Low Loss Headers

FlexEJ's range of Low Loss Headers, also known as Hydraulic Separators, covers popular sizes from DN32/70kW to DN150/1,480kW - with larger sizes and multiple circuit designs to order. These robust and cost effective units are manufactured in our UK factory and the following standard sizes are available at direct-buy prices from our web shop on a 24hr despatch basis.

LP LowLoss Header

DN32/70kW

LP LowLoss Header

DN40/110kW

LP LowLoss Header

DN50/160kW

LP LowLoss Header

DN65/280kW

HP LowLoss Header

DN50/200kW

HP LowLoss Header

DN65/310kW

HP LowLoss Header

DN80/440kW

HP LowLoss Header

DN100/790kW

HP LowLoss Header

DN125/1,230kW

HP LowLoss Header

DN150/1,480kW

Hydraulic Separation in HVAC systems

1 Hydraulic Separation2 Do I need a low loss header?3 Boiler cascades4 Flow rate & velocity5 Need something different?6 Let us help

If a system has more than one pump operating there is the possibility of the pumps interacting with one another which results in instability. To avoid this a hydraulic separator – a low loss header – is introduced into the system.

Not always, it depends on the system design and components. Low Loss Headers do introduce mixing of flow and return which results in temperature variations, this should be taken into consideration in the overall system design and control.

A very common application of Low Loss Headers is with boiler cascades, the hydraulic separation decouples the boiler cascade from the system. This should allow, with proper system design, the boilers/boiler circuit flow to optimise at best efficiency for any system conditions.

The flow rate and design flow velocity normally determine the size of the Low Loss Header body. Commonly the total boiler power and temperature difference are used as indicative of flow rate but secondary circuit flow rates may be higher and should be considered.

FlexEJ can design and build to order large, multi-circuit low loss headers, manifolds, buffer vessels and piping spools. Please let us know what you need.

Call our HVAC specialists on +44 (0) 1384 881188 or email us at sales@flexej.co.uk or use LIVE CHAT on this web site - we are here to help, please get in touch.

FlexEJ's Low Loss Headers

Robust and great value for money, FlexEJ's HVAC Low Loss Headers — also known as Hydraulic Separators — are manufactured by us in the UK to our own design. DN32 to DN150 are standard stock and available on a 24hr despatch basis directly from our web shop. Other configurations are available. FlexEJ can also manufacture to meet specific client requirements, please get in touch.

Low Loss Header Applications

The hydraulic separation provided by a low loss header allows multiple pumped circuits to work independently from one another - which is particularly important in achieving the most efficient operation and control of condensing boilers and boiler cascades.

The use of a low loss header is recommended to minimise interaction between primary circuits and the secondary circuits, the primary typically working at a constant flow rate and the secondary at varying flow rate and water temperature. For a full discussion of low loss header design please see our what is a low loss header page.

LP Low Loss Header Range

Designed for simpler, lower power systems these low loss headers have threaded connections from DN32 up to DN50 and PN6 flanges on the DN65. All include a single thermopocket. Vent and drain connections are supplied plugged, there is an optional valve kit.

LP Features

All our LP low loss headers have:

• Rating of 6 Barg at 110°C
• Carbon steel body with BSP threaded connections except DN65 flanged PN6
• Optional valve kit comprising Flamco AAV with integral shut off valve and DN25 drain valve
• Single temperature probe port supplied with thermopocket and clip
• DN32 to DN65 available from stock as standard

HP Low Loss Header Range

The high power range is designed for larger, more complex commercial systems. All sizes flanged PN16 with a temperature probe ports on all connections as standard. Supplied with Flamco AAV and DN25 drain ball valve.

HP Features

All our HP low loss headers have:

• Rating of 10 Barg at 110°C
• Carbon steel body with PN16 flanges
• Flamco AAV with integral shut off valve
• DN25 drain valve
• Temperature probe ports on all connections
• DN50 to DN150 available from stock as standard
• Custom sizes, multiple connection adaptors and specifications

Power rating and flow rate

The power rating quoted is a nominal value based on an assumed flow rate; the low loss header will perform above or below this figure.

The tables above show performance for the FlexEJ Low Loss Headers with a 20°C temperature difference at flow rates typical for the connection sizes. Please contact us for further application assistance.

All FlexEJ standard HP LLH are rated at 10 Barg at 110°C, standard LP LLH are rated at 6 Barg at 110°C, all calculated to PD5500 Category 3 and are SEP category under the PED.

Low Loss Header Calculation and Sizing

To calculate a low loss header all you need are the primary and secondary powers or flow rates – and the brand-new FlexEJ Low Loss Header Calculator.

This calculator will allow you to size a low loss header based on the flow or power in your primary and secondary circuits.

Manifold Connections, Vents and Drains

We suggest the use of distribution headers or manifold piping on all connections to the low loss header rather than making multiple connections to the LLH body itself. We will be pleased to quote manifolds on request.

The low flow velocity in the low loss header body promotes separation of air and dirt from the flow. FlexEJ provide a DN25 ball valve connection for dirt removal and a high quality automatic air vent valve with all HP low loss headers, the LP range have plugged connections and an optional valve kit.

Low Loss Header Design and Build

FlexEJ has full in-house pressure vessel and buffer vessel design and manufacturing capability. We will be pleased to quote any low loss header size, configuration or buffer vessel you may require.

If you need something even larger or more complex, we will be pleased to engineer and manufacture to your exact specifications - with connections for multiple circuits, integrated air and dirt sections, any diameter or length or any other technical requirements can usually be met, as required.

Custom built or delivered in 24hrs?

You are very welcome to call to talk through your requirements or any technicalities that are concerning you — on +44 (0) 1384 881188 — or please use the Get A Quote form below or order direct at UK factory prices from our low loss header shop pages with 24hr shipping as standard on all stock items.

Frequently Asked Questions

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