3 bathrooms for flow 9L/m, 3bar pressure - possible solution

[muggles]

Don't buy a combi

Don't buy a combi

Don't buy a combi

How old is your "old" boiler/what model is it? Old Ideals tend to be very good and worth hanging on to. You might well be better off keeping it and attaching it to your new cylinder

Don't buy a combi

 

[DP]

Muggles, combi plus unvented is good combination ( sorry did not mean to use combi 😆 word). Have done it a few times. Constant flow rate where it does not matter regards delivery (in kitchen and utility), ss heat exchanger and greater selection of boilers. UV then supplies HW to bathrooms where going flow rate is necessary

 

[Agile]

Its odd that you start by asking advice here.

Then rush into having your supply pipe replaced with 25 mm without taking our advice.

Nor do you seem to have understood the implication of the dynamic flow rate which is very important when planning systems.

Now most people choose an installer and discuss the possible solutions with him.

However, you probably think that you know better them them about plumbing and heating. Such as why a 25 mm water pipe is better than a 32 mm when you have a fetish for running four showers all at the same time!

Tony

 

[acideraser]

The advice here was to replace supply pipe and text performance after it's done hence I am replacing the pipe... and I asked here about dynamic flow but have not seen anyone rushing to explain ...

25mm pipe is because TW has 25mm mdpe from communication pipe to my stopcock. Plumber also said 25mm will be enough but I have to decide which boiler system I want, hence trying to gather as much info an advice as possible here...

 

[acideraser]

muggles, my boiler is Ideal FF340 or FF360. I don't know how old as it wa there when we moved in. It's quite noisy and I somehow have a feeling it won't last much longer, however must say it's been very good and reliable so far.

I want to get rid of water tank in loft and want to run system on mains pressure especially since I am replacing the supply pipe.

 

[Agile]

The extra cost of 32 mm pipe is perhaps just £5 or so.

The FAQ on this site explain what dynamic flow is.

You do seem to have taken some very incorrect advice! He seems to have thought that you were going to use a combi which can hardly run two showers not four. He also thinks the inlet size of a combi has a bearing on the supply pipe sizing. I dont think that he is very clever! Anyone else knows that a larger pipe size has no drawbacks at all apart from the very small slightly higher purchase cost.

We strongly advise an unvented cylinder!

Running four showers together could easily use 40 litres per minute. In that case a 25 mm pipe will start to show up the smaller diameter ( depending on the length involved ).

Tony

 

[Agile]

We strongly advise an unvented cylinder!

For four people 250 litres is adequate but 300 litres would be better as the cost is little more and it gives a bit extra stored hot water in case of extra demand from visitors etc.

Tony

 

[acideraser]

Tony thanks very much for taking your time again to respond and give me advice.
Even if I put in 32mm pipe from street valve to the house, the Thames water piece of pipe from communication pipe to street valve is 25mm so flow will be limited by that piece anyway?

Not going to use 4 showers at the same time - 2 is maximum and on rare occasion, more likely shower and a kitchen tap or dishwasher /washing machine taking cold water.

I understand unvented is the way to go if I want constant flow. Should I go for Megaflo cylinder or can be just the same make as a boiler - vaillant or veissmann in particular? Sorry if this has been answered already

 

[Dan Robinson]

Megaflow is overpriced tat IMHO.

So is Vaillant, BUT the advantage of using all Vaillant or all Viessmann is the ability to purchase a complete package which makes it all work a smidgen better and combine the warranty.

However, some of us prefer to choose to spend customer's money on the best combination of products and get the most out of both your wallet and the system.


Does involve a little more thought on the part of the installer, but do you want a box slinger, or someone who cares?

 

[Agile]

Even if I put in 32mm pipe from street valve to the house, the Thames water piece of pipe from communication pipe to street valve is 25mm so flow will be limited by that piece anyway?

That is a common misunderstanding! Seems a misunderstanding shared by your plumber!

Water cannot be compressed so when a constant flow is through a small pipe it has to go faster! When through a large pipe the same flow goes slower.

The size of pipe determines the resistance to flow.

So even with a short 25 mm section at the meter its still helpful to use the larger size of 32 mm for the rest of the supply pipe.

That lowers the total resistance and enables a higher flow rate.

Tony

 

[Agile]

Megaflo is just one brand of unvented cylinder and about the most expensive.

Their second brand name Santon is rather cheaper and one of my preferred makes.

Sometimes with more complex controls, it helps to have the same brand of cylinder as boiler although that is usually a quite costly solution.

Tony

 

[Agile]

Megaflo is just one brand of unvented cylinder and about the most expensive.

Their second brand name Santon is rather cheaper and one of my preferred makes.

Sometimes with more complex controls, it helps to have the same brand of cylinder as boiler although that is usually a quite costly solution.

Tony

 

[acideraser]

thanks again Tony. Will see with them if they can put in 32mm pipe...
Seems there is smoe sort of promotion on megaflo with 150 cashback from the manufacturer so making things a little easier.
If i got it right megaflo has built in expansion system so no need for expansion vessel. maybe there are other benefits but i have not found them yet.

Looked at Santon
https://www.plumbnation.co.uk/site/santon-premierplus-solar-indirect-unvented-hot-water-cylinders/

seems not bad, solar power option and 30 years warranty...

 

[Dan Robinson]

It is a floating baffle and a shyte idea.

 

[acideraser]

Thanks you all for your input guys, I am not getting combi .
Wouldn't even dare after all those posts

I set my mind on either Vailant 624 and Unistor cylinder or Veissmann 100W and Veissmann cylinder, but latter combination seems more expensive and from what I read here Vitodens 200 may be better option but way more expensive, also the fact that Veissmann parts may be expensive here pushes me towards Vaiilant.

I am going to have 3 different zones with underfloor heating and living room with rad downstairs, plus at least one zone upstairs for bedrooms. I understand each zone has to be controlled by a different room thermostat.
Would I get any benefit from Vaiilant weather compensation control with those multiple zones of UFH/rads or shoudl just stick to room thermostats?

Is there any specific control I should consider to benefit from same make cylinder / boiler?

Thanks again for you input!

cheers