Question about pipe layout

[cpmarvin]

hi , I have a 1930 terraced house with a Worchester 8000 35kw , which i was hopping can provide enough hot water presure. The boiler is installed almost at the ceiling level in the dinning room so the height to push the water to the shower is really low ( 1m at max). So i'm a bit puzzled why i'm having low pressure and on top of that if anyone is using a sink or toilet the pressure drops even lower.

Now before i go ahead and replace the boiler with a 45kw i figure i ask if the pipe layout i see it's optimal. I'm not a plumber but to me it looks like the cold water is not reaching the boiler due to the way the piping was layout , image boiler_initial below. What is the best practice , should the boiler cold feed be done from a T closer to the mains ? like in image boiler_post below ?

Or ... it's the mains pipe diameter or i just need to accept i need a more powerful boiler ? Just to be clear , i've check the presure on the mains and upstair toilet/sick , all is fine , it's just the moment someone opens any cold water the boiler hot presure falls.

Thx,

 

[cross thread]

Don’t waste money on a bigger boiler ,
What pressure have you when it’s flowing ?

 

[oldbuffer]

1. As above, its nothing to do with the size of boiler.
2. If its a combi boiler, the likelihood is that you have inadequate mains pressure and / or flow rate.

 

[cpmarvin]

Cold mains on the upstairs sink , flow rate is : 16L/minute , while the hot one is : 3L/minute .Will take a new presure reading and update.
Ok so in theory the pipe layout that i have , has no effect on the flow rate to the boiler ?

 

[polesapart]

And the flow rate at the kitchen hot tap?

 

[cpmarvin]

And the flow rate at the kitchen hot tap?

about 6L/minute

 

[polesapart]

I would be suspecting blocked or undersized pipework, or a restriction somewhere e.g. a valve not fully open or a choked inlet filter.

A more powerful boiler won't help.

 

[cpmarvin]

I would be suspecting blocked or undersized pipework, or a restriction somewhere e.g. a valve not fully open or a choked inlet filter.

A more powerful boiler won't help.

thanks. you mean the hot or cold one ? either way the pipes are under the tiles , so will have to check from the ceiling below.

 

[polesapart]

It would be informative to cut in a tee with a full-bore valve on the cold mains as it enters the boiler and one on the hot pipe leaving the boiler.

Comparing the flow rates on each would help indicate if there's a restriction at the boiler, before or after.

Could be something as simple as crud on the boiler inlet valve or even a valve somewhere partially closed.

 

[cpmarvin]

you mean here ?