Should radiator & tap symbols always be visible?

[ponderinspirit]

Hi everyone,

I've got a Vaillant ecoTEC plus 637 (R1) system boiler which was installed in 2013 and serviced every year since. Last year I had quite an extensive job replacing a fair few parts (expansion vessel, auto air vent, prv, pressure gauge, g10 burner gasket, electrode).

In addition to the boiler I have a megaFlo cylinder on the top floor and a Potterton control unit next to the boiler. The HW and CH on the Potterton unit has always been set to "ON". The CH is actually switched on and off via the Honeywell Thermostat situated in the hallway. The thermostat is wired to the MegaFlo. I've never played around with the settings on the Potterton or with any timers. It's always been set to On and CH controlled via the thermostat.

Recently I had a refurbished pump fitted because my old pump was giving issues (F75 & humming). I also fitted in a new pressure sensor for added measure. The boiler is now running smoothly with no humming or fault codes.

I've never really paid much attention to the screen, however I recently began to notice the radiator symbol always being present. I'm not sure if this has always been the case though. The symbol is always ether solid or flashing, but rarely disappearing. It has disappeared occasionally, but not very often. I guess that question I have is if this is normal?

Despite my central heating being switched off from the thermostat. I've tried switching the CH off from the Potterton unit, but the radiator symbol seems to always remain present. When the boiler is not in demand the symbol tends to flash.

My CH dial on the boiler is set to 65 degrees and my tap dial is set to 53. I can understand why the tap symbol appears intermittently as the MegaFlo system is sending a signal to the boiler to ignite in order to maintain heat in the cylinder, however I can't seem to figure out why the radiator symbol is present when the central heating is off. Any help would be greatly appreciated.

Please see attached pictures. Just for context, when pictures were taken the radiator symbol was flashing (not solid) and no ignition symbol as hot water was not in use. Also the CH had been switched off 5 hours prior. I double checked the thermostat and it's definitely off. All radiators are cool to the touch.

Thank you

 

[CountryFan]

Iirc the tap symbol doesn’t do anything on the plus system version and because it’s wired up to the motorised valves, the switch lives will send signals for the boiler to fire, but only the radiator symbol. I thought it was solid when no demand and flashing when there is a demand.

 

[ponderinspirit]

So currently no water is being used. CH is off. Everyone's asleep. Radiator symbol has gone! But tap symbol solid.

Could you please elaborate a little on the tap dial issue? So turning the dial wouldn't change anything? I've noticed that when I set the radiator dial, it acts like a max limiter. So if I were to set the radiator dial to 65, then the tap dial would only ever go to 65.

 

[CountryFan]

Yes, some boilers and pcb's are designed to be used as a combi, I've rarely worked on the Vaillant system boilers, but altering the tap dial has no bearing on the hot water output. Try turning the tap dial up to 65 and back down to minimum and see if the symbol disappears, could be the preheat function, but again this has no function on a system boiler.

Just looked at your photos again and the Potterton has a low battery symbol, might want to change them if applicable

 

[ponderinspirit]

Thank you. When I turn the Tap dial down (anti clockwise) the tap symbol disappears. Ignition on and water in use, but no tap symbol displaying when the dial is turned down. Water is hot though.

 

[CountryFan]

Thank you. When I turn the Tap dial down (anti clockwise) the tap symbol disappears. Ignition on and water in use, but no tap symbol displaying when the dial is turned down. Water is hot though.

Exactly the way it's supposed to work. It's not the easiest to understand when they've put X2 dials on. The hot water in either system boiler, open vented or combi boiler is heated via the central heating water. With the former 2 systems the water is stored and with a combi it's usually instantaneous, which is why the need for the dial on a combi. Hope this makes some kind of sense

 

[ponderinspirit]

Thank you. I've been experimenting with the dial and I've noticed that when I turn the dial up (say to around 60) the boiler suddenly ignites and heats up. That would suggest the dial is doing something? Perhaps trying to reach that temp?

I've been chatting to Gemini and it's told me that the tap dial can be thought of as "pre heating" the water, i.e., before the MegaFlo ultimately sends its own signal when it detects a drop, thereby taking less time for the MegaFlo to achieve it's set temperature and maintain the heat, particularly when water is in demand (say if two people are using both bathrooms simultaneously).

And If I were to turn the dial down "it could lead to the boiler cycling on and off more frequently as it tries to maintain the heat transfer. A higher boiler setting (within a reasonable range) allows for longer, more efficient heating cycles"

So if I've got this right this means that the boiler is igniting regardless of which sends the signal first, but it's presumably better to have the water warmer, particularly when in demand?

 

[CountryFan]

Pre-heat is usually for combi boilers only. I'm unsure why it's fired up in that instance, unless it was a coincidence? @ScottishGasMan might be able to explain it in more detail.

 

[ponderinspirit]

Thank you. I would like some clarification regarding the radiator symbol. After some further observation I have noted that it does disappear. However the issue I have is regarding it's presence in the first place. I haven't switched on my central heating today so I'm assuming the radiator symbol shouldn't be on display?

Whenever I turn on the hot water the boiler proceeds to ignite, the temperature rises and both the tap and radiator symbols are present.

When the hot water tap is no longer in use, the boiler ignition switches off, temperature starts to fall, tap symbol remains solid, and radiator symbol starts to flash. After sometime the radiator symbol disappears, however the tap symbol remains solid.

Both of my Honeywell motorised valves appear to be in good order (and set to auto).

I'm set the Tap dial to 60. CH dial to 65. I'm going to check the MegaFlo cylinder thermostat tomorrow. I'm presuming that's been set to 60 too.