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The Council House with its two roof mounted gilded Unicorns and facing moat, that stands behind College Green is viewed by Bristolians as an iconic building, and well worthy of its Grade II* Listed status.

The selection of this site was first mooted in 1919 and then acquired in 1933 with Mr. E Vincent Harris commissioned as the Architect.

Messrs William Cowlin & Son a Bristol firm of builders were appointed as the Main Contractor and site clearance work commenced in 1934. The foundation stone being laid in 1935. Cowlin's had completed the shell of the building by 1939 when the outbreak of WWII brought building operations to a stop. 

During the period of the war the building was temporary utilized as a “British Restaurant” to provide cheap meals for city workers, also used as a club for Services personnel and a storage area for emergency clothing supplies.

The building was officially opened by HM the Queen on 17th April 1956.

To read a copy of the following original documents pertaining to
the Engineering Services for the Council House click on any of
the three links below.

Specification for the Engineering Services Installations dated April 1937

Working (Operating & Maintenance) Instructions for the Engineering
Services dated approx. 1955

Electricity Agreement between SWEB and Bristol Council dated 1955


Central Heating

The engineering services were designed by a London Consultantcy J Roger Preston & Partners. They commenced their design of the various mechanical services from 1936 onwards. A local Heating & Ventilating firm Arthur Scull & Son submitted the successful tender and was appointed as the Mechanical Services Sub-Contractor.

The basement heating plant that includes the electrode boilers and storage vessels are still in situ complete with their associated pumping equipment, electrical control panel, automatic temperature controls, instrumentation and distribution pipework. To discover a wet heating system of this size fed by off-peak electricity, installed in the 1950’s which remained in operation until approx 2004, is a very rare occurrence, and therefore of significant historical importance.

This original central heating was replaced approx 2004, by a LPHW system with gas fired modular boiler plant sited in the roof space. The new distribution pipework was designed as a downfeed 2-pipe distribution arrangement serving radiators. All the existing Warm Air Ventilation systems were retained and connected to the new heating system.

The choice of this method for central heating a building is unusual for the 1930’s in that it is an electrical off-peak LPHW wet heating system. The system used two vertical pattern electrode boilers which used electricity during the night time period from approx 10.00pm to 7.00am. The boilers heated water over-night which was pumped  to six 9000 gallon storage vessels that acted as a thermal store for the heated water.

Bristol Corporation as it was known at that time, had part ownership of Portishead Power Station and could therefore negociate a reasonably advantageous tariff for the cost of the off-peak electricity. This obviously influenced the choice of the heat generation plant.

The electrode boilers are Sulzer Bros. manufacture using an electric supply of 6.6 kv from a dedicated transformer, which served the Council House building. The boilers have top adjustable electrodes that can be motor driven down into the boiler shell to respond to the building’s varying heating demand in relation to the difference in external ambient temperatures, experienced throughout the heating season.

Electrode Boilers  rear view

Electrode Boilers  front view

Main Boiler Control Panel
    right hand view

Main Boiler Control Panel  left hand view

Instrument Panel

Instrument Panel

A restricted view of one 9000 gallon thermal
storage vessel stripped of its thermal insulation

Internal view of one storage vessel showing its top &
bottom sparge pipes, fitted to minimize the mixing of
hot and cold water within the vessel.

The heating distribution system was designed as an up-feed arrangement using flow & return riser pipework based on the reverse return principle to provide a self balancing system. This method of designing pipework circuitry to minimize the water flow balancing was a relatively new method developed during the 1930’s. The up-feed  pipework risers were concealed in vertical wall ducts enclosed on external columns rising through the 4 floor levels.

The heating for the rooms at all floor levels was provided by embedded floor or ceiling panels, that were installed around the perimeter of the rooms. This method of heating suited the type of off-peak heat generation plant, as the lower flow water temperatures necessary for embedded heating panels made use of the higher water temperature stored in the vessels more economical. The system of automatic temperature controls provided blended water to supply the embedded panels.

Three duty/standby pump sets were fitted to distribute heat to the various items of equipment.

Circuit 1)  Primary flow and return to both electrode boilers
and thermal storage vessels.

Circuit 2)  Secondary flow and return to mixed / blended temperature
circuits serving the embedded panel system.

Circuit 3)  Secondary flow and return to constant temperature circuits
serving the three ventilation plants.


The building has three separate ventilation plants supplying filtered and heated air, to the Conference Hall; Council Chamber; Ground Floor Cash / Rents Offices. The ventilation plants have their own independent Supply and Extract ventilation systems with a constant temperature pipework distribution circuit from the thermal storage vessels. Each supply ventilation plant has been fitted with a new air handling unit, which incorporates run-round heat recovery coils.

Conference Hall Supply Air Handling Unit

Conference Hall Extract Fan

Council Chamber Supply Air Handling Unit

Council Chamber Extract Fan

Ground Floor Offices Supply Air Handling Unit

Ground Floor Offices Extract Fan

The original supply and extract belt driven forward curved centrifugal fans manufactured by Matthews & Yates in 1951 are still in operation. They have all been fitted with replacement belts and motors as became necessary due to wear and tear from over 60 years of use.

Forward curved fan blades

Installation date 1951

Domestic Hot Water Supply

The domestic hot water was also generated by off-peak electricity that heated a single storage vessel. This storage vessel was of a smaller size but similar shape to the heating vessels and installed adjacent to them. Three banks of electric immersion heaters were fitted in the vessel with each bank of heaters arranged in a group of three single phase circuits to balance the electrical heating load.

The storage vessel is fitted with internal sparge pipes to minimize the mixing of hot and cold water within the vessel.

HWS Themal Storage Vessel

Bank of 3 /1 phase Immersion Heaters

A secondary pumped circulation pipework circuit fed the various sanitaryware and kitchen equipment throughout the building.

JUNE 2012