Monitoring switch on AC unit overflow

[heffneil]

I have a bit of a problem and I was hoping you guys could help me. I have several central ac units that have an overflow outlet with a small float switch that triggers the unit to power off should the drain clog. I want to monitor this with my omnipro ii. The unit doesn't have a pan to monitor and splitting the overflow and adding a second switch would cause the unit to shut down too late. The switch carries voltage so if I just connected it to a zone I would have a problem and it wouldn't work properly. I was going to use a relay that was tied to the power and when the overflow switch is triggered power would be lost and the relay would open causing the zone to trip. That was the best solution I could come up with but there is one wrinkle and that is that when the power goes out all of the zones would then trip. That isn't terribly efficient and not the best way to handle it. Any other ideas?

Thanks!

Neil

 

[cornutt]

Not sure I understand the description... I'd wire a relay into the float switch circuit, and use its contacts to trip a zone on the OPII. Actually, I have a similar situation and I may wind up doing just that.

 

[gatchel]

This is kind of obscure but you could have 2 relays in line. One that's always powered unless the overflow switch trips which is wired to another relay using the open contacts (while powered) (N.C. on the relay) to trip the second relay to turn on which alarms the zone. No power in between relays, no false alarms.

I left out the obvious float switch or water detector options due to your comments about the lack of overflow pan, etc...

 

[heffneil]

This is kind of obscure but you could have 2 relays in line. One that's always powered unless the overflow switch trips which is wired to another relay using the open contacts (while powered) (N.C. on the relay) to trip the second relay to turn on which alarms the zone. No power in between relays, no false alarms.

I left out the obvious float switch or water detector options due to your comments about the lack of overflow pan, etc...

For some reason I am having trouble following. One thing I did think about was using the float switch to trip the relay. That relay would then trigger the disconnect for the ac handler and the zone sensor but I think without power I would still have the false positive...

Neil

 

[heffneil]

Not sure I understand the description... I'd wire a relay into the float switch circuit, and use its contacts to trip a zone on the OPII. Actually, I have a similar situation and I may wind up doing just that.

If I do that an lose power than the relay stops functioning and we get a false positive with that scenario?

 

[cornutt]

I'm afraid I don't follow the bit about the false positive zone trips. I'll try to do a drawing showing what I'm thinking of.

 

[murphy]

Hmm ... an ELK-system knows if there is AC power or not and this information can used in programming this problem. Just in case a HAI-system has not this ability, then there is an easy solution: just another relay for the AC/power which gives the information to any input (zone) of the controlling system. That's all on hardware. The rest is programming.

 

[heffneil]

Hmm ... an ELK-system knows if there is AC power or not and this information can used in programming this problem. Just in case a HAI-system has not this ability, then there is an easy solution: just another relay for the AC/power which gives the information to any input (zone) of the controlling system. That's all on hardware. The rest is programming.

I thought about this as well. I don't know if HAI has a power off flag but it would be nice. I have a whole home surge protector that whenever the power goes off it trips and says it has been hit. That being the case I need to ignore their status while power is off. I will find out about the flag otherwise I guess the relay is the way to monitor power...

Thanks,

Neil

 

[signal15]

Just put a water sensor in right below the level that the float switch trips. You'll get notified slightly in advance before the unit shuts down so you can rectify the problem with no interruption to your cooling.

 

[heffneil]

Just put a water sensor in right below the level that the float switch trips. You'll get notified slightly in advance before the unit shuts down so you can rectify the problem with no interruption to your cooling.

It isn't a typical float switch. It is a switch that is within a pvc sleeve and is somewhat sealed.

Neil

 

[signal15]

Just put a water sensor in right below the level that the float switch trips. You'll get notified slightly in advance before the unit shuts down so you can rectify the problem with no interruption to your cooling.

It isn't a typical float switch. It is a switch that is within a pvc sleeve and is somewhat sealed.

Neil

If it's not completely sealed, you can attach 2 thin stiff wires to the water sensor, and slide them down opposite sides of the tube to the level you want it to alert at.

 

[cornutt]

I thought about this as well. I don't know if HAI has a power off flag but it would be nice.

It does, and you can trigger on it.

 

[heffneil]

I thought about this as well. I don't know if HAI has a power off flag but it would be nice.

It does, and you can trigger on it.

It has

WHEN AC POWER OFF

and

WHEN AC POWER RESTORED

Which isn't a real flag.

Thanks,

Neil

 

[gatchel]

The float switch would wire into relay 1 as such that the relay 1 is constantly powered unless the float switch is in an alarm state to shut down the AHU.

You would use the C and NC terminals from relay 1 to send a signal to relay2 using a power supply of some sort to supply the proper voltage to relay 2. The PS could be anything that loses power when the there is a power failure. Relay 2's C and NO will wire back to the alarm panel with the supervision across the C and NC terminals.

If the float is activated, you get an alarm.

If the float switch is faulty and opens, you'll get an alarm.

If the power fails the power supply for relay 2 loses power and no alarm is transmitted.

You could also do this other ways which have been mentioned above.

The question is, how is your float switch wired and does it have enough current, if any at all, to drive the first relay. It it goes to a logic board of some sort you may be better off using a water sensor or something similar.

 

[HAI_fjh]

Actually the Omni has both.

You can use the Events/Triggers WHEN AC POWER OFF/RESTORED to do something when the power fails or is restored.

You also have corresponding conditions AND IF AC POWER OFF/ON to test the current power state when some other event occurs.

WHEN A/C Float NOT READY
AND IF AC POWER ON
THEN ...