Add cylinder to Combi boiler system for power shower

[Ross161]

Hello plumbing geniuses I hope you can help me.

I have a Worcester 24CDI combi, it puts out hot water at a reasonable rate, about 9l per minute at the hot tap. However I am doing a wetroom and would like the best shower I can get, so I am doubting if the combi will be able to give me the pressure I want. I am looking at an Aqualisa HiQu Digital shower if that makes an difference. They do a pumped and un-pumped system.

They also do a super-duper external pump to get the water upto 3.4 bar pressure.

If I want to go the pumped route, I know I need a good size hot water cylinder and header tank installing, and run off a separate zone from my CH on the combi. I know this is unusual but after spending so much on the batheroom I dont mind shelling out to get the most powerful shower I can.

I have a couple of questions I hope a more experienced mind can help with.
(1a) Am I mad, and should I just pay for a bigger combi boiler?

(1b) Presumably a pumped gravity fed system will deliver better flow than my combi can manage?

(2) If not, and I can get this done what is the best solution? Vented / unvented etc..?

(3) If I use the Aqualisa L340 external pump, could I end up pumping water into the shower faster that the header tank can refill the cylinder?

Does anyone have experience of using the above boiler with a mixer shower like this? I might be perfectly happy with the flow rate the combi can manage, but I am not sure what to expect.

So many questions but thanks in advance for your wisdom!

Ross

 

[SimonJohns]

You can add a cylinder on of your choice bust treat it as a heat only boiler and have all external controls. Use the hot water draw off for something on your house

As for the rest of your questions. There are far greater experienced plumbers on here with the power showers than I am


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- Sent from my iPhone using Tapatalk

 

[cr0ft]

The pressure from the combi is pretty much governed by the pressure of the water coming into the house. In most cases this will be over 3 bars but not always, especially if you live in rural locations. A plumber can do a simple pressure test to determine this. While they are doing this, get them to test the flow rate coming into your property through the mains. Flow rate required really depends on what head you are planning on fitting to the shower. A standard 3" head will be fine with what you have. Looking at a 6" head or multiple body jets? Don't expect your boiler to cope.

If you're going for the latter, your cheapest option will be a floor-standing combi-boiler such as the Worcester Bosch 440CDi. Up to 20 litres per minute of hot water then whatever flow is left from the mains to go to the cold side of the shower. If you have a decent incoming mains this will run your shower indefinitely without the requirement for expensive unvented cylinders.

Hope you're not on a water meter though!

 

[bill577]

have a plumber check your incoming pressure and flow from the mains, if you have enough then I would recommend an unvented cylinder running off your combi, if not then a vented cylinder and tank with your pumped shower would be the way to go.

 

[Ian10261]

As above but its also worth giving some thought to the waste from the shower tray. If you're pumping huge amounts of water into it then can the waste cope with it, i've actually seen this happen!!
Theres also the water regs you may want to consider, last time i looked i think you had to notify building control if you fitted a shower capable of delivering in excess of 12 ltrs per minute.

 

[Hybrid]

Theres also the water regs you may want to consider, last time i looked i think you had to notify building control if you fitted a shower capable of delivering in excess of 12 ltrs per minute.

Power shower or any pump off the mains.

 

[Howsie]

Power shower or any pump off the mains.

Only over 12 l/m.

 

[Ross161]

Thanks for all the information, I have ordered the unpumped shower and will put my faith in the combi. Worst case it will need to be upgraded but it will be a "suck it and see" exercise when the shower arrives tomorrow I will hook it up and see what happens.

 

[metaldust9]

its quite an expensive way of doing things not to mention its only a 24 kw boiler anyway so the flow rate aint gunner change no matter what you put in extra would be just as cheap to change the boiler dependent on the budjet you have

 

[SimonJohns]

its quite an expensive way of doing things not to mention its only a 24 kw boiler anyway so the flow rate aint gunner change no matter what you put in extra would be just as cheap to change the boiler dependent on the budjet you have

I think he was going to fit the cylinder as a stand alone. Not feed it from the boiler

 

[quality]

I had a recent install similar to the OP queastion
There was a Vallaint combi already insalled I fitted a 350 l twin coil with a 40 tube solar collector and a few controls.
The system is not ideal as the combi is still providing DHW to a shower where no access is possible to change but the rest of the system is ok

My statement is ! when will joe bloggs realise that combi boilers are rubbish when you want a good shower, plenty of hot water etc