Brivis Buffalo 85 EMS OH/F & OH/S errors

[Grasshopper75]

Hello everyone,

I have recently purchased a house with a Brivis Buffalo 85 EMS gas ducted heating unit. Unfortunately I have no idea on how old the unit is as there was no documentation or instructions left when I moved in. Now that winter has arrived I have powered the unit on and I have been having some intermittent issues which I am hoping some of you could assist me with.

The issues I am having are as follows;

Poor airflow from all ducts
Intermittent OH/F & OH/S errors on the control board


This morning I awoke to a cold house and no air flowing from the ducts. I checked the unit and the fan was running however the burners and pilot light were off. The control board was showing an OH/F (overheat fan?) error. I reset the unit and the pilot light kicked in and lit the burners, the fan started and I went back inside. After a few minutes I again checked the ducts and again there was nothing coming out of them. Upon returning to the unit, the burners were out, fan was running and the OH/S error was showing on the control board.

I'm trying to determine what is the likely cause of these errors? I can get to and replace the pilot burner easily if needed but I'm not sure if this will fix the problem. Having done some reading I think the flame rollout sensor might need replacing but I have no idea where to find this on my unit.

Attached are photos of my unit. The control board is currently showing everything as green however the OH/F & OH/S errors are intermittent.

Any help would be appreciated. Thanks.

90242
Brivis Buffalo 85 EMS

90243
Control Board

90244
Wiring Diagram

90245
Pilot Burner

[plum]

If it's shutting down due to o/h issues, try checking your return air filter behind the r/a grille, if blocked with dust, will cause low airflow and will overheat unit, causing it to shutdown. Also if possible check all ductwork for any damage. p.s. this model was subject to a recall by Brivis back in about 2000, which I was involved, ring Brivis to see if yours had the update. It was free at the time but they will charge you to do it now.
http://www.renovateforum.com/attachments/f193/90242-brivis-buffalo-85-ems-oh-f-oh-s-errors-brivis-1.jpg
Brivis Buffalo 85 EMS

http://www.renovateforum.com/attachments/f193/90243-brivis-buffalo-85-ems-oh-f-oh-s-errors-brivis-2.jpg
Control Board

http://www.renovateforum.com/attachments/f193/90244-brivis-buffalo-85-ems-oh-f-oh-s-errors-brivis-3.jpg
Wiring Diagram

http://www.renovateforum.com/attachments/f193/90245-brivis-buffalo-85-ems-oh-f-oh-s-errors-brivis-4.jpg
Pilot Burner[/QUOTE]