², but hard water being better suited to 40w/in² or below.

Our (Element Air) EA Range is rated at 27w/in², designed for forced air heating units, where the airflow needs to be 2m³/s. The simple way this is achieved is that every meter of element equates to 1kW, so if you want 3kW you have to bend/coil a 3m element into your available space.

Below is a detailed table of watts density in inches and equivalent cm, plus details of colour change and suitable applications.

W/in2 W/cm2  
94 14.5 Immersed only
83 12.9 Immersed only
73 11.3 Immersed only
63 9.7 Immersed / High Arflow / Machined Fit
52 8.1 Immersed / High Arflow / Machined Fit
42 6.5 Equivalent to Grill / Radiant / Orange
31 4.8 Glow Red
21 3.2 Colour Change
10 1.6 Little or no Colour Change Still Air
9 1.5 Little or no Colour Change Still Air
8 13.0 Little or no Colour Change Still Air
7 1.1 Black Heat
6 1.0 Black Heat
5 0.8 Black Heat
4 0.6 Black Heat
3 0.5 Black Heat
2 0.3 Black Heat

And for the visual learners among you, here is that same info in colourful form that I “borrowed” from a friend –

Colour Change Chart

To convert to other element diameters, please divide your solution as above by the following factors.  If you think of the 1kW, 54″ element with 2″ cold sections that we started with, only this one is 12mm in diameter, share our 20w/in² initial answer by the factor of 1.484, gives a watts density of 13.48w/in², which makes sense as a wider element will have more surface area for the 1000w to “escape” from.

8 0.99
8.5 1.05
9.5 1.175
10 1.24
11 1.36
11.5 1.42
12 1.484
12.7 1.57
13.4 1.657
16 1.98
20 2.474
50.8 6.28

When you understand all this, and realise that glowing ain’t good, you can see the sense in squeezing as much element into the space available, cos simply put, the lower the watt density, the longer it’ll last, whatever it is heating.

Thanks for visiting, please leave a comment.

Informational content provided by Jamie at ImmersionHeaters.UK or 07897 246779.

various screwplug sizes

1.25″BSP, 1.75″BSP, 2″”BSP, 2.25″ SCREWPLUGS

Informational content provided by Jamie at

Call on 07897 246779.

Examples of some of the various screwplug sizes available, these are undrilled, therefore can be used as a blanking plate or for our customers who are unsure of their requirements, to screw into their socket before anything is manufactured bespoke. Very useful!

This is the simple version,

1/2 .825
5/8 .902
3/4 1.041
7/8 1.189
1 1.309
1 & 1/4 1.650
1 & 1/2 1.882
1 & 3/4 2.116
2 2.347
2 &1/4 2.537
2 & 1/2 2.95

…and this is the complicated version,

Thread Form Type Major Diameter mm d=D Pitch mm p Threads per inch tpi Pitch Diameter mm d2=D2 Minor Diameter Male Thd. d3 Thread Height H1 Tap Drill Diameter mm
1/8 “ BSPP/BSPF 9.728 0.907 28 9.147 8.566 0.581 8.7
1/4 “ BSPP/BSPF 13.157 1.337 19 12.301 11.445 0.856 11.6
3/8 “ BSPP/BSPF 16.662 1.337 19 15.806 14.95 0.856 15
1/2 “ BSPP/BSPF 20.955 1.814 14 19.793 18.631 1.162 19
5/8 “ BSPP/BSPF 22.911 1.814 14 21.749 20.587 1.162 20.75
3/4 “ BSPP/BSPF 26.441 1.814 14 25.279 24.117 1.162 24.5
7/8 “ BSPP/BSPF 30.201 1.814 14 29.039 27.877 1.162 28
1 “ BSPP/BSPF 33.249 2.309 11 31.77 30.291 1.479 30.5
1 1/8 “ BSPP/BSPF 37.897 2.309 11 36.418 34.939 1.479 35
1 1/4 “ BSPP/BSPF 41.91 2.309 11 40.431 38.952 1.479 39.5
1 3/8 “ BSPP/BSPF 44.323 2.309 11 42.844 41.365 1.479 41.5
1 1/2 “ BSPP/BSPF 47.803 2.309 11 46.324 44.845 1.479 45
1 3/4 “ BSPP/BSPF 53.746 2.309 11 52.267 50.788 1.479 51
2 “ BSPP/BSPF 59.614 2.309 11 58.135 56.656 1.479 57
2 1/4 “ BSPP/BSPF 65.71 2.309 11 64.231 62.752 1.479 63
2 1/2 “ BSPP/BSPF 75.184 2.309 11 73.705 72.226 1.479 72.5
2 3/4 “ BSPP/BSPF 81.534 2.309 11 80.055 78.576 1.479 79
3 “ BSPP/BSPF 87.884 2.309 11 86.405 84.926 1.479 85.5
3 1/4 “ BSPP/BSPF 93.98 2.309 11 92.501 91.022 1.479 91
3 1/2 “ BSPP/BSPF 100.33 2.309 11 98.351 97.372 1.479 97.75
3 3/4 “ BSPP/BSPF 106.68 2.309 11 105.201 103.722 1.479 104
4 “ BSPP/BSPF 113.03 2.309 11 111.55 110.072 1.479 110.5
4 1/2 “ BSPP/BSPF 125.73 2.309 11 124.251 122.772 1.479 123
5 “ BSPP/BSPF 138.43 2.309 11 136.951 135.472 1.479 136
5 1/2 “ BSPP/BSPF 151.13 2.309 11 149.651 148.172 1.479 148.5
6 “ BSPP/BSPF 163.83 2.309 11 162.351 160.872 1.479 161.5

I hope these are useful for reference purposes.

More importantly for us, on a daily basis, are the following limitations as to what will fit onto the smaller screwplug sizes. We deal with up to 2.25″ only, with 2.5″ being accommodated by fitting a brass adaptor to 2.25″ screwplug.


Anything smaller than a 1.25″ screwplug will be limited to 1 element, having immediate implications for the achievable watts density.  Likewise, being limited to U bends only, makes reducing the watts density more problematic. Many domestic and commercial plumbing applications use 1.5″BSP, and are thus limited to 3 hairpins and only 1 stat pocket. maximising the immersed length of those U’s is all that can be done to reduce the watts density. To overcome the issue of only 1 stat pocket, we find ourselves increasingly selling dual control and cutout stats.

By hairpin, we mean a U bent element, and trombone indicates double looped. To determine what element is suitable, for U’s you merely double the maximum immersed length available, ie, 24″ immersed length will use u bent 48″ elements. However, if double looping is possible due to the screwplug size and other factors relating to the application (cleaning, etc), that 24″ maximum immersed length could be multiplied by up to 3.5, allowing the use of 84″ elements. See the watts density article to appreciate what a difference that will make. 48″ to 84″ almost double the hot element available, so is almost going to halve the watts density. A big issue on little screwplugs.

Thanks for visiting, please leave a comment.

Informational content provided by Jamie at

Call on 07897 246779.

What is Ingress Protection?

IP Explanation and Ratings
EN 60529 outlines an international classification system for the sealing effectiveness of enclosures of electrical equipment against the intrusion into the equipment of foreign bodies (i.e. tools, dust, fingers) and moisture. This classification system utilizes the letters “IP” (“Ingress Protection”) followed by two or three digits. (A third digit is sometimes used. An “x” is used for one of the digits if there is only one class of protection; i.e. IPX4 which addresses moisture resistance only.)
Degrees of Protection – First Digit
The first digit of the IP code indicates the degree that persons are protected against contact with moving parts (other than smooth rotating shafts, etc.) and the degree that equipment is protected against solid foreign bodies intruding into an enclosure.

  • 0 – No special protection.
  • 1 – Protection from a large part of the body such as a hand (but no protection from deliberate access); from solid objects greater than 50mm in diameter.
  • 2 – Protection against fingers or other object not greater than 80mm in length and 12mm in diameter.
  • 3 – Protection from entry by tools, wires, etc., with a diameter of thickness greater than 1.0mm.
  • 4 – Protection from entry by solid objects with a diameter or thickness greater than 1.0mm
  • 5 – Protection from the amount of dust that would interfere with the operation of the equipment.
  • 6 – Dust tight.

Degrees of Protection – Second Digit
The second digit indicates the degree of protection of the equipment inside the enclosure against the harmful entry of various forms of moisture (e.g. dripping, spraying, submersion, etc.)

  • 0 – No special protection.
  • 1 – Protection from dripping water.
  • 2 – Protection from vertically dripping water.
  • 3 – Protection from sprayed water.
  • 4 – Protection from splashed water.
  • 5 – Protection from water projected from a nozzle.
  • 6 – Protection against heavy seas, or powerful jets of water.
  • 7 – Protection against immersion.
  • 8 – Protection against complete, continuous submersion in water.

Informational content provided by Jamie at

Call on 07897 246779.

Remembering all of the aspects and considerations discussed on the “How to choose an immersion heater” page, water hardness must be taken into account when designing a water immersion heater.

A detailed description of water hardness can be found HERE, but for the purposes of this blog, we will say that hard water has a higher concentration of calcium and magnesium which leads to limescale, which we are all familiar with in kettles, etc, within the home. Whilst merely being an inconvenience in the home, (one that can be avoided by using one of these beauties which are awesome and well worth the money if like me you consume litres of water a day, highly recommend, no business interests or bias by bungs!) it can be a real issue in commercial and industrial applications.

The problems are caused by the limescale deposits building up on the hot part of the elements. Once this process starts, it becomes self perpetuating, and indeed self accelerating, if not removed by jet washing, disolving or other means. Basically, the limescale build up prevents the heat getting away from the element, acting like an unwanted insulating jacket, increasing the element surface temperature, which in turn, attracts more deposits. An example of which is shown below, courtesy of, which would perhaps be better used as a christmas tree than for making coffee!

heatingelement limescale

The easy way to maximise the working life of your immersion heaters, whether in a hard water area or not, is to minimize the Watts density. The article explains in detail a simple concept which we are using every day, maximise the element length THUS minimising the watts density THUS maximising the working life of the element, all other things being equal.

Informational content provided by Jamie at Call on 07897 246779.

Informational content provided by Jamie at

Call on 07897 246779.

Remember all of the stuff that applies to all water immersion heaters, plus for oil heaters our target is to get the watts density down to 12w/in² or below for heavy, industrial oils, and 25w/in² or below for lighter cooking oils.

POIL Oil Imersion Heater

Oil Imersion Heater

The II Range has many benefits, including bespoke screwplug size, immersed length, double stat pockets, etc, all with a 2 week leadtime. The 8mm elements can be double looped to fill your maximum available immersed length with a large overall length of element. As can be seen in the fifth image on our PII web page, the elements drop from the screwplug to your maximum available immersed length, before looping back up to within a few inches of the screwplug, before dropping back to full immersed length, then returning back up to the screwplug. This allows us to fit nearly twice the length of element possible in a plain U bent element. For example, in 24″ of maximum immersed length, we could use an 84″ element double looped.

if you have a very large tank with a massive maximum available immersed length, you may choose not to double loop, but to have plain U bent elements over a meter in length.

Informational content provided by Jamie at …who would love you to leave a comment.