Worcester Bosch Greenstar CDI E9 fault code

Worcester Bosch Greenstar CDI E9 fault code explained

Whilst the E9 fault code is probably one of the less common fault codes, if you have a Worcester Bosch Greenstar CDI boiler you may experience this fault code at some point.

The E9 fault code will cause your Worcester Bosch boiler to stop working, leaving you without central heating or hot water.

If you look in the Worcester Bosch CDI installation manual under the E9 fault code it states the following;

“Safety temp. limiter in CH flow has tripped – Check: system pressure, safety temp. limiters, pump operation, fuse on pcb, bleed appliance.”

If you are seeing the E9 fault code on your Worcester Bosch boiler, it more than likely means that your boiler has overheated.

Although like a lot of fault codes it doesn’t tell you exactly why.

Sometimes you may be able to get your boiler working again with a reset once it has cooled down, but a lot of the time the boiler may over heat again and top back to the E9 fault code.

Unlike a lot of fault codes on Worcester Bosch boilers, the E9 fault code is very specific and is trying to tell you that the boiler has overheated.

In our experience working on Worcester Bosch CDI boilers, the number one cause of the E9 fault code nine times out of ten is the pump which has failed or the boiler is low on pressure.

Some boilers are able to detect whether they have enough pressure to work safely and whether the pump is running or not, but not on Worcester Bosch CDI models.

Because of this the boiler can run dry and overheat so it’s worth checking that you have enough pressure in the boiler first.

If the pressure on the boiler was low, you could try adding some more pressure to the boiler (we recommend somewhere between 1 and 1.5 bar when cold), letting it cool down and try resetting it to see if that resolves the issue.

If your boiler is working fine in central heating mode, but only coming up with an E9 fault code when running the hot water, then the likely cause of the problem is a blocked plate to plate heat exchanger.

On the Worcester Bosch CDI, the plate to plate heat exchanger is a secondary heat exchanger which transfers the heat from the primary heat exchanger to the hot water being delivered to the taps.

This is called an indirect design combination boiler. Most modern combination boilers including every Worcester Bosch Greenstar boiler are of this design.

When these plate to plate heat exchangers get blocked they usually affect the hot water. If the blockage is really bad then it can cause your boiler to overheat as well.

When to call a gas engineer to fix your boiler

If you are experiencing the E9 fault code on your Worcester Bosch boiler, it is important to take action as soon as possible.

While some issues can be resolved by homeowners themselves, others require the expertise of a qualified Gas Safe registered heating engineer.

A persistent E9 fault code more than likely means your boiler keeps overheating, and you are probably best off not trying to keep using the boiler otherwise you could end up causing more damage to the boiler.

The E9 fault code is often caused by low pressure, a faulty pump or blocked heat exchanger, but other parts such as a faulty printed circuit board for example could also cause this issue.

This is why it is extremely important to get a suitable heating engineer with experience on Worcester Bosch boilers, otherwise you could end up wasting money fitting expensive parts to your boiler that are unnecessary.

So it usually best to get a qualified Gas Safe registered heating engineer to have a look at your boiler at your earliest convenience.

How to prevent the E9 fault code

A lot of the time certain faults on a Worcester Bosch Greenstar CDI boiler can be prevented with regular annual servicing and maintenance. This is often the case with the E9 fault code.

Servicing components like the expansion vessel, will help to ensure that the boiler holds its pressure which means that it is less likely to overheat and show an E9 fault code when you least expect it.

A lot of the parts on a Greenstar CDI boiler are non serviceable parts, this includes the pump. This means that there is nothing that can be done to these parts to extend the life of the fan and prevent the E9 fault code.

However an experienced engineer used to working Worcester Bosch boilers can perform a strength test on the pump whilst servicing the boiler.

This will enable them to try and determine if the pump is coming to the end of its life, and recommend replacing it preemptively as a preventive maintenance measure.

Most Worcester Bosch Greenstar boilers use high quality Grundfos central heating pumps. These pumps generally have a life span of somewhere between 10 – 15 years. Sometimes these pump can last as long as 20 years or more, depending on how much the boiler is used and how well the boiler has been maintained.

Worcester Bosch Greenstar CDI boilers affected by the E9 fault code

The EA fault code on Worcester Bosch CDI boilers can affect any combination boiler or system boiler.

Below is a list of Worcester Greenstar CDI boilers that can be affected by the EA fault code;

• Greenstar Classic 25 CDI, 29 CDI, 34 CDI, 38 CDI and 42 CDI combination boilers
• Greenstar Classic ErP 29 CDI, ErP 34 CDI, ErP 38 CDI and ErP 42 CDI combination boilers
• Greenstar 30 CDI and 40CDI conventional system boilers

Frequently asked questions:

Is my boiler showing an E9 fault code worth repairing ?

Yes definitely, most of the time your broken Worcester Bosch CDI boiler displaying an E9 fault code will be worth repairing. Obviously the cost to repair your boiler will be determined by which parts need to be replaced.

You would need a competent, Gas Safe registered heating engineer to have a look at your boiler and make an assessment to determine exactly which parts might need to be replaced.

Before replacing your boiler it is always worth getting a suitable Gas Safe registered heating engineer, with experience working on Worcester Bosch boilers, to make an assessment of your boiler so you can determine whether it is worth fixing not.

Can I repair the E9 fault code myself?

Sometimes you can solve an E9 fault code yourself by simply adding some pressure to your boiler, and checking the pressure periodically.

Aside from that repairing the E9 fault code will usually require removing the cover of your boiler to replace parts which you are not legally allowed to do unless you are a Gas Safe registered heating engineer.

Is the E9 fault code dangerous?

No, in general the E9 fault code on a Worcester Bosch CDI boiler is not inherently dangerous.

Modern Worcester Bosch boilers are designed with fail safes in place to make sure that the boiler will only work if it safe to do so.

Having said that the E9 fault code means your boiler is probably overheating for some reason, and an overheating boiler in general is not good.

If you are having issues with an intermittent E9 fault code, resetting the boiler is often only a short term solution to your problem, and your boiler may stop working altogether at some point.

As such if your boiler is coming up with an E9 fault code, the best thing to do it get it repaired at your earliest convenience, by a suitable Gas Safe registered heating engineer – ideally one that has experience working on Worcester Bosch boilers.