hot water cylinder....?

[PJ]

What does "indirect" & "Direct" mean when talking hot water cylinders?

[Ed Sirett]

I'm fairly sure that this is covered in the main FAQ or certinalya book on plumbing.

Essentially weather the boiler directly heats the HW used at the taps or not.

[Lurch]

On Wed, 30 Jun 2004 23:02:08 +0100, "PJ" strung together this:

The hot water tank is generally heated from the heating circuit or boiler circuit with dirty water. Indirect means that between the two fittings on the side of the water tank there is an internal coil that acts like an immersion heater and heats the water in the tank without contaminating it. Direct means that there is no coil and the fittings on the side of the tank simply flow straight into the water contained within.

[Christian McArdle]

Indirect means it has a heat exchanger coil for connection to a central heating boiler. Nowadays, a direct cylinder would only be used for electric heating via immersion or for conversion into a directly heated bank. (My heatbank uses an indirect coil, though).

There's almost no reason to buy a direct cylinder. Even if you are tempted, buy an indirect instead, as you might later decide to install central heating (in the case of electric immersion type), or install a boiler that doesn't support direct heating as it requires a pressurised primary (in the case of a direct heatbank).

Christian.