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Tim JA
Tim JA, HVAC Technician
Category: HVAC
Satisfied Customers: 2247
Experience:  Owner at Self-employed
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I have a Ferroli Optimax HE 25s boiler connected to a

Customer Question

Hi Pearl - I have a Ferroli Optimax HE 25s boiler connected to a thermostat with two switches, one for "Heating" and one for "Hot Water". I want to turn on just the Heating, but the boiler display does not come on unless I turn on Hot Water too. Do you know what could be wrong? How would I turn on just the Heating?
JA: Are you getting any error codes or blinking lights on your Ferroli boiler? How old is it?
Customer: It's a fairly old boiler I think, I've only just moved in so I'm not sure how old
JA: How long has this been going on with your Ferroli boiler? What have you tried so far?
Customer: there aren't any blinking lights or error codes from what I can tell. It does take a minute or two to boot up the display on the boiler, but all that displays in the temperatre and I am able to control the heating temp and water temp independently
JA: Anything else we should know to help you best?
Customer: So far I have tried to reset the boiler, just by holding down the reset button and then it just seems to go back to the way it was
Submitted: 16 days ago.
Category: HVAC
Expert:  Tim JA replied 16 days ago.

Good afternoon, 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 make and exact model number of the programmer. Or, attach a photo so that I can identify it.


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 16 days ago.
Sure, so the boiler is a Ferroli Optimax He25s, the timer I've just got replaced, it was a "Flash Programmer" (I can't see a model number) and I've just had it replaced today with a Nest Learning thermostat.I'll send through a video in a sec showing you exactly what I'm talkign about. The Flash Programmer and the Nest seem to function exactyl the same i.e. I need to turn on the Hot Water booster in order for the heating to come on and I can't control it independently.Give me a sec I'll send through a video...
Customer: replied 16 days ago.
Here's a quick video
Expert:  Tim JA replied 16 days ago.

In the video, at the moment near the end when you turn off the heating, is the boiler still heating the hot water?

Expert:  Tim JA replied 16 days ago.

More questions:

Do you have a room thermostat?
Do you have a motorised zone valve, near the hot water cylinder?

Customer: replied 16 days ago.
34;is the boiler still heating the hot water?" - yes the hot water at that point is still on. so basically I can turn on the hot water independently but not the heating"Do you have a room thermostat?" I have the Nest controller but it's basiclly the same as using the iPhone in the video, turning the heat up on the gas heating doesn't actualyl do anything, only turning the water on."Do you have a motorised zone valve, near the hot water cylinder?" - there isn't a motor that I'm aware of but there is a separate switch for on/off and another for bath/sink near the hot water cylinder upstairs. I never turn that on though - I'll attach another photo of the hot water cylinder
Expert:  Tim JA replied 16 days ago.

My hunch is that you're focusing on the boiler when the problem is elsewhere.

It's unclear how you ever controlled the heating if you didn't/don't have a room thermostat. Do you have a Nest Heatlink, and the thermostat? I'm not clear what the thing is that your calling a controller.

There should be only one switched live from the Heatlink to the boiler, and the boiler knows not why it's being asked for heat. If you disable the hot water heating, and let the boiler time out and shutdown, and then turn up the Nest thermostat, does the boiler ignite? If not, then the wiring at the Heatlink is wrong, or there's a motorised valve fault.