What is the purpose of a manifold in a hot water heating system?

scatgo

5FK4-WIF - Webstone 5FK4-WIF - 1-1/4" Sweat Complete Near Boiler Manifold & Piping Kit for Wall Hung Boilers

Weil-Mclain-383-100-055-Install Instructions.pdf

Page 40 in the PDF.

Jamie Hall

Used and installed properly, it ensures even distribution of flow between the various zones or loops of piping.

And it makes the whole job a lot simpler…

scatgo

Would it be necessary for a system with no zones?

EdTheHeaterMan

YES

This manifold separates the job of the boiler circulator pump from the job that the system pump must do. Here is a video that explains the concept known as primary secondary piping.

https://www.youtube.com/watch?v=0sA-b2vLU78

The reason that Weil McLain requires this piping design, the boiler pump of the Weil McLain boiler may be able to handle a very small single zone of radiators, but Weil McLain does not know where their boiler is going to be installed.  If your single zone system has a lot of resistance to flow by design, OR, if your system is radiant floor, OR, If your system has lots of valves and elbows and twists and turns, OR, if your system has any long runs of pipe from the boiler to the furthest radiator, that boiler pump may not be strong enough to push the water thru the entire system at the rate necessary to keep the heat exchanger from overheating.  So the boiler has its own pump that can move enough water internally to keep it from overheating, and the system has its separate pump that can handle the requirements of that system.   This separation of pump tasks makes it easy for the manufacturer to make a heater that will be good for just about any type of heating system,  not just your heating system.

scatgo

Great video! Thanks. And if the whole idea is to make a system that should work with any heating system a condensing gas burner should work fine with my 97 year old heating system with cast iron radiators. Right?

EdTheHeaterMan

YES. Your large volume water system will operate great with this boiler. The outdoor reset with the outdoor sensor installed will offer you a tremendous savings over the old ON/OFF boiler that it is replacing.

ON/OFF operation is less efficient than a boiler that operates for longer ON cycles.

EdTheHeaterMan

You may not think so, but the fact that once the outdoor temperature gets low enough, the boiler will run constantly and that will save you big bucks.  That is because the amount of gas that burners use changes as the outdoor temperature changes.  When it is only 40F outside you do not need a big heater, so the gas valve actually delivers less gas to the burner making that boiler virtually a much smaller boiler that uses less fuel.  and when it gets to be 20° outside and you need a bigger heater, the gas valve delivers more gas to the burner and makes the heater a larger heater.   Depending on the actual needs of your home, you may never get the burner to operate at full capacity, because you will never need it.  

The next feature is that a condensing boiler will be more efficient the colder the return water.  So if your radiator temperatures never get really hot, then the return water to the boiler will be much cooler, making more condensation, and using up more of the heat from the fuel. 

Kaos

One caveat here is that if you have a simple setup up with no zoning like an old gravity feed radiator or a loop of fin tube baseboards, you don't need PS piping (ie that manifold) or the 2nd pump.

You do have to size the boiler pump to handle the pressure drop of the existing heating system plus the modcon, but you can connect straight to it. Besides being cheaper to plumb, it is actually the most efficient way to run a mod con.