P/S Pumping Alternative Piping

try2hard

Hi everyone.

I'm drawing plans for my new radiant system to be installed this spring and I wanted thoughts on an alternative P/S piping layout. When I installed the hydronic system in my last home, I used a traditional P/S piping arrangement. My primary loop had a dedicated pump, and the boiler and three baseboard zones were piped with closely spaced tees and their own circulators (Grundfos 3 speed UP 58).

I'm trying to plan the new home for future off-grid power. I currently have grid power, but my decisions have been around solar self-consumption. With that in mind, I chose an inverter fridge and washer, LED lighting, etc. For the hydronic system, I'm using ECM motor circulators like the Grundfos Alpha to conserve energy, and likely a Taco RMB for the radiant zones.

So in an effort to reduce power needs where possible, I played with my piping arrangement, hoping to avoid a separate primary pump. Another hydronic installer friend suggested piping the system like the screenshot attached. I've not piped a system like this in the past.

What are the pros and cons versus having a dedicated primary pump? If I go this route, should I pipe the zone circuits in reverse-return for balancing purposes?

hot_rod

Many designers and installers are going with hydraulic separators instead of a site build P/S loop.

One less circ required, air, dirt, magnetic separation, simple to pipe and add in to.

Page 43 shows how multiple inputs and outputs would pipe into it.
Solar, wood fired, heat pump, any inputs.

Mixed temperature on the output side is possible with whatever device you chose for mixing.

Wood boilers typically require some sort of buffer tank, leave space for that.

https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_15_na.pdf

Gordy

Use low head loss boiler, and piping design that allows direct pumping.

try2hard

hot rod said:

Many designers and installers are going with hydraulic separators instead of a site build P/S loop.

One less circ required, air, dirt, magnetic separation, simple to pipe and add in to.

Page 43 shows how multiple inputs and outputs would pipe into it.
Solar, wood fired, heat pump, any inputs.

Mixed temperature on the output side is possible with whatever device you chose for mixing.

Wood boilers typically require some sort of buffer tank, leave space for that.

https://www.caleffi.com/sites/default/files/coll_attach_file/idronics_15_na.pdf

Thanks for the link. It's an interesting idea, new to me for sure. It does look like a slick device, not cheap though. I'm used to the closely-spaced T approach.

But since the multiple boilers and load zones on either side of the Caleffi are not piped with closely spaced T's, you're really not gaining any hydraulic separation as if you piped each circuit with closely spaced T's.

I'll most likely go with a small (slightly undersized) coal/wood hand fired boiler with a buffer tank, down the road. I was planning to connect that via a plate heat exchanger, being the only ferrous component in the system other than circulators. That would also divide the volume of water into two systems.

try2hard

Gordy said:

Use low head loss boiler, and piping design that allows direct pumping.

Too late on that one. It's arriving next week. It's a TT Challenger Combi that I got an amazing deal on. Huge help with the budget for BOS components like the Taco RMB. I can easily replace it down the road if needed. Plus I plan to use the solid fuel boiler as much as possible, with LP as a backup/supplement.

I also thought it was a unique design with the DHW built into the heat exchanger, allowing me to install now and operate for only DHW, until later this spring when I install the heating system.

DZoro

I like to bring the wood side in on the other side / return of the boiler. If the wood doesn't have enough to supply you then the gas can see that and come on accordingly. Just food for thought.

hot_rod

But since the multiple boilers and load zones on either side of the Caleffi are not piped with closely spaced T's, you're really not gaining any hydraulic separation as if you piped each circuit with closely spaced T's.


The boiler(s) and loads are piped parallel, why would you need closely spaced tees or separation? Any or all loads and inputs could run in any combination without any pumping issues.

The sep, as the closely spaced tees, just keep input and output hydraulically separated, no pumping conflicts.

Also with P/S piping the temperature around the loop changes and varies at every tee connection, with parallel piped loads, they all see the same SWT.

Solid_Fuel_Man

Consider using one Delta P or Delta T circulator, and high efficiency zone valves instead of dedicated circulators which are all going to chew up more watts than one single valve per Zone. Unless you had to have a lot of long or unequal length zones zoning with circulators is wasteful in my opinion.

try2hard

hot rod said:

But since the multiple boilers and load zones on either side of the Caleffi are not piped with closely spaced T's, you're really not gaining any hydraulic separation as if you piped each circuit with closely spaced T's.


The boiler(s) and loads are piped parallel, why would you need closely spaced tees or separation? Any or all loads and inputs could run in any combination without any pumping issues.

The sep, as the closely spaced tees, just keep input and output hydraulically separated, no pumping conflicts.

Also with P/S piping the temperature around the loop changes and varies at every tee connection, with parallel piped loads, they all see the same SWT.

I just meant that if all the zones, boiler(s) and loads were piped in a traditional P/S piping arrangement with closely spaced T's, they are all provided hydraulic separation. Multiple pumps really wouldn't affect the flow dynamics like if they we're piped in parallel, using the separator, as in the diagram.

Yes, the same SWT is also a good point for parallel piping. Or the use of a cross-over bridge in P/S.

try2hard

Solid_Fuel_Man said:

Consider using one Delta P or Delta T circulator, and high efficiency zone valves instead of dedicated circulators which are all going to chew up more watts than one single valve per Zone. Unless you had to have a lot of long or unequal length zones zoning with circulators is wasteful in my opinion.

Yes, at first the system will only supply one radiant manifold, for which I'll use either the Taco RMB or a Grundfos Alpha. And actuators for the manifold. Down the road I will be adding two additional radiant segments for a total of three.