Solving resilience issues whilst decarbonising a SEND school
A special school in Reading, for around 220 pupils aged 2 to 19, was heated by gas boilers with no spare capacity. Working with Eddisons, we designed an air source heat pump scheme with spare capacity built in, and the school stayed open during the works.
The school, Reading
The existing plant
The building dates from 2006 and has underfloor heating throughout, with a pool and air handling units on the same system.
Three gas boilers served the site. One had failed, so the other two were running flat out to keep the building warm. With no spare capacity, a fault on either of them would have left the school unable to hold temperature. The fabric was already built to a good standard, so the work focused on the plant.
Heat pumps with spare capacity
The heating is now served by propane (R290) air source heat pumps, running at 50/40 °C at the winter design condition with weather compensation. The heat pumps were sized with spare capacity, so the school can still be heated if a unit is out of service.
Hot water has its own heat pump and a dedicated cylinder at 65 °C, with an electric immersion heater as standby.
Every emitter was checked at the new temperatures. The 143 underfloor heating actuators, the pool heat exchanger and the air handling unit coils were replaced with units selected for the lower flow temperature, and the two-port valves were changed to pressure independent control valves.
Works and electricity supply
The specification required heating to be maintained throughout the works, either by keeping the boilers running until the new system was proven or by temporary heating. The electricity network connection was confirmed before the design was fixed.
Monitoring
The site is connected to Jupiter Performance. Heat pump electricity, heating and hot water heat meters and the buffer temperatures are read every 15 minutes, so the school and the client can compare the system with the figures in the funding application.
Concept sketches
Photographs
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