Substations

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Introduction

A Substation is an essential part of a heat generation, transmission and distribution system, sitting between the heat source and the buildings heating / cooling network. Its primary role is to provide hydraulic separation and to regulate the flow of hot or cold water into the buildings network using a combination of plate heat exchangers, control & balancing valves, temperature & pressure sensors and pumps.

Each substation should be designed to help maximise the efficiency of the heat generator using carefully sized components and should interface with the buildings heat network and controls to ensure the network load is always satisfied 24 hours a day, 7 days a week, 365 days a year.

We have partnered with Flamco Meibes, one of the most experienced manufacturers of substations in Europe. They have been manufacturing high quality products in the industry for over 50 Years and have a customer base spanning the whole of Europe and as far afield as Canada. Their manufacturing processes and quality control are second to none and their careful attention to detail means that you, the customer, will be provided with all the technical documentation about your product, including a full 3D Cad image, so that you can sign it off prior to manufacture. Their ability to fabricate a high quality product, together with components from industry leading manufacturers, such as Siemens, Danfoss, SWEP and Grundfos and our ability to manufacture extremely advanced heat network controls and monitoring systems means that you can be certain your substation will perform to the highest level alongside your heat network.

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Typical 3D Cad of Substation
Click here to download a typical example of the 3D Cad file provided with each project.

Our standard range of substations has been created to cover the vast majority of needs. The range covers low output, small commercial systems through to high output, large industrial systems, capable of powering an entire towns heat network. However every Substation is designed and built to order which gives us the flexibility to customise products to suit every kind of system. We also fit our Node-RED control panel which is based on open source technology, so it can be customised by us or your own in-house specialists to suit your requirements.

BASIC 'H' & BASIC 'C' Substations

As the name suggests this a basic substation designed to exchange district heat or chilled water to a heating / cooling network. One or Two plate heat exchangers, arranged in a 'Duty and Stand-by' parallel formation, with each plate heat exchanger being sized to fulfil a percentage of the load. You may choose to specify one plate heat exchanger at 100% of the load or two plate heat exchangers anywhere between 50 & 100% of the load.

Schematic

Below is a typical layout for the BASIC 'H' Substation with 2 plate heat exchangers.

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Each plate heat exchanger is fitted with a modulating control valve, to control the primary flow rate and a 2 port motorised valve to control the secondary flow. When the heat network calls for heat, the secondary control valve opens and the system pumps start to run. Temperature sensors fitted to both primary and secondary pipework feedback readings from each circuit, which are used by the NODE-Red control to position the primary side modulating control valve in exactly the right position to achieve the desired heat output on the secondary circuit. Both circuits are also fitted with Pressure sensors to feedback static and differential pressures to the NODE-Red control, which enables functions such as fault alarms if the pumps fail, or if the plate heat exchangers become blocked. The substation can be specified with or without the pump(s) mounted on the skid, either way pump speed can be controlled in conjunction with the modulating control valve to achieve a perfect balance of input against output.

In addition to the operational components each substation is fitted with filters to help prevent dirt and debris from blocking the plate heat exchangers, a heat meter to enable energy metering and monitoring, air vents, drains, safety relief valves and temperature / pressure gauges to give a visual indication of the system state.

Finally the pipework and valves are insulated to reduce heat loss to an absolute minimum, using foil coated rigid phenolic insulation. (other insulation finishes are available on request)

Options

There are a number of options when specifying your substation, each of which can be indicated on the Substation Questionnaire, however here is an explanation of each:-

Frame Style
Premium Aluminium frame - The substation framework is constructed from high grade aluminium extrusions, providing and extremely strong structure. The aluminium is left with a high quality natural finish.

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Steel frame - The substation framework is constructed from welded steel box section and finished with high gloss black paint. (other colours available on request)

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Electrical Spec
Premium Containment - Rigid cable trunking is fixed to the substation framework and used to conceal all cables running back to the control panel. This provides a very neat finish.


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Standard Containment - Flexible corrugated conduit is fixed to the substation framework and used to conceal all cables running back to the control panel. Not as neat as the premium option, but simpler to fit.


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Insulation Spec
Premium Rigid Phenolic - Rigid phenolic insulation faced with a factory applied foil vapour barrier jacket is applied to all pipework, all other valves and plate heat exchangers are insulated in moulded expanded polypropylene insulation shells if available from the manufacturer, alternatively they are insulated with boxes constructed from rigid phenolic insulation sheets. All insulation thicknesses are specified to ECA & Y50 Enhanced standards.


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Nitrile Foam - Black Nitrile foam insulation (Class O) is applied to all pipework, all other valves and plate heat exchangers are insulated in moulded expanded polypropylene insulation shells if available from the manufacturer, alternatively they are insulated with nitrile foam sheet insulation. All insulation thicknesses are specified to Part L of the building regulations - Non-Domestic Building Services Compliance Guide.


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Filling System
Automatic filling system - A Digital pressurisation unit is installed on to the substation, to ensure the system pressure is automatically topped up as and when required.
Hand filling system - A hand operated filling system is fitted to the substation, to allow an engineer to top up system pressure manually.
No filling system - The substation is supplied without any means of filling the system. A filling system must be installed separate to the substation.


Water Quality
Air and Dirt Separation - An air and dirt separation unit is installed on to the substation, to facilitate the removal of air and dirt from the primary and/or secondary system.
Magnetic Filtering - A powerful magnetic filter is installed on to the substation, to facilitate the removal of magnetite from the primary and/or secondary system.
Dosing Pot - A dosing pot is installed on to the substation, to facilitate the application of inhibitor into the heating system.


Packaging
Bubble & Shrink Wrapped - The substation is protected during transport using a thick layer of bubble wrap around the entire unit with additional bubble wrap around vulnerable components.
Premium Wooden Crate - The substation is protected during transport by encasing it in a specially constructed wooden crate.


Modular Design
Bigger substations are harder to build, transport and move into the plantroom, therefore it is often necessary to build the substation in modules which can be assembled on-site. It is therefore important that the access requirements are considered at the outset of the specification process.

Our specification questionnaire asks a number of questions about door widths and plantroom dimensions, and it is the responsibility of the customer to ensure the substation will fit through all pinch points on its way to the final installation position.

Specification Questionnaire

Click here to download a copy of our Basic Substation Questionnaire

Substation Documentation and Controls

Click here to explore the Substation controls and documentation.

Typical Outputs and Dimensions

The table below shows examples of substation outputs and estimated dimensions and weights. It is important to understand that there are a lot of variables when sizing the substation plate heat exchangers, control valves and pipework. Plate heat exchanger output is one thing, but the required flow rate, flow velocity and pressure drop has a huge impact on the pipe diameter and valve sizes, so it is entirely possible that a 100kW substation could have a greater footprint, bigger pipes and valves and therefore weigh much more than a 300kW substation. It all depends on the specification of the heat network it is connecting to.

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Technical Parameters

  • Design Temperatures - Heating Units
    • Primary flow temperature || 95°C Max
    • Central Heating temperature || 90°C Max
  • Design Temperatures - Hot Water Units
    • Domestic Hot Water || 60°C Max
  • Design Temperatures - Cooling Units
    • Primary flow temperature || 5°C Min
    • Secondary flow temperature || 7° Min


  • Design Pressures
    • Pressure Class || PN10 (PN16 or PN25 available on request)
    • Minimum Differential pressure (primary side) || 1.0 Bar


  • Connection types
    • DN15 to DN40 || BSP Parallel F/F Ends (ISO 228/1)
    • DN50 to DN250 || Flange standard ISO 7005-2 / EN 1092-2

Common Components

Depending on the control requirements, flow rates, pressure drops, and customer preference to a certain degree, we use various components as follows:-

Plate Heat exchangers
We use the SWEP SSP calculation software to size plate heat exchangers to suit the output required for each project.
Open / Close Control valve
The secondary circuit often requires a 2 or 3 way valve to control flow into the district heating network. For this we would generally use the Belimo range of Open / close ball valves, with a rotary actuator and auxillary end switches to provide a signal out to the pump(s).
Pressure independent balancing & control valve
Depending on the differential pressure and flow requirements, we use Danfoss or the Frese valves.
Differential pressure control valve
Although our preferred option is the pressure independent control valve, occasionally it may be necessary or the customer may prefer we fit a differential pressure control valve which then requires a separate open / close valve mounted inline. In such situations we use a Siemens differential pressure control valve and a Siemens 2 port valve with actuator.
Pumps
We use the Grundfos calculation software to size pumps to suit the output required for each project.
Sensors
We use a range of temperature and pressure sensors depending on the project requirements. Manufacturers include Wika, Grundfos, Tasseron, Gems and BD Sensors.
Safety Relief Valve
We use PED compliant safety relief valves from Flamco rated up to 120°C.
Controls
Our Node-RED control panels are fitted with various I/O Controllers manufactured by Brainboxes, with Raspberry PI based PID Control. You can read more about our control panels here.