combi system low pressure when two taps open

[unclebob1]

Afternoon all,

Im guessing the answer to this will be because its a combi but just want to check first...

We had a valient ecotec 28 installed a few years back, removing the old gravity fed system, hot and cold water tanks and plumbing everything in directly.

As part of that, we managed to get Veolia water to replace the lead pipe from the water main, to the boundary tap (from the boundary to the internal stopcock was done 10+ years back to 22mm) as there was a lack of water flow (not pressure!) at the kitchen tap. We have a water softener which was fitted again about 10 years back and all flow testing was done with and without the softener (the pluming in the house was done so that all cold taps could be switched at will individually by turning off one tap and turning on another). There was little difference between the flow with and without.

At the time the boiler was fitted, there was only one shower using the hot water, along with the sinks, and although there was a drop in water flow at the shower head when the tap was opened, it was still usable - the temperature maintained by a thermostatic valve.

Since then, another electric shower packed in and was replaced with a thermostatic valve.

The problem i seem to be experiencing is that the flow to the upstairs shower seems to drop more now when the second shower is on (understandably as more water is being taken from the boiler). Question is, can the boiler be adjusted by setting somewhere to take into account the extra water flow that is being requested from it? I assume if there is, it was originally set for 1 shower + sink where its now being used for 2 showers... If there is can it be adjusted by me or does it need a installer/fitter to adjust?

 

[simond]

There is no setting for hot water. A Pro28 is a small boiler with a 28Kw output and therefore you won't see any more than around 10 litres per min* out of it.

* (you could google to find out exactly how much, but bear in mind the flow rates quoted are for 35C temp rise and the Pro28 is set up for 42C).

If you want more oomph you will need a bigger combi and possibly a better water supply.

 

[unclebob1]

There is no setting for hot water. A Pro28 is a small boiler with a 28Kw output and therefore you won't see any more than around 10 litres per min* out of it.

* (you could google to find out exactly how much, but bear in mind the flow rates quoted are for 35C temp rise and the Pro28 is set up for 42C).

If you want more oomph you will need a bigger combi and possibly a better water supply.

Thanks for the info, i think it will be bigger combi rather then water supply, cold runs with plenty of flow since the pipe from the main was changed, so i'm guessing the bottleneck is the boiler... o well! just have to keep staggering showers!