Installation made easy

Small but mighty making installation simple on an internal wall or cupboard. It can go anywhere!

What you need

We’ve included: 1 x ThermoSphere Micro Electric Boiler (TSMEB) and installation instructions (including installation template).

You’ll also need: 

  • RCBO protected electrical supply
  • Isolation switch
  • Suitably rated supply cable
  • 4 fixing screws – (8 x 65mm recommended)
  • 2 15mm x 1/2″ brass adapting female couplers
  • Pressure limiting 5 bar valve
  • Shut off valve
  • Other plumbing parts to suit your application
Micro Electric Boilers – Installation 1

Key installation steps

Micro Electric Boilers – Installation 3

1. Install power supply

Micro Electric Boilers – Installation 5

2. Mark and fix to the wall

Micro Electric Boilers – Installation 7

3. Connect water feeds

Micro Electric Boilers – Installation 9

4. Wire up

Micro Electric Boilers – Installation 11

5. Flush and prime

Micro Electric Boilers – Installation 13

6. Set temperature and enjoy!

Complete installation guide

You’ve seen the simple main steps. If you’d like to learn more, we’ve created a complete live installation video where we take you through the process of fixing the Micro Electric Boiler and commissioning the system for the first time.


The small and compact A4 sized design makes it very easy to install the Micro Electric Boiler in the smallest of spaces.

Micro Electric Boiler Dimensions Drawing
Micro Electric Boiler Tandem

Is one enough?

A single Micro Electric Boiler can achieve flow rates of up to 5.6 litres per minute at a 25°C temperature rise. If that’s not enough you can install 2 units in tandem to achieve up to 11 litres per minute.

Domestic hot water systems

On demand domestic hot water such as kitchen taps and bathrooms, with temperature limiting creating safe environments. Such as care homes, where a limit of 43°C is set for hot water temperatures for the safety of residents.

Domestic hot water systems plumbing diagram
Solar thermal & heat pumps back up plumbing diagram

Solar thermal and heat pumps

A 100% efficient ‘top up’ for solar thermal and heat pump systems, allowing the heat pump to be set to run at optimum efficiency.

Wet underfloor heating systems

Providing hot water, at the exact temperature needed, for wet underfloor heating systems – no mixing required! A perfect fit for any type of residential and commercial project where space is at a premium.

Wet underfloor heating systems plumbing diagram

Our 3 top installation tips

Electrical supply

Depending on which output you choose you will need to provide a dedicated electrical supply of between 20 - 40amps. You'll also need to run suitably sized cables to handle the load and install an RCBO to protect the circuit.

Water pressure

The incoming cold water supply must be protected by a 5 BAR pressure limiting valve and a shutoff valve. There's no need to install an expansion vessel.

Fixing points

Make sure you use the existing fixing points at the four corners of the mounting boss on the Micro Electric Boiler. Do not drill any extra holes as this will void the warranty!

No such thing as a silly question

All Micro Electric Boiler models require dedicated 240v supplies. You'll need two supplies if installing 2 units in tandem.

TSMEB-5   - 20 A
TSMEB-6   - 25 A
TSMEB-7   - 30 A
TSMEB-8   - 35 A
TSMEB-9 - 40 A

The unit should be mounted vertically onto a solid internal wall, in an internal cupboard or space that can support 10KG.


Use the 4 x mounting screws in the mounting screw hole locations as shown in the instructions.


The maximum screw head diameter is 8mm. A screw head larger than 8mm will damage the mounting boss and crack
the body.


No holes are to be drilled within any other area, see instructions for further details. Any holes drilled within these areas, the sides of the unit, or opening out the cable gland fitting hole, will render the unit inoperable and irreparable and will void the product warranty.

The unit is a closed outlet water heater and is intended to operate at the pressure of the water mains, where the flow
of water is controlled by one or more taps or valves in the outlet line. The unit can be installed into any type of commercial or residential construction as per the current local Plumbing Standards.


The inlet and outlet water connections are both ½” BSP SERIES GB. There are three options for inlet/outlet connections with this unit:

  • Braided hose with seal
  • Straight copper tube
  • Braided hose without seal

It is mandatory for a water pressure limiting valve and a shutoff valve to be connected in series
with the unit‘s cold water inlet connection.


• The maximum rated operating line pressure is 1 MPA / 10 bar / 145 PSI.
• The minimum operating pressure is atmospheric pressure.
• The installation of a pressure limiting valve (a mandatory requirement) ensures that excess water pressure applied,
as result of water hammer and/or other circumstances, does not stress the appliance unduly.
• The in-line water pressure limiting valve must be rated at 5.0 BAR / 72.5 PSI / 500 KPA.
• The shutoff valve installed must not be a non-return valve.
• If the water heater is supplying a dishwasher or washing machine, a water hammer arrestor must be installed on the outlet side of the water heater.

The Micro Electric Boiler can be used with renewables in two clever ways. Use it as an efficient backup hot water source should your heat pump or solar thermal system stop working. Or you can use it to top up the warm water that your renewable system creates when set to its most efficient operating mode. For example, if the water from your heat pump drops below the temperature you like on cold days the Micro Electric Boiler can step in to give it the boost it needs for optimum comfort.

The Micro electric Boiler is an ideal hot water source for hydronic underfloor heating systems. It can provide hot water up to 60°C at up to 5.5LPM and because you set the exact temperature on the unit there is no need to mix in cold water! Its also very small (A4 size) so can be installed next to manifolds to provide short pipe runs and increased efficiency.

Step 1: Flush

• Flushing is required to clear the unit of plumbing debris that may have collected in the piping during installation.
• This is done with the electric power supply turned off.
• Flush water through the unit.
• Flushing should be allowed to continue for at least 2 minutes.
• After flushing remove the inlet filter from the cold water inlet, clean any debris due to installation and flushing and refit.


Step 2: Prime

• Turn the electricity supply on and check the LED is slow flashing GREEN. The unit is now in stand-by mode.
• Turn on the hot water outlet to a flow rate greater than 1.5 ltr/min. The unit will start heating.
• Check the LED is fast flashing GREEN and allow the unit to run for at least 3 minutes before closing the outlet.

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We close at 5pm on 24th Dec and reopen at 7.30am on 4th Jan 2022.

Orders for next day delivery will need to be placed by 4.30pm on the 23rd Dec.