Ariston Combi 23MFFI - Power Shower Problem

[Harlow55]

Even when the shower hand set has the hot water set to its hottest setting the power shower is only returning luke warm water. The boiler pressure has been set to 1.5 Bar when cold & the temperature at the boiler is set at 9 (maximum). One way to get a warmer shower, is to turn the cold water basin tap on high, but this obviously wastes a lot of water. And more recently I have reduced instead the flow of the cold water at the stop cock with similar result. (As the weather has been colder recently I guess that the incoming cold water is a few degrees colder, is this what is testing the boilers efficiency?)

The feed is via a 22mm copper pipe from the boiler to the bath & then a reducing tee to 15mm to the power shower.

Do I need a more powerful boiler? Would the problem be solved if the supply was via the basin pipe at 15mm? If anybody is able to suggest any solutions I would be very grateful. Thanks Harlow55

 

[andyscott]

Assuming everything else is working ok you need to reduce the cold water flow into (and through) the boiler. There should be a valve on the cold water inlet or the hot water outlet to allow this.
You should set the hot water on the boiler to maximum temperature and open a bath tap, and a bit at a time reduce the flow through the boiler.
When you have reduced it too much the boiler will modulate (reduce its gas consumption to stop the hot water getting too hot); you don't want this.
So you will need to keep an eye on the gas meter. The boiler should take about 40 seconds to to use 1 cubic foot (or 0.028 metres cubed if it is metric). Each time you adjust the water flow, you should check the gas meter to see if this time has increased. Once you get it to increase, adjust the water valve back one step. This is the maximum gas being used to give you the maximum temperature for the winter.
For the summer you can allow a little more flow through the boiler, with the same temperature being achieved, because the inlet water to the boiler should be around 10 deg C warmer than at present.

 

[Harlow55]

Excellent. Thanks Andy Scott. Your notes were very easy to follow, I was able to adjust the cold water inlet valve & reduce the flow & watch the gas meter. I had a test shower & didn't need to use the hottest setting. Thanks again for taking the trouble to help.