low loss headers.

[sam51]

hi guys I hope someone could put me in the right direction
doing a job at the moment a monster house, the guy will have 2 viessman 19kw system boilers, 2 250ltr unvented cylinders,
I've sized the heating load, hot water, and heat loss through pipes.
it comes to 35kw. I need to put a low loss header in, had a look at the Worcester one which has 2 boiler flows in and 2 boiler returns,
and 3 flow outlets and 3 system returns, your views on this llh,
I am unsure as to the extra pumps, that may be required. as the boiler pumps will not be adequate,
the system is this, ground floor, underfloor heating, 12kw,
1st floor 11kw,rads
2nd floor 2kw, rads.
hot water 4kw.
heat loss 4kw.
thanks guys sam.

 

[tommyad123]

4kw for 500ltr of hot water?

 

[Chalked]

The coil on a 250 can be up to 24kw

 

[tommyad123]

Like caulked said check the coil rating on the unvented cylinder

 

[sam51]

the cylinder coils are 18kw, each cylinder, have there own 22mm flow and returns from the boiler room.
so with the LLH, I can in crease boilers to suit. thanks sam.

 

[missplumb]

every circuit from the low loss header will need its own pump and be sized correctly for flowrate( or fit a commissioning set on the return).

How much was the Worcester LLH, you can have one made up, in copper to your own pipesizes and specifications by these people Headers

They are very good and are reasonable pricewise.

 

[Nostrum]

The coil on a 250 can be up to 24kw

I wouldn't add 48kw to the heat calc's just to satisfy the coils though.. would you?

I don't add anything extra for cylinders these days, just suitably timed so that the cylinder can be up to temp before the heating is required.

 

[AssuredHeating]

Can't you just put a 40kw system boiler in with an extra expansion vessel if required?

 

[Chalked]

I wouldn't add 48kw to the heat calc's just to satisfy the coils though.. would you?

I don't add anything extra for cylinders these days, just suitably timed so that the cylinder can be up to temp before the heating is required.

On this system I would add 18kw. If they have a few guests you need the recovery. If you use the vaillant controller tho it diverts all heat to got water when needed.

 

[Worcester]

I wouldn't add 48kw to the heat calc's just to satisfy the coils though.. would you?

I don't add anything extra for cylinders these days, just suitably timed so that the cylinder can be up to temp before the heating is required.

The CIBSE guide has you add 200W per person, person = nr bedrooms +1 so for a 6 bed house you add (6+1)*200 = 1400W to the heat load.

 

[Worcester]

How to size a Low Loss header?

See here for the calcs: http://www.cibsejournal.com/archive/PDFs/CIBSE-Journal-2014-02.pdf pages 58-60

Or use the CIBSE DHDG Section 13.8 and Tables 13.1a and 13.1b

Net result for a heat load of 35kW and a ΔT of 10°C you'll need a LL header of ID 46mm. i.e.54mm copper pipe.

 

[stevetheplumber]

get it welded up on a bit of 150 box steel

 

[Nostrum]

The CIBSE guide has you add 200W per person, person = nr bedrooms +1 so for a 6 bed house you add (6+1)*200 = 1400W to the heat load.

Which equates to a waste of time!