The RGI should have specified the inhibitor used on the Benchmark statement for the boiler. If you've drained and refilled with something else don't forget to update the docs and any labels on the system.
Yes, he wrote '1l'. No mention of the brand. And he left the lid and the lagging off the F&E. I wasn't impressed, especially since I was the one that got him the contract to fit that boiler in the first place. I left the Benchmark as he had left it, stuck a Sentinel label on the boiler casing, and wrote '2 litres' on the label.
Did you observe how much the height of the level in the expansion tank rose and fell between the system being cold and the system being hot?
I've had a go today at checking the water level in the F&E. It rises from 5.5" to 5.6" over a 17 x 11.5" tank. I make this 0.56pt, or 318ml, compared with 358ml in the cold feed run, if we assume the pipe contains 130ml/m.
The pipe run from the close-coupled tee to the tank is about 1.25m vertical and then 1.5m across the loft joists, giving a total of 2.75m.
So, while the expansion is not quite as great as the quantity in the cold feed, it isn't far off, and I can see that air could potentially get into the system this way, particularly when central heating is warming up a far greater quantity of water than the small amount in the primaries, boiler, and cylinder coil.
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