The Aquastar water heater is the Bosch trade name for the gas tankless water heaters and they are the most popular and reviewed (Amazon website) on demand gas appliances with several models that are Energy Star qualified.
Bosch in US offers several models that are designed for the outdoor and indoor installation, powered by natural gas or propane, used as a solar back-up, and built for smaller and larger homes.
These models include 2700ES, 2400ES, 2400E, 2400EO, 1600P, 1600H, 1600PS, 125BO, 125FX and 1000P and they come with the thermal efficiency from 80% to 87%, which qualifies, some models from Aquastar water heater series, Energy Star compliant.
The following features and safety devices are standard on the majority of Bosch water heaters including the most popular Aquastar and 2700ES 2400ES models.
There are also models that are not equipped with such
features; they have a slightly different features and
less high-tech and sophisticate elements.
Every Bosch Aquastar water heater is suitable for potable water heating; bath and kitchen, and cannot be used for space heating.
As the burner output is proportionate to hot water flow demand, the power is usually controlled by modulation on the gas valve that further controls the constant gas/air ratio; or manually with a gas control slide button (like Aquastar 125BO or 1000P models).
Bosch Aquastar water heater supports variable flow applications, with modulating water valve or adjustable water flow restrictor (like 125BO models), for improved comfort and temperature control. Minimum water pressure is needed so the unit can be activated.
The major differences between Aquastar
heaters, which are also the key
factor when planning to buy, are:
to properly size your tankless
The easiest method when choosing a water
heater is to know how many plumbing applications; showers,
dishwasher, washing machine and kitchen sink will use hot water. Based
on that or your family size, you can decide about the capacity.
Aquastar 2700 series can provide enough hot water for up to three plumbing units simultaneously, delivering over 7 gallons per minute.
Bosch Aquastar 2400 models can be used for two major hot water applications at the time, providing around 6 gallons per minute.
Aquastar 1600, 125BO and 125FX models are good enough for one bathroom homes, providing around 4.3 gallons per minute, while 1000P is used for cottages and camp houses, delivering 2.6 gallons per minute.
Note: The suggestion is to use inlet and outlet pipes no less than 3/4" or 19.05 mm, so they can supply enough water for the full water heater capacity use.
When the burner does not ignite and when the hot water is on, the electrode might be one of the causes for the problem. The electrode might not produce the spark or one of the electrodes, called the flame sensor, doesn't detect the flame ionization.
If your home requires direct venting option, the following Aquastar models are available; 2400ES and 2400E, and they come with a room-sealed combustion chamber and built-in power vent.
These models can be installed in the bathrooms, kitchen, even bedrooms, as they are indoor and room sealed, but only if using a twin pipe solution; one pipe for venting gases out and the other for fresh air intake.
If it is one pipe solution than ventilation has to be provided as the inside air is used for combustion. For these unsealed units there should be a dedicated room with proper venting.
Aquastar water heater 2700ES and 2400ES are equipped with a primary fan, mixer, and secondary fan, for better water heater performance and efficiency.
Another advantage is that they have the option to be installed outdoor, using the right vent kit (AQOK) but for the approved climate, while 2400E can be installed indoor only.
With their built-in power vent capability, you will have an option for easier installation as they are designed for vertical and horizontal vent termination.
Aquastar water heater 125FX
is using power vent
(exhaust fan) and is designed for horizontal venting
only. 125BS, if using power vent kit can use a sidewall vent. With
1600P and 1600H sidewall termination is available as long as the unit
uses the appropriate power vent kit.
1600P, 1600H, 1600PS and 125BS are models that can function as direct vent models also with a vertical termination using natural draft, while 1000P has to be used as a direct vent and vertical termination using natural draft.
For the outdoor
installation, there are two models from Aquastar
water heater series
with the great advantage; eliminating the need for a costly venting
kit, freeing up the space in your home and reducing the
and worry significantly of the potential gas and water leak.
For freeze protection, electrical supply has to be provided and to plug
in 120 V outlets.
The anti freeze kit is designed to provide protection for water heater, down to 5 F, but the suggestion is to drain the unit if exposed to long term freezing conditions.
Models Aquastar 2700ES and Aquastar 2400ES are the only two Bosch models that are EnergyStar awarded and high efficient gas tankless water heaters.
What makes these Aquastar water heater models high efficient (where EF factor is 0.82 or higher) is their efficient gas burning with high power pre-mix compact burner and the help it is getting from primary and secondary fans.
(Pictures courtesy of Bosch)