Technical data

23
STRATA1
17.0 hydraulic system
design
● The Strata 1 boiler can be operated to serve a heating load in a number of ways:
1. Constant flow temperature, with the option to set either high temperature (85°C), medium
temperature (75°C) or low temperature (55°C).
2. Direct-on-boiler weather compensated flow temperatures, with adjustable maximum flow
temperature.
3. Underfloor heating coils via a VT mixing valve with a maximum flow temperature of 55°C plus a
second circuit (eg. radiators) operating with direct-on-boiler weather compensated temperatures.
● Flow to return drop (∆t). The microprocessor controls monitor return temperature and the facility
to dictate a set ∆t (by pump speed modulation) is a standard and most important feature
and will where possible maintain the ∆t across the boiler at 20°C, as the lower the return temperature,
the higher the operating efficiency. Designing for a ∆t 20°C gives the added cost saving advantage of
smaller pipe sizes and pumps.
● The Strata 1 includes ‘in built’ primary pumps with a residual head pressure as listed below.
● Appliances may be installed as single units or in multiples.
● Single units may or may not require additional system pumps which will be dictated by the system
configuration and by the index resistance.
● Multiple units (and single units which require additional pumps), should always be installed with a low
loss mixing header or similar arrangement. - see table below.
● The Strata 1 boiler has in built domestic hot water (remote stored) temperature control ability, and if
required, the in built pumps may be used to provide the primary flow to a nearby indirect cylinder or
calorifier with the boiler controlling a diverter valve in the main flow or return pipework.
● BS 6644 Requires that the following devices shall be installed, and provision within the system design
must allow for: Low water pressure cut off device, water pressure gauge and a temperature gauge.
Boiler Power kW
Up to 45
75
100
120
150
200
250
270
300
340
Design ∆t 20°C
40mm
50mm
65mm
65mm
80mm
80mm
100mm
100mm
100mm
100mm
low velocity
mixing header
diameter
sizing guide
Tube diameters refer to steel pipe and calculated using data from
CIBSE Guide C4
The following system schematics show a number of typical installation types to which the Strata 1 boiler
may be connected.
The Strata 1 is not limited to just the systems shown, and may be used in conjunction with many
commercially available control items.
For further advice or guidance on schematic designs or control options contact MHS Boilers Ltd.
Boiler Model
45
60
75
Pressure Metres wc
3.1
3.0
2.6
in-built boiler pumps
approx residual
head pressure at
max speed