Ideal Logic Max Issue

[Kroajm]

Hello all,

I have an Ideal Logic Max system boiler with an S Plan Plus setup. Recently, the boiler has started acting a bit strange.

When the programmer is scheduled to turn off the boiler it stops firing as expected. But instead of going into standby mode with pump overrun for 10 mins or so ( this is shown as “00” on the display) the pump continues to run indefinitely and the display shows the current boiler temperature.

Checking the boiler user manual it states.

“The boiler has a call for central heating but the appliance has reached the desired temperature set on the boiler.”.

The thing is, this is an intermittent issue. It occurs maybe 50% of the time. During the issue I can see that the programmer has turned off the heating so there’s no call to the stats and I can also hear the motorized values closing. I’ve obviously turned down the stats fully but still have the same issue.

If I turn on the heating again the boiler goes from the above state to firing again as normal.

To rectify issue I have to turn off the boiler using the on/off switch on the boiler itself. I leave it for a few hours then turn it on again. It automatically goes into standby mode.

Just to note, I recently replaced the programmer but still seeing the same issue.

Any ideas would be greatly appreciated.

Thanks,
D

 

[cross thread]

Possibly a end switch on a zone valve sticking

 

[Kroajm]

That’s what I originally thought. However, if the motorized valve was sticking would the boiler not continue to fire?

 

[cross thread]

No as valve is closed nowhere for heat to go.

 

[Johntheo5]

Hello all,

I have an Ideal Logic Max system boiler with an S Plan Plus setup. Recently, the boiler has started acting a bit strange.

When the programmer is scheduled to turn off the boiler it stops firing as expected. But instead of going into standby mode with pump overrun for 10 mins or so ( this is shown as “00” on the display) the pump continues to run indefinitely and the display shows the current boiler temperature.

Checking the boiler user manual it states.

“The boiler has a call for central heating but the appliance has reached the desired temperature set on the boiler.”.

The thing is, this is an intermittent issue. It occurs maybe 50% of the time. During the issue I can see that the programmer has turned off the heating so there’s no call to the stats and I can also hear the motorized values closing. I’ve obviously turned down the stats fully but still have the same issue.

If I turn on the heating again the boiler goes from the above state to firing again as normal.

To rectify issue I have to turn off the boiler using the on/off switch on the boiler itself. I leave it for a few hours then turn it on again. It automatically goes into standby mode.

Just to note, I recently replaced the programmer but still seeing the same issue.

Any ideas would be greatly appreciated.

Thanks,
D

Generally when a demand for heat is satisfied, the motorized valve closes, the end switch switches the burner off and the circ pump (over) runs for a fixed time to cool down the boiler HEX, the circ pump then stop, when the motorized valve closes the water has to or should circulate, in sme cases the boiler has a internal by pass which may be sufficient to eventually cool down the HEX but a ABV (automatic bypass valve ) is often installed between the boiler flow&return to achieve this.
Is the boiler flow temperature reducing during the overrun period?
Some (older?) boilers I think had/have a separate stat that would keep the circ pump running until the boiler flow temperature fell by ~ 10C to switch off the circ pump.

 

[JonathanM]

Is the boiler flow temperature reducing during the overrun period?

Presumably if the motorized valves are fully closed but the switch is sticking on, the pump will just continue to circulate the system water around the bypass, gradually losing temperature. And then once it gets to 10C below set point, the boiler will fire for a few seconds, and the process will start over again.

 

[Johntheo5]

I don't think any modern boilers have the stat I mentioned above but have a fixed settable overrun time.

 

[JonathanM]

I don't think any modern boilers have the stat I mentioned above but have a fixed settable overrun time.

I wasn't talking about overrun. I meant the situation with a faulty zone valve, where the valve is physically closed, but the switch is still sending a live request to the boiler.

 

[Johntheo5]

In that case its the anti cycle time will control the off time but correct in essence.

 

[Kroajm]

Thanks for the input thus far.

I done some further testing this morning. Heating came on as scheduled between 6 - 7 AM. I checked the boiler at 7.15. Issue was present. Just to note hot water zone wasn’t scheduled so it’s not in the picture here.

When issue was present

1. Confirmed heating was turned off on programmer.
2. Turned down upstairs and downstairs stats. Didn’t make any difference
3. Boiler temperature didn’t seem to drop
4. Opened gate valve on bypass a bit more. This caused boiler temperature to drop.
5. Boiler fired for a few seconds then returned to the same problematic state. Continued in this cycle.
6. I turned on the upstairs heating via programmer and turned up the upstairs stat. Boiler fired up as normal.
7. I turned off the upstairs heating via programmer. Boiler stopped firing but it returned to the problematic state.
8. I turned on the downstairs heating via programmer and turn up the downstairs stat.
9. Boiler fired up again as normal.
10. I turned off the downstairs heating via the programmer. This time it worked and boiler went into standby.

I was under the impression that if there was no signal from programmer to stat and from stat to motorized valve then the boiler wouldn’t fire. But are we saying that if the valve sticks then it will fire the boiler regardless of whether there a call from programmer and stat?

If so, then based on above test it seems like the downstairs valve might be faulty.

 

[Johntheo5]

Yes, there is a permanent live going to the motorized valve(s) end switch, when the programmer and stat opens it then closes the end switch mechanically and signals the boiler to run, when you switch off or the stat switches off the signal the vlve closes, the end switch opens and the boiler then, via its own permanent live will keep the circ pump on for a few minutes after the burner is tripped off, obviously if valve faulty with end switch permanently closed then boiler will fire on/off on its own stat, the burner cuts out at SP+5C and refires at SP-5C plus the anticycle time.
If working normally, when the programmer or stat via the end switch, switches the burner off, the circ pump will continue to run (overrun) for the overrun time, then shuts down.
The schematic, below, isnt, quite correct as its the boiler logic that switches the circ pump on/off, its not switched on/off directly from the end switch.

 

[JonathanM]

I was under the impression that if there was no signal from programmer to stat and from stat to motorized valve then the boiler wouldn’t fire. But are we saying that if the valve sticks then it will fire the boiler regardless of whether there a call from programmer and stat?

Yes, that is exactly right. It is possible for a faulty valve to keep sending a live signal to the boiler even when there is no signal from the controls and even if it is physically closed, and this will cause the boiler to keep firing. The first time it happens it is very confusing!

It can also be confusing trying to find out which valve is the problem. You have to be methodical and logical. I have even had two valves go wrong at exactly the same time, but both intermittently, so that was really hard to diagnose.