What is a pressursed hot water cylinder and an immersion heater?

Scot_39

rottcodd said:

Probably a stupid question, but I'm a FTB and about to move into somewhere that has according to the survey "a modern pressurised hot water cylinder. There is an electrical immersion heater fitted to the hot water cylinder" 

Could someone explain as if you are talking to a stupid person what exactly the cylinder is, what the immersion heater is, what do they both do, and how do they interact with each other, and anything I can do to reduce energy costs as much as possible? 

It's simply the normal form of heating hot water in a modern all electric flat or home.

A varying in height - large normally cylindrical tank of water - volume from 100 litres to over 300ltr depending on property size - het by in your case electric heating elements.

(Mines is c120l in a 2 bed house - enough for 2 baths when mixed with cold - or 24 bathroom sinks or 12 large kitchen basins full of hot water - but as it's an older vented / gravity fed from loft tank HW tank - not used for showering)

These are called immersion heaters as directly in the water.  (That may seem counter-intuitve - electric and water mixing - but simply think of the tanks as a large well insulated "flask" and the immersion heater as a version of the 3kW element in the bottom of a fast boil electric kettle to heat it's content - that you can heat as little as once per day - and get hot water throughout the rest of day)

https://www.screwfix.com/c/heating-plumbing/cylinders/cat830982

Before combi gas boilers - gas boilers and before them home coal or wood fires - would heat a similar sized tank full of hot water.

Traditionally in older UK homes - these would be gravity fed from a cold water tank in the loft - not from cold water mains - a pressurised supply  - directly - but then these loft tanks and cold water pipes in unhet space were a risk too - e.g. freezing in winter.

Even on a good E7 off peak deal electric HW isn't as cheap to run as gas.  Hot Water is of course an all year cost - but often still a lower annual cost for many than winter room heating.

Have you considered how the flat is heated - heater types and meter type - and if it is likely suitable for E7 off peak hw and room heating  ?