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Brivis Buffalo 52 Duct Heater - Fan not shutting down

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  1. #1
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    Default Brivis Buffalo 52 Duct Heater - Fan not shutting down

    Hi All,
    I have an old Brivis Buffalo 52 Duct Heating.

    1) The gas (ignites) and heating (blowing hot air) both work fine, when the temperature reaches to a certain degree, the heater was able to switch on / off however the fan keep running regardless. Until I switch the power off.

    2) I tried to turn everything off (from the controller and power supply). Leave the wall controller off but as soon as I turn on power supply, the fan kicks in & start running and never switches off.

    3) Open the cover, no flashing lights. Just green FAN light always on.

    Below is the pic when the cover is opened.


    Any help/suggestions would be much appreciated.



    Thank you.

  2. #2
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    I don't have any specific info, but since nobody else has said anything...

    On our Buffalo (different model), there is a connection, marked "G cool" that can be used to force the fan to run all the time. I can't quite see in your photo, but I think there is nothing connected to "G cool", so presumably the controller is not being "told" to run the fan all the time.

    Based on what I have seen in other threads here, I would guess that the fan is switched by a triac, controlled by a microprocessor via an opto-coupler. The triac or the opto-coupler may have shorted, or perhaps there is a build up of dirt on the PCB. If that means nothing to you, then maybe you just have to call somebody out to have a look at it. If the controller has developed a fault, they will probably just replace it rather than try to repair it at component level.

  3. #3
    Slow but rough Uncle Bob's Avatar
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    There seems to be a wire missing on the top four way connector. That looks be the sensors connector.

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    Quote Originally Posted by Uncle Bob View Post
    There seems to be a wire missing on the top four way connector. That looks be the sensors connector.
    I think the sensors are connected via the lower four-way connector - at least the flame rollout and two overheat ones are. Our Buffalo (120) doesn't have any other sensors that I know of.

  5. #5
    Slow but rough Uncle Bob's Avatar
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    Yeah true. I didn't read the diagram right Does yours have the square four pin connector populated?

  6. #6
    Slow but rough Uncle Bob's Avatar
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    Scratch that question. the four way is right on the top of the diagram and the connector is missing.

  7. #7
    2K Club Member chrisp's Avatar
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    Start with the simple - check the 'over temp' sensors first. If they are closed, try disconnecting (one wire will do) and see if it makes a difference.

    Please be very careful though. Turn every thing off before touching any of the wiring.
    There is no middle ground between facts and fallacies - argumentum ad temperantiam

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    Quote Originally Posted by chrisp View Post
    Start with the simple - check the 'over temp' sensors first. If they are closed, try disconnecting (one wire will do) and see if it makes a difference.

    Please be very careful though. Turn every thing off before touching any of the wiring.
    Thank you all for your replies.

    Just checked again, all wires seem to be connect, nothing loosed.

    Sorry for being a noobs, where are the sensors located? What does it look like?

  9. #9
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    Check the filter, if there is one, on the return air grille. Make sure it is clean.

  10. #10
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    Quote Originally Posted by chrisp View Post
    Start with the simple - check the 'over temp' sensors first. If they are closed, try disconnecting (one wire will do) and see if it makes a difference. . . .
    As far as I know the temperature sensors are thermistors, so it is not just a matter of being "open" or "closed".

    According to this post - http://www.renovateforum.com/f193/dr...r-35hi-109773/ - the supply air thermistor is a 10K NTC (NTC meaning that the resistance decreases as the temperature increases). That post mentions a different heater model though, and I don't know for sure if the same thermistor is always used (that would make sense to me, but hey, what do I know?).

    When I get a chance, probably not today, I will check the thermistors on our Buffalo - if nothing else that might be useful for me, or perhaps somebody else, some time down the track.

    On our controller, there are two red LEDs to indicate over-temperature conditions. I think the controller pictured here is the same, with those two LEDs on the bottom RHS of the PCB that protrudes from the controller box. The actual LEDs are obscured by the wires in the photo, but the markings "HS" and "HF" are visible. If it was detecting an overheat condition, I would expect one of those to be on (would it really keep the fan running in that case?). From other threads here and elsewhere, I gather that the controller also detects a disconnected thermistor, but I don't know how it indicates that on the LEDs.

    Hopefully Plum is onto something and it will turn out to be something "simple" like a clogged up filter.

  11. #11
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    Quote Originally Posted by Ozcar View Post
    As far as I know the temperature sensors are thermistors, so it is not just a matter of being "open" or "closed".

    According to this post - http://www.renovateforum.com/f193/dr...r-35hi-109773/ - the supply air thermistor is a 10K NTC (NTC meaning that the resistance decreases as the temperature increases). That post mentions a different heater model though, and I don't know for sure if the same thermistor is always used (that would make sense to me, but hey, what do I know?).

    When I get a chance, probably not today, I will check the thermistors on our Buffalo - if nothing else that might be useful for me, or perhaps somebody else, some time down the track.

    On our controller, there are two red LEDs to indicate over-temperature conditions. I think the controller pictured here is the same, with those two LEDs on the bottom RHS of the PCB that protrudes from the controller box. The actual LEDs are obscured by the wires in the photo, but the markings "HS" and "HF" are visible. If it was detecting an overheat condition, I would expect one of those to be on (would it really keep the fan running in that case?). From other threads here and elsewhere, I gather that the controller also detects a disconnected thermistor, but I don't know how it indicates that on the LEDs.

    Hopefully Plum is onto something and it will turn out to be something "simple" like a clogged up filter.
    Buf's don't have thermistors by my recollection, they are on the H.E. models.
    Could be flames spilling out the front and shutting it down, indicating collapsed heat exchange.

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    2K Club Member chrisp's Avatar
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    Quote Originally Posted by Ozcar View Post
    As far as I know the temperature sensors are thermistors, so it is not just a matter of being "open" or "close".
    I'm not sure if they are thermistors or thermoswitches. I was just going by the circuit diagram in the photo. The symbols are somewhat fuzzy but they do look like the 'thermoswitch' type sensor. Thermistor symbol is usually are resistor symbol with a diagonal ('variable') line through it and maybe a 'T' beside it.

    Quote Originally Posted by plum View Post
    Buf's don't have thermistors by my recollection, they are on the H.E. models.
    Could be flames spilling out the front and shutting it down, indicating collapsed heat exchange.
    I don't know about the Buffalo series, but I have repaired the later Brivis HE types. The HE definitely use thermistors.

    I have seem a very simple control setup used in some very early systems (a Vulcan) where the wall thermostat simple switches on (or off) the flame. The fan was simply controlled by another internal thermoswitch on the burner that tuned on the fan once it heated up.

    I do suspect that the OP may have a faulty control board, but I think that it is also good to start with the simplest and cheapest items first. My understanding (but I could be wrong) is that the fan is usually turned on on the 'overheat' condition in an attempt to cool the unit down???

    If the sensors are thermoswitches they are relatively easy the check with a multimeter.
    There is no middle ground between facts and fallacies - argumentum ad temperantiam

  13. #13
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    Quote Originally Posted by chrisp View Post



    I don't know about the Buffalo series, but I have repaired the later Brivis HE types. The HE definitely use thermistors.

    I have seem a very simple control setup used in some very early systems (a Vulcan) where the wall thermostat simple switches on (or off) the flame. The fan was simply controlled by another internal thermoswitch on the burner that tuned on the fan once it heated up.


    Fan limit switch you're referring to.

  14. #14
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    Also agree probably is the Tek box, but the O.P. should get a qualified serviceman out.

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    Quote Originally Posted by chrisp View Post
    I'm not sure if they are thermistors or thermoswitches. I was just going by the circuit diagram in the photo. The symbols are somewhat fuzzy but they do look like the 'thermoswitch' type sensor. Thermistor symbol is usually are resistor symbol with a diagonal ('variable') line through it and maybe a 'T' beside it.



    I don't know about the Buffalo series, but I have repaired the later Brivis HE types. The HE definitely use thermistors.

    I have seem a very simple control setup used in some very early systems (a Vulcan) where the wall thermostat simple switches on (or off) the flame. The fan was simply controlled by another internal thermoswitch on the burner that tuned on the fan once it heated up.

    I do suspect that the OP may have a faulty control board, but I think that it is also good to start with the simplest and cheapest items first. My understanding (but I could be wrong) is that the fan is usually turned on on the 'overheat' condition in an attempt to cool the unit down???

    If the sensors are thermoswitches they are relatively easy the check with a multimeter.
    You and Plum are probably right about switches vs thermistors. I checked our Buffalo, and both overheat sensors measure close to zero ohms, and presumably go open for an overheat condition.

    I'm not sure about the symbols used in the diagram. The diagram on our one shows just black dots for the sensors, but a bit strangely the diagram is printed on a pretty tatty label which has been stuck over another label on the controller. The old label is a bit visible through the new one, and the symbols there might be the same as in the photo of the controller in question here:

    img_1888-medium-.jpg

  16. #16
    2K Club Member chrisp's Avatar
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    Quote Originally Posted by Ozcar View Post
    I checked our Buffalo, and both overheat sensors measure close to zero ohms, and presumably go open for an overheat condition.
    Thank for checking. This forum seems to be becoming the go-to place of info on repairing the Brivis heaters. Your observation will be of help to someone and helps us all understand these products better.
    There is no middle ground between facts and fallacies - argumentum ad temperantiam

  17. #17
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    Sticker over sticker would indicate this heater was part of the p.c.b. recall back in around 1999 or thereabouts, which I did for a couple of months.

  18. #18
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    Quote Originally Posted by chrisp View Post
    Thank for checking. This forum seems to be becoming the go-to place of info on repairing the Brivis heaters. Your observation will be of help to someone and helps us all understand these products better.
    I totally agree! Thanks Ozcar

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