Technical Note: Thermino xPlus in Temporary Continuous Electric Mode

(D0116)

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1. Introduction

1.1 General

The following instructions provide guidance for the installer and end-user of Thermino® xPlus heat batteries when used in continuous electric mode for a temporary period of time (charging via the internal heating element).

The installation of Thermino® xPlus in continuous electric mode must be carried out by a competent installer in accordance with local codes and regulations for plumbing, electrical installations and potable water supply.

Please note that using a Thermino® xPlus in continuous electric mode is not the standard intended use of the product. The primary function of a Thermino® xPlus heat battery is to be hydraulically charged by an external heat source (i.e. Heat Pump or Boiler) as a primary source of energy, with an option of adding Solar PV as an additional source of energy (requires the use of a solar power diverter). Both these options require the use of an appropriate Optimino® key from the XX01 (external heat source only functionality) and XX02 (external heat source AND solar PV functionality) ranges respectively. For detailed information on standard installation of the heat battery, please refer to the installation and user instructions manual.

The installation of Thermino® xPlus heat batteries in continuous electric mode is a temporary solution and will only be permitted for a temporary period of time under the circumstances highlighted below. Otherwise, the installation will be considered non-standard as it deviates from the intended use of the product, which will invalidate the manufacturer’s warranty:

• The Heat Pump or Boiler is yet to be installed and commissioned.

CAUTION

The guidance and instructions outlined in this document are only applicable for the first-time installation of a Thermino xPlus product.

Once an external heat source is commissioned (eg. heat pump or boiler) and the primary circuit (ports B to C) of the heat battery has been exposed to system water, it is no longer suitable for use in potable hot water applications. Therefore, any Thermino xPlus installed and commissioned as per the user and instructions manual (document) D0084 MUST never be reconfigured to operate in continuous electric mode.

1.2 Symbols Used

1.3 Abbreviations

The following abbreviations are used throughout the document:

• DHW – Domestic Hot Water

• PDC – Power Diversion Controller

• PV – Photovoltaic

2. Safety

2.1 General Safety Notices

CAUTION

Each heat battery must be protected by its own dedicated MCB and have a double pole isolating switch with a contact separation of at least 3mm in both poles, which is located in close proximity to the heat battery. For required MCB specification, please refer to Table 1 in document D0084.

3. Accessing Continuous Electric Mode in Thermino xPlus products

NOTICE

Please note that using Thermino® xPlus heat batteries in continuous electric mode is not the intended use of the product. This can lead to increased electricity consumption, resulting in higher energy costs. Be aware that this may affect the energy efficiency of the product. Therefore, extended use of Thermino® xPlus heat batteries in continuous electric mode is not recommended and is restricted to the circumstances mentioned in the Introduction.

NOTICE

Engaging the volt-free switch below will put the Heat Battery into electric operation mode. This can lead to increased electricity consumption, resulting in higher energy costs. This should be explained to the end user and the switch labelled accordingly.

To operate Thermino® xPlus heat batteries in continuous electric mode, the heat battery must have a VOLT-FREE jumper cable installed between terminals 1 & 2 in the controller wiring strip (without an Optimino key except in the circumstance of PV utilisation via a PDC) AND must be plumbed and commissioned like its Thermino ePlus relative. Please follow the market-specific instructions below in conjunction with the above guidance for the correct installation and commissioning of the product.

When using Optimino key 'PV02' and power diverter is installed (refer to document series D0085 for compatible solar power diverters and wiring settings), the unit will charge via solar PV if PV energy is available. If scheduled reheat times are programmed on the PDC, the unit will charge via grid supply during these periods.

3.1 For products installed in EU & UK

To operate Thermino xPlus heat batteries in continuous electric mode:

• Follow the Installation, Plumbing and Commissioning instructions as outlined in the Thermino ePlus installation & user instructions manual (document D0083):

  • Follow Figure 8 for the hydraulic installation requirements of Thermino xPlus models (sizes 150, 210 and 300)

  • Note the caption in Figure 8 in document D0083 refers to the Thermino 300 ePlus plumbing requirements, however for this use-case, it is the correct plumbing arrangement for all dual circuit (4 pipe) Thermino models, which includes all Thermino xPlus models (sizes 150, 210, 300) being used in continuous electric mode.

• Install a VOLT-FREE jumper cable between terminals 1 & 2 on the controller wiring strip

NOTICE

To preserve the potability of the fresh water circuit (ports D to A), a Thermino xPlus that has been originally installed as per document D0084 (system water in the primary circuit, ports B to C) must not be reconfigured for use in continuous electric mode.

4. Installation of an External Heat Source

CAUTION

When installing an external heat source with the Thermino xPlus heat battery, the heat battery MUST be re-plumbed and re-commissioned as outlined in the Thermino xPlus installation & user instructions manual (document D0084).

CAUTION

The guidance and instructions outlined in this document are only applicable for the first-time installation of a Thermino xPlus product.

Once an external heat source is commissioned (eg. heat pump or boiler) and the primary circuit (ports B to C) of the heat battery has been exposed to system water, it is no longer suitable for use in potable hot water applications.
Therefore, any Thermino xPlus installed and commissioned as per document D0084 MUST never be reconfigured to operate in continuous electric mode.

NOTICE

For detailed wiring, hydraulic installation and commissioning instructions, please refer to the heat battery Installation & User Instructions manual.

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Document Part Number: D0116

Version Number: 1.0

Publication Date: 02.02.2026