Flow too high for combi boiler?

[Roonaldo]

Hi, we moved home recently and have an issue with the hot water/shower.

When the hot taps are open fully, the water is only warm. When the taps are open less the water is piping hot. This is also apparent in the shower. We have an electronic shower, and it never really gets hot enough.

We have an Ariston E-combi 24, and live in a valley so the mains water pressure is quite high. I think the flow is too high for the boiler to cope with, hence when the hot tap is open fully, its only warm, and the shower is not hot enough as you can't control the flow rate.

How could I resolve this, without lowering the water pressure too much (for a nice shower). Do I need to get a flow reducing valve fitted? PS I don't know anything about plumbing/boilers, but would make sense to me?

Thanks in advance,

 

[transam]

A 24 k.w combi will produce approx 9.5 litres amin at atemp rise of 35 degs C , so if your incoming water main has a temp of 10 degs C the boiler will raise it by 35 degs C to a temp of 45 degs at a flow rate of 9.5 litres a min .

 

[Roonaldo]

Thanks, thats interesting. Not knowing my flow rate, I did a simple test. I can fill a jug with 14 litres from the kitchen cold tap in 1 minute.

I'm guessing my flow rate is too high. What shoud I do to bring this down? What would be the optimum flow rate for my boiler?

I also have my boiler turned up to the max and DHW temperature dial on max aswell, to try to give it the best chance, is this the best setting/OK in long term?

Thanks again,

 

[D_Hailsham]

Thanks, that's interesting. Not knowing my flow rate, I did a simple test. I can fill a jug with 14 litres from the kitchen cold tap in 1 minute.

You need 2.5kW for every litre/min to raise the temperature 35C. So, if your flow is 14 litre/min, you need a 35kW boiler. If your boiler is 24kW and the flow rate is 14 litres/min, the temperature will only rise 25C, which would be OK in the summer when incoming water is 15-20C, but not so hot (pun intended) in the winter when the incoming water may only be 5C.

 

[Roonaldo]

Thanks, rather than swap the boiler for a 35kw model, which sounds expensive, surely I can just reduce the flow rate to around 9.5 l/min?

Whats the best way to acheive this?

Thanks again,

 

[Keston]

Thanks, rather than swap the boiler for a 35kw model, which sounds expensive, surely I can just reduce the flow rate to around 9.5 l/min?

Whats the best way to acheive this?

Thanks again,

Run outside and find your water meter turn it down from there...

dont let anyone see

 

[tamz]

Throttle the flow rate through the boiler by turning down the slotted valve on the cold inlet. Most newer combis have a flow restrictor built in which stops too much running through.

Think of your combi like an electric shower, if you increase the flow the temperature drops because it can't heat enough to keep up.

If your shower is still a problem fit a pressure balancing valve

 

[transam]

Regulate the flow & temp on the tap when u are useing them !!

 

[Roonaldo]

Regulate the flow & temp on the tap when u are useing them !!

I should have been clearer, sorry. The taps aren't a problem, I can regulate these as suggested. It was more to illustrate that as the flow rate goes up, the less hot they become.

The shower is the issue, I cannot control the rate of flow for the shower. There is an on/off button and temp control. The shower never gets hots enough, warm at best.

Please bear in mind, I'm new to combi boilers, and am learning how they work. I'm used to turning on the shower/taps and hot water coming out

 

[Roonaldo]

Throttle the flow rate through the boiler by turning down the slotted valve on the cold inlet. Most newer combis have a flow restrictor built in which stops too much running through.

Think of your combi like an electric shower, if you increase the flow the temperature drops because it can't heat enough to keep up.

If your shower is still a problem fit a pressure balancing valve

Thanks, I'll have a look when I'm back home.

Where would you fit a pressure balancing valve should one be needed?

Thanks,

 

[kev25v6]

Check under the bath for the water pipe to the electric shower. If there is an isolation valve on it, try turning it a touch to slow the flow of water to the shower and it should heat it up a touch more.Most people would have had one fitted when the shower was installed. On my combi boiler there is a small screw that can limit the flow of water to the boiler on top of the 3 port valve. Ive set mine so when the bath tap is fully open the water entering the boiler is at the max flow rate for the boiler, about 9.5l a min same as yours. Even in the winter though i still have to turn the flow down at the tap as it struggles to heat the water. Thats the problem with these cheaper low powered combis.

 

[tamz]

Where would you fit a pressure balancing valve should one be needed?

On the supply pipes to the shower.

Here

http://www.rwc.co.uk/public/gplumb/pequal.pdf

The shower can probably be adjusted to give a higher temperature. If you have the manufacturers instructions it will tell you how to adjust the temperature range.

 

[Roonaldo]

Where would you fit a pressure balancing valve should one be needed?

On the supply pipes to the shower.

Here

http://www.rwc.co.uk/public/gplumb/pequal.pdf

The shower can probably be adjusted to give a higher temperature. If you have the manufacturers instructions it will tell you how to adjust the temperature range.

I don't think you can adjust the temp range. There is a "black box" in the loft which has the cold and hot feeds going into it, then the shower feed comes out the other end. I spoke to aqualisa support and they said the thermostat etc is all electronically controlled and cannot be altered.

My shower is below.

http://www.aqualisa.co.uk/Our-produ...cealed-with-wall-mounted-fixed-head/?area=197

 

[Roonaldo]

Check under the bath for the water pipe to the electric shower. If there is an isolation valve on it, try turning it a touch to slow the flow of water to the shower and it should heat it up a touch more.Most people would have had one fitted when the shower was installed. On my combi boiler there is a small screw that can limit the flow of water to the boiler on top of the 3 port valve. Ive set mine so when the bath tap is fully open the water entering the boiler is at the max flow rate for the boiler, about 9.5l a min same as yours. Even in the winter though i still have to turn the flow down at the tap as it struggles to heat the water. Thats the problem with these cheaper low powered combis.

Thanks for the info, anyone know if an Ariston e-combi has one of these screws to reduce the flow, and if so where?

Thanks again,

 

[tamz]

I spoke to aqualisa support and they said the thermostat etc is all electronically controlled and cannot be altered.

Wrong info.

Check page 8 point 14 here

http://www.aqualisa.co.uk/upload/INSTALLATION GUIDES/Install_AxDigCon.pdf

anyone know if an Ariston e-combi has one of these screws to reduce the flow, and if so where?

Just adjust from the slotted screw on cold inlet. It does the same thing.