Switch to a combi boiler

[Johntheo5]

Sorry I wasn’t clear it’s a tank booster so is 450l of water pumped ( salamander tank boost) 3 bar upto 80l/min .
Yeah I’ve had the water board out checked it in the road was 11 they said that’s plenty good enough they have to supply a min of 7 .
I think the easy answer is to just get a better combi with higher flow rates.

I can’t fit both the tank and a hot water cylinder in the airing cupboard , I would have to loose one

Maybe carry out a easy test first re boiler output as (if)16.7LPM at 42C isn't a bad output, most people would be happy enough with a 35kW combi as long as not trying to run 2 showers at the same time.
Suggest setting the DHW temp to 60C, open all HW taps and shower, this ensures that the boiler will run flat out, take a photo of the gas meter and exactly (to the very second) take another photo. The boiler output will be the 3 minute gas consumption X 20 X 11 X 0.88 ish, kW

 

[Randers123!]

No I had a bigger gas pipe fitted I think 28mm or 22 of the top of my head , like I say I’m never getting anywhere near those numbers out of the hot tap , because there’s a little red restrictor built into the cold water supply in boiler , I’ve spoke to glow worm if I removed that temporarily the flow rate is amazing but the boiler than struggles to heat the water to the correct temperature and maintain a nice shower.
My main question is do all combis have this ?
As they are kinda sold with false claims , for example you never gonna get 14.3l/min when the inlet is restricted to 12l/min .
I’m currently looking at the Worcester Bosch Greenstar 550CDI which is claiming 25l/min

 

[Elsa TLC]

If the problem is two showers at a time you could try smaller shower heads.
A 35kw combi should give a very good shower. With 2 smaller heads it should give 2 okish showers

 

[Elsa TLC]

No I had a bigger gas pipe fitted I think 28mm or 22 of the top of my head , like I say I’m never getting anywhere near those numbers out of the hot tap , because there’s a little red restrictor built into the cold water supply in boiler , I’ve spoke to glow worm if I removed that temporarily the flow rate is amazing but the boiler than struggles to heat the water to the correct temperature and maintain a nice shower.
My main question is do all combis have this ?
As they are kinda sold with false claims , for example you never gonna get 14.3l/min when the inlet is restricted to 12l/min .
I’m currently looking at the Worcester Bosch Greenstar 550CDI which is claiming 25l/min

Send pictures and dimensions of your boiler cupboard

 

[Johntheo5]

No I had a bigger gas pipe fitted I think 28mm or 22 of the top of my head , like I say I’m never getting anywhere near those numbers out of the hot tap , because there’s a little red restrictor built into the cold water supply in boiler , I’ve spoke to glow worm if I removed that temporarily the flow rate is amazing but the boiler than struggles to heat the water to the correct temperature and maintain a nice shower.
My main question is do all combis have this ?
As they are kinda sold with false claims , for example you never gonna get 14.3l/min when the inlet is restricted to 12l/min .
I’m currently looking at the Worcester Bosch Greenstar 550CDI which is claiming 25l/min

All/most combis do have this restrictor for the very reason that you have posted the above, ie, fantastic flowrates but then cannot heat the water to your desired temperature, most will install the restrictor to allow a flowrate that gives a temperature rise of 35C, in some cases, 40C rise, so your 35kw boiler should have a restricted flowrate of 14.3LPM to give that 35C rise or if their standard is a 40C rise, 12.54LPM, a 25kW combi will be restriced to either 10.24LPM or 8.96LPM, hence the suggestion to ensure that you are getting your full 35kW rating, if you are, and still not satisfied, then either install a higher powered combi or go back to your stored hot water.

 

[Randers123!]

Maybe carry out a easy test first re boiler output as (if)16.7LPM at 42C isn't a bad output, most people would be happy enough with a 35kW combi as long as not trying to run 2 showers at the same time.
Suggest setting the DHW temp to 60C, open all HW taps and shower, this ensures that the boiler will run flat out, take a photo of the gas meter and exactly (to the very second) take another photo. The boiler output will be the 3 minute gas consumption X 20 X 11 X 0.88 ish, kW

I will do this test today at some point , so take the photo 3 minutes apart ? Just to be clear while the boiler is running flat out ? I’ll report back

 

[Johntheo5]

I will do this test today at some point , so take the photo 3 minutes apart ? Just to be clear while the boiler is running flat out ? I’ll report back

Yes, increase the DHW temperature to 60C first and open all HW outlets, including the shower, the boiler will then run at its full output and take those readings exactly 3 minutes apart.

 

[Randers123!]

Yes, increase the DHW temperature to 60C first and open all HW outlets, including the shower, the boiler will then run at its full output and take those readings exactly 3 minutes apart.

Had all taps running , although they were all weak and luke warm , DHW is already on max setting 60c

 

[Johntheo5]

Those two meter readings are the same?, you take the first reading with the boiler firing flat out, then, with the boiler still firing flat out, take the second reading exactly 3 minutes later, subtract one from the other to get the 3 minute gas consumption etc.

 

[SimonH2]

Had all taps running , although they were all weak and luke warm , DHW is already on max setting 60c

You need to read the display on the meter not the in-home display - that doesn't update in real-time.

 

[Madrab]

What Glowworm boiler is it and what's is it's KW rating?

What is it you are trying to achieve here? Are you running more than one bathroom or is it just the impact to the single shower if someone say uses another HW outlet?

 

[Randers123!]

You need to read the display on the meter not the in-home display - that doesn't update in real-time.

 

[Randers123!]

What is it you are trying to achieve here? Are you running more than one bathroom or is it just the impact to the single shower if someone say uses another HW outlet?

The shower is not the best , as we were used to a power shower before and yes if someone turns on another h/w tap in the house it’s dreadful . Just trying to achieve a solid hot water system , we about to install an extra bathroom in our loft too not that anyone would shower at the same time.

 

[Johntheo5]

Unfortunately!!, that equates to a boiler output of 35.6kW so the boiler is achieving its rated output.

 

[Randers123!]

Unfortunately!!, that equates to a boiler output of 35.6kW so the boiler is achieving its rated output.

Ah thanks I don’t doubt the boiler is not working correctly , it’s great if you live on your own and have a good water supply but we are a busy house of 4 , and used to having a gravity fed system with a power shower