The surface temperature for snow melting is controlled automatically to reduce operating energy costs. The 654 has an automatic start and stop function when used with the Snow/Ice Sensor 090 or 094. Automatic start with a timed stop is available when used with the Snow Sensor 095. The 654 can operate a dedicated hydronic boiler or a mixing device. Isolation relays are required to operate line voltage pumps. Electric systems require a separate GFCI and electrical relay contactor.

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The temperature of the coolant in a water cooling circuit varies during the operation, which means that the volume of the fluid is not constant. The cooling system includes a lot of lines, fittings and components which all have some pressure-based flexibility. There may be some air or other gases in air pockets of a system, or some air mixed with coolant especially after filling the system. To compensate all these variations, the system must be equipped with a compensating pressure vessel which is often called “Expansion vessel”. This vessel is filled with coolant liquid and gas (air or nitrogen). The gas gives the flexibility to the cooling system. The expansion vessel supplies some coolant to the system when there is lack of it and prevents pressure loss and cavitation in the suction side of the pump. The vessel receives some coolant from the cooling circuit when the coolant temperature increases and the coolant expands. The main purpose of the expansion vessel is to keep the system pressure constant.

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One essential requirement for a reliable cooling system is to know how much coolant there is in the system. It is easy to understand what happens when oil level in a car engine is too low. However, very few do understand the importance of the right coolant level for a cooling system functionality.

In small systems a vessel made of fiber-reinforced plastic is acceptable when it is equipped with needed instruments. It is light but still technically strong.

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The volume of the expansion tank must be big enough for all compensation needs of the cooling system. In big systems with outdoor water-to-air heat-exchangers the volume may be hundreds of litres. The needed volume must be calculated for each case separately. The calculation must include separately the volume for coolant and gas as well as the filling pressure of the gas. The filling level of the coolant must be marked to level indicator to make it easy for maintenance personnel to make right filling.

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The task of the liquid coolant is to transfer heat. The cooling capacity of the coolant is at its best when there is no air or gas mixed in it. When the cooling system is filled with coolant, air or gas mixing in the coolant can’t be avoided. This is the case in new installations and when servicing and performing system maintenance.

To make the process easier to follow, there is also a sight glass to the system to monitor the coolant quality visually:

In smaller systems it takes less than half an hour and in bigger system around an hour to get small air bubbles out of the coolant. Half an hour vs. several days is a significant difference.

WORDS: Arto Verronen, Strategist, Member of the Board For more information please contact Ismo Lehtonen, Sales and Marketing Director  +358 40 669 2220 ismo.lehtonen@adwatec.com

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The pressure level of the cooling system may decrease with time. As there are many components, connections and pipes in the complete cooling set-up the pressure decrease may be coming from a leak in the system or from air escaping the system. Often the leaks are minimal and not easily visible. The question for the maintenance staff is then simple: should coolant or air be added to system?

The expansion vessel is one of the key components of the cooling system and correctly selected high quality components ensure the reliability of the cooling system. There are principally two expansion vessel designs:

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How do different expansion vessel designs handle the coolant volume monitoring issue? An expansion vessel in which the coolant is in direct contact with the gas has several advantages:

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This article will highlight some crucial characteristics of expansion vessel designs that are used in liquid cooling systems. The following topics will be covered:

The loss of cooling may cause a fatal safety risk or major production losses. In the worst case a ship may lose its propulsion power and ends up drifting uncontrolled.

Air is mixed in the coolant as very small air bubbles. These bubbles are difficult to separate from the system and de-airing may easily take several days. This is an issue especially in unexpected service cases when there is no time for long lasting processing. As a solution, Adwatec has developed an automatic de-airing system. Together with Adwatec tank construction the de-airing happens fast and the cooling system can be taken into use quickly. The air removal continues during the operation and the air is collected to expansion vessel.

To avoid galvanic corrosion in the system, carbon steel and copper-based materials must not be used, not even in fittings. For that reason, the expansion vessel should be made of stainless steel.

In addition to reduced cooling capacity the air or gas may also cause cavitation in pump impellers and unexpected behaviour of the system. These issues are even more dramatic when the coolant is a water-glycol mixture instead of pure water.

The Snow Melting Control 654 is designed to operate electric or hydronic equipment to melt snow or ice from any surface including driveways, walkways, patios, business entrances, parking ramps, loading docks, hospital entrances, helipads or car wash bays.