Should I get a new manifold?

[mousebndr]

I have a manifold with 1" in/out for the main line and 3/4" in/out for the zones.

However I want to bring 1 1/2" from the boiler into the manifold and then 1" out to the zones.

Does anyone think adding 1" pipe to the 3/4" outlet on the manifold would be all that much of a reduction in performance? Seems to me likes its a bit like adding another join in the pipework or an elbow.

 

[Tennman]

It is. The pressure drop or energy loss is a big function of the gpm you're pumping thru that 3/4". If zone flow is so low that a 3/4" line would have been fine to begin with.. I'd say no big deal. But if it was my system and I was investing in 1" zone lines I'd do the manifold right just so I wouldn't be wondering everytime I looked at it. Others here with zone lines hopefully will chime in, but I'm the type that hates remorse on stuff I build. But no question on the physics of accelerating flow thru the 3/4" and then letting it slow to lower feet/sec velocity into the 1". That brief acceleration of flow is wasted energy.

 

[Bob Rohr]

The manufacturer of the manifold should be able to show you the flow rate for the entire manifold, and the branches. A typical radiant manifold would have a cv of 1- 1.25 per branch or loop. So 1.25 gpm flow with a 1 psi drop. High flow manifolds used for snow-melt and commercial work could be 3- 3.5 Cv.

The key is how many gpm you want to move thru the branch or connection. You can exceed the Cv number but it could add a lot more pressure drop and start making noise if the flow is too great. Excessive flow may also start eroding the components. Generally you will not find a fitting larger than 3/4" to fit onto the branches of typical radiant or hydronic manifolds.

For higher flow, say above 3 gpm, consider a GEO manifold. They have 3/4 and up sized branches. I've seen some with 2" branches on a 6" manifold. Some installer build their own manifolds with copper or threaded tees and close nipples.

So determine the total flow for all the loads you are connecting, then how much every branch needs to flow.

hr

 

[maple1]

Are you changing your entire zone pipings to 1"? And zones themselves? If not, I'm not sure what upping from 3/4 to 1 on the manifold would do - if so, that sounds like a ton of work. That's without knowing anything about your zones though...

 

[mousebndr]

Thanks guys

I have attached my flow calc to add a bit more detail.

Zone 2 is my problem, there is 17 m of pipe before we hit the first radiator which creates a fair bit of head. If I were to replace the run to the first radiator with 1" pipe I drop from 5.7 m to 3.9 m of head.

Our pipe work is a parallel flow and return with radiators tee'd off type design.

Have also attached the flow diagram for the manifold but I dont really know what I am looking at

 

[Bob Rohr]

you have two choices, select a pump for zone 2 that will move the required GPM of 6.5 at the head indicated 18', or reduce the head by changing the piping and or fittings. A Grundfos 26-99 on speed 1 looks like it would do the job. Or you could increase the pipe size. The restriction at the manifold would cost a little pressure drop, probably only a foot of head or so to have that restriction from 3/4- 1" at the manifold.

If electrical consumption is a concern the Grundfos "Mini Magna" would be an ideal pump for a system like yours with multiple zones. It looks like the entire 3 zones requires about 17 gpm at 18' of head. Add the GPM requirement of all the zones, the pump needs to move 17 GPM, around 170,000 BTU/hr at 20 degree delta T. The piping, fittings emitters determine the resistence to flow (head) Use the head requirement of the most restrictive zone, looks like Zone 2 is 18'. So 17 GPM at 18' of head. The Grundfos Magna 40- 120 fits nicely at those specs.

Usually those zone calc sheets have a summary sheet or number at the end. The assumption report shows the total heat load in BTU/hr of whatever metric unit you speak Also it would indicate total GPM, head, and BTU/hr to be pumped. That summary sheet is used to size the boiler and select the pump size.

The Alpha and Magna pumps are high efficiency ECM motors and delta P. This means the pump is always adjusting it's output to match the load as zones turn off and on. The AutoAdapt features of these pumps allows the pump to "learn" your system and can save 60- 70% electrical energy by this means.

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[mousebndr]

Thanks Bob

Have been checking out the Magnas, curious why you thought the Magna 40-120 would be the pump? I would have thought the 32-80 or 40-80 would fit within the spec nicely.