FAQ : WATERSTAGE™ (Air to Water)

Before you buy


What is a heat pump?


Absorbing the free energy from atmosphere. Heat pump system requires only 1 kW of electricity to generate 3 to 5 kW thermal energy.

What is an ATW?

It makes an economical and clean hot water heating system by heat pump.

What is the advantages of ATW?

  1. Less CO2 emissions
  2. Low running cost
  3. Clean and health
  4. Easy installation and maintenance

What is possible?

It reliably delivers "comfort water" to all spaces in the home up to the living room, bed room, bath and swimming pool.

What is difference between air conditioner and ATW?

The ATW system take energy from the air and give it to a water circuit. The air conditioner take it from the air and give the energy to the air. ATW system are mainly used for heating application. With air conditioner cooling and heating are possible.

Is ATW clean and safety?

For Operating an ATW it needs no chimney. Around your building no pollution will occur. The maintenance cost are low, compared to gas or oil boiler.

How about running cost of ATW?

Running cost is low and economical by high efficiency heat pump technology.

What kind of construction is needed for ATW?

For Split type units it's pipe work for the refrigerant circuit and for Monobloc system it's only the hydraulic pipe work. In addition some electrical wiring is necessary for both systems.

Is it possible to install ATW to an existing house?

This is quite easy. Due to small pipes and wires it's not a big issue to install an ATW system in an existing building.

Is it possible to install ATW by use of an existing pipe?

For that case there are some hydraulic pipes existing it would be possible. With existing refrigerant pipes it's not recommended to use them.

What is needed for quotation for installing ATW?

It's necessary to know the heating demand of a building. This can be calculated by a heating expert. For existing houses you can refer to the former energy bill to find the annual consumption.

Where can I ask to have a quotation?

Please ask your purchase retailer or dealer.
If you can't inquiry, contact our service in your area.


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Function and Specification


How durable is the outdoor unit to sun/wind/rain?


Fujitsu's Outdoor Units are designed to live outside your home, as long as they have been installed and secured correctly these units can withstand day to day wind, rain and sun.

Is it a problem to install ATW to cold region?

No, it's not a problem. There is no operation limit with the ATW system. The Heat pump will operate at each minus temperature. For that case the heat pump can't supply the heating demand, there is an electrical backup heater integrated.

Is no problem to install ATW to snowy area?

Due to the integrated defrost operation it's also no problem to use this unit at a snowy area. It's allowed to protect the unit against snow but it's not mandatory.

Is timer function available?

With the Siemens controller a week timer with three time periods a day is available.

Is it a problem to operate ATW continuously during the heating season?

No, this is no problem.

Is it possible to extend the system later?

Yes, a bundle of different options are available. With that the system can extended afterwards.


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What maintenance is required from me for my new ATW?


Please ask your installer to give you a demonstration on how to take care of your ATW system.

Does an ATW ever need recharging ?

If an ATW unit is installed correctly then it should never need to be recharged. There is no such thing as stale gas or expired gas, the only reason for recharging will be if there is a leak in the system and this can be checked by a qualified technician.

Is it necessary to add some water regularly?

If the hydraulic system is sealed properly it shouldn't be necessary. Otherwise it's easily possible to fill up the water level.

Is it necessary to do regular maintenance?

Due to any regulations it's not necessary to do so. But it's recommended to let an expert have an eye on the installation from time to time.


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How to use


Do you pay attention to save the energy consumption?


If you answer this question with "yes" the ATW heat pump is the right system for you.

Do ATW Heat Pumps need a backup heater?

Air to Water Heat Pumps do not require a backup heater. A Heat Pump is capable of providing all of a property’s heating and domestic hot water.
The used electrical heater inside is for backup or emergency purpose only.

I have not used ATW for a long period.
What do I have to do before start the operation?

Exercise a visible inspection at the outdoor unit that the air flow over the unit is not blocked. Than go to the indoor unit and start the system. There are no more things to consider.

If I would not use ATW for a long period, what should I do for ATW?

Set the unit into standby mode. A frost protection is than working and prevent the hydraulic system. No further action necessary.

What should I do before winter?

Nothing. The Heat pump recognises the outdoor temperatures and switch on the heating system automatically. There is no need to do any further action.


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What sorts of things aren’t covered under warranty?

What sorts of things are covered under warranty?


Please ask your purchase retailer or dealer.

Poor Cooling or Heating performance:

Please contact your installer for handling this case.

The unit operates differently from the Remote Control Unit's setting:

Please check the installation place of the room thermostat.

Doesn't operate at all:

Please contact your installer for handling this case.

Doesn't operate immediately:

Indoor unit

If the units do not start directly please check for some error indication. Either at the indoor unit or the outdoor unit.

In the case of an outdoor unit failure, it's possible to operate heating mode by the electrical backup heater.
Please make sure to let the system repair quite quick in order to avoid exceeding the electrical bill.

How about operation noise?

Indoor unit

The outdoor unit contains a compressor and a fan. Both item will create a noise during operation. That this will be no problem it's necessary to find a proper place for the unit where this noise will be no problem. Keep in mind, it's possible to decrease a noise by increasing the distance.

There is water coming out of the outdoor unit. What is the reason for that?

Outdoor unit

During Heating operation and low outside temperatures, water will be produced from time to time unit according to automatic defrosting operation.

What is Automatic Defrosting Operation for?

Outdoor unit

With low outdoor temperature in combination with high air humidity water turns into ice crystals due to a low surface temperature at the heat exchanger . If this increases to much, this will reduce the efficiency.
To avoid this situation an automatic defrost operation is implemented. At this time the melted ice will come out of the unit.

Should I take care of the out coming water?

Indoor unit

According to the low outside temperature this water will turn rapidly into ice again and can create a slippery ground around the outdoor unit. Please, take care that the unit is not placed next to pedestrian path.


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Can I re-use the piping which is already installed for my old heat pump ?


It is not recommended to re-use the same piping and cable for new units as different systems have different piping and electrical requirements.

What happens if piping is less than the minimum recommended length (3 metres/5 metres)?

If the product is installed with less pipe work than the minimum requirement specified by Fujitsu engineers, noise and/or vibration issues may occur and also the system may not perform as well as it is designed to. We do not recommend this.

Can I put a cover over the front of my outdoor unit to make it less visible?

The outdoor unit of your split system needs to have adequate clearance around it to ensure it operates correctly. If you would like to conceal your outdoor unit, talk to your installer.

What is the best location to install the outdoor unit ?

It is advised to install the outdoor unit in a safe, dry and well-ventilated area. Make sure you meet any local council rules and/or regulations. Keep in mind the location of your bedrooms and of course your neighbours. If you have any questions, consult the installation manual and it will guide you.

Where should I install the indoor unit?

Indoor unit can place at the basement, the utility room or even the kitchen (Please don't place it next to the cooking stove)

Where should I install the outdoor unit?

It is advised to install the outdoor unit in a safe, dry and well-ventilated area. Make sure you meet any local council rules and/or regulations. Keep in mind the location of your bedrooms and of course your neighbours. If you have any questions, consult the installation manual and it will guide you.


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Please download it on our web site or local web site.

Operation manual

Please ask your purchase retailer or dealer.
If you can't ask someone, contact our service in your area.


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Different Options, like room thermostat, remote controller, WebServer, swimming pool kit and so on.


Please ask your purchase retailer or dealer.
If you can't ask someone, contact our service in your area.


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