User Operating Instructions

The Horstmann Electronic 7 Water Heater Controller has been especially developed to control the immersion heater as economically and conveniently as possible.

During the night, water in the tank will be heated by cheap night-rate electricity, ensuring a tank of hot water is available for the morning.

Depending on the size of the tank and usage of hot water, this will usually last a day; however, if required, more hot water can be heated at any time by using the boost button which switches on the immersion heater for one hour.

Alternatively if it is known that extra hot water will be required every day, the boost element (in the tank) can be programmed so that it will heat only a small part of your tank. This is normally the upper element in the tank and can be programmed to come on once each day at a set time.

Some tariffs offer additional cheaper electricity periods during the day time; the Electronic 7 has extra off peak switching periods available to accommodate this.

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The Electronic 7 - an overview

The simple instructions in this user guide are designed to help you with programming and operation of the unit.

LCD Display: The LCD display allows the user to view the current time and set programme times.

Indicators: Illuminated indicators give a visual feedback to the user indicating the status of the programmes or boost operation.

1 - Timed display indicator
2 - LCD Display
3 - Boost Button
4 - Switched Output control

Manual Boost:

To use the manual boost, press the "BOOST" button on the unit which will then boost your tank for 1 hour and then switch off.


Switched Output

In the "OFF" position the electrical supply to the immersion heater(s) is disconnected even though the clock, display and indicator lights continue to operate. In the "TIMED" position the over-night immersion heater will be switched on and off at the programmed switch-time settings, at other times the boost facility is available

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Time Display

The Electronic 7 is fitted with an automatic clock that is pre-set on manufacture and should not normally require any adjustments by the user.

The summer/winter setting is automatically selected and will automatically change.

This is indicated on the screen next to the appropriate setting.

Therefore no adjustment is needed to be made by the user for the summer/winter clock change.

Should a minor correction to the clock be necessary or if the unit has been reset then see the section on setting the clock.

On installation the installer will have selected whether the Electronic 7 will switch at GMT times throughout the year or whether the timings need to alter as the clocks change.

For example:

GMT/BST - Switching time will be changed by one hour. In the GMT/BST mode the clock display will match the actual switching time.

GMT ONLY - Switching will always take place at GMT times (summer and winter). Although the clock display will show the correct time.

Setting Time Of Day

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Setting Off-Peak Heating Periods

Resetting The Unit

Sometimes electronic equipment can become scrambled or frozen. To overcome this you should reset the unit.

This can be achieved by holding down "BOOST, MINUS, PLUS & SELECT" simultaneously.

The unit will now revert back to pre-set factory default off peak times and the current time will show the time as it was at the time of re-set.

The hour will be flashing and should be adjusted as detailed in the section Setting the time of day.

Default Time Settings

After re-setting the unit the off-peak heating times will revert back to the default factory settings, these are shown above, however if you wish to change these times please proceed as instructed in the SETTING OFF-PEAK HEATING PERIODS part of this manual.

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Programmed Boost

This setting is not recommended for single element installations and is normally only used with twin or dual immersion heaters.

With the "TIMED BOOST" indicator on the right hand of the screen selected the boost, or upper element within the tank will heat up at the same time automatically everyday.

This can be turned on and off by pressing the "SELECT" button.

To Set Boost Programme

Battery Reserve

The Electronic 7 is designed to be permanently connected to the mains electricity supply.

This unit has a non-rechargeable long-life battery which will maintain the display and switch time settings for approximately 2 years with the mains electricity supply disconnected.

This should be sufficient to cover all power interruptions during the life of the unit.

Neon Indicators

There are two neon indicators on this unit, one to indicate when the boost is active and the other to indicate when the timed off-peak is active.

With the "SWITCHED OUTPUT SWITCH" in the "OFF" position the indicators lights will still illuminate but no electrical switching will take place.

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Service and Repair

The Horstmann Electronic 7 is not user serviceable, so please do not try to dismantle the unit.

In the unlikely event of a fault developing try resetting the unit, which is in this manual under "RESETTING THE UNIT".

If this fails to resolve the problem then please contact your installer or a local heating engineer or a qualified electrician.


(Q) There is no display on the screen?

(A) Ensure there is mains supply getting to the unit and that the battery switch on the rear of the unit is in either the GMT/BST or GMT ONLY position.

(Q) The display has become frozen?

(A) This could be due to local electrical interference. Using the RESET procedure in this manual may ratify the fault.

(Q) The neon indicator will illuminate but there is no hot water?

(A) Ensure the SWITCHED OUTPUT switch is in the TIMED position. If this still fails to rectify the problem please contact a local heating engineer or a qualified electrician.

(Q) How do I change the back-up battery?

(A) You cant as it is an integral part of the unit, and therefore would invalidate your guarantee if you dismantled the unit.

(Q) I want to adjust my off-peak times, how is this achieved?

(A) Please go to "SETTING OFF PEAK PERIODS" in this manual.

(Q) What does the indicator next to the word "TIMED BOOST" mean?

(A) If there is an indicator next to this word on the right hand side of the screen, then this means the boost programme is selected. Please see "BOOST PROGRAMME" in this manual.

Horstmann Controls Limited

South Bristol Business Park,
Roman Farm Road,

Web site:

Leaflet number NP0083079000 - Issue 1

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