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.

 

[pappasmurf]

WHPES As i have said before the plumbers i have called in are real numptys!... and so i have to gain the knowledge and have some sort of idea where to go with this install. it seems all the good and "Knowlegable" plumbers are up north!...lol

 

[pappasmurf]

vern i had always said i would go for the Megaflo 300l cylinder but gray0689 has suggested the ACV cylinder (tank in tank system) with unbelievable reheat times (not sure wot the after sale support will be like?), so am seriously considering this cylinder aswell.
Thanks for the "only use copper" pipe tip as apposed to plastic.

Am i right to believe that the secondary return that you and others have mentioned is there to eliminate cold water stagnent in the pipework when DHW is not being used for a while, and this cold water should be removed periodacally through the day to prime the DHW system with "instant" DHW at the outlets when the outlets (taps/showers) are used? and is 15mm copper pipework sufficient for this purpose?

Had a look at the megaflo commercial!... too much of a big beast to house in my installation!

you are right i have a standard gas meter (which will be moved to the outside of the house; currently under the stairs). There will be no gas fires but there will 2 Baumatic gas Hobs in addition to the 2 WB 24Ri boilers (Ovens will be electric). So hopefully the plumber will size the copper pipework up accordingly (22mm or 28mm)! so hopefully will not run into gas pressure inlet problems.

I have also looked at the WB low loss header(LLH) and seems like a "Toy" comapred to other headers i have seen on the internet!... i wanted to know how can you suggest using this LLH without working out the pipework sizes or flow/return calculations? I mean will this toy of a unit suffice for my domestic install (you mentioned "pumps Pipeworks, expansion vessel etc sized to suit site and system condition)?
In my underfloor heating there will be 3 manifolds (1 downstairs/1 upstairs/1 for the loft conversion) so will we have enough ports on this LLH to supply these demands?

 

[pappasmurf]

vern spoke to WB this afternoon and was sent a PDF of their recommended system install plan using their LLH. i have attached this PDF. On page 11 of this PDF it shows a full system diagram of how to hookup this LLH.
From what you described earlier about distribution to the underfloor heating manifolds on the secondary flow and return; as i mentioned earlier i have 3 heating manifolds and all the ports on the LLH on the secondary side would be used on the 2 branches for the first 2 manifolds (ground floor and first floor), so how would i connect the 3rd (last) manifold (the loft rooms) using this WB low loss header?
Also since each underfloor heating manifold has a circulating heat pump on its own corresponding manifold can i omit the heating pump in this WB plan just before their Radiators are, i.e where the corresponding new underfloor heating manifolds will be situated? oh no just realised you can't attach the PDF as it is too big a file i hope you know what i mean though

 

[Howsie]

Post up on the plumber wanted section. This isn't a complicated set up at all.

 

[vern]

vern spoke to WB this afternoon and was sent a PDF of their recommended system install plan using their LLH. i have attached this PDF. On page 11 of this PDF it shows a full system diagram of how to hookup this LLH.
From what you described earlier about distribution to the underfloor heating manifolds on the secondary flow and return; as i mentioned earlier i have 3 heating manifolds and all the ports on the LLH on the secondary side would be used on the 2 branches for the first 2 manifolds (ground floor and first floor), so how would i connect the 3rd (last) manifold (the loft rooms) using this WB low loss header?
Also since each underfloor heating manifold has a circulating heat pump on its own corresponding manifold can i omit the heating pump in this WB plan just before their Radiators are, i.e where the corresponding new underfloor heating manifolds will be situated? oh no just realised you can't attach the PDF as it is too big a file i hope you know what i mean though

I will keep it brief as you really need someone on site!

Option 1.......If you use WB LLH you can common the upstairs and loft F&R's just run the circs to the upstairs UFH manifold and tee off to the loft UFH manifold, 28mm should do it, BUT i dont know the load or length of runs.
No you need a pump from the secondary's to the UFH manifolds the manifold pumps only circ through UFH pipe and mixing valve due to resistance, you also need a pump for each boiler on the primary's making 5 pumps (1 for each boiler =2,.......1 for each manifold=2 as up and loft are common'ed up..... 1 x DHW coil on megaflo........ + 1 bronze for DHW secondary re circs making 9 as you have 3 already on the UFH manifolds built in!!!

Option 2.......Use a broag LLH header which has 2 x 1" primary's for 2 boilers and 1 x "2" secondary's come off in 54mm or 42mm copper with reducing tees as needed for 3 x UFH manifolds and 1 dhw ..Totals pumps 10 as above + 1 pump for loft maifold as it would be not common'ed up to upstairs!

Option 3 ......Junk the 24 Ri ,bash in a 40 CDi (actually 41KW) no LLH Commercial spec grunfos pump for primary's say 42mm copper so 11/2" flanged, 4 zone valves (DHW,1 for each UFH Manifold) with autobypass honeywell DU146........5 pumps = 1 x main 1 x bronze secondary 3 already fitted on UFH manifolds, ensure megflo has a balancing valve fiited on return from coil, to obtain 20 deg diff, as 1/1/2" pump will send it through the coil too quickly on DHW mode only, Autobypass will sort the rest, and UFH manfiolds will look after themselves due to mixing valve etc...........
Aww Cr@p book me a hotel!!!!

 

[Gray0689]

You don't always need a LLH
For your set up I'd be looking at weather compensation unit controlling mixing valve and 1 large pump a grundfos magna modulating pump

Disregard the oil boilers
But similar to what you want 3 floors all underfloor with a few rads in a circuit and towel rails in a circuit
And a 500ltr buffer tank

 

[pappasmurf]

vern what have you been smokin!...lol...lol.... man looks like you've had your 3 weetabix today...lol...well done
i was gonna post on here just now that i think i have also sussed it out aswell; i went for the option 1 aswell, only i went one better in that i thought we could just tee off again from the second floor manifold to the loft manifold without using even the second pump or mzv. checked with wavin today and was advised that with the heating calculations that they had done we should only need 8.5Litres/min (Total) from the downstairs heating pump to supply "All" 3 manifolds and that a standard grundfos pump should be fine. i don't need another motorized zone valve anywhere else on this heating circuit as the manifolds and controls will cater for these anyway
i can't ditch the 24Ri option as i have just bought this and a second back up boiler is really useful as my neighbours have found out; the hard way!!!....
I have redrawn the WB low loss header circuit to fit my spec and wouldn't mind sending it to you for approval if could have a look for me

 

[pappasmurf]

gray0689 these pictures look very commercial!...lol... your sending me at a different tangent now weather compensation unit/ grundfos magna modulating pump!... i was thinking of using the new grudfos alpha 2 which i think should be ok, pls advise

 

[vern]

Here a picture of a broag LLH (very compact black box) it is rated @ 80 - 120 KW, here it is with 2 x WB 30CDI system boilerswith vertical flues, feeding the heat, along side a 300L megaflo



Not our best....... but gives you a visual...... we only had 3 days as we had the nursing home shut down, and had to join on to what was there pipe and system wise, and they would not allow us to move the washer or dryer you see in the pics making it very tight!! in this time we had to move some rads fit a new remote repressurisation unit and strip out a packaged burner ACV combi and flue, which was where the Megaflow is now sat

 

[Dannypipe]

I always love pics of Gray's (Alex) work.

Just art. Always brilliant work.