Danfoss Cold Store Protection Systems Application guide

Cold Store Protection Systems

Cold Store Protection Systems

Application manual

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Index

General information

4

1.Frost heave prevention system 5

2.Protection against

condensation on floors	13
3. Freeze protection of
doors and gates	16
4. Frost protection of
pipes in cold stores	19

5. Frost protection of

drain lines of cooling equipment 23

6. General installation guide	24
7. Case story	28

Our quality management system and compliances

ISO 9001	TS 16949
ISO 14001	PED

Along with full compliance with EU directives and product approvals

Let DEVI do the work

DEVI - an abbreviation of Dansk El-Varme Industri - was established in Copenhagen, Denmark, in 1942. As from January 1st 2003 DEVI has become a part of the Danfoss Group - Denmark's largest industrial Group. Danfoss is one of the world's leading companies within heating, cooling and airconditioning. The Danfoss Group has more than 23.000 employees and serves customers in more than 100 countries.

DEVI is Europe’s leading brand of electrical cable heating systems and electric pipe heating systems with over 70 years of experience. The production of heating cables takes place in France and Poland while the head office is situated in Denmark.

Cold stores, Ice stadiums and alike

This design guide presents DEVI’s recommendations for design and installation of frost heave prevention systems and frost protection for cold room doors, drain lines, and fire protection sprinklers and pipes. It provides guidance for a heating cable layout, electrical data and system configurations.

Following DEVI’s recommendations will ensure energy efficient, reliable and maintenance free solution for constant wattage heating cables with 20 year warranty.

General information

In cold stores, ice stadiums, etc. the temperature is always within the range of –20 and –30 °C, however cold leak occurs even if the floor

is insulated properly. This means that materials which are in contact with the soil, such as foundation and floor areas, will absorb the cold and let the ground freeze. Water, contained in the soil, will change volume when turning into ice and can cause substantial damage due to frost erosion.

Furthermore, in areas where very cold dry air meets warm moist air, the moisture contained in the warm air flow may settle on the cold surface and turn into ice. Ice conduces unwanted freezing of

elements such as cold store doors/ gates or door frames and can cause: damage to the door structure, weather stripping, disabling closing the door tightly and leading to increased energy consumption, etc. Another problem, that occurs in a drainage system of refrigeration equipment, is condensation freezing and inability of free water flow.

DEVI offers reliable and energy efficient cable heating systems to prevent frost heave and ensure frost protection of doors drain lines and firefighting piping. DEVI has supplied various range of such systems to 5 continents over many years.

Benefits

•Eliminate risk of foundation damage – ice buildup in the foundation, which can result in problems such as: uncontrolled movement or elevation of

the building foundation causing damage to the construction. DEVI prevents frost heaving damage in commercial freezers & ice stadiums by eliminating the possibility of such ice buildup.

•Investment safety – reduces the possibility of cold storage stock loss or destruction of the building due to the damaged foundation.

•Reduced energy loss - smooth operation of doors, protects the construction and prevents energy loss through untightly closed doors.

•Safety of working environment - prevents slippery floors and ensures frost protection of firefighting pipes and sprinklers.

•Power saving solution – DEVI uses Advanced Controls to ensure power saving by: minimizing running time of the system, while maintaining the appropriate foundation temperature to prevent its freezing.

•Space saving – as compared to alternative solutions, DEVI system is less complicated, easier for planning & installation and requires no extra space.

•Lower initial costs – competitive solution with over 50% lower cost of the system, comparing to Pumped Fluid solution (Glycol) in pipes built into the foundation.

•No Environmental Concerns – DEVI electric heating systems do not pose any environmental hazards, e.g. glycol leak into the soil. DEVI systems use electric heating cables instead of glycol-water mixture.

•Lowest ownership costs - 20 years of full warranty from Danfoss Group and 50 years of expected lifetime for all DEVI serial resistive heating cables.

4 Application manual · Cold Store Protection Systems · VGLUB102 · ©DEVI

1. Frost heave prevention system

1.2. System Description

The main object of heating, in the Frost Heave Prevention System, is to provide frost protection of foundation in premises where temperature is constantly maintained below zero (cold storages, ice stadiums, etc.).

Installation of an indoor frost protection system is required and electrical heating cables embedded in concrete is a solution to prevent frost heaving. Frost heave can cause floor slab cracking, damage to support structures and foundations. In such cases underfloor heating is needed in order to avoid freezing or other related problems and

prevent destruction of foundation structures.

The heating cable in this case is located below the main floor insulation of the cold storage,

typically in the sand backfill or in concrete screed.

For safety reasons: two identical parallel heating systems should be installed (main and reserve).

Frost Heaving

As the soil temperature under a freezer drops below zero, the moisture contained in the soil freezes up and expands significantly.

This ice formation results in floor cracking and its change of elevation or “heaving”.

Ice formation can lift up columns, push over foundation walls

and rip open roofs. Almost all components of the cold store can be repaired, whilst the major part of space is still used for storage, but this doesn’t apply to the floor.

The problem cannot be solved by insulation alone.

Application manual · Cold Store Protection Systems · VGLUB102 · ©DEVI 5

1.2. Products

Heating cables

To prevent ground freezing the heating system may include the following resistive (constant wattage) heating cables:

DEVIflex™ 6T, DEVIflex™ 10T,

DEVIflex™ 18T;

DEVIbasic™ 10S, DEVIbasic™ 20S.

DEVI resistive heating cables allow safe, efficient and economical cold store installation.

Note. The number at the end of the cable’s name refers to its specific output in W/m, at voltage of 230 V or 400 V. Letter “T” means twin conductor cable (Twin), letter ”S” – single-conductor cable (Single).

DEVIflex™ is a twin conductor heating cable for installation in concrete floors, pipe heating etc. The cable complies with IEC 60800:2009 class M2, and is designed for applications with the high risk of mechanical damage. It is supplied in readymade sets with 2,3 m cold lead (supply cable), sealed joints and end muff.

Cable diameter is Ø 6,9 mm.

The cable is available for 230 V power supply.

Cables of 6, 10 or 18 W/m (230 V) linear output are available.

Available cable length:

DEVIflex™ 6T: 30 - 200 m;

DEVIflex™ 10T: 2 - 210 m;

DEVIflex™ 18T: 7 - 170 m.

DEVIbasic™ is a single conductor heating cable complying with IEC 60800:1992 and intended for installation in concrete floors, for pipe heating etc. It is supplied in readymade sets with 2x3 m cold

leads and sealed connection muffs.

Cable diameter is Ø 5,5 mm.

DEVIbasic™ 20S is available for 230 V and 400 V power supply voltage.

To decrease linear output (W/m) the 400 V cable can be connected to 230 V means – in this case the cable linear output is 6,6 W/m.

Available cable length: DEVIbasic™ 10S, 230 V: 21 - 407 m; DEVIbasic™ 20S, 400 V: 56 - 229 m.

DEVIflex™

DEVIbasic™

Fixing

In case of heating cables application, it is recommended to use fitting bands to fix the cable to the floor, e.g. DEVIfast™ metal galvanized fitting band. It should be attached to the floor (e.g. nailed down) in parallel lines usually at intervals of 100 cm or using one meter of fitting

band per each square meter of cable installation. The same applies to DEVIclip™ C-C and Montagestege™ plastic bands.

For quick cable fixing to reinforced mesh DEVIclip™ Twist plastic fixing is recommended.

For cable fixing to metal columns etc. Alutape adhesive aluminum tape is recommended.

6 Application manual · Cold Store Protection Systems · VGLUB102 · ©DEVI

Thermostats

For control of Frost Heave Prevention System the DEVIreg™ 330 (-10…+10 °C) thermostat with DIN rail attachement is recommended. Additionally a wall mounted DEVIreg™ 610, IP44 can be used.

All thermostats are equipped with wire temperature sensors –

NTC 15 kOhm @ 25 °C with 3 meter long cable.

To provide correct temperature measuring the sensor cable should be of e.g. 10 m, to measure the temperature in the heated area (depends on the local conditions). 10 m long sensor is available, but needs to be ordered separately.

Note! For safety reasons: installations in cold storages should contain

two independent circuits (main and reserve) controlled by separate thermostats.

DEVIreg™ 330 DEVIreg™ 610

Products - general overview of Frost Heave Prevention Systems

	Product	Options	Description
	DEVIflex™	DEVIflex™ 6T, 230 V;	Twin conductor, 100% screen.
			6, 10 W/m (230 V).
	Resistive heating cable	DEVIflex™ 10T, 230 V
			DIN IEC 60800:2009 M2
	DEVIbasic™	DEVIbasic™10S, 230 V;	Single conductor, wire screen.
			10 W/m (230 V), 20 W/m (230 V/400 V).
	Resistive heating cable	DEVIbasic™20S, 400 V
			DIN IEC 60800:1992 M2
	DEVIbasic™	DEVIbasic™ on drum,	Single conductor, wire screen.
			Max. 20 W/m; max. 400 V.
	Resistive heating cable	0,0134 - 34,1 Ohm/m
			DIN IEC 60800:1992 M2
	Assembly kits	DEVIcrimp™ assembly kit	For single conductor cable.
		DEVIcrimp™ CS2A/CS2B	For twin conductor cable
	DEVIreg™ thermostat	DEVIreg™ 330 (-10…+10 °C)	-10…+10 °C, 16 A, IP20, DIN rail
	DEVIreg™ thermostat	DEVIreg™ 610	-30…+50 °C, 10 A, IP44,
			on wall/pipe installation
	Temperature sensor	10 m, PVC	Wire sensor, Ø 8 mm, IP65,
			NTC 15 kOhm @25 °C
	Temperature sensor	40 m, silicone covered	Wire sensor, Ø 5 mm, IP67,
			NTC 15 kOhm @25 °C
		DEVIfast™ Metal	25 m pack; galvanized metal, fixings every 2,5 cm.
	Fixing	DEVIclip™ C-C	10 x 1 m; plastic, fixes cable Ø every 1 cm.
		Montagestege™ 6 mm	1 m; plastic, fixes cable Ø 5,6-6,5 mm every 2,5 cm.
		Montagestege™ 8 mm	1 m; plastic, fixes cable Ø 6,6-8 mm every 2,5 cm
	Fixing	DEVIclip™ Twist	Bag with 1000 pcs.;
			Ø 17 mm; fixing cable to reinforced mesh
	Fixing	Alutape	Glued aluminium tape 38 mm x 50 m;
			0,06 mm; max. 75 °C

For details please refer to the DEVI Catalogue.

Application manual · Cold Store Protection Systems · VGLUB102 · ©DEVI 7

1.3. System design

The heating cable for the Frost Heave Prevention System is located under the main floor insulation of the cooling facility, typically into sand backfill or concrete screed (fig. 1 and fig. 2).

Heating cable should be placed under the insulation layer of the floor to offer frost protection. Cables should be placed directly on top of the hardened concrete only, as an option can also be separated from the floor surface with the damp proof membrane. The cables should be installed at least 5 cm below the insulation. The floor construction must comply with local norms and regulations.

Floor in cold store		Floor in cold store

Reinforced concrete	Reinforced concrete
Thermal insulation	Thermal insulation

Concrete

Concrete

DEVIfast™ fitting

Sand backfill

Sand backfill

Reinforced mesh

	Ground	Ground
Fig. 1 – Heating cable in in the concrete screed		Fig. 2 – Heating cable in the sand backfill

Installed output

Under normal conditions calculated values of heat loss aren’t very high, e.g. 3-8 W/m² only. However it is recommended to use 15-30 W/m²

as a standard value or at least 15 W/m² for frost protection installations. In any case an output value should

be calculated and correspond to downward heat loss.

The foundation cooling rate depends on:

•the rate of heat/cold emission through the floor;

•soil/ground temperature;

•interior temperature of the cold room or surface temperature of ice stadiums etc.

To estimate the required power density in [W/m²] of the freeze protection system, the thermal resistance of multilayer floor construction should be calculated. While comparing actual values of all layers the thermal resistance of each layer, except the insulation layer, should be neglected.

Heating system output can be determined from the following formula:

P = Δt · U · 1,3 [W/m²],

where

Δt – the temperature difference between ground/soil and cold store interior [°C];

U – the floor heat transfer factor, typically for insulation only [W/m²·°C]; 1,3 – safety factor.

For insulation U value can be determined as follows:

U = λ/δ = (thermal conductivity coefficient [W/m·K]) / (thickness [m])

Calculation example

A cold store has the following parameters:

The U-value of the insulation: U = 0,04 / 0,2 = 0,2 W/(m²·°C).

Output calculation is 7,8 W/m², but as per recommendations, the installed minimum should be 15 W/m²!

Cold store temperature: -25 °C.	Δt = +5 °C - (-25 °C) = 30 °C.
		For example, three lines of DEVIflex™ 6T
Ground temperature: +5 °C.	Calculation of heating system output	per m² provide 18 W/m² output and
	per square meter:	ensure cold store protection against
Insulation: 0,2 m thick,		frost heaving.
λ = 0,04 W/m·°C.	P = 30 °C · 0,2 W/(m²·°C) · 1,3 =
	= 6 W/m² · 1,3 = 7,8 W/m².

8 Application manual · Cold Store Protection Systems · VGLUB102 · ©DEVI

C-C distance

There must not be any subzero temperature gaps between the heating cable lines! Otherwise it will not prevent frost heave!

The temperature distribution in geometry of cold store floor has to be evaluated. The result depends on a number of parameters, the main are the following:

•thermal conductivity of the ground;

•linear output of the heating cable;

•C-C distance.

The thermal conductivity of the soil may vary significantly during

operation, hence in practice following simplification rule is often used:

to ensure even heat distribution with no cold gaps the maximum central-central distance (C-C distance) between the heating cables should not exceed 50 cm (fig. 3). In other words, an installation of minimum 2 meter

heating cable per m², is necessary.

C-C ≤ 50 cm

Fig. 3 – Heat/cold distribution and max C-C without cold gaps

It's very strongly advisable to always place a second supplementary cable loop with the same C-C distance.

For installations with max. C-C distance of 50 cm power output per 1m² for some cable types is the following:

DEVIflex™ 6T – 12 W/m²;

DEVIflex™ 10T – 20 W/m²; DEVIbasic™ 20S, 400 V connected to 230 V – 19,8 W/m².

Recommendations: the preferred C-C distance between cable lines is 33 cm. It allows implementation of a simple rule for cable length calculation – 3 m of cable per 1 m².

For example three lines of DEVIflex™ 6T per 1 m² provides 18 W/m² (230 V) output. It is applicable for almost all types of cold stores, ice stadiums etc.

Minimum requirement: 10 W/m cable should be installed with a C-C distance of maximum 50 cm.

Safety

For safety reasons two identical heating systems should be installed in parallel – the main and the reserve one.

Elements for such system are following:

•two identical parallel circuits of heating cable (main and reserve);

•two identical thermostats with temperature sensors for each cable;

•alarm signals in case of reserve cables operation – light and acoustic alarm;

•two separate power supply lines;

•separate fuses, RCD relays, contactors, etc.

Please note that the reserve cable	The C-C distance is determined as a
system is obligatory for this type	median line between the main and
of installations. Reserve cables are	reserved cable, see fig. 4.
usually mounted in parallel to the
main cable with a distance of	Note! One thermostat per heating
2,5-5 cm, to the primary system.	cable should be installed.

C-C	C-C	C-C
2,5-5 cm
Main cable
Reserve cable

Fig. 4 – Main and reserve heating cables

Application manual · Cold Store Protection Systems · VGLUB102 · ©DEVI 9