Bosch Therm 520PN NG & LP Tankless Water Heater

The new Bosch Therm 520PN comes set for either NG (Natural Gas) or LP (Liquid Propane).  The 520PN has a standing pilot and is a naturally drafting heater and requires no power to operate.  This unit is basically for 1 major application at a time such as 1 shower at a time.  The Bosch 520 PN Needs to be vented vertically with a 5" B-vent up through the roof for a minimum of 6' to the raincap.  If the heater has to be vented out the sidewall then you must use the AQ4 Powervent kit and this kit would require 110V power.  The gas connection at the bottom of the heater is a standard 3/4" connection.

The new Bosch Therm 520PN is a direct replacement for many of the older model heaters.  Below is a list of the units that the 520PN would replace.  Please keep in mind to always be aware of gas line sizing and the length of the gas line run.

The Bosch Therm 520PN could replace:

Bosch 1600P or 1600H: (If either one of these units was vented horizontally out the sidewall with the AQ4 powervent kit then that same AQ4 powervent kit can be used for the new Bosch Therm 520PN)

Bosch Aquastar 125B, 125X, 125HX, 425PN or the 425HN: (If any of these units was vented horizontally out the sidewall with the AQ1 powervent kit then that AQ1 powervent kit WILL NOT work for the new Bosch Therm 520PN.  You would need to install the new AQ4 powervent kit for the new Bosch Therm 520PN)

ELM Le Blanc 170VP or 125VP:  (If either one of these units was vented horizontally out the sidewall with the AQ1 powervent kit then that AQ1 powervent kit WILL NOT work for the new Bosch Therm 520PN.  You would need to install the new AQ4 powervent kit for the new Bosch Therm 520PN)

The Bosch Therm 520PN is a direct replacement for the older tankless water heaters listed above but you still always want to make sure and refer to the installation manual and follow the gas line sizing chart and venting requirements.  Please also refer to local code for all other restrictions and approvals.

Bosch Greenstar Gas-Fired Condensing Boilers

Bosch has a new line of Greenstar Gas-Fired Wall-Hung Condensing Boilers and they are all very efficient and simple to set and operate.  Space heating boiler for connection to a hot water tank with unsurpassed performance and control. With special insulation to ensure ultra quiet operation and the exclusive keypad safety lock feature to prevent unwanted tampering with heating controls, this unit is the ideal "green" upgrade for detached & terraced houses and is also suitable for apartments.

There are 5 different model Greenstar Boilers designed for space heating only and they are sized by thier BTU capacity. 

• Bosch Greenstar 57, (57.2K BTU), 98.7% efficiency
• Bosch Greenstar 79, (79.2K BTU), 98.7% efficiency
• Bosch Greenstar 100, (100.8K BTU), 98.5% efficiency
• Bosch Greenstar 131, (131.9K BTU), 97.5% efficiency
• Bosch Greenstar 151, (151.6K BTU), 96.8% efficiency

The energy-savings and environmental features are:

Aluminum-Silicon heat exchanger delivers high efficiency with low temperature applications

Low NOx emissions ahead of 2012 SCAQMD regulations

Simple, intelligent control options optimize efficiency and fuel consumption

Low electrical consumption when the boiler is in standby mode

Electronic ignition

Anti-cycle and modulation control

These Greenstar condensing space heating boilers can be used for either Natural Gas or Liquid Propane installations.   The heaters come preset for Natural Gas (NG), but can be converted to Liquid Propane (LP).  A gas conversion kit is included.

The Greenstar boilers come with a temperature control FW 200 that can either be mounted to the heater or mounted to the wall beside the heater.  This module allows the heater to be set for different temperatures, zones and the time of day the heater comes on and goes off.  The FW 200 control also comes with a temperature probe that goes to the outside and detects and monitors the outside temperature and then allows the heater to remember the coldest and warmest times of the day and year.

The Greenstar condensing space heating boilers are specifically designed for space heating only but can also be used for Domestic Hot Water (DHW) when they are piped to an indirect tank and using a pump, aquastat and check valves.

Gas Conversion of Pro Gas Tankless Water Heaters

Some of the Bosch Professional gas tankless water heaters can be converted from one gas type to the next, i.e. from Natural Gas (NG) - Liquid Propane (LPG) and also from LPG - NG.  The Gas Conversion Kit, part #8719002176 includes a jumper for placement on the control board, a set of instructions for calibrating the gas and air mix and also some stickers to be placed on the heater stating it has been converted. 

The tools required for the gas conversion are:

• Flat and Phillips Screwdrivers
• #40 torx driver
• Digital CO2 Gas Combustion Analyzer
• This procedure must be performed by a licensed gas technician

The Bosch Professional Non-condensing heaters such as the 940ES/940ESO/830ES/715ES/635ES and the Evolution 500 CAN be converted using the gas conversion kit.

All of the Bosch Therm condensing heaters such as the C1210ESC/C1210ES/C1050ES/C950ES/C800ES and Integra 500 CANNOT be converted as the units have a special plate built into the burner tray.  This extra plate in the burner tray was designed and instlled to give the heater the ability to be installed at higher elevations up to 8000'.

Also the Bosch Therm 660EF/660EFO/520PN/520HN/425HN/425EF/330PN CANNOT be converted as they are not designed at all for gas conversion.

Flow & Temperature Adjustment for Bosch Therm 520PN

The new Bosch Therm 520PN comes in either natural gas or liquid propane and has a control knob for adjusting the water flow and a slide adjustment for adjusting the heat on the front of the heater.

The Bosch Therm 520PN is a 117,000 BTU Gas Tankless Water Heater. The control knob on the right is the Temperature Adjustment knob and is for adjusting the flow of water through the heater which has the ability to speed the flow of water up making it cooler or slowing it down and making it hotter. The slide control in the middle is for adjusting the temperature of of the water by adjusting the height of the flame. When the slide is positioned on the small flame symbol the burners will be low and when the slide is on the high flame symbol the burners will get higher and the temperature hotter.

Below is how turning the Temperature Adjustment knob effects the heater:

Knob Position		Clockwise		Counter-clockwise
Degree Rise		90° F		45° F
Activation Rate		0.5 GPM		1.1 GPM
Max Flow Rate		2.0 GPM		3 .7 GPM

As the temperature adjustment knob is turned counter-clockwise, the output temperature will lower and the activation rate of the heater will be raised. Turning the knob clockwise will raise the temperature and lower the activation rate.

When sliding the slide adjustment to the left, (small flame symbol) the heater will give lower flame and cooler temperatures and sliding the slide to the right will give hotter tenmperatures and a higher flame.

The Bosch Therm 520PN has a gas control slide that modulates burner input in response to flow. Its purpose is to ensure that the hot water temperature will remain steady, although the water flow demand might vary.

Bosch Therm C1210ES/ESC vs Bosch Pro GWH C920ES/ESC

Recently the Bosch Pro GWH C920ES/ESC was changed to the new model name Bosch Therm C1210ES/ESC. The model name was changed to reflect gallons per minute (gpm) at a 35 degree temperature rise. So the Bosch Therm C 1210 ES/ESC reflects a 35 degree temperature rise at 12.1 gpm. Along with this name change came many new features:

• Comes equipped with freeze prevention now.
• Has the capability to accept preheated water up to 140 degrees and is approved for Domestic Hot Water (dhw) and space heating applications in conjunction with an indirect tank.
• Has the ability to be cascaded using the Intelligent Cascade Kit for up to 24 units and would produce up to 290 gpm.

The Bosch Therm C1210 ESC commercial unit also has the ability to reach a maximum temperature of 180 degrees for commercial use.

The temperature range for the Bosch C1210ES is from 100 - 140 degrees. With the use of the Bosch Therm High Temperature Kit the unit would have the ability to reach up to 180 degrees.