What lesson can be learnt from this?

[clf-gas]

Whats FHW and I will look at the papers.

DHW

Think Craigs had a few bevies and meant DHW

You know me to well Dave

Was it the installer you found the fault Vinno, or yourself

 

[sooey]

Agile wrote

But I usually give free advice on this web site although recent developments might cause me to consider reviewing that.

That would be a shame Tony, I personally find yours, and others posts very helpful in my attempts to get my head around how these dammed combis work.

 

[mehran]

That is a shame, ravenheat may get slag here but you should always found out what is wrong before simply changing the boiler.

your story is not uncommon if that gives you any comfort

 

[doitall]

Unless the cold to the boiler is restricted, then the hot and cold would be balanced, or am I missing something

 

[clf-gas]

Unless the cold to the boiler is restricted, then the hot and cold would be balanced, or am I missing something

would the cold supply be restricted through the boiler whilst in DHW mode but the cold supply to the mixer un-restricted

 

[doitall]

Unless the cold to the boiler is restricted, then the hot and cold would be balanced, or am I missing something

would the cold supply be restricted through the boiler whilst in DHW mode but the cold supply to the mixer un-restricted

Maybe but the pressure would be equal

 

[clf-gas]

Unless the cold to the boiler is restricted, then the hot and cold would be balanced, or am I missing something

would the cold supply be restricted through the boiler whilst in DHW mode but the cold supply to the mixer un-restricted

Maybe but the pressure would be equal

Im not thinking outside the box here, what am I missing

 

[corgiman]

I had this on an old 350 WB and was nearly tearing me hair out (not that I had much to tear to begin with) untill i was about to change the DHW HE and turned the water off but the hot tap still had pressure

so I began to isolate stuff and found the shower was eff'd

but I must say I would have probably come to the same conclusion as you vinno but I was luckier easliy missed I would say

someone else has probably said it but I am far too fat and lazy to read all the posts

 

[doitall]

Unless the cold to the boiler is restricted, then the hot and cold would be balanced, or am I missing something

would the cold supply be restricted through the boiler whilst in DHW mode but the cold supply to the mixer un-restricted

Maybe but the pressure would be equal

Im not thinking outside the box here, what am I missing

Not a lot clf-gas

just me thinking, when I shouldn't.

If the pressures are equal how can it back up

 

[chrishutt]

If the pressures are equal how can it back up

Static pressures would be equal but dynamic pressures would be very different. The flow restriction through a combi results in very low dynamic pressures downstream.

 

[mehran]

if you got a 16l/m cold water supply and the flow restrictor on boiler is 10l/m, then the cold water leaking in to you hot is not going to try to top up the diff?

i take the cold water is a bit like electrics, find the path of least resistant

 

[clf-gas]

Unless the cold to the boiler is restricted, then the hot and cold would be balanced, or am I missing something

would the cold supply be restricted through the boiler whilst in DHW mode but the cold supply to the mixer un-restricted

Maybe but the pressure would be equal

Im not thinking outside the box here, what am I missing

Not a lot clf-gas

just me thinking, when I shouldn't.

If the pressures are equal how can it back up

Praise the lord for that, thinking I needed to stay off the Stella and Vodka on me days off

Its like Chris says on the post above, in layman terms passage of least resistence and all that

 

[doitall]

If the pressures are equal how can it back up

Static pressures would be equal but dynamic pressures would be very different. The flow restriction through a combi results in very low dynamic pressures downstream.

But that would only work if another outlet was opened when using the shower.

 

[clf-gas]

Sorry Doitall, don't know your name

If mixer shower is on and cold is at lets say 1.5 bar and hot 1.2 bar after the boiler, then would'nt cold fight hot to 0.3, hot winning by 0.9 bar...... or is the drink saying go to bed Craig, golf at 6.30am

 

[chrishutt]

But that would only work if another outlet was opened when using the shower.

I don't think the shower would have to be in use because shower valves generally mix the hot and cold water before the on-off control valve. It is only the non-return valves that stop cold flowing across to hot pipes and vice versa.