Pressure drop not enough to fire dhw combi

[GazzaQ]

Currently have 14Mx15mm run from combi to tap dhw. If I replaced the last 6M section with 22mm pipe would this help? Taps closer to boiler have no problems firing the boiler.

 

[ShaunCorbs]

No I’m guessing your having problems with an outlet ?

 

[Deleted member 120897]

What Combi boiler is it?

 

[GazzaQ]

What Combi boiler is it?

It's a potterton 30 HE

 

[GazzaQ]

It's a potterton 30 HE quite old I suppose but like I said, works fine at the closer outlets

 

[Deleted member 120897]

Some Combi‘s have a Venturi which can affect hot water delivery. What actually happens when running hot water for the furthest outlets?

 

[GazzaQ]

Some Combi‘s have a Venturi which can affect hot water delivery. What actually happens when running hot water for the furthest outlets?

What actually happens is we get no hot water. The pressure from the hot tap seems too low to fire up the boiler. I'm asking will changing to 22mm from 15mm for the last 6M help increase the demand on the boiler?

 

[ShaunCorbs]

Do you have a decent cold pressure where the problem area is ?

 

[GazzaQ]

Do you have a decent cold pressure where the problem area is ?

Yes

 

[Timmy D]

It’s flow rather than pressure.

Could be partially blocked aerator on tap. Remove and clean if you can. Test with aerator off.

Is it thermostatic? Could be dodgy cartridge allowing cold through when it should be hot. If cold coming through, then boiler doesn’t know to come on.

Disconnect tap connections under tap, run hot feed into a bucket and see if boiler comes on.