The Tesla UK Incoloy Immersion Heater with Copper Thermostat Pocket is the mid-range option in the Tesla domestic heater line-up, recommended for moderate to hard water areas where a plain copper element would scale up too quickly but a full titanium element is not required. It uses a standard 2-1/4" BSP boss and is rated 3kW at 240V across the full length range.
This variant is supplied complete with a dual safety thermostat matched to the element length, a sealing washer, and full fitting instructions. It is manufactured to EN 60335-2-73 and BEAB approved (Certificate No. 21089), with Kiwa water regulations approval. Select the correct length below (11" to 36") to match your existing cylinder boss and thermostat pocket depth.
Please Note: The thermostat pocket on this variant is copper, not Incoloy or titanium. Tesla recommends against fitting copper-pocket elements into stainless steel cylinders, as galvanic corrosion can eventually perforate the pocket. For stainless steel cylinders, choose the Incoloy-with-Incoloy-pocket or Titanium variant instead.
Incoloy Element for Moderate-to-Hard Water
Incoloy is the manufacturer-recommended material for moderate to hard water areas, offering better scale resistance than a plain copper element while remaining more cost-effective than titanium.
Dual Safety Thermostat Included
Every length is supplied complete with a combined thermostat and safety over-temperature cut-out, factory pre-set to 60°C with an 85°C manual-reset cut-out.
Thermostat Length Matched to Element
Stem length increases with element length — 7" for 11"-14" models, 11" for 18"-23", and 18" for 27"-36" — ensuring accurate temperature sensing depth in every size.
BEAB & Kiwa Approved Throughout
Manufactured to EN 60335-2-73 and BEAB approved (Certificate No. 21089), with Kiwa water regulations approval and a non-asbestos gasket or WRAS-approved seal as applicable.
Seven Lengths to Match Every Cylinder
Available from 11" up to 36", covering combination cylinders through to the largest 42" x 18" domestic cylinders, all sharing the same 2-1/4" BSP boss.
Vertical or Horizontal Mounting
Lengths of 14" or shorter mount horizontally; lengths over 14" are designed for vertical, top-entry fitting, with approximately 60mm clearance required at the element tip.
| General Specification |
| Manufacturer |
Tesla UK Ltd, Sutton Coldfield, West Midlands |
| Element Material |
Incoloy |
| Thermostat Pocket Material |
Copper |
| Boss Size |
2-1/4" BSP |
| Power Rating |
3kW @ 240V |
| Approval Standard |
EN 60335-2-73 (BS EN 60335-2-73) |
| Safety Certification |
BEAB Approved, Certificate No. 21089 |
| Water Regulations |
Kiwa approved |
| Thermostat Type |
Combined dual safety thermostat with manual-reset over-temperature cut-out |
| Thermostat Pre-set |
60°C (adjustable, cut-out at 85°C) |
| Sealing |
Non-asbestos gasket or WRAS-approved ‘O’ ring, as applicable |
| Cable Rating |
Minimum 1.5mm² heat-resistant cable required (installer-supplied) |
| Max System Temperature |
75°C (per BS699 / BS1566 / BS3198 domestic hot water systems) |
| Recommended Water Hardness |
Moderate to hard water areas |
| Installation Guidance |
| Combination Cylinders |
11", 14" or 18" recommended |
| 36" x 18" Cylinders |
23" or 27" recommended |
| 42" x 18" Cylinders |
27", 30" or 36" recommended |
| Mounting Orientation |
14" or shorter: horizontal. Over 14": vertical (top-entry) |
| Clearance |
Approx. 60mm clearance required between element end and cylinder wall/base |
| Stainless Steel Cylinders |
Not recommended due to copper thermostat pocket — choose an Incoloy or Titanium pocket variant instead |
| Length |
Boss |
kW @ 240V |
Thermostat Length |
MPN |
| 11" |
2-1/4" BSP |
3 |
7" |
TIH540 |
| 14" |
2-1/4" BSP |
3 |
7" |
TIH545 |
| 18" |
2-1/4" BSP |
3 |
11" |
TIH547 |
| 23" |
2-1/4" BSP |
3 |
11" |
TIH548 |
| 27" |
2-1/4" BSP |
3 |
18" |
TIH550 |
| 30" |
2-1/4" BSP |
3 |
18" |
TIH555 |
| 36" |
2-1/4" BSP |
3 |
18" |
TIH560 |
Important Safety Information: This is a mains-voltage electrical heating product for installation into a water-filled cylinder. Installation, wiring and testing must be carried out by a suitably qualified electrician or a Part P registered competent person, in accordance with current IEE wiring regulations. The appliance must be earthed and wired through a double-pole isolator with a contact separation of at least 3mm in all poles. The heater must never be switched on unless fully immersed in water.
What water hardness is this Incoloy element suitable for?
This variant is recommended by the manufacturer for moderate to hard water areas. For hard to very hard water, a Titanium element is advised for longer service life.
Why does the thermostat pocket matter?
The thermostat pocket is the sealed tube the thermostat sensing rod sits inside. This variant uses a copper pocket, which is suitable for standard copper cylinders but not recommended for stainless steel cylinders due to the risk of galvanic corrosion.
How do I choose the right length for my cylinder?
As a guide: combination cylinders generally take 11", 14" or 18" models; 36" x 18" cylinders typically take 23" or 27"; and 42" x 18" cylinders take 27", 30" or 36". Always use the largest length your cylinder can accommodate for the most efficient heat cycle.
Does this heater include a thermostat?
Yes. Every length is supplied complete with a dual safety thermostat matched to the element length, pre-set to 60°C with an 85°C manual-reset safety cut-out, along with the correct sealing washer or O-ring.
Can I fit this in a stainless steel cylinder?
This is not recommended. Because this variant has a copper thermostat pocket, fitting it into a stainless steel cylinder can cause galvanic corrosion which may eventually perforate the pocket. Choose the Incoloy-with-Incoloy-pocket or Titanium variant instead.
