Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Control components for DHW preparation by heat exchanger

M.Sc. Jan Eric ThorsenApplication Center

Danfoss A/S District Heating Controls

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Example multifunctional controller

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Why multifunctional controller ?

•One controller•Space savings•Reduced assembly costs•Flexible functionality

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

The ”optimum” control conceptdepends on:

• Primary supply condition• Demand to control performance• Demand to functionalities

T

DH DHW

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Primary supply conditions

Q1 ; T11 = 60-100°C T

T22 = 45 - 55°C

Q2 = 0-0,2 l/s ; T21 = 10°C

dP = 0.5 to 6 bar

T12 = 15-25°C

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

C o n s t a n t p e r m a n e n t d e v i a t i o n f r o m s e tp o i n t a f t e r a t e m p e r a t u r e c h a n g e , + / - 2 K

M a x i m u m p e r m a n e n t t e m p e r a t u r eo s c i l l a t i o n s , + / - 2 K

M a x i m u m t e m p e r a t u r e d e v i a t i o n a f t e r am o m e n t a r y l o a d c h a n g e , 1 0 K

T r a n s i e n t t i m e a f t e r a l o a d c h a n g e < + / - 2 K w i t h i n 1 2 0 s e c

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Functionalities /Control performance

•Idle temperature (at no DHW tapping)

•DHW Circulation

•Priority function DHW/Heating

Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Q2

TQ1

Thermostaticcontroller

Proportionalflow controller

Basic control components

Differential Pressurecontroller

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Q2

Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Thermostaticcontroller

Q2

TQ1

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Thermostaticcontroller

Q2

TQ1

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Proportionalflow controller

PM controller

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Q2

Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Proportional flow controllerwith a temperature controllerserial connected

PTC controller

11

T

Q2

Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

DCW

DHW

Heatingflow

Heatingreturn

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DH Flow

DH Return

Temperature controller parallel connected with proportional controller plus dP controller

AVTIController

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Example AVTI controller

Danfoss AVTI valve, dP station = 4.0 bar, T11 = 90°C

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10 12 14 16 18 20 22 24 26

time [min]

Tem

p [

°C]

0

100

200

300

400

500

600

700

800

Flo

w [

l/h]

T22 Q2 Q1

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

TT

T

Heatingreturn

Heatingflow

Combined therm. and prop. control (reduced stand by temp.)

Therm. control with reduced stand by temperature control and DHW priority

Other combinations

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Thermostatic variants

T

Therm. controller with “special” position of sensor

T

Therm. controller with “Heat Bridge”

AVTB with GeminaHeat bridge

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Recommendations:

• constant dP and T11, or accept seasonal adjusting• ”free” setting of stand-by temperature

- (additional thermostatic controller)• Preventing high temperature peaks

- (preventing lime scale deposits)

• variable dP and T11

• comfort of high standby temperature

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Proportional controller:

Thermostatic controller:

Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Recommendations:

Serial coupling:

Parallel coupling:

• variable T11, variable dP• control performance• ”free” setting of stand-by temperature

- (additional thermostatic controller)

• variable T11, but constant dP• control performance• comfort of high standby temperature

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Euroheat & Power, 2. RTD Workshop, High Efficiency – Improved Building Installations and Customer Comfort, Brussels 2-3 February 2006

Trend within compact DHW/H sub stations:

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• Towards compact multifunctional controllers

• Fulfilling specific demands > flexibility