Bosch Appliances 125B LPS Burners do not Ignite When HOT Water is Turned on, Gas pressure too low

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To test the thermocouple, disconnect the thermocouple lead to the ECO. Insert a multi-meter probe into the thermocouple lead and attach or hold the other lead to the metal gas valve (DC common). Light the pilot flame and hold button, meter reading should be 24 mVDC or more. If the reading is 24 mVDC or more the thermocouple is good. To test the electromagnet, re-connect the thermocouple lead to the ECO, light pilot and hold button while taking a reading between the ECO leads and the metal gas valve (DC common). The reading should drop to 19 mVDC or less. If it does not, replace the electromagnet.

BURNERS DO NOT IGNITE WHEN HOT WATER IS TURNED ON

1. Pilot is not on.

Light the pilot. See lighting instructions.

2.Gas valve button not positioned on Burner Position

Be sure once the pilot flame is on, that after a 15 to 20 second wait, the main burner button ( ) is pushed all the way in.

3.Cold incoming water connection made to wrong side of heater

Make sure cold water inlet connection is on the right side of heater when you are facing the heater.

4.Water flow rate at hot water tap is too low. Note: The AquaStar models 125B”S” require 0.5 gallon per minute flow to activate the burners. This is a flow which would fill a quart jar in 30 seconds.

5.Cold water inlet filter on heater is dirty.

Remove filter and clean. This screen filter is located at the inlet side of the brass water valve (fig. 11, #34). Check and clean faucet aerators too.

6. Crossover in household plumbing

The AquaStar burner activates when there is sufficient water pressure drop in the AquaStar water valve assembly — ie. when a hot water faucet is opened. If there is a crossover in the plumbing, the necessary pressure drop in the AquaStar will be insufficient, or totally eliminated. A plumbing crossover can be caused by a bad washer at a single lever faucet or incorrect plumbing or a mixing valve in the line, etc. which permits hot and cold water to mix in the plumbing. The crossover will create a back pressure in the system preventing the pressure drop in the Aquastar — i.e. cold water is entering the water heater from both sides and the burners will not come on. To confirm there is no crossover in the plumbing, shut off the cold water supply to the AquaStar. Open your hot water taps. There should not be any water flowing. If there is water flowing, there is a crossover in the plumbing. This is a plumbing problem, not an Aquastar problem. Please contact your plumber.

7.Water valve parts may be dirty or components damaged.

Water valve and component parts must be totally free of dirt. First check that the venturi is free of dirt particles. In hard water areas, mineral deposits can eventually (3 to 5 years in hard water areas) corrode the water valve parts to a point where they will need replacing.

Any sign of moisture or corrosion at the joint of the water valve and the gas valve is a sign that the water valve assembly components need to be replaced immediately.

Note: Water valve for model 125B”S” is part # 8707002393 for both LP and NG models. (Contact service person to clean water valve or replace if corrosion is present).

PILOT LIGHT GOES OUT DURING OR IMMEDIATELY AFTER HOT WATER HAS BEEN USED

1. Gas pressure too low

Very low gas pressure may be caused by low delivered gas pressure, a jammed gas regulator or undersized gas lines. If the gas lines are undersized, there may still be the specified static gas line pressure. However when the water valve opens,and gas enters the burners, the pressure could drop sharply, causing the pilot flame to go out.

Have a gas technician confirm the gas pressure both static and at maximum Btu output. Specifications for your heater are on page 2.

2. Pilot may be dirty or weak

See Page 13 for instructions on pilot maintenance.

3.Burners are not shutting down immediately when hot water is turned off

Note: If burners don’t shut down immediately when the hot water is turned off, the heater will overheat and the ECO will shut-off the gas. Rebuild the water valve assembly using the repair kit from CEC (part #8 703 406 204).

WATER IS TOO HOT

1. Water flow rate is too low. Increase the flow rate.

2. Not enough cold water mixing at faucet

Contact your plumber to adjust mixing valves on faucets.

3.The heater’s fixed degree rise is too high for user The calibration nut for the thermostat assembly at the gas valve can be adjusted upward to lower the temperature rise. A seal of paint coats two adjusting nuts there, the thin up- per one is a lock nut while the lower one is the adjuster. Loosen the lock nut one first. Tighten the adjuster nut in- crementally upward and check water temperature, stop when

satisfactory. Then tighten down the lock nut. Caution:

Never back the adjuster nut downward to the last thread unless the thermostat is being replaced. This is a gas seal.

WATER IS NOT HOT ENOUGH

1.Water flow rate is too high. Decrease the flow rate.

2.Btu input is too low due to insufficient gas pressure It is extremely important for a tankless instantaneous water heater to have the right size gas line to obtain the correct gas pressure

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Contents Table of Contents For Your SafetyFeatures Unpacking the Aquastar HeaterRequired Natural Gas Pressure at inlet tap Front View Side View Model 125BSTOP a Front B Back Sides Floor C Vent Diameter General Rules to Follow For Safe Operation Proper Location for Installing Your HeaterClearances Combustion AIR RequirementsAquastar 125 B S is design certified for mounting on a wall Mounting InstallationFigure a VentingFigure C 720 606 Masonry Chimneys6 Adaptor Used on High Altitude Vent Adaptor for High Altitude InstallationsFor LP GAS GAS Line Sizing For Natural GASAbove 4.500 ft consult your local gas supplier Maximum Inlet GAS Flow Pressure SettingGAS Line Sizing Water ConnectionsTo Turn OFF GAS to Appliance For Your Safety Read Before Lighting the PilotOperating Instructions What to do if YOU Smell GASPilot burner with air screen/ pilot orifice Maintenance and ServicePilot Light will not Light Pilot Lights but Flame Goes OUT When Button is ReleasedWater is not HOT Enough Burners do not Ignite When HOT Water is Turned onGas pressure too low Water is TOO HOTUnbalanced pressure in waterlines HOT Water Temperature Fluctuates / Unit DeactivatedDiagram of AquaStar 125 BS Interior Components Diagram and Parts List Interior Components Diagram Parts List 125BS Flow chart of Aquastar 125 BS General Limited WarrantyMaintenance Table see

125B NGS, 125B LPS specifications

Bosch Appliances has long been a revered name in the home appliance industry, recognized for its commitment to quality, innovation, and energy efficiency. Among its impressive lineup, the Bosch 125B NGS and the Bosch 125B LPS stand out for their advanced features and technologies that enhance the cooking experience in modern kitchens.

The Bosch 125B NGS is a gas cooktop designed for those who appreciate the precision of gas cooking. With its sleek stainless-steel design and intuitive controls, this appliance adds a touch of elegance to any kitchen. One of its main features is the rapid heating capability, thanks to the powerful burners that provide quick and even heat distribution. The cooktop includes multiple burner sizes, allowing users to choose the right heat level for various types of cooking, from simmering sauce to boiling pasta.

Additionally, the Bosch 125B NGS is equipped with an automatic re-ignition system, enhancing safety by ensuring that burners reignite if they go out. This feature is particularly beneficial in busy kitchen settings where distractions can occur. The continuous grate design allows for easy movement of pots and pans across the cooking surface, making multi-tasking a breeze.

On the other hand, the Bosch 125B LPS offers an electric alternative with a more modern flair. This built-in induction cooktop harnesses the power of induction technology, which uses magnetic fields to directly heat pots and pans. One of the key characteristics of this model is its exceptional energy efficiency, as it only heats the cookware, resulting in less wasted energy and cooler cooking surfaces. The Bosch 125B LPS features a touch control panel that allows for precise temperature adjustments at the touch of a finger.

Moreover, the model includes safety features such as a child lock and automatic shut-off, ensuring peace of mind for families. The sleek and minimalist design of the Bosch 125B LPS makes it a favorite among those who value aesthetics as much as functionality.

Both the Bosch 125B NGS and 125B LPS reflect the brand’s dedication to high-quality craftsmanship, innovative technology, and user-friendly operation, making them exemplary choices for anyone looking to elevate their culinary experience. Whether you prefer the hands-on approach of gas cooking or the quick precision of induction, Bosch offers reliable and versatile solutions to meet your kitchen needs.
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