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Your salesman is correct. the carrier VAV ( unless you have the newest program) must have a carrier vav controller to operate. ( even if just one with a space sensor) The linkage is the communication from one vav ( or group) box to the rtu

Carrier vav and vvt systems operate off linkage so the system works off of space demand, not just a constant discharge temp. ( much more in depth then that though)

I am in the middle of trying to help someone change the same constant volume units you have to VAV operation. Can it be done sure, cheap no, the humidimizer function gets tricky though.

Originally Posted by tech45

Wow , I'm having the opposite problem , I need VAV units and have constant volume. From the way it sounds I might just be better off. Mine have " humidimizer " that will be re-purposed to " vav-Imizer " .

Our salesman on this is in his 20's and swears that a VAV system MUST include Carrier VAV controls. He also used the term " linkage ". I said that I do not need the unit controller to do anything with the existing boxes. Have not heard a word from him since.

Wow , I'm having the opposite problem , I need VAV units and have constant volume. From the way it sounds I might just be better off. Mine have " humidimizer " that will be re-purposed to " vav-Imizer " .

Our salesman on this is in his 20's and swears that a VAV system MUST include Carrier VAV controls. He also used the term " linkage ". I said that I do not need the unit controller to do anything with the existing boxes. Have not heard a word from him since.

was the unit they sent you a 0-10 or 3 step vfd?

Originally Posted by mfia321

Carriers RTU open has to be one of the worst unit controllers out there. Documentation is poor and integration info is lacking. We had the a similar issue but we needed a multi-zone vav rtu open unit. The sales engineer said over and over that what he submitted was right and a for a vav system. Get the units on the roof and they are vav units.... single zone vavs units. Called carrier guys and he claimed they are vav units but after we explained the difference between single zone and multi zone vav he claimed they didnt have a unit like that. Problem was I had the manual for it in my hand. Carrier refused to make right and send the right controller, so we ripped out the rtu open controllers and programmed our PCG controllers for the job.

Carriers RTU open has to be one of the worst unit controllers out there. Documentation is poor and integration info is lacking. We had the a similar issue but we needed a multi-zone vav rtu open unit. The sales engineer said over and over that what he submitted was right and a for a vav system. Get the units on the roof and they are vav units.... single zone vavs units. Called carrier guys and he claimed they are vav units but after we explained the difference between single zone and multi zone vav he claimed they didnt have a unit like that. Problem was I had the manual for it in my hand. Carrier refused to make right and send the right controller, so we ripped out the rtu open controllers and programmed our PCG controllers for the job.

Originally Posted by Cool breeze 38

Hopefully it doesn't happen again. But if it does tell the fool to get a controls expert (what us carrier guys are called in the program) to clip the std rtu file in. If they say they cant email me his phone number.

They fired him recently lol so chances are it wont. I am very green when it comes to Carrier... trying to learn

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Originally Posted by Reefer636

Had this same exact situation happen 6 months or so ago. Salesman bought carrier vav rtus for a constant volume system ended up putting zone controller in each unit so it had a space temp and setpoint and ran duct static sensor. One of the dumbest things I have had to do. And explaining to the customer how there slider space sensor worked was fun..

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next time use a ZS2P-car for a wall stat

Originally Posted by Reefer636

Had this same exact situation happen 6 months or so ago. Salesman bought carrier vav rtus for a constant volume system ended up putting zone controller in each unit so it had a space temp and setpoint and ran duct static sensor. One of the dumbest things I have had to do. And explaining to the customer how there slider space sensor worked was fun..

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Hopefully it doesn't happen again. But if it does tell the fool to get a controls expert (what us carrier guys are called in the program) to clip the std rtu file in. If they say they cant email me his phone number.

Had this same exact situation happen 6 months or so ago. Salesman bought carrier vav rtus for a constant volume system ended up putting zone controller in each unit so it had a space temp and setpoint and ran duct static sensor. One of the dumbest things I have had to do. And explaining to the customer how there slider space sensor worked was fun..

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Originally Posted by orion242

Option 3 Salesman fixes his mistake...

that would only apply to a constant volume unit. And swapping a unit after its already on the roof and the customer is asking when his cooling is going to be on doesnt really allow the time for a new unit to be delivered. On the constant volume its best to just load the std rtu programs. set it for LC weather maker which used a 0-10 vfd control. Move the wires from input 11 to 10. disconnect the pressure transducer from input 1 and it will run as a staged air volume unit.

Option 3 Salesman fixes his mistake...

Carrier 48LCB as a stand alone non vav system

The 48 LCB unit has the vav rtu board factory installed. It will only run with linkage.

Now that I have my test center up and running I stated to play with the vav_rtu_opn options. This is what I am finding while I am trying all different scenarios. The vav rtu opn will only run with linkage to a carrier VAV open controller. This is the only way this will operate. Its in the units documents saying this also.
So we get the salesman that doesn't know the difference and sells someone the wrong unit. There are two options.

Option 1 install a vav rtu open and put its space sensor in the return or in the space. This is done with a duct probe or space sensor (10k type 2) into the t55 input or a zs sensor to the r net. You can also network a space temp into the vav controller and it will work off of that. When a schedule is set for the vav controller with a valid space temp the rtu will run, and run off that single space temp sensor. The vav rtu opn board does not have the ability to have its own space sensor.

Option 2 since the rtu standard and the vav rtu programs use the same driver you can load the standard rtu open program and graphic into vav rtu opn board. This can be done by clipping the controller, or just loading the equipment and view files. You will need the touch file is you are using the equipment touch or system touch. Regardless of how you will need the ivu tech tools ( field assistant and or app loader) to make this work. You would move the two wires from input 11 to 10. And disable the static sensor and remove the wires from input 1.


Word on the street is there is a new version coming out that does not require this and will work with other control systems. I'll share as soon as I get it.