High pressure showers and combi boilers suitability

[catnipsta]

Can somebody please tell how I can use high pressure showers (like Hansgrohe raindance shower systems) with a condensing combi boiler ?

The Hansgrohe shower requires a flow rate of 28 l/m at 3 bar, however I am struggling to find a boiler on the market that is even close to these requirements(the best available on the market provides only 15.5 l/m).

Can I add a high rated pump? or is this ..as I am told...illegal, since it is not legal to connect a pump to mains cold water ( as it is the case with combi systems)

many thanks in advance

 

[Slugbabydotcom]

Forget the combi and go unvented

From experience even a 50 litre storage combi runs out after about 8 mins

I've recently fitted a 300 litre pre-plumbed megaflow cylinder and Baxi megaflow combi for a similar scenario.

You dont have to use megaflow stuff. There are other manufacturers of boilers and unvented cylinders which could be a cheaper option.

 

[ChrisR]

My Raindance is fine thanks, 20 year old system, but a 4 bar pump.

 

[Slugbabydotcom]

My Raindance is fine thanks, 20 year old system, but a 4 bar pump.

Can somebody please tell how I can use high pressure showers (like Hansgrohe raindance shower systems) with a condensing combi boiler ?

 

[catnipsta]

So in order to use one of these HP systems, it is best to have a large cistern & cylinder with a good pump and a decent system boiler?

I would need to sacrifice the extra space and also the convenience of the hot water on demand from a combi.

 

[Slugbabydotcom]

If you go unvented you wont need the large cistern, just the Megaflow. Any other make of unvented cylinder will require a small space for a pressure vessel

With a vented system that Chriis has you will have a larger than normal cistern you will also need the noisy shower pump

Unvented cylinders can be dangerous if not fotted correctly so they must be fitted by approved engineers only.

 

[catnipsta]

Thank you Slugbbaydotcom for your advice..much appreciated.

I did misread Vented as Unvented...

The unvented cylinder seems the best option...would I need a System gas boiler then?

 

[Slugbabydotcom]

I saved myself the headache about the slection of boiler and UV Cyl by just getting a pre-plumbed megaflow and the Baxi megaflow boiler to compliment it. The customer had faith in Baxi products and money wasn't the issue. I fitted a boiler buddy and flushed the system. It should give a long service and the shower is amazing. The guy is over the moon and NASA are mountiing a special shuttle mission to get him back.

Just one thing though make sure your mains flow rate and pressure are adequate before you commit to an unvented system

The megaflow operation is quieter still if you can get a 22mm cold water supply to it like I did

 

[catnipsta]

I currently only have a 15mm pipe for my cold mains...when tested the cold at the kitchen service valve, I got 3.5 bar pressure and 15 l/m.

is that a normal and adequate supply?

 

[Slugbabydotcom]

I currently only have a 15mm pipe for my cold mains...when tested the cold at the kitchen service valve, I got 3.5 bar pressure and 15 l/m.

You wont get more than 15 litres per min with unvented then as it is restricted by the mains supply, so your only feasible option I would say is to get a conventional system with Vented hot water and a shower pump. Unless you fancy renewing your water service to 25mm with a 22mm internal supply as well. Even then depending on your circumstances I cant guarantee you the 28 l/m flow rate but you shouldn't be too far off the mark. If long runs are involved then going a size up on the water service could be needed

Make sure your mains stopcock is fully open, that there are no unecessary restrictions such as half open isolation valves to your test tap and check the flow rate again.
15 l/min is still a decent flowrate but you may have to check your specific shower details and see if all of the 28 l/min is essential or just a recommendation.

Have a word with the manufacturers as they will be able to give the best advice for their product.

If 15 l/m is workable then you may be best going back to plan A but remember that you cant pump it