Looking for feedback on primary secondary distribution system design

ThatF_inGuyInNY

The home is an 1800sq ft 1935 colonial with original cast iron piping and radiators and an oil boiler. The plan is to add sections of radiant floor to parts of the home that not well heated. Eventually, some of the radiators may be taken offline if necessary. The plan is to build the distribution system, tie in the radiators with pex home runs, then run pex radiant circuits and balance as needed. An additional radiant manifold is added to the lower area for eventual basement radiant floor circuits.

I didnt draw up a circuit diagram, but it should be fairly obvious from the rendering. Designed with B&G circuit setters for their ubiquity and cost.

Secondary risers are 1-1/4" copper, manifolds are 1" copper, DHW is 3/4" (feeds an indirect with 3/4" S/R). Pex connections are 1/2" copper crimp. The distribution is constrained be the size of the board.

Heres the render https://imgur.com/MApZxdJ

Looking mainly for feedback on the design of the system, not the numbers

Zman

• Where is the expansion tank? Sizing it can be tricky on older systems with large pipes.
  
• I would eliminate every one of the air vents and install one air separator in a location where it picks up all of the flow (bottom left somewhere). The big air bubbles will come out in the initial purge, it's the microbubbles that you need to worry about. The vents you have drawn will help a little on the initial purge, but will perpetually leak and drive you nuts every day afterward. Vertical models are available if space is an issue.
  
• Unless you own a hydronic manometer, balancing manifolds with flow gauges or caleffi quick setters would be more practical.
  
• Watch your common piping sizing, 2-3ft/sec should keep the circs from fighting each other.
  
• Be sure to size the mixing valves with a CV ~= design GPM.
  
• Combining upper and lower radiant would save space.
  
• You will need flow checks on all loops, given your space constraints, integral circulator checks would make sense.
  
• In an older system, a mag/dirt separator should be considered.
  
• What are you thinking for a boiler?
  
• DHW Priority?
  
• Outdoors reset?
  

ThatF_inGuyInNY

Zman said:

• Where is the expansion tank? Sizing it can be tricky on older systems with large pipes.
  
• I would eliminate every one of the air vents and install one air separator in a location where it picks up all of the flow (bottom left somewhere). The big air bubbles will come out in the initial purge, it's the microbubbles that you need to worry about. The vents you have drawn will help a little on the initial purge, but will perpetually leak and drive you nuts every day afterward. Vertical models are available if space is an issue.
  
• Unless you own a hydronic manometer, balancing manifolds with flow gauges or caleffi quick setters would be more practical.
  
• Watch your common piping sizing, 2-3ft/sec should keep the circs from fighting each other.
  
• Be sure to size the mixing valves with a CV ~= design GPM.
  
• Combining upper and lower radiant would save space.
  
• You will need flow checks on all loops, given your space constraints, integral circulator checks would make sense.
  
• In an older system, a mag/dirt separator should be considered.
  
• What are you thinking for a boiler?
  
• DHW Priority?
  
• Outdoors reset?
  

Where is the expansion tank? Sizing it can be tricky on older systems with large pipes.

Not shown, will be part of the boiler piping per the manual

I would eliminate every one of the air vents and install one air separator in a location where it picks up all of the flow (bottom left somewhere). The big air bubbles will come out in the initial purge, it's the microbubbles that you need to worry about. The vents you have drawn will help a little on the initial purge, but will perpetually leak and drive you nuts every day afterward. Vertical models are available if space is an issue.

My concern was the initial purge. I can swap the auto hyvents for manual purge valves, but it would make me feel better to avoid having high points with no ability to purge. Dont know if thats a valid concern.

Unless you own a hydronic manometer, balancing manifolds with flow gauges or caleffi quick setters would be more practical.

The plan was to isolate each line and balance based on dT. Alternatively, I can adjust based of room temp using sensors. I really want to avoid using a pre-fab manifold. quick setters are nice, but double the cost. I've also heard the built in gauges arent particularly accurate. Not sure how true that is.

Watch your common piping sizing, 2-3ft/sec should keep the circs from fighting each other.

Im at approx 4ft/sec with every zone running using the current 1-1/4 commons, assuming the in-floor branches pull the full volume. However, the common water temp will be 180F, and the in floor branches will be ~120F so they will pull less and re-circ through the mixers. I have not attempted to calculate this just yet. I can step up to 1-1/2 if needed, but Im not convinced of that yet.

Be sure to size the mixing valves with a CV ~= design GPM.

done

Combining upper and lower radiant would save space.

Im having trouble figuring how I would do this to allow the zoning I want. I want the upper floors on one zone and the basement on the other. Unless I zone each circuit independently, I cant really zone them the way I want. Also, The basement radiant will be over a slab while the upper floors will be under a wood subfloor. I felt it best to allow the ability to dial each branch temp separately to account for this. Not 100% sure its necessary, but the zoning issue tipped it toward designing it this way.

You will need flow checks on all loops, given your space constraints, integral circulator checks would make sense.

Was planning to use circs with IFCs

In an older system, a mag/dirt separator should be considered.

Its in the picture on the top left branch. I've heard from others to incorporate this into the common return pipe. Thats probably better, but it fits well where it is and the dirt will primarily be coming from the high temp cast iron branch so I figured it would work here. I was planning to add a strainer on the boiler piping.

What are you thinking for a boiler?

current is a cast iron oil boiler. Only heat available to me is oil, so I will replace the current old unit with a new one (most likely a WM WGO-3R). I will add a temp bypass to the boiler piping per the manual.

DHW Priority?

Yes, done with the circ controller

Outdoors reset?

Possibly, though Im not convinced it will do much since I need to keep return temps above 140F

Thank you, these are all good points

hot_rod

no problem with all those high point air vents as long as they are Caleffi😉

We offer check valve caps if any are in jeopardy.

ThatF_inGuyInNY

hot_rod said:

no problem with all those high point air vents as long as they are Caleffi😉

We offer check valve caps if any are in jeopardy.

appreciate the CAD model library thats worth my business