Hi,

I planning on descaling the DHW heat exchanger on my combi. It's an
Ariston Microgenus 27 and the rate of flow has gradually declined since
it's been installed (over three years ago). The descaling looks like an
easy enough job, and removing the heat exchanger itself is dead easy,
but before I make a complete fool of myself I've never really
understood exactly how the combi does the DHW. Do I need to drain the
boiler completely (and all the rads) or is just turning off the cold
water feed to the combi enough?

On Wed, 19 Apr 2006 11:49:33 -0700, Martin Pentreath wrote:

Hi,

I planning on descaling the DHW heat exchanger on my combi. It's an
Ariston Microgenus 27 and the rate of flow has gradually declined since
it's been installed (over three years ago). The descaling looks like an
easy enough job, and removing the heat exchanger itself is dead easy,
but before I make a complete fool of myself I've never really
understood exactly how the combi does the DHW. Do I need to drain the
boiler completely (and all the rads) or is just turning off the cold
water feed to the combi enough?

Have you got the service manual?
It will almost certainly involve draining the water out of the boiler but
not the rads.




--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

On Wed, 19 Apr 2006 11:49:33 -0700, Martin Pentreath wrote:

Hi,

I planning on descaling the DHW heat exchanger on my combi. It's an
Ariston Microgenus 27 and the rate of flow has gradually declined since
it's been installed (over three years ago). The descaling looks like an
easy enough job, and removing the heat exchanger itself is dead easy,
but before I make a complete fool of myself I've never really
understood exactly how the combi does the DHW. Do I need to drain the
boiler completely (and all the rads) or is just turning off the cold
water feed to the combi enough?

You'll need at least to isolate the primary side as well, but most boilers
have valves on the flow & return so you shouldn't have to drain the rads.