Condensate pump
Encyclopedia
A condensate pump is a specific type of pump
used to pump the condensate
(water
) produced in an HVAC
(heating or cooling), refrigeration
, condensing boiler
furnace or steam
system. They may be used to pump the condensate produced from latent water vapor
in any of the following gas mixtures:
Condensate recovery systems help you reduce three tangible costs of producing steam:
, but in commercial applications they range in size up to many horsepower and the electric motor
is usually separated from the pump body by some form of mechanical coupling. Large industrial pumps may also serve as the feedwater pump
for returning the condensate under pressure to a boiler.
Condensate pumps usually run intermittently and have a tank in which condensate can accumulate. Eventually, the accumulating liquid raises a float switch
energizing the pump. The pump then runs until the level of liquid in the tank is substantially lowered. Some pumps contain a two-stage switch. As liquid rises to the trigger point of the first stage, the pump is activated. If the liquid continues to rise (perhaps because the pump has failed or its discharge is blocked), the second stage will be triggered. This stage may switch off the HVAC equipment (preventing the production of further condensate), trigger an alarm, or both.
Some systems may include two pumps to service the tank. In this case, the two pumps often alternate operation, and a two-stage switch serves to energize the on-duty pump at the first stage and then energize the remaining pump at the second stage. This second stage action is in addition to any triggering of other system changes as noted for a single pump installation. In this way pump runtime is shared between the two, and a backup pump is provided in case one pump fails to function as designed.
Small pumps have tanks that range from 2 to 4 litres (0.5 to 1 gallon) and are usually supported using the flanges on their tanks or simply placed upon the floor. A plastic impeller in a molded volute
at the bottom of the pump provides the pumping action; this impeller is connected to the motor via a metal shaft that extends downwards from the motor mounted above the tank's top. Large pumps are usually pad-mounted drawing liquid from a tank (sump) below the floor. The smallest pumps may have no tank at all and are simply placed within a container such as the drip pan of a dehumidifier
appliance.
In industrial steam systems the condensate pump is used to collect and return condensate from remote areas of the plant. The steam produced in the boiler can heat equipment and processes a considerable distance away. Once steam is used it turns to hot water or condensate. This pump and possibly many more around the plant returns this hot water back to a make-up tank closer to the boiler, where it can be reclaimed, chemically treated, and reused, in the boiler, consequently it can sometimes be referred to as a condensate return pump.
In a steam power plant, particularly shipboard ones, the condensate pump is normally located adjacent to the main condenser hotwell often directly below it. This pump sends the water to a make-up tank closer to the steam generator or boiler. If the tank is also designed to remove dissolved oxygen from the condensate, it is known as a Deareating feed tank
(DFT). The output of the DFT supplies the feed booster pump which, in turn, supplies the feed pump (feedwater pump) which returns the feedwater to the boiler so the cycle can start over. Two pumps in succession are used to provide sufficient Net Positive Suction Head to prevent cavitation and the subsequent damage associated with it.
This pump is usually associated with a much larger tank, float switch, and an electric motor than the example above. Some systems are so remote that steam power is used to return the condensate where electricity is impractical to provide.
The output of small condensate pumps is usually routed to a sewer
, drain, or the outside world via PVCl
plastic
tubing. If the outlet of the line is at a higher level than the tank of the pump, a check valve
is often fitted at the outlet of the pump so that liquid cannot flow backwards into the pump's tank. If the outlet is below the tank level, siphon
age usually naturally clears the output line of all liquid when the pump is deenergized. In cold regions of the world, it is important that condensate lines that are exhausted outside be carefully designed so that no water can remain in the line to freeze up
; this would block the line from further operation.
Condensate is not pure water. If it is being condensed from an air stream, it may have dust
, microbes, or other contaminants in it. If it is condensed from steam, it may have traces of the various boiler water treatment chemicals. And if it is condensed from furnace exhaust gases, it may be acid
ic, containing sulfuric acid
or nitric acid
as a result of sulfur
and nitrogen dioxide
s in the exhaust gas stream. Steam and exhaust condensate is usually hot. These various factors may combine (along with local regulations) to require careful handling or even treatment of the condensate and condensate pumps used for these services must be appropriately designed.
Understanding and Solving Equipment Stall
Pump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...
used to pump the condensate
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
(water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
) produced in an HVAC
HVAC
HVAC refers to technology of indoor or automotive environmental comfort. HVAC system design is a major subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer...
(heating or cooling), refrigeration
Refrigeration
Refrigeration is a process in which work is done to move heat from one location to another. This work is traditionally done by mechanical work, but can also be done by magnetism, laser or other means...
, condensing boiler
Condensing boiler
A condensing boiler utilizes the latent heat of water produced from the burning of fuel, in addition to the standard sensible heat, to increase its efficiency.-Principles of work:...
furnace or steam
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...
system. They may be used to pump the condensate produced from latent water vapor
Water vapor
Water vapor or water vapour , also aqueous vapor, is the gas phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Under typical atmospheric conditions, water vapor is continuously...
in any of the following gas mixtures:
- Conditioned (cooled or heated) building air
- Refrigerated air in cooling and freezing systems
- SteamSteamSteam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...
in heat exchangers and radiators - The exhaust stream of very-high-efficiency furnaces
Condensate recovery systems help you reduce three tangible costs of producing steam:
- Fuel/energy costs
- Boiler water make-up and sewage treatment
- Boiler water chemical treatment
Construction and operation
Condensate pumps as used in hydronic systems are usually electrically powered centrifugal pumps. As used in homes and individual heat exchangers, they are often small and rated at a fraction of a horsepowerHorsepower
Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...
, but in commercial applications they range in size up to many horsepower and the electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
is usually separated from the pump body by some form of mechanical coupling. Large industrial pumps may also serve as the feedwater pump
Boiler feedwater pump
A boiler feedwater pump is a specific type of pump used to pump feedwater into a steam boiler. The water may be freshly supplied or returning condensate produced as a result of the condensation of the steam produced by the boiler...
for returning the condensate under pressure to a boiler.
Condensate pumps usually run intermittently and have a tank in which condensate can accumulate. Eventually, the accumulating liquid raises a float switch
Float switch
A float switch is a device used to detect the level of liquid within a tank. The switch may be used in a pump, an indicator, an alarm, or other devices....
energizing the pump. The pump then runs until the level of liquid in the tank is substantially lowered. Some pumps contain a two-stage switch. As liquid rises to the trigger point of the first stage, the pump is activated. If the liquid continues to rise (perhaps because the pump has failed or its discharge is blocked), the second stage will be triggered. This stage may switch off the HVAC equipment (preventing the production of further condensate), trigger an alarm, or both.
Some systems may include two pumps to service the tank. In this case, the two pumps often alternate operation, and a two-stage switch serves to energize the on-duty pump at the first stage and then energize the remaining pump at the second stage. This second stage action is in addition to any triggering of other system changes as noted for a single pump installation. In this way pump runtime is shared between the two, and a backup pump is provided in case one pump fails to function as designed.
Small pumps have tanks that range from 2 to 4 litres (0.5 to 1 gallon) and are usually supported using the flanges on their tanks or simply placed upon the floor. A plastic impeller in a molded volute
Volute
A volute is a spiral scroll-like ornament that forms the basis of the Ionic order, found in the capital of the Ionic column. It was later incorporated into Corinthian order and Composite column capitals...
at the bottom of the pump provides the pumping action; this impeller is connected to the motor via a metal shaft that extends downwards from the motor mounted above the tank's top. Large pumps are usually pad-mounted drawing liquid from a tank (sump) below the floor. The smallest pumps may have no tank at all and are simply placed within a container such as the drip pan of a dehumidifier
Dehumidifier
A dehumidifier is typically a household appliance that reduces the level of humidity in the air, usually for health reasons. Humid air can cause mold and mildew to grow inside homes, which pose various health risks. Very humid climates or air make some people extremely uncomfortable, causing...
appliance.
In industrial steam systems the condensate pump is used to collect and return condensate from remote areas of the plant. The steam produced in the boiler can heat equipment and processes a considerable distance away. Once steam is used it turns to hot water or condensate. This pump and possibly many more around the plant returns this hot water back to a make-up tank closer to the boiler, where it can be reclaimed, chemically treated, and reused, in the boiler, consequently it can sometimes be referred to as a condensate return pump.
In a steam power plant, particularly shipboard ones, the condensate pump is normally located adjacent to the main condenser hotwell often directly below it. This pump sends the water to a make-up tank closer to the steam generator or boiler. If the tank is also designed to remove dissolved oxygen from the condensate, it is known as a Deareating feed tank
Deareating feed tank
A Deaerating Feed Tank , often found in steam plants that propel ships, is located after the main condensate pump and before the main feed booster pump....
(DFT). The output of the DFT supplies the feed booster pump which, in turn, supplies the feed pump (feedwater pump) which returns the feedwater to the boiler so the cycle can start over. Two pumps in succession are used to provide sufficient Net Positive Suction Head to prevent cavitation and the subsequent damage associated with it.
This pump is usually associated with a much larger tank, float switch, and an electric motor than the example above. Some systems are so remote that steam power is used to return the condensate where electricity is impractical to provide.
The output of small condensate pumps is usually routed to a sewer
Sanitary sewer
A sanitary sewer is a separate underground carriage system specifically for transporting sewage from houses and commercial buildings to treatment or disposal. Sanitary sewers serving industrial areas also carry industrial wastewater...
, drain, or the outside world via PVCl
Polyvinyl chloride
Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...
plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
tubing. If the outlet of the line is at a higher level than the tank of the pump, a check valve
Check valve
A check valve, clack valve, non-return valve or one-way valve is a mechanical device, a valve, which normally allows fluid to flow through it in only one direction....
is often fitted at the outlet of the pump so that liquid cannot flow backwards into the pump's tank. If the outlet is below the tank level, siphon
Siphon
The word siphon is sometimes used to refer to a wide variety of devices that involve the flow of liquids through tubes. But in the English language today, the word siphon usually refers to a tube in an inverted U shape which causes a liquid to flow uphill, above the surface of the reservoir,...
age usually naturally clears the output line of all liquid when the pump is deenergized. In cold regions of the world, it is important that condensate lines that are exhausted outside be carefully designed so that no water can remain in the line to freeze up
Freezing
Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....
; this would block the line from further operation.
Condensate is not pure water. If it is being condensed from an air stream, it may have dust
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...
, microbes, or other contaminants in it. If it is condensed from steam, it may have traces of the various boiler water treatment chemicals. And if it is condensed from furnace exhaust gases, it may be acid
Acid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
ic, containing sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
or nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
as a result of sulfur
Sulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...
and nitrogen dioxide
Nitrogen dioxide
Nitrogen dioxide is the chemical compound with the formula it is one of several nitrogen oxides. is an intermediate in the industrial synthesis of nitric acid, millions of tons of which are produced each year. This reddish-brown toxic gas has a characteristic sharp, biting odor and is a prominent...
s in the exhaust gas stream. Steam and exhaust condensate is usually hot. These various factors may combine (along with local regulations) to require careful handling or even treatment of the condensate and condensate pumps used for these services must be appropriately designed.
External links
Types of Condensate RecoveryUnderstanding and Solving Equipment Stall