Bosch aq 250 manual

This is not an error code; it is a flashing status message that tells you to check; the wiring connection, gas pressure as it might be too low, voltage as it doesn't meet the required VAC, the unit that might not be properly grounded or the issue with the control board. The primary fan spins slowly when the water heater is working. Check the wiring connection on the fan and control board. The voltage must be VAC and the element correctly grounded. Does the venting system meet the code and manufacturer requirements?

Ensure that the gas pressure is as required because the low pressure leads to fan rotation problems. No signal from the fan's rotational speed sensor.

The sensor might be broken. Check the wire connection on the control board and fan. The voltage needs to be VAC and adequately grounded. Ensure that a fan and control unit are not damaged. Check the wire connections on the water valve and control panel. The temperature detected by the outlet temperature sensor is over F. Ensure that the sensor is working correctly, and the wire connections are not loose.

Another reason for the high temperature is the sediment build-up, so descaling is needed. Check the sensor and wiring connections as this sensor is in charge of protecting the unit from freezing. The unit will shut down if the temperature of the exhaust gases is above F. Check and clean the heat exchangers if needed. Reduce the maximum power and water temperature. Note : Professional installation and repair are recommended.

The backflow temperature sensor reacts when the temperature is over F. Check the vent pipes if they meet the code and requirements, look for damages and obstructions. Check the wire connections on the sensor and control board. Ensure the venting system is per codes and instructions. Descale the unit if necessary. The ionization electrodes are not making sparks when water is flowing.

There are many reasons for this problem and here are some; low gas pressure, the fan speed is low, wire connections are loose, the air in the gas line, no gas. Ionization electrode failure during water heating. The reasons might be; obstructed venting system, low gas pressure, and CO2 readings, the fan speed is too low. The issue with the hardware or software. First, try to reset the error code; there might be confusion inside the computer.

Check if the wire connections are properly linked to the computer board or the board is not damaged. The problem is with the ionization rod at standby. Check connections to the electrodes; it should be securely connected. Other reasons might include damaged elements or a control board. The problem is with the gas valve circuit. It only takes a minute to go downtstairs to switch valves. We also used our tankles water heater to fill a gallon hot tub. If anyone decides to start a class action suit against bosch for selling a Known piece of junk, the sx tankless water heater, please contact me, I will be one of the first people to sign on.

I bought more than one of these units for my home and rentals and have had all the problems everyone else is having right down to the crummy customer service.

Please count me in if you do take action against bosch. Post a Comment. I've had the Bosch Aquastar SX tankless water heater for a little over 4 years now. And I have to say it's been nothing but a pain in the ass. We built this house in 04 and our goal was to build a very green energy efficient house. Tankless hot water does make sense and when its working, it works well; producing endless degree hot water.

The initial problems I had were a loud groaning when the SX fired up, intermittent cold water surges, random errors that shut the unit down. There are several factors that might explain the miriad of problems I encountered. New Model - When I purchased the SX , it was a very new model, and it is obvious that Bosch was still in the process of working out the bugs.

At one point they sent a revised controller that was supposed to work better and later they sent an attenuator that would solve the loud groaning sound it made when it started. In the end they ended up sending me an entire new unit.

Self Install - Based on a friend that installed his Aquastar himself, I decided I'd save the money and do it myself - big mistake. The actual installation wasn't that hard, but as it turns out there are internal adjustments that in theory don't have to be made, but in my case were essential to get the unit operational. The adjustments required a manometer to monitor the incoming pressure and a CO2 analyzer to monitor exhaust.

Again without the tools, there's no way to accurately adjust the incoming LP pressure. Well water, not city water - I'm also on a well system, so my pressure ranges from 40 - 60 psi.

In addition, when my well pump would kick in, a slight lull in the pressure caused the SX to shut down. So imagine you are in the shower, the pressure in the tank hits 40, the pump kicks in, Bosch shuts down, it then takes another 30 seconds for the Bosch to produce hot water. Meanwhile you are receiving cold water in the shower - not fun.

This was eventually fixed when after two plumbers could not properly adjust the pressure tank, I called the drillers that drilled my well. From the time you turn the hot water on, it will take the Bosch at least seconds to actually produce hot water. Add to that the time it takes for the hot water to travel through your pipes to the tap. And if you shut the water off for just a second and turn it back on, it's got to go through the entire startup cycle again, meaning another 30 seconds of cold water out the hot water tap.

So you can't wash the dishes and turn the hot water on and off and expect to have constant hot water. This is more annoying than you might think. The end result is you do waste quite a bit of water, so if you live in a dry place and water is not plentiful , a tankless water heater might not be for you.

Minimum water flow - if you turn a tap on but just want a small amount of hot water, it may not be enough flow to fire up the SX and you'll just get cold water. A tankless hot water heater is more complex than a standard hot water heater. Just the other day I got an EA error. I called Bosch and after 20 minutes of waiting for tech support, they had me disassemble the unit and clean the ignition contacts with steel wool.