Burner Control -Landis Gyr LOA21 171B27

[dickiejay]

Hi I am having poroblems with this burner control. It is a brand new unit, as are the High and Low stats, etc etc.

Boiler fires but disregards the cut off signals from the High and Low stats. Once power is pushed through to the burner motor it doesnt release it even if the stats are both disconnected. The wiring is exactly as supplied new but there is obviously a problem somewhere. An electrican has checked the wiring and he suspects that there is a backfeed from somewhere. Please Help!!!

Richard

 

[Burnerman]

Have you a frost thermostat somewhere?
John

 

[dickiejay]

Hi John

Thanks for replying.

No frost thermostat fitted. The boiler stopped working before christmas. Had severla plumbers in who all diagnosed different things. The actual problem was faulty High Stat.. replaced both High and low stats, fitted new burner control unit but once it starts it wont cut out unles you power off completely.

If I disconnect the stats by pulling the snap conector out it carries on - which makes me believe that the power to the burner is coming form teh burner control unit itself.

Thansk again

 

[Burnerman]

A curious one...obviously if you provide the control box with a continuous live feed, the burner will keep running ad infinitum, and the stats are surely there to interrupt the feed before reaching the burner - which makes me think there is a wiring issue here.
John

 

[dickiejay]

Thanks again John

Yes thats definitely teh case. The live feed is inbto the control unit - just doesnt disconnect after its fired.

The live then pases up to the stats and back in again on a different pin. I wonder if its worth pushing teh feed in through the stats rather than the control unit??? This can then drop the live feed if stats ut in/out ??

I do have a fully qualified Electriian looking at this and a heating engineer - both baffled!!! We have religously followed teh shematics.

 

[Burnerman]

The burner live feed would go through the stats first - its the only way to control the burner.
Personally I can't see anything wrong in what you are attempting.
Wishing you luck!
John

 

[oilhead]

What boiler is it?
Does it have a postpurge PCB?

 

[dickiejay]

Hi Oilhead

Thanks for reply.

Its a Eurocal boiler with an ECOFLAM minor burner unit. I dont know what a post-purge pcb is.

I think the issue is with the control unit and wiring. Although it is wired exactly as before I replaced the LOA21 with an LOA24. The echematic looks exactly the same I have to say.

 

[oilhead]

The LOA 24 vis a direct replacement for the LOA 21. Did you at one time have an old BHO box fitted? If so there will be an adaptor base fitted. When tis was done, then the thermostat loop should have been re-directed from pins 7-9 to pin 6 in the old base.
If you only have one base, then it is a simple check to ensuure correct wiring.
I am confused when you talk about high and low stats, are you meaning control and limit?
The power feed should come in through the two stats in series so that if either becomes satisfied it cuts off power to the burner. I can see an electrician may be confused by it, but a heating engineer should hav eno problem.
If you do have a two stage burner with high and low stats, then the schematic shows how to wire up for this.
In short, you should only have one basic feed to this box, and that should come through the control and limit stats.

 

[dickiejay]

Thanks again. Just noticed we are practically neighbours.

We did actually find that problem late yesterday. When the boiler was installed they didn't wire the power correctly - as you rightly said. Now the boiler works fine and cuts in and out via boiler stats, room stats and cylinder stats. I dont know how it worked before.

 

[pereivers]

I stumbled on this item while trying to solve my change-over.
I have a heating installation, oil fired. The oil burner was controlled by a LOA21.171.A27. I replaced the unit by a LOA24.171.B27 and the burner then started properly, but will not shut off by either room control or heater temperature control, nor both. If I push the reset button, the burner stops, and starts again if both controls are ON again. The alarm light in the reset button is never lit.
If I darken the light sensor, the unit stops immediately, alarm light goes on, and there are no repeat tries to start the burner again.

When equiped with the LOA21 unit, all worked as it should.
In the installation, there is no oil preheating. pins 3 and 8 are not connected, neither are pins 6 and 7.

Any help would be appreciated.