Reminder of important aspects of VRV refrigerant …server.mmc.bg/Актуални новини...

RAPID NEWS ▌▌█ EXTERNALNo: RN/DACE/BDS/ DACE-##-##

Date: 22.03.2019Author: Michal Galuska

SUBJECT : Reminder of important aspects of VRV refrigerant piping design not handled by selection software

Dear Madam, dear Sir,

With this Rapid News we would like to alert and remind you about several design aspects about VRV

refrigerant piping that are not accounted for in Daikin selection and design software. It is important to

keep in mind that the output reports from Daikin selection software are schematic only and do not

constitute a design document suitable for final installation.

Prior to executing installation, a qualified and authorized designer must evaluate and design the exact

details of the installation, most notably the proper positioning of indoor and outdoor units and the routing

and fixation of refrigerant piping, which, amongst other requirements, must comply to EN 378-2, section

6.2.3.3 Requirements for piping installed at site.

Thermal Expansion of Refrigerant Piping

It is important to keep in mind that refrigerant piping of direct expansion systems, namely heat-pumps,

can be exposed to vastly varying temperatures of the refrigerant flowing inside – from as low as -30°C

during defrost operation to as high as +80°C during heating operation. This constitutes a temperature

change in excess of 100°C. Taking into account the thermal expansion coefficient of copper (approx.

1.6∙10-5 m/(m∙K)), a 10 m long copper refrigerant pipe can expand or contract by more than 1.6 cm during this temperature change. This means that adequate measures must be taken to avoid that the

refrigerant piping or any of its components (such as Refnet joints, headers, elbows, etc.) are exposed to

stress from this expansion and contraction. Below is a non-exhaustive list of measures to take to avoid

stress on refrigerant piping from thermal expansion:

< Information herewith provided is subject to change without notice > of 6DAIKIN AIRCONDITIONING CENTRAL EUROPE HANDELSGMBHCampus 21, Businesspark Wien SüdEuroparing F12/402, 2345 Brunn am Gebirge, Austria

Tel.: +43 2236 325 57 100Fax: +43 2236 325 57 910

http://www.daikin-ce.com3.12.8 SD v.2


Avoid rigid fixation of refrigerant pipingThe following ways of supporting refrigerant piping is recommended to allow for movement of the piping:


Tel.: +43 2236 325 57 100Fax: +43 2236 325 57 910



Example: 20.00 m

HEATING

19.97 m

DEFROST

> 10 m > 10 m

Leaks

Avoid long runs in a single straight line or carefully evaluate their impactCarefully evaluate the impact of running the refrigerant piping in a single straight line over a long

distance. This is especially critical of larger-diameter hard piping. Keep in mind that Refnet joints can

not work as thermal expansion compensation measures.

Be also careful about the branching out to opposing sides. If the branches continue in a straight line in

rigid hard-copper piping, the expansion and contraction of the branch pipes may cause a repetitive

bending of the Refnet joint, causing fatigue stress damage leading to the development of leaks:


Tel.: +43 2236 325 57 100Fax: +43 2236 325 57 910



Every 10 m of straight piping where the ends must not move= 1 expansion deviation (30 cm x 30 cm)

30 cm

30 cm

Note:The expansion loop CAN be in any orientation plane (horizontal / vertical / inbetween)

When the design requires long pipe runs in a single straight line and there is a risk that the expansion

and contraction of the piping could cause excessive stress on system components, design expansion

compensation loops in the piping by making a deviation of at least 30 x 30 cm:

Expansion compensation loops are not necessary when using half-hard piping (from piping reels),

provided that there is a reserve for contraction when laying the piping – this means the piping should not

be forced into a perfect straight line.

Please take into account that Daikin selection software does not and can not evaluate the

above risks and does not propose any expansion compensation measures within the piping schematics.

The fact that no expansion loops or deviations are proposed on the piping schematics from the selection

software does not mean they are not necessary in the particular design.


Tel.: +43 2236 325 57 100Fax: +43 2236 325 57 910


http://upload.wikimedia.org/wikipedia/commons/d/dc/Nuvola_apps_important_yellow.svg


Minimum 1 meter

Minimum 0.5 metersMinimum 0.5 meters

Provide straight sections of piping before and after Refnet jointsTo allow refrigerant flow to stabilize and also to reduce any potential stress from thermal expansion and

contraction on a Refnet joint, provide straight sections of piping before and after Refnet joints:

Bad example:Piping turns immediately before and/or rafter the Refnet

joint may lead to unequal refrigerant distribution, leading

to capacity deficiencies in one of the branches and

possibly also flash-gas and noise occurrence.


Tel.: +43 2236 325 57 100Fax: +43 2236 325 57 910



Example:Operation sound = 39 dB(A)Max. sound = 47 dB(A)

Noise of similar levels as emitted by BS-Box can also be emitted from connected refrigerant piping.

Additionally, keep in mind that databook noise values are from measurements made in anechoic chambers. Noise measured in a real application will be higher due to reflections from surrounding surfaces.

Keep in mind refrigerant piping may also be a source of noiseDaikin publishes noise data for its finished units, but keep in mind that also the refrigerant piping may be

a carrier of some noise. This is especially true of refrigerant piping connected to Branch Selector Boxes

(BS-Boxes) of Heat Recovery systems, the noise of which is solely generated by refrigerant flow. Hence

a similar level of noise as published for the BS-Boxes can be emitted from refrigerant piping connected

to the BS-Boxes within several meters of the BS-Box.

To prevent the noise from refrigerant piping being a problem for the building occupants, take the

following design precautions:

Run the refrigerant piping through spaces that are not noise sensitive (e.g. hallways)

Run the refrigerant piping through spaces not exposed to occupied spaces (e.g. inside a closed

false ceiling, and/or for instance in isolated cable trays)

Apply double thermal insulation or additional sound-absorbing materials around the piping

Keep the distance between the BS-Box and occupied space at least 5 meters, as indicated in the

BS-Box installation manuals

In case of questions please do not hesitate to contact your Daikin representive.

Strategic Business Development DepartmentDaikin Airconditioning Central Europe GmbH


Tel.: +43 2236 325 57 100Fax: +43 2236 325 57 910


Reminder of important aspects of VRV refrigerant …server.mmc.bg/Актуални новини...

Documents

Transcript of Reminder of important aspects of VRV refrigerant …server.mmc.bg/Актуални новини...