#120

[@SanaUllah-b3t2u]

Hi Paul, many thanks for sharing and taking your time to explain yet another master piece, Apologies in advance for being a pain, let's say we have a scenario where we have AHU and FCU to serve cooling to two different space areas of the same chiller system. I found online an example that I wanted to share it with you basically it's called Primary-Secondary chilled water system. Where we have X amount of chillers. Primary system has low head primary pumps which maintain the constant chilled water flow in the system and secondary system high head with secondary pumps to maintain variable chilled water flow depending on the demand. Secondary pumps are fitted with VFDs to control the flow rate in the secondary circuit as per the load condition. The secondary system is suppling chilled water to eg AHU's, FCU's load etc and has 2 way valves with 0 to 10v actuators, which then put back to the chillers through return loop. The 2 way valves has end switches integrated into the BMS system to monitor the 2 way vales operation and also as a safety feature for the chillers. I wanted to add end switches because previously I was in the situation where we had a brand new RAF typhoon site with 4 chillers. The problem was chillers would go into fault if there is no flow in the system, ie we got primary pumps are running and secondary pumps are running with no fault on the system what so ever and we are asking for the chillers to run on the same time. So the flow prove would take time to register healthy condition and in the mean time chillers would pick up no flow and goes into fault, therefore we added on time delays. The problem was client has to manually reset the chillers by powering them down individually, which was a right pain. I hope I have given enough system info this time and apologies if I am missing some info. Many thanks

[@NiagaraTridium]

See kzbin.info/www/bejne/eZewc6Nra7eLeKc is this what you mean ?

[@SanaUllah-b3t2u]

@NiagaraTridium Hi Paul, many thanks for the reply and reposting it, I haven't had a chance to look at it yet. However, I will be doing this tonight and will get back to ya. You are legend and BMS guru, lol. Cheers 🍻 Ah, also, the linear sequencer is working grand. However, when the system is shut down, eg, time schedule or temperature setpoint reaches, it shuts down the system, but chillers are still running with linear sequence 1 minute as it goes through the off sequence. I was just wondering if there is a way to go around this. For example, if the chillers could just shut down immediately when there is no demand without going through the 1 minute off sequence period. I looked at module settings, but there are no options within the block. Pumps off delay 5 minutes is exactly what we wanted as that would disperse cooling from the system, and if the chillers are still running, there is a slight possibility we could freeze the system and could cause issues. What's your take on this please thanks.

[@NiagaraTridium]

@@SanaUllah-b3t2u I have changed this in the revised logic.

[@SanaUllah-b3t2u]

@NiagaraTridium Morning Paul, that makes perfect sense. Thanks for that. Correct me if I am wrong, please. we have 2 secondary pumps. We can just add a second numeric writable for pump 2 VSD control of the same loop ? Cheers

[@NiagaraTridium]

@@SanaUllah-b3t2u yes you can use a second ao for the 2nd pump speed from the same.pi speed loop.