Turn on the CH, or if its a combi, open a hot tap.
Go to the gas meter and measure the rate of gas consumption. If it's an old meter, time how long the needle takes to go round once.
For a 30kW boiler, it should take 35 seconds...
Some good stuff here...
I turned on 11kW of burners on the gas hob, while the DHW was on, and measured a total flow rate of 116 cu.ft/min at mains.
So that at least is not the problem.
I have a combi boiler that appears to be functioning properly save for one thing. The hot water (DHW) is not getting as hot as it should be.
If I measure the gas flow at the mains I see it uses:
81 cubic feet per minute on both central heating (CH) and DHW.
According to the spec, CH...