Master/slave

[Jeremy325]

Hello everyone I am new to site. I have visited many times great site.
Ok I have two 30ra 030 aqua snaps. They both have MBB version 4.0. The problem is that my control point is getting down to 32 or so degrees because it is looking the common dual sensor and the other chiller water temp that is not running and compensating for the water temp difference in the two. The maste slave is not working correctly. I have been on phone with carrier tech support for hours the above is what they said. Any ideas on what to do. Thanks guys

[spinning wheel]

Page 26 of the install/ service book that came with the unit. Labled configuring and operating dual chiller control. This is where you will find how to set up the units. Make sure that units are piped correctly, in parallel config. Then check common sensor location and make sure that you are reading correctly the water temp. One chiller must be master, and has the common water sensor. Then the two chillers are connected with the CCN bus. I have done this many times and it always works. The only problem ever was when the welders put the common sensor location in an air pocket in the piping. The master chiller makes runs like normal until it sees that the load is being lost, then the other chiller is called on by the master.

[Jeremy325]

I have got it set up correctly i believe. I have contacted carrier and they wa;k through the config tables the problem is that the control piont is floating so much. The set piont is 45. the control piont is around 32 or even lower at times. Carrier said it is the version of the MBB and the way it controls the algr. between the two. Is ther a better way to set these two up. the dual sensor is in the common loop and landed on the master.

Hope this make sense

[Dallas Duster]

Hello everyone I am new to site. I have visited many times great site.
Ok I have two 30ra 030 aqua snaps. They both have MBB version 4.0. The problem is that my control point is getting down to 32 or so degrees because it is looking the common dual sensor and the other chiller water temp that is not running and compensating for the water temp difference in the two. The maste slave is not working correctly. I have been on phone with carrier tech support for hours the above is what they said. Any ideas on what to do. Thanks guys

So I take it that this is in a parallel configuration with no isolation valves on the chillers?

[Jeremy325]

Yes parallel and it has isolation valves on both Ew and LW

[Dallas Duster]

Yes parallel and it has isolation valves on both Ew and LW

What is your DLWT reading compared to the LWT on the chiller that is running ?

[Jeremy325]

LWT=49.9 dual = 54 entering and leaving of other chiller that is not running is 57 my control point is around 32
Thanks for your help

[Dallas Duster]

LWT=49.9 dual = 54 entering and leaving of other chiller that is not running is 57 my control point is around 32
Thanks for your help

In theory they should be reading the same . It's trying to compensate for blended water it doesn't exactly know you have iso valves. You have something going on with your sensors is my guess.

[Jeremy325]

Ok what would the ISO vavles do? Should I turn the slave valve off and see if dual sensor is the same as LWT

[Dallas Duster]

Ok what would the ISO vavles do? Should I turn the slave valve off and see if dual sensor is the same as LWT

Ok I must have missed something I thought you said you had auto isolation valves on each chiller. And yes close the slave off and see what happens. And what is the unit tripping off on?

[Jeremy325]

No it has manual full port ball vavles. The alarm is T116 Sorry for not clarifying the vavles

[Dallas Duster]

No it has manual full port ball vavles. The alarm is T116 Sorry for not clarifying the vavles

How cold is your leaving water getting when this alarm comes in anywhere close to 32?

You could close the ball valve and see if the alarm goes away and see if your DLWT and LWT match up.