Hydraulic SeparationMoving Beyond Priamry / Secondary Piping...

presented by:John Siegenthaler, P.E.Appropriate DesignsHolland Patent, NYwww.hydronicpros.com © Copyright 2012, J. Siegenthaler, all rights reserved. The contents of this file shall not be copied or transmitted in any form without written permission of the author. All diagrams shown in this file on conceptual and not intended as fully detailed installation drawings. No warranty is made as the the suitability of any drawings or data for a particular application.

primary!circulator

closely!spaced!

tees

parallel!primary!circuit

load!#1

load!#2

load!#3

balancing valves

crossover!bridge

Hydraulic SeparationIt’s not just about hydraulic separators...

Today’s topics...• What is “common piping?”• Whatʼs the relationship b/w common piping & hydraulic separation?• It doesnʼt have to be perfect• What is the ideal hydronic header?• Achieving hydraulic separation using low resistance heat souce• Achieving hydraulic separation using closely spaced tees• Achieving hydraulic separation using a buffer tank• Achieving hydraulic separation using a hydraulic separator• Divide & Conquer• Examples of systems using hydraulic separation

What is “COMMON PIPING?”

The degree to which two or more operating circulators interact with each other depends on the head loss of the common piping.

The lower the head loss of the common piping the less the circulators will interfere with each other.

common piping

circulator 1

circuit 1

circuit 2 circulator 2

Itʼs the piping components shared by two or more circuits.

When the head loss of the common piping is very low, there is “hydraulic separation” between the circuits.

Very little head loss occurs!in this portion of the circuits.

common piping circulator 1

circuit 1

circuit 2 circulator 2

When the head loss of the common piping is very low, there is “hydraulic separation” between the circuits.

Very little head loss occurs!in this portion of the circuits.

common piping circulator 1

circuit 1

circuit 2 circulator 2

Assume that circulator 1 is operating, but that circulator 2 is off. The lower (blue) system head loss curve in figure 2 applies to this situation.

flow ratehe

ad lo

ss (f

eet o

f hea

d)0

0

pump curve!(circulator 1)

circuit 1 head loss curve including !common piping (both circulators on)

circuit 1 head loss curve including !common piping (1 circulator on)

VERY small decrease in!circuit 1 flow rate!

when circuit 2 is on

very small change in!head loss across!common piping!when both circuits are on

flow rate in circuit 1 when it is the only circuit operating

flow rate in circuit 1 when BOTH circuits!

are operating

Next, assume circulator 2 is turned on, and circulator 1 continues to operate.

The flow rate through the common piping increases, and so does the head loss across it.

However, because of its spacious geometry, the increase in head loss across the common piping will be very slight. The system head loss curve that is now “seen” by circulator 1 has very slightly steepened. It is the upper, (green) curve shown in figure 2.

The operating point of circuit 1 has moved very slightly to the left, and as a result, the flow rate through circuit 1 has decreased very slightly.

Very little head loss occurs!in this portion of the circuits.

common piping circulator 1

circuit 1

circuit 2 circulator 2

Imagine a hypothetical situation in which the head loss across the common piping was zero, even with both circuits operating.

Because NO head loss occurs across the common piping, it would be impossible for either circulator to “influence” the other circulator.

This would be “perfect” hydraulic separation.

Fortunately, perfect hydraulic separation is not required to ensure that the flow rates through independently operated circuits remain reasonably stable.

Almost Perfect Is Good Enough:

The higher the flow resistance of the common piping, the more each circulator will “influence” flow in the other circuit (e.g. the lower the hydraulic separation of the circuits.

common piping (with HIGH FLOW RESISTANCE)

circulator 1

circuit 1

circuit 2 circulator 2

Common piping with high flow resistance is NOT good:

common piping and !heat source have!

HIGH FLOW RESISTANCE

ON ONlarger

circulatorsmaller

circulator

P=22 psibackseated!flow checkP=17psi

common piping and !heat source have!

high flow resistance

large circulator

small circulator

ON

∆P p

rodu

ced"

by c

ircul

ator"

@ 0

flow

= 4

psi

∆P= 5 psi

∆P =

5 p

si

no flow

P=12 psi

P=17 psi

P=13

psi

P=16

psi

ON∆P= 10 psi

High flow resistance common piping - something to avoid

5

10

15

0

head

add

ed (f

eet)

0

6

4

2

02 4 6 8 10

flow rate (gpm)

pump curve!for small circulator

!P=Head

()

D 144

" #$% &'

4 psi ∆P at 0 flow

Multi-zone system - using zone circulators

low flow resistance headers

other zone circuits

low flow resistance heat source

zone circulators with spring-loaded

check valves

purging!valves

OK

other zone circuits

zone circulators with spring-loaded

check valves

purging!valves

compact mod/con

boiler

NOT OK

• Always keep the flow resistance of the “common piping” as low as possible. This provides hydraulic separation between circulators.

• Always provide a check valve on each zone circuit.

high flow resistance of compact boiler creates flow “bottleneck”

circuit 2 circulator 2

common!piping

circulator 1

circuit 1

common!piping

circulator 1

circuit 1

circuit 2 circulator 2

common!piping

Divide & Conquer:Hydraulic separation allows designers to think of an overall system as a collection of independent (“hydraulically isolated) circuits.

From the standpoint of hydraulics, each circuit can be designed as if itʼs a stand-along circuit.

More on this later...

load!#1

load!#2

load!#3

closely!spaced!

tees!(typical)

primary!circulator

secondary!circuit

secondary!circuit

secondary!circuit

secondary circuit

primary!circuit!

(series)

Primary / Secondary piping - where it all began...

Primary / secondary piping, using closely spaced tees, is now well known and often used in North America.

But primary / secondary piping is not the ONLY way to create hydraulic separation...

Primary / secondary piping, is one way to achieve hydraulic separation between circulators.

Both series and parallel primary/secondary systems require a primary circulator.

This adds to the installed cost of the system AND adds hundreds, even thousands of dollars in operating cost over a typical system life.

load!#1

load!#2

load!#3

closely!spaced!

tees!(typical)

primary!circulator

secondary!circuit

secondary!circuit

secondary!circuit

secondary circuit

primary!circuit!

(series)

SERIES primary loop

primary!circulator

closely!spaced!

tees

parallel!primary!circuit

load!#1

load!#2

load!#3

balancing valves

crossover!bridge

PARALLEL primary loop

Series and parallel primary/secondary systems

An example of primary loop circulator operating cost:

Consider a system that supplies 500,000 Btu/hr at design load. Flow in the primary loop is 50 gpm with a corresponding head loss of 15 feet (6.35 psi pressure drop). Assume a wet rotor circulator with wire-to-water efficiency of 25 is used as the primary circulator.

The input wattage to the circulator can be estimated as follows:

W = 0.4344× f ×ΔP0.25

= 0.4344× 50× 6.350.25

= 552watts

Assuming this primary circulator runs for 3000 hours per year its first year operating cost would be:

1st year cost = 3000hryr

⎛

⎝⎜

⎞

⎠⎟

552w1

⎛⎝⎜

⎞⎠⎟

1kwhr1000whr⎛⎝⎜

⎞⎠⎟

$0.10kwhr

⎛⎝⎜

⎞⎠⎟= $165.60

Assuming electrical cost escalates at 4% per year the total operating cost over a 20-year design life is:

This, combined with eliminating the multi-hundred dollar installation cost of the primary circulator obviously results in significant savings.

cT = c1 ×1+ i( )N −1

i

⎛

⎝⎜⎜

⎞

⎠⎟⎟= $165.60×

1+ 0.04( )20 −10.04

⎛

⎝⎜⎜

⎞

⎠⎟⎟= $4,931

An example of primary loop circulator operating cost:

Question: What is the “ideal” header in a hydronic system?Answer: One that splits up the flow without creating head loss

Think about a “copper basketball” with pipes sticking out of it in all directions.

very low head loss!

inside header

Wouldnʼt this be pretty close to an ideal header???

So why donʼt we build headers like this???

very low head loss!

inside header

“Short / fat” headers are GOOD!

Instead, we approximate the ideal header by making it “short” & “fat”

shortfat

Long / skinny headers are BAD!

So whatʼs EXACTLY is a short / fat header???

shortfat

max (design) flow rate

select pipe size that yields a flow velocity no higher than 2 feet per second

very low flow resistance!

common piping!

size headers for max flow velocity of 2 ft/sec

low flow resistance

heat!source

The “short / fat” headers hydraulically separate the distribution circulators from each other.

The low flow resistance heat source maintains low flow resistance of common piping

Hydraulic separation achieved by low flow resistance heat source & “short / fat” headers.

The “short / fat” headers hydraulically separate the distribution circulators from each other.

closely spaced tees

very low flow resistance!common piping!

high flow ! resistance boiler

size headers for max flow velocity of 2 ft/sec

Hydraulic separation achieved by closely spaced tees & “short / fat” headers.

The closely spaced tees hydraulically separate the heat source from the header system.

multiple!boiler!

controller

ouside!sensor

closely!space!tees

zone circulators!(w/ check valves)

air!vent

drain!valve

purge!valves

"short/fat" header

supply !temperature!sensor

A

B

The “short & fat” header and close spacing between supply and return connections results in a low pressure drop between points A and B. Each load circuit is hydraulically separated from the others.

• Header should be sized for max. flow velocity of 2 feet per second

• Each circuit must include a check valve.

• The supply temperature sensor must be downstream of the point of hydraulic separation.

• The header can be vertical (as shown) or horizontal.

Hydraulic separation achieved by closely spaced tees & “short / fat” headers.

The “short / fat” headers hydraulically separate the distribution circulators from each other.

buffer!tank

very low flow resistance!common piping!

size headers for max flow velocity of 2 ft/sec

boiler!circulator

high flow resistance boiler

Hydraulic separation achieved by buffer tank (piped as shown ) & “short / fat” headers.

The buffer tank hydraulically separate the heat source from the header system.

to / from other heating

zones

wood gasification boiler

VENT

ThermoCon tank

Hydraulic separation achieved by buffer tank

earth loop circuits

purging!valves

VENT

temperature!sensor

chilled water

cool

ing

mod

e

reversing!valve

cond

ense

r

evap

orat

or

insu

late

all

chille

d w

ater

pip

ing!

to p

reve

nt c

onde

nsat

ion

chilled water air handlers

ThermoCon tank

zoned chilled water cooling

Only tanks with sprayed foam insulation should be used for chilled water storage.

Hydraulic separation achieved by buffer tank

Hydraulic Separation in “Micro-load” systems:The small insulated tank provides:• Thermal buffering• Hydraulic separation• Air separation and collection• Sediment separation and collection

indirect water heater

thermostatic!radiator valves!(TRV) on each!

radiator

TRV

TRV

TRV

TRV

TRV

manifold!station

TRV

variable speed!pressure-regulated!

circulator

outdoor!temperatue!

sensor

buffer tank, also serves as hydraulic separator,!air separator, dirt separator

hydraulic separator

very low flow resistance!common piping!

high flow ! resistance boiler

size headers for max flow velocity of 2 ft/sec

The “short / fat” headers hydraulically separate the distribution circulators from each other.

Hydraulic separation achieved by hydraulic separator.The hydraulic separator hydraulically separates the heat source from the header system.

diam

eter

= 1

"

flow velocity = 4 ft/secdiameter = 3"

flow rate = 6.5 gpm

flow velocity = 0.44 ft/secflow rate = 6.5 gpm

area = A

area = 9Aalmost zero

pressure drop b/w!upper and lower

connections

air bubbles can rise faster than the downward water flow

dirt particle drop into lower bowl

drain valve

air ventWhatʼs going on inside a hydraulic separator?

The low vertical velocity inside the separator produces minimal pressure drop top to bottom. Thus there is very little tendency to induce flow on the load side of the separator.

drain valve

air vent

"STANDARD"!hydraulic !separator

What does the “coalescing media” do inside a hydraulic separator?

The coalescing media creates tiny vortices that cause gas molecules (mostly oxygen and nitrogen) to form microbubbles. The media also helps microbubble merge together and rise upward out of the active flow zone.

upper coalescing media encourages!air bubbles to form

drain valve

air vent

air bubbles "ride" up the vertical filaments of the coalescing media - out of the active flow zone

lower coalescing media encourages!dirt particle to drop!out of active flow zone

HIGH PERFORMANCE!(air & dirt removal)!hydraulic separator

drain valve

air vent

high performance!(low velocity zone)!

dirt separator

high performance!(microbubble)!air separator

drain valve

air vent

WELD

WELD

drain valve

air vent

CUT

CUT

Why companies that offer air and dirt separators also offer hydraulic separators...

drain valve

air vent

heating!load(s)

boiler circuit

distribution system

air!separator

sediment!strainer

closely!spaced!tees

heating!load(s)

boiler circuitdistribution

system

Hydraulic!Separator

High performance hydraulic separators provide three functions:

1. hydraulic separation2. air separation 3. dirt separation

1. Flow in the distribution system is equal to the flow in the boiler circuit.

2. Flow in the distribution system is greater than flow in the boiler circuit.

3. Flow in the distribution system is less than flow in the boiler circuit.

Each case is governed by basic thermodynamic...

As the flow rates of the boiler circuit and distribution system change there are three possible scenarios:

T4T3

T2T1f1 f2

f3 f4

NOTE:

=f1 f3 (always!)

f2 f4=NOTE:

(always!)

In this case only:!

T1 T2T3 T4

==

Case #1: Distribution flow equals boiler flow:

Very little mixing occurs because the flows are balanced.

T4T3

T2T1f1 f2

f3 f4

NOTE:

=f1 f3 (always!)

f2 f4=NOTE:

(always!)

Case #2: Distribution flow is greater than boiler flow:

Mixing occurs within the hydraulic separator.

T2 =f4 − f1( )T4 + f1( )T1

f4

⎛⎝⎜

⎞⎠⎟

The mixed temperature (T2) supplied to the distribution system can be calculated with:

Where:f4 = flow rate returning from distribution system (gpm)f1 = flow rate entering from boiler(s) (gpm)T4 = temperature of fluid returning from distribution system (°F)T1 = temperature of fluid entering from boiler (°F)

Case #3: Distribution flow is less than boiler flow:

T2 =f4 − f1( )T4 + f1( )T1

f4

⎛⎝⎜

⎞⎠⎟

The temperature returning to the boiler (T3) can be calculated with:

Where:T3 = temperature of fluid returned to boiler(s) (°F)f1 = flow rate entering from boiler(s) (gpm)f2, f4 = flow rate of distribution system (gpm)T1 = temperature of fluid entering from boiler (°F)T4 = temperature of fluid returning from distribution system (°F)

Heat output is temporarily higher than current system load.

Heat is being injected faster than the load is removing heat.

T4T3

T2T1

f1 f2

f3 f4

NOTE:

=f1 f3 (always!)

f2 f4=NOTE:

(always!)

Mixing occurs within the hydraulic separator.

Sizing of Hydraulic Separators:

Hydraulic separators must be properly sized to provide proper hydraulic, air, and dirt separation. Excessively high flow rates will impede these functions.

The piping connecting to the distribution side of the Hydro Separator should be sized for a flow of 4 feet per second or less under maximum flow rate conditions.

The “size” of a hydraulic separator refers to the nominal piping size of the 4 side connections (not the diameter of the vertical barrel).

Pipe sizeof

hydraulicseparator

1” 1.25” 1.5” 2” 2.5” 3” 4” 6”

Max flowrate

(GPM)11 18 26 40 80 124 247 485

union connections

flange connections

Typical European concepts for multiple mod/con installation:

Typical European concepts for multiple mod/con installation:

Boiler manifold with integral hydraulic separator (courtesy Sinus North America).

Form fitting insulation is supplied with all manifolds.

Flexible piping connects each boiler to low manifold. (Boilers have integral circulators and check valves.)

Notice that two additional boilers can be added to the front side of lower manifold.

Here's what the real products look like…

How about 8 mod/cons with integral hydraulic separator… (courtesy Sinus North America).

Think of the output per unit of mechanical room floor area…

Each boiler can be independently serviced .

Flexible piping connects each boiler to low manifold. (Boilers have integral circulators and check valves.)

Example of Hydro Separator Installation in New System:Magna Steel Corporation - Connecticut

Photos courtesy of Peter Gasperini - Northeast Radiant

Example of Hydro Separator Installation in Old System:

Because hydraulic separators remove sediment fromsystems they’re ideal for applications where new boilers are retrofit to old distribution systems.

Example of Hydro Separator Installation in Old System:Because hydraulic separators remove sediment from systems theyʼre ideal for applications where new boilers are retrofit to old distribution systems.

hydraulic!separator

supply!temp.!sensor

from existing system

sediment capture!and removal

multiple!boiler!

controller outdoor!temperature!

sensor

existing cast-iron radiators (converted from steam)

existing piping

mod/con boiler!w/ compact heat exchanger

supply!temperature!

sensor

ECM!pressure!regulated!circulator

vent

hydraulic!separator

A hydraulic separator is a great way to interface a new mod/con boiler to a older “steam conversion” system.

WHY?

Dirt separation is especially important in older systems with iron components.

fluid feeder

earth loop circuits

purging!valves

purge

variable-speed!pressure-regulated!

circulator

geothermal manifolds

hydro!separator

to / from!other heat pumps

heat

ing

mod

e

reversing!valve

cond

ense

r

evap

orat

or

water-to-water!heat pump

zone!valve

balancing!valve

Hydraulic Separators will likely become a key component in multiple ground source heat pump applications.

The will allow the flow rate in the earth loop to be different than the flow rate through the heat pump array - more on this later...

temperature!sensor

VENT

fluid feeder!(optional)

earth loop circuits

purging!valves

purge

to / from other heating zones

variable-speed!pressure-regulated!

circulator

geothermal manifolds

hydro!separator

water-to-water!heat pump

chilled water buffer tank

temperature!sensor

warm water buffer tank

circulator!w/ check

3-way!diverter!

valve

insu

late

all

chille

d w

ater

pip

ing!

to p

reve

nt c

onde

nsat

ion

chilled water air handlers

varia

ble-

spee

d!pr

essu

re-r

egul

ated

!ci

rcul

ator

insu

late

all

chille

d w

ater

pip

ing!

to p

reve

nt c

onde

nsat

ion

reversing!valve

cond

ense

r

evap

orat

or

compressor

TXV

heat

ing

mod

e

size all header piping for maximum flow velocity of 2 ft/sec to provide hydraulic separation

fixed speed!or!

variable-speed!circulator

12D AAB

B

AAB

B

circulator!w/ check

reversing!valve

cond

ense

r

evap

orat

or

compressor

TXV

heat

ing

mod

e

12D AAB

B

AAB

B

circulator!w/ check

reversing!valve

cond

ense

r

evap

orat

or

compressor

TXV

heat

ing

mod

e

12D AAB

B

AAB

B

3-way!diverter!

valve

Hydraulic Separators will likely become a key component in multiple ground source heat pump applications.

circuit 2 circulator 2

common!piping

circulator 1

circuit 1

common!piping

circulator 1

circuit 1

circuit 2 circulator 2

common!piping

Divide & Conquer:Hydraulic separation allows designers to think of an overall system as a collection of independent (“hydraulically isolated) circuits.

From the standpoint of hydraulics, each circuit can be designed as if itʼs a stand-along circuit.

• Simplifying system analysis• Preventing flow interference

Divide & Conquer:

LWCO

cast-iron sectional boiler!with oil burner

brass unions!(typical)

PRV

closely spaced tees

3/4"

cop

per

Webstone!purging!valves

variable speed!pressure regulated!

circulator!set for ∆Pc

!mix supply!sensor

1.25" copper 12D

3/4"

cop

per

1" c

oppe

r

3/4"

cop

per

3/4"

cop

per

1" c

oppe

r

3/4"

cop

per

3/4"

cop

per

3/4"

cop

per

outdoor!sensor

TRV

TRV

TRV

TRV

TRV

TRV

thermostatic radiator valves!on each panel radiator

12- circuit manifold distribution system

using PEX or PEX-AL-PEX tubing

panel radiator

MRH

L

12D

356 injection mixing controller

closely spaced tees3/4"

cop

per

balancing!valve

outdoor!sensor

purging!valves

1" c

oppe

r

!mix supply!sensor

1" c

oppe

r

1" c

oppe

r

1" c

oppe

r

1.25" copper 12D

manifold B

manifold A

2" copper supply!and return headers!

keep as short as possible

2" copper

2" copper

1.25" copper

3/4" copper

12D

1" copper

12D 12D

3/4"

cop

per

return temperature!sensor for 356!

mixing controllers

!indirect water heater

12D

2" air separator3/4" fast fill piping

3/4" cold water supply

12D

manifold G!(garage)

strap-on!aquastat!contacts!

close at 100ºF!open at 50ºF

P1

P2

P3

P4

P5

P6

P7

P8These panel radiators are representative!of second floor heating distribution system!exact size and number of panels may vary,!but all are supplied with 1/2" PEX-AL-PEX tubing, and controlled by individual thermstatic radiator valves.

30 psi!PRV

fill/purgesupply sensor

3/4"

cop

per

12DHW

CW

P&TRV

tank acqustat

floor!drain

1.25" copper

swing!check

manifold C

manifold D

manifold E

manifold F

!brazed plate SS!heat exchanger

to / from other!radiators

This portion of system filled with 40% solution of inhibited

propylene glycol

3/4"

cop

per

3/4" copper

manifold H (2nd floor)

manifold I (2nd floor)3/

4" c

oppe

r

3/4"

cop

per

3/4"

cop

per

variable speed!pressure regulated!

circulator!set for ∆Pc

356 injection mixing controller

356 injection mixing controller

balancing!valve

zone valves

all three injection pumps!equipped with internal!

check valves

Divide & Conquer:

In a complex system like this...

How does the water know where to go???

P1

cast-iron sectional boiler

P2

P3

P4

P5

manifold H (2nd floor)

manifold I (2nd floor)

P7

P8

TRV

TRV

TRV

TRV

TRV

TRV

P6

low flow resistance heat source!+ short / fat headers

In this system, hydraulic separation was achieved using “short / fat” header in combination with low flow resistance heat source.

Hydraulic separation allows designers to think of an overall system as a collection of independent (“hydraulically isolated) circuits.

Divide & Conquer:

You find it: Where is the hydraulic separation in this system?

reversing!valve

cond

ense

r

evap

orat

or

TXV

cool

ing

mod

e

VENT

temperature!sensor

insu

late

all

chille

d w

ater

pip

ing!

to p

reve

nt c

onde

nsat

ion

chilled water air handlers

to / from other heating

zones

buffer tank

heating is off

chilled water

variable-speed!pressure-regulated!

circulator

electric!heating!element

DHW P&TRV

water heater

geothermal manifolds

earth loop circuits

purging!valves

You find it: Where is the hydraulic separation in this system?

closely!spaced!

tees

air handler w/ drip pan

indoor unit

INSI

DE

OUTS

IDE

!outdoor unit

thermostatic tempering valve

indiret water heater with auxiliary electric element

motorized diverter

valve

make-up!water &

supllemental!expansion

tank

variable speed!pressure regulated!

circulators

purge!valve

flow setterzone valve

low flow resistance headers

chilled water cooling

low temperature space heating

Hydraulic Separators now available in North America

Sinus North AmericaPrecision Hydronic

Products

Bell & Gossett

Taco

SpirothermCaleffi

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