Greenspring CWi47 VS Rinnai 26i VS 2X Greenstar 42CDi for two simultaneous showers

[woking]

Hi Guys,

I am hoping to get some advice from you to know what to ask my heat engineer to design / install.
The aim is to have enough hot water to run two showers simultaneously without use of unvented cylinder. I am planning to move boilers to the low pitch loft (second floor) and could not fit decent vertical unvented there. There is also a bit of work be needed to reinforce the loft to accommodate large cylinder. I have Greenstar 24 System boiler that I could re-use as a system boiler and install high performance hot water only boiler or possibly replace it by two 42CDi.

Here are options I am considering please let me know if there are any other high flow water only boilers I should consider:
1. Greenstar 24 System + Greenspring CWi47
2. Greenstar 24 System + Rinnai Infinity 26i
3. Greenstar 42 + Greenstar 42
4. Greenstar 42CDi + Greenspring CWi47

Have any of you installed / had any feedback from people using first two boilers or similar setup to option 3?
I am planning to upgrade gas supply pipe and getting U16 meter and also replacing current water mains (30 meters run from outside stopcock to the house) with 2 X 32MDPE water mains with the view to achieve decent water flow / pressure and be able to use one of the above setups.
I recently got waterboard to replace my old and rusty water meter and measure flow/ pressure. They said at the meter (about 30 meters from the property) I have 40L/ flow and 2.75bar.

Any thoughts or advice would be much appreciated and I hope not to cause too much controversy :smile:

 

[woking]

Re: Greenspring CWi47 VS Rinnai 26i VS 2X Greenstar 42CDi for two simultaneous shower

Got some updates from the board engineer visit today:
It seams that I get around 20l/min from my outside tap (it was 12l/min when measured from the kitchen tap). While flow at the stopcock is around 40L/Min. Engineer was convinced that both pipes from the 100mm water mains to my stopcock / meter and from the meter to my house should be 25mm black polypipe. Previous owner must have downsized somewhere under the current kitchen floor from 25mm to 15mm copper I have as my water mains coming into the house now.
Pressure at the water stopcock is 2.75 and at garden tap only 2.0bar. He is not sure what might be causing it. We had checked pressure with different gauges though as his did not fit my outside tap.
What we have agreed on is that he will request for my 20-30 years old stopcock to be replaced and being really nice to me he asked for very short run of water mains from 100mm mains to the new stopcock to be replaced as well hoping it might help to increase the flow I am getting now.
I also spoken to waterboards’s development services who mentioned that minimum charge for replacing the mains pipe and meter to 32mm is £600. All information I could get from them is that for 60L/min they will require 32mm mains pipe and for 50L/Min it is up to me if I wanted 32mm or wanted to stay with 25mm.
I might not need to pay more than £600 as the pipe run is only around 1 meter or so.
I guess my best bet is to ait until stopcock and pipe from the mains are replaced and taking it from there.
When I asked engineer what is the highest flow he has seen around my town he mentioned 50L/Min from the garden tap but at slightly heir pressure. I am guessing this might be limitation of 15mm copper pipe or possibly 15mm meter.

Could anyone share their experience of installing hot water only boiler and what was the mains flow / pressure and where customers happy with the results and able to run two good flow shower at the same time?

 

[woking]

Re: Greenspring CWi47 VS Rinnai 26i VS 2X Greenstar 42CDi for two simultaneous shower

Hi guys,
I have some news after upgrade of my water mains and more questions 

I’ve gone for 32mm from boundary to the house. It has increased my flow considerably and I now seem to have less pressure drop when fully opening kitchen tap.
Depending on the water pressure I am now getting between 34 and 40L/Min from the garden tap that I’ve upgraded to ¾ inch tap fed by 22mm copper pipe.
I think my main issue at this point is my mains pressure. Most of the time it is around 2 Bar static and falls to about 1.8 bar if I fully open kitchen tap. Sometimes is goes up to 2.8 bar and not very often drops to 1.8 bar static. In general it seems to drop by 0.2 Bar when I fully open kitchen tap.
I still hope to use Rinnai HW only heater and combiboiler for heating and possibly to feed one of the showers. I got National Grid to upgrade my gas supply and fit U16 meter around end of September.
Should I abandon my idea about placing boilers to the loft with this mains water pressure?
What pressure of hot water combiboilers usually provide? Is it as high as incoming water pressure or would they reduce it quite a bit?
Having used shower body jets in a hotel recently I was hoping to install them as part of my project but they seem to require 2 Bar which I will probably not get with my mains pressure.
Is there such thing as quiet booster pump or they all will be very noisy? It could probably be ok if they produce same level of noise as dishwasher (around 40db) but most of them seem to make at least 70db which is more like washing machine spinning at 1400 RPM)