NAE, FX15 and LON
I'm building a BMS based on NAE and FXs talking to each other via LON. I managed to connect FXs to NAE and download points for each FX which was quite a struggle Now I can read all the output NVs through NAE, but I can't read any input NVs and therefore change their values.
In the FX builder you can put the point on the network as a permanent point or as a volatile point. Permanent means that the value is stored in the memory of the FX and volatile means that the value is gone when the power supply is gone, right?
To protect the set points and all that, the FX programmer put all the points on the network as permanent points, what seems to be resonable.
Anyway, I took one FX program, changed some points into volatile points, downloaded it into FX, extracted the xif file and attached it to NAE's Lon Trunk and after all that I was able to see the points that I changed into volatile points.
And here's my question: is it the only way of having the ability to change the value of a point? It just has to be a volatile point?
I called a JCI guy with that question and he answered yes, but to be honest, I don't trust him
If it's true, then let suppose the NAE breaks down and the electricity goes down for a moment - all the FXs lose their set points and the AHU under them won't work properly if you start them manually.
Thanks for your time
When you make it a "permanent storage" point it becomes a configuration parameter (CP) in the lon profile. It seems as if there is no way to map a CP back to Metasys, none that I have found anyway. Maybe it has to do with the number of times you can write data into the novram?
I normally use a local display for the controller and change the set points there. It is very annoying, let's see what the LON guru's have to say.
I haven't dealt with the products you are talking about but I can give a bit of insight to the LON side of things.
If you write directly to an nvi and the controller loses power then when power is restored the value you wrote to the nvi will go away and it will go to default. For example many times I setup ASC's so customers only write to the nviSetpoint. If I have them write direct to that point then after a powercycle the value comes up as 621.81 - the default value which becomes invalid then the controller operates to the Configuration Parameter Setpoints. Of course this also annoy's customers - 'yesterday I set it to 72 and now it is set for 621.8'
Why not write direct to the configuration parameter setpoints? Well you can but the controllers I've dealt with have a limit of 10,000 max changes to that configuration parameter. I want to maximize the life of the controller so I have the customer write to the nvisetpoint, which doesn't have a limit, and besides using one setpoint is typically easier for customers, they don't flip heat & cool settings. Typically what I do is write some kind of logic in another contoller that the setpoint is orginated in and this point is where the setpoint is written to, and then create a binding between the two controllers. Now on a power cycle the ASC still goes to default but once it restores communication it gets the last actual setpoint sent to it and updates.
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Not sure if you can do this with FX but when I work with programmable lon controllers I just set up a range to look for in the device say for temp set point 45-80 and if outside that range it defaults to say 70. That way if the snvt goes to 621 it will revert to the default until the system sends the correct set point out again. This seems to work but if you are using non programmable you may need to do something different. I use this type of program so if the front end goes down or we are doing the field devices and someone else has the front end at least I know if something happens everything will go to the defaults in the sequence. You could do something like this just as crab master is saying and bind this set point out to a non programmable devices snvt which I have been forced to do on occasion also.
To change CP you only can do it with FxcommPro Lon. What i found out today is that you make a xml file which you can import in your integration tool. then you will see it as UCP but yoa can write to it. What you see is the raw value. I used the Nodebuilder resource Editor and add the fmt. and other files. Re sarted the lns server and opend the device and I was able to write a value on the CP. The value of the permanent point was 20.00 and as raw value it shows 07D0. It is possibel to change the CP. Mmy next step will be investigaste or I can use a normal value instead of the raw value.
Has someone els already a solution for this?
Those NAEs sure make things easy.
Put a little hair around the NAE's rj45 connector.....and Oh baby! Us control guys wouldn't need any thing else in this world.
Originally Posted by NINAX
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