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Tim JA
Tim JA, HVAC Technician
Category: HVAC
Satisfied Customers: 2424
Experience:  Owner at Self-employed
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How do I change my setting on my Worcester Bosch boiler from

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How do I change my setting on my Worcester Bosch boiler from Eco to Pre Heat. Is it controlled by the RFRP thermostat as I cannot change it using the settings on the boiler panel.
JA: Are you getting any error codes or blinking lights on your Bosch boiler? How old is it?
Customer: It is one year old . there are no error codes no blinking lights. If I hold the ECo button for 5 seconds it changes to Pre Heat andwithin another few seconds changes back to Eco.
JA: How long has this been going on with your Bosch boiler? What have you tried so far?
Customer: I have tried periodically to change the setting but failed evry time
JA: Anything else we should know to help you best?
Customer: I hold the Eco button for 5 seconds as suggested. It changes to Pre Heat and within a very short period of time changes back to Eco

Good evening, and welcome to the Technical section in JustAnswer, an independent paid question and answer platform that matches customers' questions to experts in various skills. My name is ***** ***** I'll be happy to help you today.

So that I can give you accurate guidance, please let me know the exact model number of the boiler.


There's no time pressure on this topic - it will stay open to you for many days, and you can reply at any time. I will be away from my desk sometimes, but will respond as soon as I can.

Customer: replied 10 days ago.
Hello Tim, thw model number of the boiler which was new when installed in September last year is : Worcester Greenstar 28cdi compact .

OK thank you.

When you press the Eco button, to switch to Eco mode, does the "eco" button light up green?

Customer: replied 10 days ago.
it lights up green and stays on whlist the eco button is depressed. There is a clock symbol on the screen after the word Eco.

And when you release the Eco button does the green light stay on?

Customer: replied 10 days ago.
for about 10 seconds with the temperature showing and the clock symbol.

OK I need a bit more information to make sure I know which boiler you have, and also the programmer.

On the rating label, somewhere on the boiler casing (probably underneath), there's a "G.C." number - please could you tell me that?

Also, what's the make and model of your programmer or programmable thermostat?

Customer: replied 10 days ago.
GC 47-406-77 Programmable thermosat EPH RFRP-OT Room thermostat wireless

OK please bear with me for a few minutes.

At the moment my conclusion is that there's a boiler fault. However, I'm going to think on this a bit further. I have an appointment at 8pm for one hour, so I will post again after 9pm.

Customer: replied 10 days ago.
Thank you . I look forward to hearing from you. Mike.

You definitely don't have any other programmer in the house that might be connected to the boiler?

Customer: replied 10 days ago.
No this is the only programmer in the house.

Are there any white boxes near the boiler, other than the receiver for the RFRP thermostat?

Customer: replied 10 days ago.
I had overlooked that. It is an EPH 1A -OT

OK. Beat with me. I suspect that's an OpenTherm adapter, which could mean that the boiler Eco mode is being controlled by the thermostat.

Customer: replied 10 days ago.
thank you.Hopefully the thermostat can be re programmed simply to change the mode from eco to reheat and vice versa.

Well, yes, ideally. I suspect it's defaulting to Pre-Heat mode.

Customer: replied 10 days ago.
do you mean defaulting to eco mode ?

Hm. Re-reading your initial post I see your point. You want to change to pre-heat.

So, to recap, you're pressing the Eco button in order to turn off Eco mode?

Customer: replied 10 days ago.
according to the manual I should press the ECO mode button for 5 seconds to change to preheat mode

Could you tell me a bit about the history of the installation? Was this installed for you, or did you inherit the system?

Customer: replied 10 days ago.
It was suppilied by a bona fide company and installed by their recommended engineer with who I was very impressed. However he didn't give a comprehensive itroduction to the programmer which may be where the problem now lies. in the past we have only had a simple thermostat in the house to operate the previous boiler and have never used a programmer.

Hm OK.  This is going to come down to whether or not that engineer used the OpenTherm interface to the boiler.
The 1A-OT appears to be a receiver..  Is that the only white box near the boiler?

Customer: replied 10 days ago.
nothing else.

OK. My delayed meeting is starting so I will investigate after 9pm.

Customer: replied 10 days ago.
ok, thanks .

The slight difficulty I'm facing is not knowing whether the installer connected the receiver to the boiler using its OpenTherm interface, or just as an external thermostat.  If I investigate both possibilities I won't know if I'm on a wild goose chase or if the boiler has a fault, or if there's an incompatibility with EHT's implementation of OpenTherm.
So, it would be best to look at the electrical connection on the receiver.  All you need to do is power off the heating system (or just the receiver) unmount the receiver from its backplate, and take a photo of the connections.

Customer: replied 10 days ago.
where do I power off the heating system. I have never done this before/

Yes - "Where?!" is a common question.
Look for a SFCU next to the boiler, or a plain switch.  Different installers have different styles.  Failing that there might be a dedicated circuit from your consumer unit - if it's nicely labelled then have a look and see what's marked there.  It ought to be a 6A MCB if it's a dedicated circuit.

Customer: replied 10 days ago.
It's ok . I have phographed the inside of the receiver. How do I get the image to you?

Please see the following guidance on attaching photos:

Customer: replied 10 days ago.
Hi, I have taken a photyo but sadly I cannot understand the process of getting it to you . Can you recommend an easy way as I am not computer savvy.

OK.  I'll create a Google Photos album and you should be able to drop it in there.  Give me a few minutes.

You should be able to see this album and drop photos into it.

Customer: replied 10 days ago.
Hi Tim, I have written back to explain that I feel that I am now out of my depth and I am only used to sending a photo to an e mail address.

OK.  Bear with me for a moment...

Can you see the information at the following link?

Customer: replied 10 days ago.
I can
Customer: replied 10 days ago.
I have managed to send you the photo of the treceiver on the softus site.

Received. Give me a minute...

Customer: replied 10 days ago.

With the Eco light illuminated green, what happens if you press the Eco button for much less than 5 seconds? For example, for about 0.5 seconds.

Customer: replied 10 days ago.
I hade to press for 1.5q seconds for anything to happened . ECO went off and whas almost immedaiatley restored, Green light stayed on all the time

OK.  I have to conclude that there is something wrong with the pre-heat function.
Since the boiler is so new, I'm sure that manufacturer's warranty will cover any fault.  However, I recommend that you first contact the installer and ask them if they know if any reason why pre-heat mode can't be operated..

Tim JA and other HVAC Specialists are ready to help you
Customer: replied 10 days ago.
Ok will do and thank you for your patience . I agree it should be down to the installer in the first place and then if necessary the supplier/manufacturer. Thank you very much for your efforts. Mike Fisher.

You're welcome Mike.  Thank you for your rating and your kind bonus.  Do you let me know how you get on with the installer - you can always come back to this topic if you have any follow up questions.
Did you get the receiver back in place and the system on again?

Customer: replied 10 days ago.
thanks Tim. All back to ' normal' but installer needs to investigate, I think.
Again many thanks for all your help.
Mike Fisher


Thank you for your rating, and your kind bonus.  I'm glad that I could help.
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Have a wonderful week :-)