How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • Go back-and-forth until satisfied
    Rate the answer you receive.
Ask JamesI Your Own Question
JamesI, Developer
Category: HVAC
Satisfied Customers: 6322
Experience:  I have a portfolio of renovated houses, including DIY projects from installing bathrooms and new heating systems to rewiring.
Type Your HVAC Question Here...
JamesI is online now

I have aHoneywell Y9420S controller for my central heating.

This answer was rated:

I have aHoneywell Y9420S controller for my central heating. I have twice encountered a problem when the house power has had to be turned off.... electrician work in the house. When the power returns my ST9420C works for a period of time and then displays a flashing RF sign next to the heating on indicator and a message stating no signal... Obviously, this usually means low battery in either the DT92E or the ST 9420C. However, both units have had new batteries installed. So we have had a very chilly night once or twice. However, over night maybe after 6 to 7 hours the whole thing sorts itself out and fires up the boiler. Also the controller loses dates and times information... the back up battery doesn’t appear to work. I obviously put the info back but doesn’t appear to make much difference. Can you help please.
JA: What's the brand and model of your central heating? How old is it?
Customer: A Main HE boiler and about 10 years old.
JA: How long has this been going on with your central heating? What have you tried so far?
Customer: This only happens when the power has been turned off for electrical work. I have followed the manual instructions in the event of a power cut. It appears to be a RF communication problem which rights itself after a period of time, usually after 6 hours or so.
JA: Anything else we should know to help you best?
Customer: I don’t think so. There doesn’t appear any logic in why after several hours it communicates correctly. Could it have anything to do with the back up feature of the system not working?

Hi, thank you for choosing Just Answer, my name is ***** ***** I will help with your query today.

The RF issue may often point to the fact the appliance needs to rebind, when you have the fault have you gone through the rebinding process?

Secondly I note the boiler is 10 years old but old are the honeywell devices?

Customer: replied 7 months ago.
Slightly younger maybe 8 years old.
Customer: replied 7 months ago.
I don’t know what the ‘ rebidding’ process is.

Have a look at page 16 (section 6) here, this explains how to rebind the components if they lose their RF signal.

With regard to the loss of memory most likely this is due to a depleted battery in the ST9420C. The battery isnt designed to be replaced as it should last the life of the product (typically 12 years), however in this case if you happy to re-program it each time you have a power cut I would live with it, otherwise you can follow instructions here or replace it with a compatible model.

Is there anything else I can clarify for you

Customer: replied 7 months ago.
Sorry James... that’s very helpful and thank you.

So I can close the question please rate the response provided using the star rating at the top of this page.

JamesI and other HVAC Specialists are ready to help you