I have an inset gas coals fire with output of up to 9kw and have been advised (although the fire has been in place for 10 years plus) that I need a permanent open 100mm vent in an outside wall to meet gas regs. Would it be possible to fit a restrictor valve onto the gas supply to reduce the fire output from 9kw to 7kw and avoid fitting the vent? If so any ideas where such a valve could be purchased.
Fitting a restrictor would contravene current regulations, as when an appliance is installed, the pipework supplying the appliance with gas must be appropriately sized so as to allow it's maximum heat input requirement. The restrictor would increase pressure losses as well as impede the flow of gas.
It's not possible to put a restrictor inside the appliance as this would be classed as a modification which hasn't had the manufacturer's approval.
Even if the gas fire has an adjustable regulator fitted, the ventilation requirement would still be dependant upon it's maximum setting.
You have a few options, including, check the appliance manufacturer's instructions and see what they say about ventilation requirements, fit the appropriate vent or down-size with a new fire.