Ideal Icos boiler - pump overrun

[iparm00]

We moved into a house that has got an Ideal Icos HE24 condensing boiler.
We noticed that sometimes when the CH clicks off, there is a bang in the pipes.

I assume that this is happening because residual heat in the heat exchanger is "boiling" the water in the boiler when the pump stops running.

The CH system is wired up with the pump coming on at the same time as the call for heat from the boiler, so there isn't a "pump overrun" wired up at the moment on our system.

I was wondering if this boiler has got a terminal on it that is for a pump overrun, but the manual for the boiler is pretty sparse when it comes to details on how to wire it up.

The manual say there is live L1, L2, L3.

L3 is permanent Live.
It says L1 and L2 should be joined if there is no room stat
On the wiring diagram one option says that if a stat is used, then the stat gets wired to L1, and L2 gets wired to "system controls"
Another option has "system controls wired into L2 (with the room stat being part of "system controls") and in this diagram L1 is left disconnected.

At the moment my "system controls" are wired into L2 with L1 left disconnected.

So my question is if anyone knows what L1 and L2 are supposed to be?
(Is one call for heat, and the other a pump-overrun)

Any help gratefully received.

 

[corgiman]

L1 = 240v ou to external controls
L2 = switch live back to boiler

no pump over run needed

the bang is probably your three port valve.

 

[gas4you]

AFAIK the only Icos that has pump over run fitted is the system version, or at least it was when I was stupid enough to fit Ideal boilers

 

[iparm00]

Thanks for the replies.

Corgiman, you say the bang might be my three port valve - can you explain more...

Is my 3-port valve on the way out and needs replacing. Or is the by-pass on the system not letting enough "by-pass"?

Thanks...

 

[Gas2Air]

Have you got a 3port or 2 2port valves? Usually the noise you describe is the valve shutting rapidly mostly because it has been fitted the wrong way round.

 

[ambi]

Iparm, have a look at my posts recently. Have the same boiler and recently had very similar problems. Cured yesterday/today by lowering the boiler stat setting. If it is turned right up I bet you have got the same problem! There are 6 settings including min & max. What one is yours currently set at? If it is higher than 4 ( about 1 O`clock position) try lowering back to 1 O`clock positon and monitor. I would be very interested in your feedback on this as it has totally cured my problems. Good luck!

 

[ambi]

//www.diynot.com/forums/viewtopic.php?t=158396

 

[iparm00]

ambi,
I tried lowering the temperature to "noon". I don't think it has made a difference in my case.

This morning at 4:30AM I was woken up by a vibration in the CH system. I got up to investigate. It wasn't clear where it was coming from. It didn't seem to come from the boiler, and I would guess it was coming from where the pump and 3-port valve are located. The pump is only a few months old.

I am beginning to suspect the 3-port valve. Corgiman suggested above it might be the 3-port valve, and it looks pretty old.

Q) Do these 3-port valves start to wear out and cause vibration etc?
Q) Can a 3-port vavle cause a bang when the pump switches off?

 

[snb]

some of these 3 port valves can be damaged if the temperature of the water that flows through then exceeds 80degrees. They have a rubber ball which comes loose from it's spindle. The cheaper valvesare far more prone to this. The other fault that causes this is a knackered syncron motor. It is easiest and quite cheap to to replace this motor first. Other wise it requires a partial drain down to allow the whole 3 port valve to be changed.

 

[ambi]

Pitty that!..Before you go changing anything.Start from scratch, make sure you have bled everything and are running your pump on the lowest speed your system will take.

 

[Bluebongo]

L1 = 240v ou to external controls
L2 = switch live back to boiler

no pump over run needed

the bang is probably your three port valve.

Hi, corgiman. With respect, surely the pictorial wiring diagram on p. 29 of the HE15 i&s manual shows / implies that
L1 = switch live back to boiler, and L2 =240v to external controls? Also, please explain what ou stands for. Thanks.

 

[ianmcd]

Hi, corgiman. With respect, surely the pictorial wiring diagram on p. 29 of the HE15 i&s manual shows / implies that
L1 = switch live back to boiler, and L2 =240v to external controls? Also, please explain what ou stands for. Thanks.

As that post was 14 years ago dont go holding your breath for a reply