The power station in Mill Lane housed the two main engines, three auxiliary standby engines and the control gear in two halls. The main power units were four-cylinder engines manufactured by Mirrlees, Bickerton and Day of Hazelgrove, Manchester, each of 1,000 horse power coupled to D.C. dynamos of approximately 135 kilowatt output manufactured by Crompton. The supply of current to the public commenced in mid-February 1915.

Between the engine and the dynamo was a massive flywheel, about 12 ft. in diameter, and weighing some ten tons, with the lower half of the wheel within a concrete pit forming part of the foundations. The pit also housed the barring gear, - a long pivoting steel bar which engaged gearing on the inside of the flywheel rim, enabling the engine to be turned over manually into the correct position for starting. Starting was effected using compressed air from a high pressure chamber kept charged by the engine while running.

The auxiliary engines used in emergency were of a type which required a 'hot spot' on the cylinder head achieved by heating with an external paraffin blowlamp until red hot, now obsolete technology. The auxiliary engine in the main hall was of Petter manufacture giving a 60kw output and the one in the second hall, referred to as 'the little Allen', gave 12kw output. The original but disused World War I tank engine was in another bay, no longer in commission in the late 1930s.

Circulating pumps forced heated water to the top of a cooling tower, a tall slatted wooden structure built over a pond and located in the open at the end of the engine house (just inside the present yard entrance to Messrs J.T. Williams, garden machinery [no longer there]). The hot water dripped down over the slats into the pond, cooling in the process and entered a deep well before recirculation.

At one end of the main hall on a raised platform were located all the control gear, meters and switches. The latter were of the heavy copper knife blade type which when operated on load (with thick rubber gloves) produced a vivid blue flash. Meter readings of power generated were recorded at regular intervals in the log and here, too, supply was carefully balanced to demand.

Between the works and the General Manager's house at 61, Clwyd Street, was a single storey building which accommodated large rectangular glass tanks containing lead plates in sulphuric acid, connected in series. These batteries met the low overnight demand for electricity (approx. 20kwh per night in 1939) when the engines were turned off, and were kept charged during the day by the main plant. 

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The works operated on a two shift system between early morning and late evening when the plant was generating, and with a skeleton staff overnight while on battery operation.

Diesel fuel supplied by the Anglo American Oil Co., was stored in large surface storage tanks. A fatal incident occurred in July, 1931, when a 16 year old apprentice, Maldwyn Williams, was overcome by fumes from a fuel tank.

Periodically, the engines were dismantled for inspection and overhaul. Mr. Morris Evans recalls that one of his first jobs as an apprentice was to crawl inside the engine cylinders of about 24" diameter to polish the cylinder head. A large overhead travelling crane lifted and moved the very heavy engine parts.

In addition to work within the station, an outdoor section dealt with the overhead and underground power lines, and all the other distribution equipment. Transport consisted of one 500 cc. B.S.A. motor cycle with box side car which transported the tools and equipment.

Ruthin was lavishly decorated for the Silver Jubilee of 1935 and the Coronation of 1937. RESCo contributed with a series of spectacular fountains in the shape of Prince of Wales feathers, illuminated by coloured lights after dark. These were in the River Clwyd upstream of Pont Howkin and operated by a pump on the river bank. Other 'Crown' displays and illuminations were set-up in the town.

Personnel working for RESCo in the 1930s included Mr V. Botham, General Manager, 9 operational and 3 external staff, one apprentice, the office manager and the showroom attendant.

Ownership changed in 1935 when Ruthin Corporation purchased RESCo from Western Electric Co., and consideration of a change-over from D.C. to A.C. began. Formal consent to the changeover was received from the Electricity Commission in January, 1939. The change from D.C. to A.C. resulted from the development of the National Grid. Electricity could be generated more economically at very large power stations and transmitted over long distances at very high A.C. voltages which could be transformed before local distribution using cables of relatively small size.

Conversion from D.C. to A.C. brought many changes. Mr D.H. Roberts was appointed General Manager to implement the new plans. New primary substations, one adjacent to the old works and another in Wernfechan, were built in 1938. An overhead 11,000 volt A.C. supply was brought down the Vale from a grid line from Dolgarrog to a point near Parc y Dre. This then went underground to the Mill Lane substation via Borthyn, crossing the River Clwyd alongside Pont Howkin, and onto Wernfechan.
The substations housed transformers which converted the incoming supply from 11,000 volt to the standard 240 volt output. Oil-quenched circuit breakers were the new technology which performed the function of the old copper switches used on the former D.C. supply.

Mr S. Thornton was appointed Change-over Engineer to deal with the modifications required. Problems arose for consumers with D.C. equipment, which could not be converted to A.C. Many customers with D.C. only wireless sets had to be supplied with rectifiers. Others with universal sets required a small internal change to operate on A.C. Wartime difficulties in obtaining parts caused many delays.

Ruthin Castle and Messrs Ellis's Mineral Water Works had special problems because of radiographic equipment at the castle, then a medical establishment, and much D.C. driven machinery at Ellis's. Arrangements were made for a continuing D.C. supply by the installation of a mercury arc rectifier at the substation to convert incoming A.C. current into D.C.

The changeover from D.C. was made progressively in the early 1940s over a two-year period completed by October, 1941. The old D.C. engine-sets which had served so well for nearly 30 years delivered their last D.C. current in Ruthin in the summer of 1941. The machinery was sold for £500 and dismantled by Messrs Bouchers and shipped to a new location in England. A strange silence descended on Mill Lane, but not for long! This old quarter soon throbbed with incessant hammering to 'Music While You Work' as cases were made for shells produced in the old gaol.

The showroom in Clwyd Street was occupied by a government ministry office during the war years and RESCo operated from an office in the town hall, a small storeroom at the rear of the storeroom, and a workshop, charging plant and stores in a shed alongside the Mill Lane substation.

Tariffs applied by RESCo during its 27 years of operation are briefly summarised as follows:
1915    7.5d     kilowatt hour
1923    1/-        kilowatt hour
1937    4.65d    kilowatt hour
1940    3.52d    kilowatt hour

When RESCo became part of M.A.N.W.E.B after nationalisation, an initial two-part tariff gave an average price of 4.5d / kilowatt hour.  Ruthin's thirst for electricity evolved as follows: -
    Units (kwh) sold         Max. demand     – kilowatts
1915 [part year]    12,354    15.6
1917    17,481        20.16
1941    350,000        238.00
1947    616,000    ----
1993    8,000,000*    3,000.00            * = best estimate available.
(One unit =1 kilowatt hour, equivalent to one bar electric fire for one hour)

Ruthin's thirst for electricity multiplied by approximately 20 times during the operation of RESCo and has increased a further estimated 23-fold in the half century since.

The availability of an ample A.C. supply facilitated the post-war revolution in lifestyles and standards of living. Today's basic domestic electrical appliances - refrigerators, washing machines, television sets and countless others - would not otherwise have been possible. Is the cycle of privatisation - municipalisation - nationalisation - privatisation now complete?  Not likely!

NOTES - The writer lived by the power station at 63 Clwyd Street until 1943. Thanks are due to Mr Morris Evans for his contributions to the article and for checking the script. The help of Mr D.C. Newis of Manweb for consumption and other data is also acknowledged.

POSTSCRIPT  Mr David Rickman has found that some of the technical information quoted was not quite correct and further research has established the following details, viz. main engine horsepower, 200 b.h.p. each; dynamo manufacturers, Brush Electrical Co.; cylinder diameter, 12 inches; flywheel diameter/weight, 6ft. / 3½ tons.

The two Mirrlees engines were installed respectively in the late 1920s/early 1930s to increase the station output.
Acknowledgements: Mirrlees Blackstone, Stockport; Garcke’s Manual of Electricity Undertakings.