Reverse Return CH Piping

[chris watkins]

who did those drawings out of interest chris?

Me if they are good, Me mate is not.

 

[cr0ft]

Thanks all. From some initial reading on low loss headers the diameter should be 3x the primary diameter. Is this accurate? I would be running 2x 35kw system boilers into 35mm primary pipework. I will reverse return connect the boilers to the primaries.

1x 300L unvented cylinder for hot water. Will be a 3 zone heating system.

Exact heating load for the property has been calculated at 63KW.

Happy with the plans on how to run these, this all makes sense. I'm happy with the pipe sizing stuff but how do I design my low loss header for the system?

The meter is a U16 meter and the gas pipe run is very short, around 4m.

This is new to me and I like a challenge and want to get it right!!

 

[tolly]

Thanks all. From some initial reading on low loss headers the diameter should be 3x the primary diameter. Is this accurate? I would be running 2x 35kw system boilers into 35mm primary pipework. I will reverse return connect the boilers to the primaries.

1x 300L unvented cylinder for hot water. Will be a 3 zone heating system.

Exact heating load for the property has been calculated at 63KW.

Happy with the plans on how to run these, this all makes sense. I'm happy with the pipe sizing stuff but how do I design my low loss header for the system?

The meter is a U16 meter and the gas pipe run is very short, around 4m.

This is new to me and I like a challenge and want to get it right!!

Why not speak to your viessmann rep Croft. They make their own range of LLH's so could poimt you in the right direction and help with controls etc.

 

[cr0ft]

Thanks will give them a call on Monday. Any more info helpful too. I get the impression these can be made of of large bore copper pipe easily enough though for systems this size?

 

[chris watkins]

Header basics

Try these they will make you one with the configuration you require & out of copper so no 42mm M/Irons ! etc & cheaper than the boiler manufacture ones.

You can take the 2 boilers into it on their own 22mm's if the runs are short as per my second drawing. Do the proposed boilers require / have their own circulators (shunt)?

Then on the other secondary side of the LLH you can choose to have either a single F&R with just one big circulator feeding each circuit or 3 individual pairs each with their own small circulator.

I prefer the latter as it makes the controls easier, the circulators can be sized & set for its own circuit rather than having one large going summer or winter trying to cover all eventualities.

 

[cr0ft]

Thanks Chris,

Will go with separate circulators (4 off) on the secondary side. The boilers are system boilers so have their own pumps.

Am going to see if I can design my own and make one using large bore copper pipe. More interesting and A chance to use my degree for once!

 

[chris watkins]

Honestly get a quote from VA I found it just wasn't worth doing it myself you get it all with silver soldered joints AAV, D/O & munson rings to fix it to the wall with all in its own presentation box.

 

[stevetheplumber]

just out of interest in the drawing chris put up the flow and return to the cylinder is tapped of pipework rather than having its own tapping on the LLH any reason for this ?

 

[chris watkins]

just out of interest in the drawing chris put up the flow and return to the cylinder is tapped of pipework rather than having its own tapping on the LLH any reason for this ?

These drawings were produced to show level 3 students a couple of different options after they had designed there own systems with twin boilers & LLH.

The one you are referring to steve is based on what most of the manufacturers were offering at the time i.e. 2 in, 2 out of the LLH with 40 FI con's, so there was no choice but to tee off of a larger F&R to feed the cylinder & heating. I don't know what is on offer now a days?

 

[cr0ft]

Ok folks. Would appreciate more experienced eyes looking at this to see if I have missed anything important: -

2x 35KW Viessman System Boilers connecting into a 35mm primary flow/return to the LLH. Boilers connected in reverse return configuration. 22mm magnetic filters fitted to return pipework to both boilers. Obviously being system boilers they will have their own pumps in there to push water to LLH.

LLH, 67mm diameter, height to suit so that there is a gap of 400mm min. between each flow and return. Flows at the top, returns at the bottom. Drain cock on bottom of LLH, air vent on top.

Outputs from LLH - 22mm hot water flow and return, pumped from a normal domestic CH circulating pump.

CH flow/return risers - 35mm initially dropping to 28 then 22mm as it tees off to each floor. Total of 6 CH zones each under 100m2, one of these is a 35m2 underfloor heating circuit in the kitchen by the plant room. CH circuit pumped by a 10m head pump which switches on with the boilers as soon as any of the zone valves open up. Each zone plumbed without reverse return and balanced accordingly on completion of work.

Central heating zones all controlled by one programmer with each zone having it's own room thermostat. UFH obviously controlled by it's own programmer/thermostat. TRVs fitted to all radiators. 22mm Automatic bypass valve fitted at top of riser, is this necessary if both boilers have a bypass valve anyway??

Is there anything else really obvious I am missing, obviously aware of the need for blending valves and manifold for underfloor heating.