Hello

I have 1 or 2 220v 15amp ventilation vans in each of my barns. Currently they are just on a on/off switch. I would like to be able to put them on a timed relay system where I could have them run for say 5min every hour from 7am to 7pm. I have have been able to figure out how to do this using 2 programmable relays, 1 for 12hr on/off and another for 5min every 60min, but is there a single relay I could program instead of requiring 2? Preferably one that actually keeps track of the current time so that I wouldn't have to reset the first relay at exactly 7am if there is a power failure?

Thanks
-Marc

 

INTERMATIC
I have a box of these. 2hp motor, 21A (sorry I see mine are 120V only) There is a button for every 15 minutes of the day. That does not solve the 5 minutes you want. Not right but an idea. I was going to put these on ebay.com soon to reduce my inventory.
The clock is 120V but the relay is 220 so if you found 120V for the clock it might work.
If money was no item. (lol) use two of these. Set one to the correct time and the other to 10 minutes early (or late) Run the power through so both have to be on for power to get to the fan motor. (series wired) The two timers will overlap by 5 minutes causing the power to be on 5 minutes not 15 minutes.

 

I have a point of caution which is that some of those small plug in timers, such as one that I have just recycled, are built so poorly with such a poor grade of plastic that they fail at the most inconvenient time, and then never function again.There are timers, sometimes used for vent controlling, that are capable of being set for multiple cycle times during the day, by adding trippers. one of those, switching on a simple triggered "Delayed OFF" timer, set to switch on for the set interval and then switch off, could be triggered each hour to deliver it's five minutes "ON" time each time it is triggered. Those can be much smaller timers. Still two timers, but not similar times.
There are also some interesting concept mechanical timer schemes that could be a fun project if you had lots of time to spend on it.

 

A programmable timer rather than a programmable relay can be programmed to start 'at 7am each day for 12 hours' rather than 'every 12 hours' and most incorporate a battery backup to maintain time across power interruption.

 

COST and availability would probably be issues with programmable timers having the capability of switching those motors at that power rating: 15 amps@220 volts. They are not the common "window fan" sized motors.

 

I've found 7 day timers but I haven't found one that lets you have multiple on/off cycles within each day

 

I've found 7 day timers but I haven't found one that lets you have multiple on/off cycles within each day

I have seen them, I believe the brand was "intermatic", which is an OK company, been around many years. The problem will be that the number of operations in a day is limited by the trigger pieces.
The device you could utilize is a small PLC (Programmable Logic Controller)
Actually, contact "Automation Direct" because they have some unusual products.
AND some good customer assistance engineers.

 

I am thinking that the barns are a big investment and so any control system for those fairly powerful fans needs to be well protected and shielded so as to avoid any fire hazards. Of course the TS may already have provided all of that protection.
The scheme that will provide both reliable timing and adequate protection can use a small 24 volt powered PLC with batteries backup and an internal clock to provide the fan operation per that schedule quite well, and also it can switch on lighting as needed. An actual motor control contactor can be included in the enclosure to assure that the motor is protected, as well as being controlled.