Can a combi run 2 body jets and a fixed head?

[Jackuzi]

Hi all,

1st question on here so please be gentle! (For a wee while anyway)

I am gutting and refitting the en-suite and bathroom and want to install 2 concealed body jets and a fixed shower head over the bath in each. I want to run these using triple thermostatic mixers (Hudson Reed) with the 2 jets running off the bottom tap and the shower head running of the other.
My Combi is a Worcester 28CDi.
Is this likely to work okay?
I presume it depends on the amount of mains pressure I've got. I found a pressure test kit on screwfix for about £12, would this be okay? Do i need to connect it in the bathroom to get the most accurate result?

Thanks,
Glen

 

[ChrisR]

You'll get about 10 litres per minute, tad more in the summer. I doubt that'll be enough.

 

[Jackuzi]

I forgot to mention I will only be using one bathroom at a time. Can I check the flow rate by filling a water bottle and timing it?
Also, is the flow rate more important than pressure then?

 

[HarrogateGas]

It will not cope with the shower and body jets..........have a rethink!

 

[Jackuzi]

Have a rethink! What options do I have from those reponses? a) Don't do it b) Don't do it!!

Seriously though is this to do with the boiler? I could always buy a better boiler if it will work on another. I want to stick with Combi though. Any suggestions?

The other thing, I take it the body jets will just trickle then will they. I don't mind if they just deliver the water without being forceful.

More advice please?

Thanks

 

[Nige F]

you need to calculate the amount of water that will pass through the jets, shower et. al when it`s running @ full flow.....then you need to check the amount of water at the desired (point of use) temperature the combi can pass when raising said water from a nominal winter incoming mains water temperature of ,say 1deg. C........so you need all the manufacturers figures The general consensus from experience rather than maths. calculations is that "it`ll never work"I`ll add "No combi will do it."....that`s only an opinion, and I`m an old school craft plumber.If I could`ve done maths @ school I`d have become an architect I`m just a failure

 

[Paul Barker]

Why not install a dhw cylinder, you already have the boiler. Unvented or gravity and pump. If you do go gravity, you could use the combi for the shower head to great effect and pump the body jets.

ALternatively a Worcester 40kw combi would manage one jet and shower head, but would wain with two jets and a shower head.

Or add an instant hot water heater run them together either series or parallel.

 

[corgiman]

Sorry Jaq But Combis are NOT a panacea they DO NOT do everything


and unfortunatley you will always get the response DONT DO IT DONT DO IT when it cant do it


funny that

 

[pierrot]

8) you`l have to move to an unvented cylinder to deliver that amount of flow.

 

[Jackuzi]

Sorry Jaq But Combis are NOT a panacea they DO NOT do everything


and unfortunatley you will always get the response DONT DO IT DONT DO IT when it cant do it


funny that

I understood the responses but my reply was because they could have offered further advice in the way that Paul and Nige have (thanks to you both).

I didn't realise you could have a DHW Cylinder on a combi, I thought it was either combi or std and tanks.

Off I go to google that option. Thanks all.

 

[ChrisR]

There are always solutions if you have space and money. Stooge around this site and you'll get some ideas:
http://www.heatweb.com/editorials/heatbanks/compare1.htm

Wherever it says "boiler" you can use a combi. You may need some extra bits of plumbing and lateral thinking on the part of the plumber, but the flowth is out there.

Do some noddy sums. If you work on 10 litres/min, and a vertically faced jet with 100 holes 1mm diameter, one metre above the floor, then the initially horizontal spray comes out at 4.6 mph which isn't thrilling, and hits the floor 1 metre out from the head. That ignores air resistance and all that, which will make it worse.

That isn't running water - it's walking! Better start measuring your holes.

 

[Nige F]

A friend of mine`s got a low pressure cistern fed hot cylinder on a combi.feeds hot/cold water to the bath via a pump..........the basin and wc are mains fed.and the hot to the basin and kitchen sink are combi fed....the coil inside the cyl is on the radiator circuit .all the other rads are on thermo valves....in the summer ,you shut the rads.. you have to run the domestic hot water @ boiler temp,and run the rads/hotwater together in the winter that`s the only drawback.....what genius thought this setup out.......

 

[Jackuzi]

Thanks guys, bloody hell..can of worms time then. So if I've got this straight in my head, you install a cold tank and a cylinder for the hot storage. The Combi heats the water for the hot storage and then you use this water to supply the shower only?
Do you use a pump on the shower feeds?
I do have room in my loft to do this. I suppose the deciding factor will be the costing of it.
The other thing I could do is to proceed with my plans to plumb in the 2 jets and then later if I need to improve things is to add in this extra tank storage system and re jig the plumbing.
My initial thought was the performance I would get from this set up would depend on the total number and size of the holes on the jets and shower head ie. body jets with just a few needle holes and the fixed head with a low number also. Am I way off with my thinking here? Wouldn't that be the same a having one shower head with lots of holes?

 

[ChrisR]

Nobody thought about it very much! A temp operated valve on the cylinder would make it a lot better.

 

[Nige F]

cheapo job.