Central heating layout

[kmac]

Hi all,
I've just moved into a 1930's semi with no central heating, just storage heaters and an old immersion heater, so i'm planning on ripping it all out and putting in a new Combi system - the only thing is i've only ever fixed/added onto systems before not run from scratch.
(Obviously getting someone fully qualified to handle the actual boiler work(!) but there's so much work that needs doing that i need to cut some costs somewhere...!)

i've drawn a layout - does this look correct or have i made too many mistakes to know where to start??
I must admit i wasn't sure on the return, if it need to come back the first rad, rather than the hall rad?

Do the main rings need to be all in 22mm with just the tees off being in 15mm?

The dining section at the back hasn't been built yet, and the builder has costed for a screeded floor - can the Hep2o barrier pipe be laid into that? What about the joints or do i need another solution altogether?

Sorry, rookie questions here i know!

Any help massively appreciated!!



Cheers,
Kev

central-heating-layout

• kmac
• 29 Jan 2014
• 1

possible errors

 

[Whitespirit66]

Couple of small alterations I would make to save pipe runs -

GROUND FLOOR - Run the return pipe from boiler in same direction as flow pipe as it leaves boiler, ie. taking them both to the rad on top right first. They will both terminate at rad on bottom of diagram. Just saves having a seperate route for retun pipe.

TOP FLOOR - Where your F and R pipes emerge middle left from downstairs, needs to tee here - take 2 pipes upwards for the rad at the top. Then 2 pipes downwards as you have to the 2 rads at bottom. Saves having the long run through house from 2 bottom rads to rad at top.

Maybe you have routed your pipes that way for a reason, and what you have planned will work. My two amendments will save some work and unnessary pipe runs if it can be done this way.

 

[ALEC1]

although reverse return which is what this is saves on balancing...

 

[Norcon]

Its all wrong.
Run 22mm straight to upstairs over to the right hand wall as the crow would fly.
Then just T off with 15mm runs.

Never split f&r on separate runs. Always keep them paired and compact.

 

[ALEC1]

nothing wrong with reverse returns... saves on balancing and is an accepted way to install heating systems...

whats wrong with them nor con?

 

[Norcon]

How do you zone that abortion between upstairs and downstairs?

About a dozen extra bends and a lot more pipe needed also.
And nearly double the amount of floor chanelling!

 

[ALEC1]

good point reverse returns make zoning difficult!

 

[thompo]

You can lay plastic in the screed or subfloor, using a "pipe in pipe" system so if it ever failed you can (in theory!) pull the pipe out and replace it without disturbing the floor.
Given the roll lengths and flexibility of plastic you can avoid any joins below the surface, which i think is a requirement for building control anyway.

If your fitting a whole new system would it be worth considering wet UFH for the bathroom? Im sure it would be more economical to run than electric?

 

[D_Hailsham]

although reverse return which is what this is saves on balancing...

But it's not a reverse return. To be a RR. the return to the boiler has to be connected to the furthest radiator, which is the one at the top of the upstairs.
As in this pic.

Untitled

• D_Hailsham
• 30 Jan 2014
• 1

 

[ALEC1]

agreed, the floor on the left is, but the floor on the right is not.... my bad!,

 

[kmac]

Abortion, ouch!


Thanks for your replies all; i've only been in flats before so i wasn't sure how to join the upstairs successfully...
The boiler is to go under the stairs but there's a 90 degree bend in them so i don't think i can go directly up from it, but if i can i'll tee of there instead.
The old immersion heater and cold water tank are directly above where the planned system jumps floors so i was planning on using the old boxing around those pipes.

Does this new system make sense - does the whole downstairs ring need to be 22?

Would it make more sense it flowed the other way round to avoid the extra pipework that ive put in to go around the concrete floor in the downstairs bathroom?

@Thompo - thnks for the screed advise - what about the joins that are in there?
Re the UFH -it's a very small bathroom - prob only need 1.5m electric mat in each (some of the downstairs 'bathroom' is to be partioned off into a tiny utility room)

Thanks again all.

Central Heating v2

• kmac
• 30 Jan 2014
• 1

 

[D_Hailsham]

Does this new system make sense

Yes

does the whole downstairs ring need to be 22

Probably not. Do you know the kW output of each rad and which boiler will be installed? If so, can you provide this info?

Would it make more sense it flowed the other way round to avoid the extra pipework that ive put in to go around the concrete floor in the downstairs bathroom?

Yes.

 

[kmac]

Thanks @D_Hailsham;

If i run it the other way round so it's going clockwise should i run the flow into the left hand side of the rad so that it still flows in a straight circle; or wouldn't it matter if it still flowed into the right?

i'm planning on putting a Worcester 28 or 30cdi in, the rads need to be the following wattages if this helps:

Hall: 850kw
Front rm: 1400
Rear rad: 1300
Rear rad: 1300

Front bed: 800
Front bed2: 500
Back bed: 800

Cheers,
Kev

 

[newbuildinstaller]

Another thread with people over thinking simple systems!! it doesnt get any easier than a combi...

down stairs on a zone, 22mm flow and returns to the middle ish and 10mm from a manifold.

upstairs on a zone 22mm flow and returns to the middle ish and 10mm from a manifold

easy!! and cheap!! and quick!!

 

[D_Hailsham]

If i run it the other way round so it's going clockwise should i run the flow into the left hand side of the rad so that it still flows in a straight circle; or wouldn't it matter if it still flowed into the right?

Doesn't matter.

It's preferable for the TRV/wheel valve to be on the flow and the lockshield is on the return.

the rads need to be the following wattages ....

That adds up to 6950 Watts. Have you compared it to the recommended boiler size using Whole House Boiler Size Calculator?

I know you will be having a combi boiler, so you need to set the Hot water allowance to 0. The calculator will then tell you how much heating you need. Compare this to the 6950 Watts for the rads.

i'm planning on putting a Worcester 28 or 30cdi in,

Both are combi boilers and have minimum CH output of about 7kW. This means that the boilers will be running in on/off mode all the time. It would be better to choose a boiler which can modulate lower.

Have you measured the incoming cold water flow rate?

AS for pipe sizes, boilers are now designed to work with a 20C temperature difference between flow and return. (Previously it was 10C/11C.) This has two effects:

1. water flows slower through the pipes, so there is less friction, meaning pipes can be smaller.

2. Radiators give of less heat, (Catalogues assume a 10C differential), so you need to install rad which are 20% larger.

Assuming a 20C differential, 15mm pipe can be used for the main pipe work and 6mm or 8mm for the connections to each rad.