automatic dpdt switch for 2 regenerative blowers

Thread Starter

frichard21

Joined Apr 22, 2022
4
Hi there!!!. I am trying to find a way to enable a relay posing as a dpdt switch in order to do an automatic trasnfer from one blower to another (both 220 v 440 watts single phase) for an aquaponic system, in case of blower malfunction due to open or short circuit. This is to prevent massive fish mortality due to low oxygen levels.
 

Reloadron

Joined Jan 15, 2015
6,712
So you have two blowers 220 VAC 440 Watts so normal load current is 440 / 220 = 2.0 Amps. Using a switch you want a switch rated at the required voltage and current. This allows you to switch Blower A or Blower B. A Single pole double pole switch with a center Off would allow Blower A or Blower B with center Off (no blower). Neutrals would all be common and no need to switch them, The same can be done with a SPDT relay or you can use two SPST relays
Under what conditions would you want to switch from A to B blower? They make airflow paddle switches to detect if airflow is or is not present. Outline exactly what you want to happen and in sequence. Airflow paddle switch sensors are pretty common.

Ron
 

Thread Starter

frichard21

Joined Apr 22, 2022
4
So you have two blowers 220 VAC 440 Watts so normal load current is 440 / 220 = 2.0 Amps. Using a switch you want a switch rated at the required voltage and current. This allows you to switch Blower A or Blower B. A Single pole double pole switch with a center Off would allow Blower A or Blower B with center Off (no blower). Neutrals would all be common and no need to switch them, The same can be done with a SPDT relay or you can use two SPST relays
Under what conditions would you want to switch from A to B blower? They make airflow paddle switches to detect if airflow is or is not present. Outline exactly what you want to happen and in sequence. Airflow paddle switch sensors are pretty common.

Ron
Malfunction due to open circuit (blown coil) or short circuit. In any case the system should detect the anomaly and should switch to the other blower in order to prevent fishes from dying
 

Reloadron

Joined Jan 15, 2015
6,712
Then a simple approach would be a paddle type air flow sensor on each blower. You don't need fancy as all you care about is that there is airflow, yes or no. You choose a sensor based on normal air flow. You designate one pump as your primary pump. When the primary pump fails you transfer to the second pump. Less dimensions of how these pumps move air, things like air out design it's difficult to link to sensors. The air flow sensor outputs drive a few DPST relays which control your pumps and handle transfer. The sensors also can drive an alarm so you know when a pump fails. Fuse the pumps so if a pump develops for example a locked rotor you just have a fuse blow. With the numbers you provided the pumps draw about 2.0 Amps so fuse at about 3.0 amps with a slow blow fuse.

A circuit? There are several design schemes which will work. Simple using a relay and a few discrete components or take the sensor outputs and use a small uC (micro-controller). The latter will requite some minor programming skills. Either way it starts with sensing the airflow which is there or not there. The sensors drive a few relays with 220 VAC coils and contacts capable of handling about 5.0 Amps (leaving headroom for current) 220 VAC. You need to choose airflow switches suitable for your systems, things like rate of airflow. With a bit more information I am pretty sure anyone here can give you a rough circuit.

Ron
 

ThePanMan

Joined Mar 13, 2020
436
You say "Blower". I'm familiar with blowers that blow air. I've not seen or heard of using a blower to blow air into a tank or pond. Are you talking about an air pump? If so - that's a different kind of switch than a paddle switch. I agree with @Reloadron using simple paddle switches but wonder how you start up the system. When you apply power - which blower will be on? Or are you thinking of a single paddle switch mounted in the airstream of blower #1 to cancel blower #2? That would insure that when you turn power on (or after a power failure) blower #1 will always be the primary source.

If you're talking about an aquarium type air pump, a rather large one, then in the air hose you would need a one way air valve so that air pressure could be measured in that tube. Should that pump fail, pump #2 comes on. But the one way air valve insures air from pump #2 doesn't read the pressure on line #1. So instead of a paddle switch you need a simple air pressure switch and a one way valve.
 

Thread Starter

frichard21

Joined Apr 22, 2022
4
You say "Blower". I'm familiar with blowers that blow air. I've not seen or heard of using a blower to blow air into a tank or pond. Are you talking about an air pump? If so - that's a different kind of switch than a paddle switch. I agree with @Reloadron using simple paddle switches but wonder how you start up the system. When you apply power - which blower will be on? Or are you thinking of a single paddle switch mounted in the airstream of blower #1 to cancel blower #2? That would insure that when you turn power on (or after a power failure) blower #1 will always be the primary source.

If you're talking about an aquarium type air pump, a rather large one, then in the air hose you would need a one way air valve so that air pressure could be measured in that tube. Should that pump fail, pump #2 comes on. But the one way air valve insures air from pump #2 doesn't read the pressure on line #1. So instead of a paddle switch you need a simple air pressure switch and a one way valve.
That is the kind of blower I am referring to:
https://www.amazon.com/dp/B00OJF8ONW?psc=1&ref=ppx_yo2ov_dt_b_product_details
Regenerative Blower 0.37Hp, 220V/1Phase, 50CFM, 56"H2O Max Press, Goorui GHBH 0D3 12 1R1
Those are the kind of devices which are used for aquaculture: a lot of air but not much pressure (not required)
Those are the ones I have
 
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ThePanMan

Joined Mar 13, 2020
436
Thanks for the info. I've never seen such a blower used in aquatics before. So I'm assuming you must have a huge tank. Since that pump develops such high pressure and a paddle (or vane) switch would be impractical, the next best approach I can think of would be to use a pressure transducer. Again, with a back-flow preventer. When (if) pump #1 fails the pressure will drop. When the pressure drops it can activate a relay that switches pump #2 on. You could build an electronics package, but why?! More expense and greater chance for failure.
 

Thread Starter

frichard21

Joined Apr 22, 2022
4
Now after reading your answers I feel kind of ashamed because I was thinking on a fancy Arduino type system. These simplistic approaches are good enough for my purposes. Thanks!!!
 

Reloadron

Joined Jan 15, 2015
6,712
Now after reading your answers I feel kind of ashamed because I was thinking on a fancy Arduino type system. These simplistic approaches are good enough for my purposes. Thanks!!!
Well most definitely a blower. :) Oh, hey if you want to incorporate and Arduino or other uC that is easily done as the Arduino looks at data from your air flow sensors and does the decision making. The link gives the inlet and outlet diameters along with expected air flow. Really all just Digital In Out logic. Include and alarms you may want. I would control your blowers using relays or solid state relays having 3 to 32 volt control so they interface easily with your uC (Arduino).

Ron
 
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