Carrier 33ZCFANTRM

[coolairman]

We are servicing a building with a hundred or so of these controllers. Every so often one will fail and crash the bus, and lose comm for the whole floor. Is there anything we can do besides replacing the whole controller?
Any help appreciated.
Coolairman

[mechmike2]

Are they all on 1 comm bus? I believe recommended is appx. 55 devices per bus. Also be sure it is only terminated at 1 point. Have had issues with bypass controllers locking up and taking down entire buses but that is on zoning systems. Unsure if that is what you have.

[hvac69]

I personally have never seen one take the entire bus down. Do you just reset power to it and everything comes back on line? Check the polarity of the 24vac feeding it. If you have one that locks up to the point it does I would replace it. Carrier states 128 devices per bus but I have never maxed out a bus, usually use bridges.

[dlove]

I have these and never had this issue.

So everything is working, then one fails and the whole bus goes down? Do you know why the controller is failing? are you using routers? can you check the alarm log and see what your getting? Does the controller work once you reset it or is it burned out?

[coolairman]

These are on VAV boxes. It is set up on an Ivu with bridges. When one of these fails, I have had 4 in the last 2 years or so, most or all of the controllers on that floor will not communicate, until the comm cable is lifted from the bad controller, replace the controller and the problem goes away. The controllers are a little pricey and the bldg is on a full service contract. I guess I was wondering if there was a way to repair the comm portion of the controller without replacing the whole thing.
Thanks for your responses.
Coolairman

[Balibe]

Have to tried RAM Flushing the bad controller? It will reset it to how it is shipped from the factory. Pull power, short Com1 & Com2, reapply power, the pull the jumper after 10-15 seconds. This will reset the address to 0,140 and the parameters to default.

I deal with a lot of these, in my years I have only had one take down an entire bus. Seems odd you have 4 in 2 years. Have you checked with Carrier? What revision software in the controllers?

[coolairman]

Thanks Balibe, I'll try that on the next one.

[BarbaryCoast]

One thing I've dealt with is having to check the baud rate on the controller through Network Tools. If i remember factory is 9600, but I had to relocate a few controllers from different floors and for some reason they were set at 19200 and the whole bus was crashing. This may or may not help, but I thought I'd throw it out there.

[dlove]

These are on VAV boxes. It is set up on an Ivu with bridges. When one of these fails, I have had 4 in the last 2 years or so, most or all of the controllers on that floor will not communicate, until the comm cable is lifted from the bad controller, replace the controller and the problem goes away. The controllers are a little pricey and the bldg is on a full service contract. I guess I was wondering if there was a way to repair the comm portion of the controller without replacing the whole thing.
Thanks for your responses.
Coolairman

yes if there is a short in the comms it will shut that bus down, same if you cross a wire or ground it. have you ever figured out why the controllers short out?

Im sure these are made to be thrown away. Unless you can find someone who will repair them. i would send it back to carrier and ask to see if they can send this back to the factory to see what they find. are you getting spikes off your transformer? weird

[mbarson]

I have had two times that bad actuators for the baseboard have caused large comm issues. If you have reheat or baseboard actuators connected try removing them from the VAV and see if it helps.

[381engineer]

Sorry in advance for a slight hijack.
i just took over two building with the same controllers and I've got a large number of controllers where the airflow readings seem to read way low.
Any know issues with the pressure transducer on these? These were all installed in 2004, New VAV (Titus) boxes with new controllers.

Eventually I'll have to dig up a flow hood and confirm.

Thanks