Bosch Greenstar Combi 151 Problems And Their Solutions

The Bosch Greenstar Combi 151 is a great option for space heating and Domestic Hot Water provides. It also comes at an affordable price and 98% efficiency.  While it is a reliable machine, sometimes you might face problems while using it or installing it. 

Here are some common problems which you might face with your machine and some handy solutions to solve them.

Issues With Bosch Greenstar Combi 151

The Bosch Greenstar Combi 151 mainly faces problems with its boiler not heating properly or gas leaking from the machine etc. Let’s dig deep into the reasons causing all these problems.

  • Boiler Not Heating Properly
no heat from Bosch Greenstar Combi 151

Sometimes you might notice that the boiler or your Bosch Greenstar Combi 151 is not working properly or not heating properly. There might be many reasons behind this.

The heating system of your machine might have some trapped air inside it. The pressure of the water system might also be low, causing the boiler not to heat up properly.

Another reason might be the temperature of the boiler. It might be set too or the radiator valves of the thermostat may be set too low.


You can easily fix the boiler by adjusting the temperature of the radiator valves and also try rising the central heating flow if it is low. You can also try resetting the water pressure if it is low.

Also, remember to check and set the temperature of the thermostat higher than the room temperature. This is how you can easily fix the heating problems of the boiler.

  • Boiler Losing Pressure

Sometimes the water pressure of the boiler starts slowing down. This usually happens because there might be a leakage in the water line. Usually, the leakages are seen on the pressure release valves or radiator pipes.

It is not easy to understand whether the water is leaking or not because you can’t hear the sound as the water directly goes to the drain.


Make sure to check the radiator valves and pressure release valves regularly and check if there is any leakage. Also, make sure to tighten the nuts and bolts to secure the fittings of the machine.

If these are not causing the pressure to become low, you can call a technician to check the heat exchanger and PRV valves.

  • Boiler Leaking Gas
Bosch Greenstar Combi 151

You can easily understand when your boiler is leaking gas because you will be able to smell the gas leaking from the tank. This is the most common problem with the boiler.

The reason behind this can be a poorly fitted gas hose or a loose nut or bolt attached which needs to be tightened.


If you smell the gas leaking, the first thing you must do is make arrangements to let the gas out. Open the doors and windows to let the gas out.

Now find out where the leak is and it’s best to call a technician to fix it for you. Change the gas pipe if needed as well.

  • Boiler Making Banging Noises

Sometimes the boiler makes weird banging noises. This might occur when the thermostat is faulty or if the water pressure goes down for some reason. It can also be limescale build-up inside the boiler. 

These would cause the boiler to make banging noises inside it as the air gets inside the heating system.


The only way to get the noise fixed is to fix the boiler. First, you need to find out the reason and fix the part by calling a technician. It is not safe letting the banging sound stay for a long time. So, try and fix it as soon as possible.

  • Boiler Leaking Water

If you are using the boiler for a while now, you may notice a slight water leakage from it. This may happen due to worn-out parts of the boiler.

As the pipes through which the water passes are made of plastic, they may melt or get vaporized when used for a long time. This might cause water leakage.


First of all, find the place where the leak started. If it is a minor leak then you can simply use tape to cover it up. But if the leak is big, then you need to replace the whole plastic pipe to stop the leak.

Is Bosch Greenstar Combi 151 Worth It?

To judge if the Bosch Greenstar Combi 151 is worth using or not let us look into the specifications it comes with.

  • It has a Broad BTU Output Range with 95% AFUE efficiency
  • Installing this model is very easy due to the integral pump being standard in all of its models available
  • The heat exchanger contains silicon which extends the life of the boiler and a little maintenance is needed.
  • It comes with a compact design that is available both in wall-hung and floor-standing which are helpful for limited spaces and quick fixes.

The features mentioned make it easy for you to understand that it is a low-maintenance device and high-efficiency to work.

Overall, this model of boiler is worth using. You just need to keep an eye on its working mechanism and look if it needs maintenance or not.

Frequently Asked Questions(FAQs)

Why does my Bosch Greenstar Combi boiler keep cutting out?

If your boiler keeps cutting out, it might be having some problems like water pressure drop, faulty elements, loose nuts and bolts or overheating sometimes. This problem needs to be fixed immediately. So, if you are unaware of what is initiating the problem, contact a technician.

How do you drain a Bosch Greenstar Combi boiler?

To drain the machine, firstly flush it quickly then turn off the boiler and unplug it from its connection. Now, open the drain valve to drain the boiler after turning off the water valve. After draining the boiler flush the tank using water.

Why is my Bosch Greenstar Combi boiler not giving me hot water?

If your boiler stops supplying hot water, it means the heating system is having problems. It might be due to some air trapped inside the heating system or the system may get overheated, causing it to stop working.

Are Bosch Greenstar Combi boilers noisy?

The Bosch Greenstar Combi boilers are not usually noisy but they may make some banging noises if air gets trapped in them or limescale is build-up inside the heating system.

Final Words

Although the Bosch Greenstar Combi 151 problems might seem a bit too much to handle, they can easily be fixed if you know some tips and tricks. That is what we tried to help you with by making a troubleshooting guideline for the model.

Now that you know what problems you might face using it or what is causing them in the first place, it will be easier for you to do its fixes. Although it’s always wiser to take some expert advice before trying it out by yourself.

Ralph Wade

Hey...Ralph is here! So, did you find this article useful? If so, please leave a comment and let me know. If not, please tell me how I can improve this article. Your feedback is always appreciated. Take love :)

2 thoughts on “Bosch Greenstar Combi 151 Problems And Their Solutions

  1. The output water is no longer heated after a few minutes. The error code “EA appears and once you push the reset button the water heater turns back on.. The problem is it will again at some random time turn off again and you have to push the reset button again . This has been going on for months.
    It is a Bosch Greenstar Combi 151p

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