Bosch GWH 1600 H troubleshooting?

Q. Pilot Lights But Goes Out When Button is Released?

A.

1. When lighting pilot, ensure that the gas control slide button is fully depressed and held in for at least 20 seconds after pilot is lit.
   
2. Verify that the gas type (indicated on rating sticker located on right hand side of cover) is the same as the gas type you are using. NG is a natural gas unit and LP is for liquid propane.
   
3. If using a power vent, check the safety spillage switch reset button (the safety spillage switch is wired through the water heater's thermocouple circuit). The spill switch should be located at top of water heater close to draft diverter (See AQ4 Power Vent manual - PDF).
   
4. Check all connections of the pilot safety circuit. The pilot safety circuit consists of a thermocouple, temperature limiter (ECO), flue gas sensor, safety spillage switch (on models with optional powervents only) and the electromagnet (See parts diagram for locations). Clean sensor connections with light sandpaper if corrosion is evident. The electromagnet connection is a 5mm nut (from the thermocouple) which screws into a larger 17mm nut on the electromagnet. Tighten both nuts snugly but do not over tighten.
   
5. Pilot flame should be blue in color and completely engulfing the tip of the thermocouple. If not, have a licensed gas technician verify gas pressure is in accordance with manufacturer's specifications (See Bulletin: CT-04) and clean or replace the pilot orifice (See Bulletin: CT-22).
   
6. Have a licensed gas technician verify the proper operation of the thermocouple by measuring the millivoltage from the thermocouple lead to ground. The proper reading should be 24mVDC or greater when the pilot flame is lit. If the reading is lower, the thermocouple may be defective (See Bulletin: CT-02). Call Bosch Water Heating for further instruction.

Q. Pilot Does Not Light?

A.

1. Verify that gas supply is on at natural gas meter or propane tank. Make sure all manual gas shut off valves are in the open position. Have licensed gas technician confirm adequate gas pressure at the inlet tap on the heater inlet (See bulletin: CT-04). If gas is not present, verify manufacturer supplied Maxitrol regulator is in the upright position. The arrow on the back of the regulator should point in the same direction as gas flow.
   
2. If the unit was just installed or the gas lines have been worked on, there may be air in the gas line. Centered in the sparking position, push in the gas control slide button while pressing the pilot igniter button every few seconds. It may take several minutes to bleed air out of the gas line.
   
3. Verify that a spark is appearing at the pilot while gas control slide button, centered in the single flame position, is being firmly depressed. Repeatedly push in pilot igniter button to light the pilot. If no spark is present, verify proper wire connection to the electrode.
   
4. Pilot assembly may be blocked. Clean or replace the pilot orifice (See bulletin: CT-22).

Q. Pilot Goes Out During or After Hot Water Use?

A.

1. Pilot outage during use typically results from the heater's safety overheat/high limit sensors interrupting the pilot circuit. These heaters do not have a thermostat. If the inlet water is preheated, the unit will overheat, stopping the flow of gas. Supply the heater inlet with a cold water line only.
   
2. Incorrect venting by reducing pipe diameter, improper use of elbows or not meeting required vent length are common causes that deactivate the pilot safety circuit. Confirm that venting is in accordance with manufacturer's specifications (See Section 3.6 of installation manual).
   
3. Confirm that the combustion air requirements are in accordance with manufacturer's specifications (See Section 3.5 of installation manual). Proper venting and combustion air will ensure a proper draft (See Bulletin: CT-03).
   
4. Confirm that the burners in the water heater go off immediately when the hot water is turned off. If they remain on or shut down slowly, then the temperature limiter (ECO) will interrupt the pilot circuit and shut off all gas to the heater. The water valve assembly, which actuates the gas valve, may be dirty and requires periodic maintenance (every 2 - 5 years depending on water quality and use) (See Bulletin: CT-23).
   
5. Check all connections of the pilot safety circuit. The pilot safety circuit consists of a thermocouple, temperature limiter (ECO), flue gas sensor, safety spillage switch (models with optional powervents only) and the electromagnet (See Section 8.2 of installation manual for part locations). Clean sensor connections with light sandpaper if corrosion is evident. The electromagnet connection is 5mm nut from the thermocouple which screws into a larger 17mm nut. Tighten both nuts snugly but do not over tighten.
   
6. Verify that pilot flame completely engulfs the thermocouple tip. If pilot is too small, clean pilot orifice (See Bulletin: CT-22).
   
7. If the water has a high mineral content, the heat exchanger may be scaled internally. This restricts the water path, causing the water to over heat which shuts all gas off to the heater (See Bulletin: CT-21).
   
8. If steps 1 through 7 do not correct the problem, then confirm that the gas pressure is adequate (See Bulletin: CT-04). Contact your original installer or a licensed gas technician to obtain this reading.

. Burners Do Not Light With Water Flow?

A.

1. Verify that the pilot is lit.
   
2. Verify that the gas control slide button is on or between the 1 flame and 3 flame positions.
   
3. Verify that the cold water supply is connected to the right side of the heater.
   
4. Close installer supplied cold water shut off valve (if none installed, install before proceeding). Open all hot water faucets supplied by the heater. Wait 5 minutes and check all faucets. Any water running is a sign of a plumbing crossover. Consult a local plumber or service person for help in correcting a plumbing crossover.
   
5. Verify that water flow through the water heater is sufficient. Turn temperature adjustment knob all the way clockwise. Fully open a hot water faucet and fill a quart container. If the container fills in 30 seconds or less, the flow rate (1/2 gallon per minute) is sufficient to activate the heater.
   
6. Inspect the water path outside of the heater for obstructions. Make sure all outlets (i.e. showerheads, faucet aerators and whole house filters) are clear of debris. Also, the water heater's inlet filter screen should be inspected and cleaned (See Bulletin: CT-12).
   
7. The water valve assembly, which actuates the burners, requires periodic maintenance (every 2-5 years depending on water quality and use) (See Bulletin: CT-23).

Q. Hot Water Temperature Fluctuates at Tap?

A.

1. Close off installer supplied cold water shut off valve (if none installed, install before proceeding). Open all hot water faucets supplied by the heater. Wait 5 minutes and check all faucets. Water running is a sign of a plumbing crossover. Consult a local plumber or service person for help in correcting a plumbing crossover.
   
2. Check for a clogged inlet water filter screen (See Bulletin: CT-12).
   
3. Hot water is very hot out of the tap, requiring a lot of cold water to be added in order to attain a useable hot water temperature. The addition of too much cold water will overpower and slow the flow through the tankless water heater, decreasing it below activation point, which shuts off the burners. The end result is nothing but cold water coming out of the outlet. Reduce the need for cold water mix by setting the gas slide control button towards the single flame position for lower hot water temperatures (See Bulletin: CT-07).
   
4. These heaters are designed to modulate gas flow to the burners when water flow varies. If the water pressure in the home is erratic and the water flow is not consistent while a tap is opened, the temperature of the hot water will fluctuate. The minimum water pressure for the home should be 30psi or greater. For installation on a private well system with the use of a pressure tank, the lowest pressure range setting recommended is 30-50 psi (2.07-3.45 bar). The use of a pressure reducing/regulating valve before the water heater (directly after pressure tank on well systems) is an effective way to maintain constant water pressure to the water heater. Watts brand 25AUB- ¾" or N35B-¾" pressure reducing/regulating valves or equivalent are suggested.
   
5. If the inlet water temperature is not constant, the hot water temperature from the water heater will fluctuate. The heater will modulate its burners when the flow rate is changed; it does not have a thermostat and will not adjust to changes in inlet water temperature.
   
6. If the inlet water temperature to the water heater is above 70°F, the heater may produce outlet temperatures that are too hot for most users. A temperature balance shower valve can automatically mix in cold water to reduce such hot water temperature. However, this can slow the flow within the tankless water heater, decreasing it below the activation point, which shuts off the burners. In the event of any temperature instability with the use of a temperature balance shower valve, refer to shower valve manufacturer's instructions for internal adjustment setting. An adjustment should be made to minimize the amount of cold water the valve is adding.
   
7. The gas pressure also needs to be stable and adequate. Ensure that gas pressure is in accordance with manufacturer's specifications (See Bulletin: CT-04). Contact your original installer or a local certified gas technician to obtain this reading.
   
8. A water valve which has not been serviced regularly may not open the gas valve consistently. The water valve requires periodic maintenance (every 2-5 yrs depending on water quality and use) (See Bulletin: CT-23)

Q. Water Is Too Hot?

A.

1. Verify that gas type indicated on rating sticker located on right-hand side of cover, coincides with the gas type you are using. NG is a natural gas unit and LP is for liquid propane.
   
2. Adjust the gas control slide button from three flame position towards the one flame position for cooler temperatures. If the water is still too hot, the temperature adjustment knob on the water heater maybe set too high. Lower the setting and test water temperature. This knob turns counter-clockwise for lower temperatures and clockwise for higher temperatures.
   
3. Inlet water is preheated. The heater does not have a thermostat and will not modulate flame height in order to prevent overheating. It is designed for cold water at the inlet only. Replumb the heater with cold water to the inlet.
   
4. Increase the water flow rate. Restrictions in the water path can slow the flow of water through the heater, resulting in very hot outlet temperatures. Restrictive showerheads and faucet aerators should be cleaned or replaced with less restrictive ones. In addition, the water heater's inlet filter should be cleaned and inspected (See Bulletin: CT-12).
   
5. If water is still too hot, follow additional steps to lower outlet temperature. (See Bulletin: CT-07).
   
6. If the water has a high mineral content, the heat exchanger may be scaled internally. This restricts the water path, causing the water to boil and produce extremely hot temperatures (See Bulletin: CT-08).

Q. Water Is Not Hot Enough?

A.

1. Verify gas type indicated in rating sticker located on right-hand side of cover, coincides with the gas type you are using. NG is a natural gas unit and LP is for liquid propane.
   
2. Flow at one particular tap is too great or too many fixtures are running at one time. Lower the water flow to stay within heater's specifications.
   
3. Ensure the gas control slide button is all the way to the 3 flame position. In addition, the temperature adjustment knob on water heater maybe set too low. Turn the knob clockwise for higher temperatures and test the water temperature.
   
4. Shut off installer supplied cold water shut off valve (if none installed, install before proceeding). Open all hot water taps supplied by the heater. Wait 5 minutes and check all taps. Any water running is a sign of a plumbing crossover. Consult a local plumber or service person for help in correcting a plumbing crossover.
   
5. Inspect the water path outside of the heater for obstructions. Make sure all outlets (i.e. showerheads, faucet aerators and whole house filters) are clear of debris. Also, the water heater's inlet filter screen should be inspected and cleaned (See Bulletin: CT-12).
   
6. The water valve may be dirty, prohibiting it from fully opening the gas valve. This part needs to be periodically serviced (every 2-5 yrs depending on water quality and use) (See Bulletin: CT-23).
   
7. Gas pressure is too low. Ensure that gas pressure is in accordance with manufacturer's specifications (See Bulletin: CT-04). A gas pressure reading is needed to proceed further. Contact your original installer or a local certified gas technician to obtain this reading.

Q. Burners Do Not Operate Cleanly; Yellow Flames When Operating?

A.

1. Verify gas type indicated in rating sticker located on right-hand side of cover, coincides with the gas type you are using. NG is a natural gas unit and LP is for liquid propane.
   
2. Gas pressure may be inadequate resulting in improper combustion. Ensure gas pressure is in accordance with manufacturer's specifications (See Bulletin: CT-04). A gas pressure reading is needed to proceed further. Contact your original installer or a licensed gas technician to obtain this reading.
   
3. For proper combustion at high elevations the inlet gas pressure should be set at installation to the value shown in table 3 (see below):
   

   Altitude	Natural Gas Inches W.C.	Liquid Propane Inches W.C.
   0 ft - 2,000 ft	5.7"	10.5"
   2,000 ft - 4,500 ft	4.6"	8.4"

   Above 4,500 ft consult your local gas provider.

   (while operating at maximum BTU). A gas pressure reading is needed to proceed further (See Bulletin: CT-04). Contact your original installer or a licensed gas technician to obtain this reading.
4. Ventilation is not adequate. Ensure that adequate combustion air is being supplied to the unit in accordance with manufacturer's specifications (See Section 3.5 of installation manual) (See Bulletin: CT-03).
5. Make sure the water heater is vented properly. Check for proper draft and ensure venting is in accordance with manufacturer's specifications (See Section 3.6 of installation manual. (See Bulletin: CT-03).
6. The water heater has burners much like a furnace. It is essential that they remain clean and are supplied with adequate air for combustion. If the flames burn yellow or orange, it is strongly recommended that the burners be removed from the unit and cleaned (See Bulletin: CT-13). Once the burners are removed, the fins in the top of the heat exchanger can be accessed from below and brushed or vacuumed clean.

Q. Burners Ignite Without Water Flow?

A.

1. The water valve may be dirty and sticking, prohibiting it from fully closing the gas valve. This assembly needs to be periodically serviced (every 2-5 yrs depending on water quality and use) (See Bulletin: CT-23).

Q. Low Hot Water Pressure?

A.

1. Confirm that there is adequate water flow rate through the unit. With cold supply shut off to the unit, disconnect hot outlet side to the unit. Place a quart jug under hot outlet to catch water. Open cold supply and measure flow rate out of the unit. With temperature adjustment knob set all the way clockwise, the flow rate should be close to 2 gpm, filling the jug in 7.5 seconds. With the temperature adjustment knob set all the way counterclockwise, the flow rate should be close to 4gpm, filling the jug in 3.75 seconds. If the flow rate is not adequate, inspect and clean the inlet filter screen (See Bulletin: CT-12).
   
2. Confirm that the incoming water pressure to the unit is above the required 30psi.
   
3. Inspect the water path outside of the heater for obstructions. Make sure all outlets (i.e. showerheads, faucet aerators and whole house filters) are clear of debris.
   
4. Be sure to run only one major application at a time with this unit. Opening too many taps at one time can disperse water flow resulting in a diminished flow pressure at all outlets.
   
5. If the water has a high mineral content, the heat exchanger may be scaled internally. This restricts the water path, causing diminished water flow (See Bulletin: CT-08).

Q. Noise When the Heater is Running?

A.

1. Confirm adequate flow rate through the unit. With cold supply shut off to the unit, disconnect hot outlet side to the unit. Place a half gallon jug under hot outlet to catch water. Open cold supply and measure flow rate out of the unit. With temperature adjustment knob set all the way clockwise, the flow rate should be close to 2gpm, filling the jug in 15 seconds. With the temperature adjustment knob set all the way counterclockwise, the flow rate should be close to 4gpm, filling the jug in 7 seconds. If the flow rate is not adequate, inspect and clean the inlet filter screen (See Bulletin: CT-12).
   
2. Inspect the water path outside of the heater for obstructions. Make sure all outlets (i.e. showerheads, faucet aerators and whole house filters are clear of debris. Restrictions in the water path can slow water flow through the heat exchanger causing it to boil and make noise.
   
3. If the water has a high mineral content, the heat exchanger may be scaled internally. This restricts the water path, causing the water to boil resulting in noise and overheating (See Bulletin: CT-08).

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