Bosch Water Heaters - Recent Questions, Troubleshooting & Support

If your Bosch Highflow 21e hot water system is experiencing fluctuations in water temperature while showering, it could be caused by a few different factors. Here are some possible reasons for this issue:

1. Flow rate too high: The hot water system may not be able to keep up with the demand if the showerhead or tap is allowing too much water to flow through. This can cause the water temperature to drop suddenly. Try reducing the flow rate by turning down the tap or using a low-flow showerhead.
2. Water pressure fluctuations: If the water pressure in your home fluctuates, it can cause the hot water temperature to vary. This can be caused by various factors, such as other appliances using water at the same time, or changes in municipal water supply pressure. Installing a pressure regulator or a flow restrictor may help to stabilize water pressure.
3. Blocked or dirty water filter: A clogged or dirty water filter in the hot water system can restrict water flow, causing the water temperature to fluctuate. Check the filter and clean or replace it if necessary.
4. Malfunctioning thermostatic mixing valve: The thermostatic mixing valve (TMV) regulates the water temperature in the hot water system. If it's faulty or dirty, it can cause temperature fluctuations. A licensed plumber or technician can inspect the valve and replace it if necessary.
5. Faulty temperature sensor or control board: If the temperature sensor or control board in the hot water system is faulty, it may not be able to maintain a consistent water temperature. A technician can diagnose the issue and repair or replace the faulty component.

If you're unsure about how to diagnose or fix the issue with your hot water system, it's best to contact a licensed plumber or technician for assistance.

The lpg either cylinder or gas tank must have a pressure reducing valve which sets the gas pressure to that required by the boiler.
After that valve the piping is the same as for any gas boiler.Where the pipe goes through the wall floor of similar - make sure the pipe has a sheath to protect it from gouges and or wet

The regs - Not sure about the USA but here in UK we have comply. different regs for tank or cylinder
The lpg supplier is a good source of info

The Bosch JSRZ 5-T PG tankless gas water heater may not start automatically because of problems with the magnetic sensor valve, power supply, or control unit/thermostat. Possible troubleshooting steps are:

• inspect the water inlet valve and replace if faulty
• confirm that power to the unit is functioning
• if the problem continues, seek professional repair service.

Do you live in a climate where the hot water line could have frozen? If your heater did freeze up, that could be very bad. This is because water actually expands when it freezes and can do a lot of damage to pipes and to the water heater itself. My other thought is possibly a clogged in line water filter. But typically a clogged water filter would make it run with reduced pressure rather than a complete shutdown all water flow.

https://www.fixya.com/support/t13643459-a2_af_error_codes

If the thermocoupler is defective the gas to everything is shut off. The coupler is the bulb that sits ib the pilot flame If it doesn't heat up it will sense no pilot and shut the gas off. They don't cost much and are easy to change. Good Luck, Ned

need control tested to find what failed

It could be the thermostat sensor They usually have a carbon buildup. They are easy to install and not that expensive. Good luck

That particular tankless water heater has hydro-generated ignition. In order for it to function, it requires a certain water pressure and velocity. You can try turning on the hot water in two location in your house to see if that gets it started. If it does, try getting a higher flow shower head, or removing the limiters in your faucets.

My partner has a neckar W8/10 butane water heater that continually switches itself off during use, is there a way of curing this problem as the installer seems to have disappeared and is not responding to phone calls or messages

your not making sense with you question --state it goes cold in middle of shower --but state it will stay hot or cold forever ----if its the latter continued hot till you shut off water that normal working if the unit shuts down during shower then you have a problem ----unit is set at one temp and runs at that temp and you use shower 1 handle / 2 valve what ever you own to adjust temp their are really only 4 reasons stops making hot water ----2 are usually well water supply --incoming water pressure /flow or to cold ----other are gas valve -or sensor so i would look into your shower handles since almost all have adjustments and anti scold safety

SEEMS LIKE CALLING A LOCAL PLUMBER IS BEST WAY

most likely. contact a dealer for advice

try Bosch tech support .

check to see if voltage correct if not replace board if ok bad ignitor

possible missing or bad gasket or o ring

If there is not a clicking sound, it almost always means the main ignition or control unit (box with red and green lights and wires coming from it) is not getting the supply voltage. The voltage is supplied by a generator that is getting energy from the flow of water (the "hydro generator"). First disconnect the wire connector at the hydogenerator and check the voltage while water is running. The manual says you should read 1.6 VAC (I read 2.5 VAC). Make sure your voltage reader is on AC, not DC. If you have at least something like 1 VAC, then the next thing to check is the "microswitch" that allows the hydro generator voltage to reach the ignition unit. To check it, disconnect the other wire connector that is on the black wire coming from the hydrogenerator that is closer to the ignition unit. Then with the water running, stick a small screwdriver in the male plug side to short the two wires in order to bypass the microswitch (per Bosch tech support instructions). You should now here clicking and see the unit work. This is what happened with me and tech support said I needed to order a new microswitch and gave me a part number and telephone. But don't stop reading here. You can see the microswitch when looking up at the underneath of the unit. It's a small white 1x1 inch box-like shape held by 1 screw. After removing it, I noticed the microswitch had a removable cover (which is strange for a switch) and opened it to discover the internal switch can actually move inside because it "automatically adjusts" itself when it is first put in (it stays more firmly, but not rigidly in place when the cover is on). So you can mess up when putting it in. Don't bump it. It can easily get out of its working range of motion, which is why mine stopped working: it was a bad design to use this type switch in this application. So I slide the internal switch back close to the spring side ("default" position), put the cover back on, carefulyl screwed it in place, and now it works.

The purpose of the mechanical microswitch is to not allow the hydroenerator voltage to the ignition unit unless the "pushrod" has opened the main gas supply. It prevents clicking if there is no supply gas, so it is not needed (you can electrically bypass it with a splice) if everything else is working fine. But don't blame me if you do this and for some reason it ruins the more expensive ignition unit. The microswitch is turned on by the pushrod when the pushrod leaves it's default position. The the pushrod moves only about 2 to 3 mm when you turn on the water. You can see the pushrod when you unscrew the microswitch, and you can watch it move. The problem is that the microswitch mounting is not precise enough for the small pushrod movement and the pushrod's default position can change with age of the diaphragm or change in the grease. So their automatically adjusting microswitch that makes up for lack of precision in design and pushrod movement can stop working when the pushrod changes position. My unit was 2 years old.

If you can't hear clicks, then very likely it is the "microswitch" that is a rectangular white plastic box that can be seen at the bottom of the unit from underneath. It's purpose is this: when there is gas pressure, a pushrod turns the switch on, thereby allowing electrical current to flow from the "hydrogenerator" to the igniter unit. The hydrogenerator generators from about 1 to 2.5 volts AC (not DC) when water is flowing, powering the generator which powers the igniter unit....assuming the microswitch is allowing electrical current (the voltage) to pass through. It is a "self-adjusting" switch because the pushrod can come out at different pressures. So if your gas fluctuates, the microswitch will be fixed to a higher pressure level, but not be able to turn on if the pressure drops. This is because the pushrod is not pushing as far. It's simple to unscrew the plastic box and push the teethed switch setting back to the initial default position, and then carefully replace the plastic cover. Then do it again next time it stops working, a year or two it seems for many people. You can take out the switch and connect it's two wires directly, but if there is no gas pressure and you let water flow through, the igniter unit will constantly be sparking and thereby might fail early. If there is no gas pressure, then maybe it is because of a local leak and thereby bypassing the switch is a built-in explosion hazard, but that would require the sparking to no longer be internal to the ignition unit.

WOW!!! Great answer by Steve (I know Steve Spam...real name Richard). Lot of time on his hands (37000 answers). Can we get real professionals answering questions. Thank you Richard...let's just call you Dick for short.

You are looking for a mechanical problem for an electrical issue. This unit is controlled by an electronic board. That board is the cause of your issue. They are about 300 dollars.