# Tech notes

These articles in Adobe PDF format are intended for colleagues and school science students. Nothing more than arithmetic is needed – no fancy maths.

The calculations, and the handy rules from which they derive are mine in the sense that I worked through them and found them, and didn’t rip them off from someone else. However, they are all indebted to the many people, famous and obscure, who figured out how nature works – hard-won knowledge indeed. I haven’t time, inclination or resources to pursue breaches of copyright. All I ask is that you don’t pass off the material as your own – in any case, you may be copying my mistakes!

Heating water – how long does it take to heat a quantity of water? – a handy rule: File: Heating water.pdf

Hot water flow rate and combi boiler size – how to calculate one from the other without a manual: File: HW flow rate & boiler size.pdf

Gas rate and gas flow rate – why gas flow rate can be more accurate and useful than “gas rate” (boiler input power): File: Gas rate & gas flow rate.pdf

Gases – heavier or lighter than air? – we can work it out for some common gases, without textbook or internet site: File: Gases – heavier or lighter than air.pdf

Condensing boilers – how much condensate does a condensing boiler produce, and how much energy is saved by condensing water vapour in the flue gases into liquid water? All calculated from basic chemistry & physics: File: Condensing boilers – water produced – energy saved.pdf

The carbon footprint of burning natural gas – how much carbon dioxide is produced – again calculated using basic physics and chemistry:  File: Carbon footprint of burning gas.pdf

Flue gas carbon dioxide and oxygen – the relationship between them explained in numbers and a graph: File: Flue gas carbon dioxide and oxygen.pdf

Expansion vessels, as found in boilers in sealed systems – some notes: File: Boiler expansion vessel.pdf

How fast does gas flow in our pipes? Some straightforward calculations, and answers we can relate to: File: Speed of gas.pdf

Gross and net heat inputs explained, along with how daft efficiency figures can appear in calculations: File: Gross and net and weird efficiency.pdf

Central heating water quality: File: Heating water quality.pdf

Heat flows – how energy moves in a heating system: File: Heat flows.pdf