Megaflow cold feed.

[natwill]

Hi,
I recently purchased a Megaflow HE Indirect Unvented Cylinder CL210L to install in a property with 4 bathrooms.
While installing the cylinder i was advised by another plumber that due to the demand on the flow of the hot water that i should supply the cylinder with a 28mm cold supply and keep the hot water supply as the 22mm.
I would like to ask wether this is a good idea or that, by having a 22mm outlet that it wouldn't matter as the flow rate would still be the same?
Thanks

 

[Toddyplumb]

Do you have your unvented ticket ?

 

[ferret]

28mm mains feed always on 210 megaflo

 

[natwill]

Thanks for ur replys,
Yeh i've got my unvented ticket.
So ferret are u saying i should supply the cylinder with 28 even if the connection to the cylinder has a 22 inlet?

 

[oldplumber]

2.3 WATER SUPPLY
Bear in mind that the mains water supply to the property will be supplying both the hot and cold​

water requirements simultaneously.

It is recommended that the maximum water demand be

assessed and the water supply checked to ensure this demand can be met.
NOTE: A high mains water pressure will not always guarantee high ​

​

fl ow rates.

​

​

Wherever possible the main supply pipe should be in 22mm. The minimum mains water supply requirements should be 0.15 MPa (1.5 bar) working pressure and 20 litres per minute flowrate. At these values outlet ​

​

fl owrates may be poor if several outlets are used simultaneously, the
higher the available pressure and fl owrate the better the system performance will be.



Never seen a 28mm cold water supply to a mega flo, seems bit ott and expensive, especially as manufacturers instructions dont require it, see above

​

 

[Zammo1001]

If everything is ok with the pressure/flow rate if you check it. Why not just fit an Accumulator for the Hot water demand for 4 bathrooms

28mm to 22mm won't do anything as what you have mains side is what you get and we have to put up with that.

I would like to know what this plumber suggested like how much 28mm to install prior to the connection and so on

 

[Dannypipe]

Never heard of that. The connection to the cylinder is 22mm, so run it in that.

If there was a 28mm connection to the cylinder then it might be a different story, but even then it would be pointless if the mains supply wasn't larger than 22mm.

Some people have some funny ideas. He probably believes his own views are correct and thus makes a rod for his own back.

As old plumber states, the most important factors are to properly test your supplies, preferably at peak times (not always possible I know!) and run your supply in 22mm.

Thats what I do and never had a problem yet...fingers crossed I never do!

 

[Gray0689]

Never seen a 28mm cold feed to a unvented cylinder 22mm is standard
28mm
Won't make any difference at all waste of time and money as will have to be reduced down at cylinder

 

[justlead1]

Hi Why is it we often run a 22 mm gas pipe to a boiler when the inlet is 15 mm?

 

[wnjswozo]

😱

Hi Why is it we often run a 22 mm gas pipe to a boiler when the inlet is 15 mm?

i hope you only touch water and not gas

 

[Gray0689]

Gas is not like water you need the volume not flow that why it important to size gas pipes correctly

 

[Dannypipe]

You can tell someones not trained when they say, 'oh you must run 22mm to a combi, or it's a bodge'

Er, no. You must run the correct sized pipework to the boiler from the meter to have no more than a 2mbar pressure drop.

So that could mean running in more or sometimes less than 22mm.

 

[justlead1]

Hi Interesting please explain.

 

[Toddyplumb]

You mean 1Mbar drop 😱😉
Volume is just a measurement of internal space , volumetric flow rate is what you need

 

[ecowarm]

If everything is ok with the pressure/flow rate if you check it. Why not just fit an Accumulator for the Hot water demand for 4 bathrooms

28mm to 22mm won't do anything as what you have mains side is what you get and we have to put up with that.

I would like to know what this plumber suggested like how much 28mm to install prior to the connection and so on

A megaflo does the same as an "accumulator" and if a ballanced cold supply there is no need for 28mm 22 will be perfect. (providing you have required pressure/flow rate)

Eco

 

[turnpin]

as per manufacturers instructions? 🙂 regards turnpin

 

[justlead1]

Hi. The frictional resistance that causes pressure drop on gas pipe work is fundamental knowledge when practicing gas fitting, as the consequence of getting it wrong are dangerous. However the same applies with water if system performance are the goal. As a thought why do we not run a 10 metre length of say 4 mm pipe to feed a 1/2" HP ball valve. If you see my point.

 

[Toddyplumb]

Have done just that in 10mm on mains pressure and works a treat.

 

[Dannypipe]

Yes meant 1, but must have hit 2.

You're kind of missing the point of what I was saying though.

Oh and I'm sure we all see installations where there is more than 1Mbar drop, but the boiler is functioning perfectly.

 

[Toddyplumb]

I was pulled on a gas safe inspection pressure drop was 1.2 or 3 difficult to tell really it was that marginal but ended up putting in an extra length of 28mm on calculated figures and fittings should have just been in🙄
I knew what you meant and I agree entirely

 

[justlead1]

So have i toddy, but like me i bet, never measured it against 15 mm. Cost and time are always in the equation. The bigger the pipe diameter the greater flow at point of use.

 

[Dannypipe]

I was pulled on a gas safe inspection pressure drop was 1.2 or 3 difficult to tell really it was that marginal but ended up putting in an extra length of 28mm on calculated figures and fittings should have just been in🙄
I knew what you meant and I agree entirely

Right, which is the point I was making. There are a lot of installers who assume that 22mm all the way to the boiler is ok.

When what should actually should occur is a pipesizing calculation.

But that's an ideal world, and it often doesn't happen, and frankly a lot of the time it's all ok.

Combustion anyalisers can prove just such a fact.

I do it properly, by the book. But what I'm saying is when people say, 22mm to a combi always...alarm bells should ring.

 

[justlead1]

Danny I wish i had not. But i was making the point, pipe sizing is equally as important when carrying out plumbing as it is with gas. Like a lot of us. I have been called out by people who have parted with large amounts of money having plumbing installation carried out. Only to find the system does not deliver that what was expected.

 

[Zammo1001]

A megaflo does the same as an "accumulator" and if a ballanced cold supply there is no need for 28mm 22 will be perfect. (providing you have required pressure/flow rate)

Eco

Eco

I wasn't saying 28mm is needed i am saying 22mm is fine the way i was puting it was 28mm will do nothing more for you than the 22mm will already do

 

[ecowarm]

Hi,
I recently purchased a Megaflow HE Indirect Unvented Cylinder CL210L to install in a property with 4 bathrooms.
While installing the cylinder i was advised by another plumber that due to the demand on the flow of the hot water that i should supply the cylinder with a 28mm cold supply and keep the hot water supply as the 22mm.
I would like to ask wether this is a good idea or that, by having a 22mm outlet that it wouldn't matter as the flow rate would still be the same?
Thanks

All this gas talk is abit off topic?/??////?