pipe sizes for complete heating/DHW system

[pappasmurf]

Can someone pls help...... just bought a new house. After major works and extensions (Rear and Loft), (next year), will be an 8 bedroom, 4 shower room (no baths), 2 kitchens with full underfloor heating on all floors in the house.

The system will have 2 Worcester Bosch 24Ri (heat only boilers); 1 for the DHW, 1 for the Underfloor heating. No header tank.
I have already updated my mains supply from the street to 32mm poly pipe. The pressure is approx.3 bar and approx.20 lt/min.
There will be an indirect 300lt unvented megaflow cylinder feeding all the DHW (4 shower rooms,2 kitchens).

What i need to know is what size of pipework should i be feeding this circuit?.... i have always assumed that in plumbing, the bigger the better!... is this so?

I was thinking of supplying the cylinder with this 32mm MDPE pipe and then on the outlet from the cylinder feeding the house with 28mm MDPE and eventually reducing to all shower rooms/kitchens back down to 22mm and then further to 15mm. is this correct? as i am hoping to ensure good/reasonable flow rates to all services as possible espcially if more then 1 or 2 services are used at the same time.
will i also need an accumulator up in the loft conversion?.... if so what size pipework will i need for this aswell?

The underfloor heating in the entire property will be piped hot from heating manifolds using the "Wavin" brand.

 

[tamz]

I think you need to speak to a plumber (a good one) and either let them do the work or work alongside you.
You need a bit of a rethink on what you are planning.

 

[on31ll]

you will need a plumber with his unvented ticket to install the unvented cylinder. when you get a plumber round with a G3 qual he will talk you through it of how he would install it. hope this helps

 

[pappasmurf]

tamz i have spoken to 2 plumbers but these people are really thick!....they really don't know much about the science and design of a complete system!... they only know the basics!..... also can you please elaborate on what you mean about re-think on what i'm planning 🙁

 

[pappasmurf]

on31ll same reply to you aswell... pls read above 🙁.... the reason i am having 2 WB boilers is because i have just installed a new one of these boilers and so will only need one more.... hope this helps abit.

 

[Gray0689]

As said by tamz rethink what your planning and get a decent plumber in

 

[pappasmurf]

Gray0689... please please please will someone elaborate on this "rethink" what i'm planning sentence, before i call in a decent plumber!.... i thought i had listed "all" the requirements of what i think i need from a system?

 

[tamz]

tamz i have spoken to 2 plumbers but these people are really thick!....they really don't know much about the science and design of a complete system!... they only know the basics!..... also can you please elaborate on what you mean about re-think on what i'm planning 🙁

This is what the world has become unfortunately but there are still some good guys out there. You just need to sift out the dross. The job is slightly different to the norm but nothing difficult.

You should think about linking your boilers to run of a header. That way you also have a back up if one of them goes down.
You are correct in your 300 litre DHWC will be best with a 32 supply but the outlet needs sized to suit your load. Bigger is not always best, it is a waste of water, but it is much better than too small which is a waste of time. It only takes a few calculations to work out.
You should consider a secondary return (also needs sized correctly) MDPE is not used inside a house. If you prefer plastics use polypipe, hep, speedfit, unipipe or whatever you like.
Whether or not you would need an accumulator, only the man on the job can advise correctly on that.

If you put up your location there may be someone on here who would be willing to get involved. There are a few knowledgeable guys on here.
Good luck

 

[pappasmurf]

tamz thanks for your reply 🙂... if when i call these guys over how will i know if their talking rubbish?... is there any tell tale signs that i can pick out in the conversation that will expose them as cowboys?.... actually one guy did mention not going to 32mm on the cylinder output and that 28mm should more then suffice. but neither of them did any calculations, so i don't know how they derived this information?....infact absolutely no calculations were made or discussed in their visits!
i do however have calculations from the underfloor heating manfacturers (Wavin)... but they were not able to help with full "system" design 🙁
i even did a search on yell.com to find a heating engineering design firm, but all i was getting was bog standard plumbers 🙁... i am in the Hounslow/middlesex area. pls help 🙁

 

[snowhead]

With the size of property and number of rooms and outlets you will be having, you won't get a solution from the local 1 man plumber round the corner.
What you have is more like a small commercial setup.
You need someone with experience of DESIGNING and installing large systems.
Someone who's does hotels would be ideal, cause it sounds like that's what you have.

 

[pappasmurf]

snowhead my neighbour opposite has exactly the same house and setup up as what i have just described!... only thing is they don't have underfloor heating but radiators. i have included a couple of pictures of their setup in the loft. they also have 4 shower rooms and 2 kitchens and they have absolutely no problem! and as i said before i tried looking on the internet in yell.com for HEATING DESIGNING ENGINEERS and it just comes up with your bog standard plumbers!View attachment 8287

 

[Gray0689]

No one is going to give you a heating design unless you pay for it
The best way to go about your job is get recommendations from family friends ect
Your house sounds a simple enough lay out
The only problem you may have Is stored hot water 4 shower rooms it used at once is a lot of hot water
But a good sized cylinder with a fast recovery will sort that
Ps the pic of that cylinder don't use who ever put that in its not good
Hair felt lagging pitiful

 

[AWheating]

i agree with tamz and also agree there are some issues with the cylinder in the picture.

Any small/medium sized company should be able to design with drawings and provide design liability for your installation. Agree that if they get to install the installation then they can wave the design fee.

another alternative is to speak to boiler or cylinder manufacture about designs.

hopefully somebody on here is near you and can help.

 

[pappasmurf]

Gray0689 I don't mind paying someone to design a system but i don't know anyone (family or freinds) that are into plumbing/electrics/building works etc!.... and as i have said before i haven't felt comfortable with any of the plumbers i have spoken to 🙁
also as i have specified earlier the system will have a 300lt Megaflow cylinder. also what type of lagging would you recommend as appose to hair felt?
AWheating what exact issues are you refering to?.... can you recommend a company that will design this system?
i have also today spoken to Worcester Bosch as they also do the Low Loss Headers but wasn't able to ascertain much from the technical girl as to what setup i would need for my particular system. she just recommended one of their approaved installers for system designing/installation. I did tell her that one of the numptys i had round was from their list of "Approved" installers and that he didn't have a clue!... he actually suggested i draw/plan the system for him and he will do the monkey work!
as i have also mentioned i am in the hounslow/middlesex area..... pls someone help 🙁

 

[Gray0689]

Gray0689 I don't mind paying someone to design a system but i don't know anyone (family or freinds) that are into plumbing/electrics/building works etc!.... and as i have said before i haven't felt comfortable with any of the plumbers i have spoken to 🙁
also as i have specified earlier the system will have a 300lt Megaflow cylinder. also what type of lagging would you recommend as appose to hair felt?
AWheating what exact issues are you refering to?.... can you recommend a company that will design this system?
i have also today spoken to Worcester Bosch as they also do the Low Loss Headers but wasn't able to ascertain much from the technical girl as to what setup i would need for my particular system. she just recommended one of their approaved installers for system designing/installation. I did tell her that one of the numptys i had round was from their list of "Approved" installers and that he didn't have a clue!... he actually suggested i draw/plan the system for him and he will do the monkey work!
as i have also mentioned i am in the hounslow/middlesex area..... pls someone help 🙁

Armaflex lagging for a roof space
Why a megaflow?
I'd go with an acv cylinder far better and quicker re heat time
Do you have a set of drawings on PDF?

 

[pappasmurf]

i mentioned a megaflow cylinder because i was told they were "The" Rolls Royce of all cylinders!....both in terms of design/re heat times and after sales guarantee.
which set of drawings are you refering too?.... house planning application drawings?

 

[TBServices]

You need to find a plumber who you are confident can do the work, and give him the job. No one is going to invest the amount of time it will take to design your entire plumbing system on the off chance they'll get the job.


Sent from my iPad using Tapatalk HD

 

[pappasmurf]

i specefied a Megaflow because i thought they were "The" Rolls Royce in terms of design/build/re-heat times and after sales guarantee.
which set of drawings are you refering to?... i have full planning application drawings of the property done by my architect if thats what you mean?

 

[AWheating]

AWheating what exact issues are you refering to?.... can you recommend a company that will design this system?
i have also today spoken to Worcester Bosch as they also do the Low Loss Headers but wasn't able to ascertain much from the technical girl as to what setup i would need for my particular system. she just recommended one of their approaved installers for system designing/installation. I did tell her that one of the numptys i had round was from their list of "Approved" installers and that he didn't have a clue!... he actually suggested i draw/plan the system for him and he will do the monkey work!
as i have also mentioned i am in the hounslow/middlesex area..... pls someone help 🙁

the lagging is inadequate, it should be min 19mm armaflex, the base it sits on looks poorly designed/constructed for the weight, the expansion vessel looks unsupported, its hard to tell but it looks like the pressure relief may be remote from the cylinder and if so theres a lever valve between it and the vessel. Would also hope theres a 2 port valve somewhere.

i dont know any local to you, a quick google search found Plumbing Central Heating Designers and Building Services by MK.Mechanical Services Ltd, Midlands, Uk

 

[pappasmurf]

AWheating your suggestion on my neighbours installation is much appreciated. but lets come back to my spec 🙁
That link you've sent is a company based in Leicester!.... surely there must be a company in London (The centre of the universe)?
Gray0689 had a look at the ACV cylinder that you were refering to.... wow wot a product, well impressed 🙂. the 600L model should also sort out the 4 shower/2 kitchen usage (at the same time) problem that you mentioned earlier 🙂

 

[Gray0689]

If your in London there is a couple of boys on this site who could possibly help you out
But you do relies you will have to have a large budget
Ps you will also need a secondary return on hot water

 

[AWheating]

AWheating your suggestion on my neighbours installation is much appreciated. but lets come back to my spec 🙁
That link you've sent is a company based in Leicester!.... surely there must be a company in London (The centre of the universe)?

was it not you who asked about the issues with the pictured install? so why sad face?

as regards the company i linked they dont need to visit your house (although probably best) to do you a design if you have full set of building layouts they can use them to create the design. If you want to find one in london use google as i did to find the link i gave, try abit harder! as its the cenre of the universe there should be loads or phone british gas.

 

[WHPES]

Look for plumbers who have been established ages and have a good reputation locally.

 

[vern]

I love jobs like this done a fair few, but your too far!

If you go for the 300 l megaflo, get the titanium option kit, it basically another 3 kw immersion heater and stat, that goes in the standard cylinders blank, it will come with 1 x 3 kw immersion as standard, meaning you have hot water back up if a pump or boiler goes down, an electrician can wire via 2x2.5 mm cables back to your consumer unit depending on length of run etc...

As others have said use the secondary return tapping, pipe in 15 mm Do not use any plastic if you intend to run the loop 24 hrs a day or it will leak within 2 years, use copper, if the loop is timed you can use plastic, but do a proper job and use copper.

28 mm cold feed off 32 mm PE should be fine, as the PRV and outlets are only 22mm compression anyhow, BUT if you have a lot of occupants or intend to use multiple showers or outlets go for the megaflo commercial it has a 6 bar PRV as standard and much bigger inlets and outlets, I need to visit site to spec accurately!

i will post up how to do the boilers in a bit.

 

[vern]

Regards boilers.....
i assume you have a domestic gas meter a U6' which can pass 6 m3 per hour, 2 x 24 RI's on full chat will use around 5.2 m3 per hour depending on return temps, if you have a range cooker and gas fires this needs to be taken into consideration as you may run into gas pressure inlet problems (a good installer will know this)

Connect 2 x 24RI's via the Bosch low loss header, it has 2 inlets sets for 2 boilers, and 3 x outlet flow and returns, use one set of outlets for the hot water cylinder, 2nd for the UF heating manifolds downstairs, 3rd for UF heating manifolds upstairs.
do not Connect the boilers separately as you have no back up of a tandem system, also do not tandem them up in reverse return as you loose the efficiency and balance of a low loss header!

Pumps, pipework, expansion vessel etc etc sized to suit site and system conditions.