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Hi Gents.

Looking for a bit if advice regarding low loss headers.
I have fitted a few with my old employer where he would get them made up custom.

However im now out on my iwn and want one made up however im unsure of whats best practice for the primary circuit connectioms on the header itself.

He used to have the flow at the top and the return at the bottom on one side of the header with all the secondary flows and returns on the other side

Os it better to have the primaries like that or have them centred between the secondsry flow and secondary returns?

Ibe added a god awful drawing for a example. One example is in blue the ither in red.

Also an e gineer has recently told me that hes heard multiple outlet headers have problems but cant rwmember what and i cant remember any issues. Anyone shed any light on this?
 
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You need the site specific information to design / calculate a low loss header to ensure that the velocity is sufficiently reduced. If you don’t want to do this (on a simple system), the boiler manufacturer can generally give a good indication of the size of header required.

I suspect that your former employer knew a lot more that he was letting on, if he was designing multiple outlet low loss headers and having them custom made ( presumably in copper).

For most domestic applications a quadruple orifice, two inlets and two outlets, is satisfactory - but it needs to be correctly sized.
 
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It is an iterative process - three main criteria, size it so that the pressure loss is as small as possible, without the header being enormous;
delta T needs to be considered to ensure that the entry T for the secondary circuits is sufficiently high; generally flows are at the top and returns at the bottom. Personally, I prefer vertical low loss headers to incorporate sludge collection - but horizontal are often easier to configure.

To properly determine the requirements you need the full system outline design with proposed flow rates, emitter size and the capacity of the intended boiler(s).

If you are doing this for the first time engage the help of the boiler manufacturer - as a minimum they will be able to give you the sizing range of suitable headers. If the header is more than a four port design, engage someone to design it for you - there is a real risk of getting low flow temperatures into some of the circuits when you have multiple flows.
 

king of pipes

Esteemed
Plumber
Gas Engineer
Made 100 's in my time usually from low carbon steel pipe with either screwed sockets or short threaded Stubb's of pipe ready to accept a valve or fitting usual set up would be like this below size would normally be 50mm -65 mm diameter minimum for a domestic job right up to 8" was the biggest, length was often determined by the amount of circuits taken off it allow at least a 100 mm between connections and never opposite each other, your other option is to go stainless steel an get it made it's alot lighter to work with . Cheers kop
 

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Thank you for your replies guys its very helpful.

If i could ask some questions based on your feedback.
Its my first time designing one sonwant to understand tbe process as much as possible.

In layman terms what is the delta t. Is this basically when ypir calculating the size kfna rad for a room? Ive had a quick google but not aure if im understanding that right.

Ive read a lot aboit the flow rates but im unsure of how you actually calculate this?

In terms of problems with reduced flow with multiple outlets this is what im worried about in terms of design of the header.

I am going to attach a photo of a header i did with previous boss few years back. You will see the primary flow and return, im.wondering if thats the best place for them or how ibe marked them in marmer so they re morw central to thw flows and returns.

Any other feedback on whats right or wrong about it is welcome also.

20191126_201430.jpg
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What i am proposing is similar but with different specced pumps with a 50kw Keston boiler.

4 zones. Ones UFH then 3 floors of heating seperated.

(Hot waters done on system on other side of house)

Also is it better pracrice to put check valves on all the returns on the secondary circuits to prevent heating creep?
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer

Let me know if you need any more info got a llh calc somewhere
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Thank you
Someone else posted this linknearlier and im nkt sure if im juse dense but i understood lart of it but not others.

For example the 3 possible scenarios, for ecample when the distribution flow is less than boiler flow so you get mixing, i take it that means the returns cooling the flow via the header?
How do you prwvwnt that from happening
Too much flow eg too much kw for the load

Easy way to look at it 40 kw boiler 20kw load so you will require more flow to get rid of the heat or down rate/ size the boiler for the load pipework
 
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Thank you
Someone else posted this linknearlier and im nkt sure if im juse dense but i understood lart of it but not others.

For example the 3 possible scenarios, for ecample when the distribution flow is less than boiler flow so you get mixing, i take it that means the returns cooling the flow via the header?
How do you prwvwnt that from happening
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Sorry that last one was horrendous for typos. Too keen to get what i want to say out there!
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Let me know if you need any more info got a llh calc somewhere
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Too much flow eg too much kw for the load

Easy way to look at it 40 kw boiler 20kw load so you will require more flow to get rid of the heat or down rate/ size the boiler for the load pipework
Ahh i see

Well how do you calculate that then?
I dont understand how the flow rates of each circuit are worked out
 
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ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Flow rate (l/s) = KW / (SHC * DT)

SHC is the specific heat capacity of the fluid in the pipe.

For example the flow rate of 60kw Heating system with a delta t of 20degress is

60 / (4.2 * 20)

= 0.71 l/s

now

You can calculate heat output of a pipe

15mm copper holds 0.00014m3 so 0.14litres

Heating is designed around 1.5m/s velocity

Using the above formula 15mm pipe can take

1.5 * 0.14 * 4.2 * 20 = 17.6kw
 
Very impressive photograph. If you know the person who specified that header (and assuming that the system performed) - go and have a chat with them, you will learn a lot more in a face to face dialogue than you will from an internet forum.

The sort of header that you have posted, we would buy in at around £300 if fabricated in 76mm or £450 if fabricated in 108mm - so you need to get the design right.

Delta T ( in respect to low loss headers) is difference between secondary flow and secondary return temperatures. The risk with multiple outlet headers is getting a too low a flow temp on a circuit that is not designated for UFH.

Out of curiosity where is the bottom right (lowest) return on the header coming from?

With respect to your question reference the three conditions of header behaviour; equal to boiler flow, less than or more than - you cannot control them, you design to header to match as closely as possible to the expected boiler flow.
 
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ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Very impressive photograph. If you know the person who specified that header (and assuming that the system performed) - go and have a chat with them, you will learn a lot more in a face to face dialogue than you will from an internet forum.

The sort of header that you have posted, we would buy in at around £300 if fabricated in 76mm or £450 if fabricated in 108mm - so you need to get the design right.

Delta T ( that is the issue in low loss headers) is difference between secondary flow and return temperatures. The risk with multiple outlet headers is getting a too low a flow temp on a circuit that is not UFH.

Out of curiosity where is the bottom right (lowest) return on the header coming from?
expansion vessel normally or drain off (or both)
 
Very impressive photograph. If you know the person who specified that header (and assuming that the system performed) - go and have a chat with them, you will learn a lot more in a face to face dialogue than you will from an internet forum.

The sort of header that you have posted, we would buy in at around £300 if fabricated in 76mm or £450 if fabricated in 108mm - so you need to get the design right.

Delta T ( that is the issue in low loss headers) is difference between secondary flow and return temperatures. The risk with multiple outlet headers is getting a too low a flow temp on a circuit that is not UFH.

Out of curiosity where is the bottom right (lowest) return on the header coming from?
[/QUOTE/

Thats my old boss. I installed it but like i said ive never designed one.
However i used to have to explain a lot of things to him so unsure if hes wotked this out or hes had it done for him previously so uses the same template everytime.

However that one is almost identical to the one ive drawn up but every zone would be 28mm aoart from bottom zone which would be 22mm for UFH.
And in 76mm.
(Was going to use VA Heating)

The bottom one is for feed and expanssion. Via expanssion vessel and robokit
Flow rate (l/s) = KW / (SHC * DT)

SHC is the specific heat capacity of the fluid in the pipe.

For example the flow rate of 60kw Heating system with a delta t of 20degress is

60 / (4.2 * 20)

= 0.71 l/s

now

You can calculate heat output of a pipe

15mm copper holds 0.00014m3 so 0.14litres

Heating is designed around 1.5m/s velocity

Using the above formula 15mm pipe can take

1.5 * 0.14 * 4.2 * 20 = 17.6kw

Im going to have to have a ltactice at these calculations when ive got pen and paper to hand.
What are the asteriks representing im the bottom one?
 
Drain off valve is integral and at the bottom of the header. If the lower right hand tapping is to a secondary expansion vessel - why is it at floor level next to the washing machine??
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Im going to have to have a ltactice at these calculations when ive got pen and paper to hand.
What are the asteriks representing im the bottom one?
Times eg x so

1.5 x 0.14 x 4.2 x 20 = 17.6kw
 
Drain off valve is integral and at the bottom of the header. If the lower right hand tapping is to a secondary expansion vessel - why is it at floor level next to the washing machine??
Im not sure i understand your question? Is there an issue with it being there? Unless im missing something obvious
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Drain off valve is integral and at the bottom of the header. If the lower right hand tapping is to a secondary expansion vessel - why is it at floor level next to the washing machine??
Elbowing back to under the boiler at floor level maybe due to size and weight eg not wall mountable etc
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Im not sure i understand your question? Is there an issue with it being there? Unless im missing something obvious
No there isn’t
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Ahh yeah that so

Yes it was a big one i thinl from memory maybe 40 or 50 ltr floor standing one
Just incase you don’t know how to work expansion size out

Either 1l per kw or 1l per rad will get you close enough (over sized)
 
Times eg x so

1.5 x 0.14 x 4.2 x 20 = 17.6kw
Ahh that seems extremely obvious now you ve pointed it out.

So if my circuits are 28mm would o substitute 28mm figures in tjat calculation for x 3 zones

Then the same for 22mm x 1 zone and then add them together for the figure of the kw of the load?
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Just incase you don’t know how to work expansion size out

Either 1l per kw or 1l per rad will get you close enough (over sized)
Well ive sort of done that ive done 50 ltr vessel for the 50 kw boiler. However they are adding a couple of rads so you reckon upsizing it is wise or overkill?
 

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