I have an oil heating system, and also I have an open coal fire , the coal fire also heats the water through a back boiler and a neutralising tank , when the coal fire is on the water starts boiling, the only way i can stop it is to put the oil central heating on to circulate the water, is their any way i can run the circulating pump without having to put the boiler on. Could i fit an override switch so that I can turn the circulating pump on when the water starts boiling, is their any problems in doing this?