Differential pressure bypass vs balancing valve (vs maybe a dP pump)

ThatF_inGuyInNY · July 2022

Hi All

I am designing a manifold system for low temp radiant loops. The current design includes 8 loops, which would cover the whole house (upper floors, not basement, approx 1800sq ft). However, the plan is not to install all loops at once. I have two loops installed (done during renovations) and ready to be hooked up. I designed the manifold to accommodate the whole house so that in the future, the existing radiators could be taken offline and replaced with radiant loops.

All loops will have individual balancing valves.

Because the system will be sized for the whole output, but only running a few loops initially, I want to include a a differential bypass between the supply and return. It seems to me, that a balancing valve could accomplish the same thing, just not automated. The advantage of the balancing valve is no moving parts (theoretically more reliable), cheaper initial cost and more compact (easier to integrate into my design). The downside is that I would have to adjust it manually each time I added a loop. I am ok with this and maybe even prefer it as it would be one less thing to diagnose if issues come up.

Alternatively, I could install a dP pump. My hangup here is that I am not using zone valves, so it seems like a waste. The plan is to balance the system using balancing valves and maintain a constant temp throughout the home. Once the flow is set, it should not need adjustment until another loop is added.

Am I missing any details about what a DPV offers over a balancing valve? Do they truly accomplish the same thing?

Big Ed_4 · July 2022

Are you trying to use one circulator without zoning to deliver an even comfort though out the house ?

hot_rod · July 2022

Will you add actuators to the manifold at some point?
If not a single speed circ sized for all the eventual loops, head and gpm is one possibility.

Until all loops are added, yes you want a bypass, or a circulator that you can adjust to match the requirement of what you keep adding. Ideally you would know what the required gpm and head is every time you add a loop or zone to dial in the pump.

A delta P circ with an adjustable speed range control would be ideal. Saves energy and should be able to match the changing loads.

Or add a dynamic balance valve on each loop. You purchase these balance valves at a specific gpm and they modulate to that requirement. They work great with ∆P circulators by the way. As the valves modulate, so does the circulator.

You could use a manual balance valve on each loop, they need to be re-adjusted every time you add a loop, and with a fixed speed circ, you would still need a pressure bypass..

A pressure bypass valve is fairly simple, a spring and rubber flat disc. But they are parasitic devices, it sheds away pump capacity, but does not save energy. You are just "slipping the clutch" so to speak.

Spend the bucks, buy an electronic ∆P circ. Check www.dsireusa.org, there were some rebates available for installing electronic pumps in some areas.

ThatF_inGuyInNY · July 2022

hot_rod said:
Will you add actuators to the manifold at some point?
If not a single speed circ sized for all the eventual loops, head and gpm is one possibility.

Until all loops are added, yes you want a bypass, or a circulator that you can adjust to match the requirement of what you keep adding. Ideally you would know what the required gpm and head is every time you add a loop or zone to dial in the pump.

A delta P circ with an adjustable speed range control would be ideal. Saves energy and should be able to match the changing loads.

Or add a dynamic balance valve on each loop. You purchase these balance valves at a specific gpm and they modulate to that requirement. They work great with ∆P circulators by the way. As the valves modulate, so does the circulator.

You could use a manual balance valve on each loop, they need to be re-adjusted every time you add a loop, and with a fixed speed circ, you would still need a pressure bypass..

A pressure bypass valve is fairly simple, a spring and rubber flat disc. But they are parasitic devices, it sheds away pump capacity, but does not save energy. You are just "slipping the clutch" so to speak.

Spend the bucks, buy an electronic ∆P circ. Check www.dsireusa.org, there were some rebates available for installing electronic pumps in some areas.

Honestly, as I typed everything out, it started becoming clear to me that I was avoiding dP pumps for no good reason. Even if it runs static pressure all the time, its still going to use less energy than a dumb pump. I had a Grundfos UPS15 pump sized up for my head/flow requirements and it looks like the GF dP ALPHA2 pump is maybe $130 more and drops in the same footprint. Im not sure I can even get a bypass valve and fittings for the amount.

Dave Carpentier · July 2022

The Alpha2 would also be a good choice should you someday decide to insert zone valves.
The 15-55 model will do 0-6 gpm at a steady 12ft of pressure at it's max delta-P setting.

Paul Pollets · July 2022

I'd be using the Alpha pump. Stopped having to use PBV's more than 15 years ago.

HomerJSmith · July 2022

A differential pressure bypass valve and and a balancing valve have different design usages. They provide different functions.

Differential pressure bypass vs balancing valve (vs maybe a dP pump)

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