Safety is paramount for ehc so the comet electric combi boiler comes with a high current thermal cut-out and other built in safety features. These systems are a great alternative for homeowners interesting in replacing older oil fired boilers. Turned up on time despite atrocious weather conditions quickly sorted out the blockage.". We can install, service or repair all gas appliances. Replacing an oil-fired boiler is typically a bit more expensive the oil tank itself occasionally.