combi boiler question

bcoleman

Hi,

Should the DHW flow from a combi boiler be the same upstairs as it is downstairs?

Reason I ask is that the flow downstairs seems to be pretty good but upstairs it's not much more than a trickle!

It's playing havoc with my shower (mixer taps) so any help would be much appreciated.

Thanks

roger196

The pressure from the mains powers the hot water going through a combi. There will be some drop as there is restricted flow around the heat exchanger etc. The flow is also restricted so the water heats up enough. Many are deigned to heat 5 litres of water per minute through 35degrees centigrade.
1 bar( 14 lbs/sq inch) of water pressure will support 30 foot of water, so a ten foot difference between ground floor and first floor should only drop the pressure by .33bar. Look for isolation valves not fully open or flexible pipe kinked or too tight a circle. Dismantle hot tap to check that washer has not perished. Is it the shower which has low pressure ( try cleaning all the little holes in the showerhead, check that flexible tube not perished inside...easiest by substitution) or the hot bath tap.

bcoleman

Thanks Roger - I'll try looking for any isolation valves and at the layout of the pipes. It shouldn't be a problem with the shower or mixer taps as they are brand new (and the same thing happened on the old taps too!)

gas4you

I don't know of any combi that is designed to supply less than 9 litres/min at a 35c rise :think:

bcoleman

Thanks guys.

Ok - I measured the hot water flow last night and - to my great suprise - it is exactly the same upstairs as it is downstairs - around 7 l/m. My eye's must have been deceiving me!!

Anyway, I measured the cold as well and it's coming through at around 12 l/m and I think this is what's making it very hard to get the right temp on the mixer shower - just a tiny turn of cold and it get's very cold!!

Apart from fitting thermostatic taps, is there an easy way of evening up the hot and cold flows? Could I, for example, fit a ballofix (not sure if this is the right spelling!) valve to the cold water feed under the bath to reduce the cold water flow to something more manageable?

Thanks for any other help you can give!

roger196

gas4you wrote: »

I don't know of any combi that is designed to supply less than 9 litres/min at a 35c rise :think:

Thanks for pointing this out.