Controller needed: Exhaust fans on, dehuey off?

[Lazyman]

Hey guys, so I've learned that running a dehuey while the exhaust fan is on is really dumb in a couple ways.

First, you're sucking out treated air, while fresh air is being introduced. The air exchange should be much faster than a dehuey can treat it.

Second, the power used by a couple large dehueys hits a couple thousand watts fast. If the fans are exhausting, why run the (now immaterial) dehuey at the same time?

My fans usually do a pretty good job of dropping temps, and they don't short-cycle. They usually do a fair job of dropping the RH too.

Who makes a controller that will deactivate the dehumidify circuit when the exhaust cooling circuit is engaged?

I can control the power load via Sentinel 120v relays, but I need a controller that has this option. So far the closest I've seen is the ability to connect or divorce the cooling and dehumidify circuits, which doesn't accomplish my goal here.

Thanks!

 

[queequeg152]

you dont need or want a controller at all. not a shitty plastic box from a hydro company at least...

you need a hawkeye type split current sensor and relay and thats it.

its super simple. you install the current sensor onto the HOT leg that is running your fans. NOT both the hot and neutral, but ONLY the hot leg.

if you put the coil around both, it will have a much harder time detecting the current as you will have current flowing both directions. most current sensors will not work at all when put around both the hot and neutral.

if your fans are running off of an appliance cord and you do not want to cut into the cord to expose the hot... then you need a current splitter installed at the plug where your fans plug in. then you will put the coil around the 1x or 10x coil.... 10x is really only needed for very small loads like a thermostat wire or something stupid tiny.

then you run power to a normally closed relay, with the current sensor acting as the interrupt switch... so what will happen is, fans turn on, then power runs through the coil, your current sensor reads this current, then closes the contacts within the switch completing the circuit to your relay coil... when then opens up your dehumidifier circuit shutting them down.

you might want to also add a delay on make/break relay in series with your relay to prevent short cycling to your dehumidifier... but then again most dehumidifiers will have this built in already, so its probably not needed.

 

[queequeg152]

fyi: this is a current splitter... its literally just a plug that takes your hot leg and seperates it from the neutral conductor, then routs it once around the 1x opening, and then routs it 10x around the 10x opening.

https://www.amazon.com/Extech-Instr...1490050129&sr=1-1&keywords=plug+line+splitter

a reading at 1x will yield a reasonably accurate current. around the 10x opening will be approximatly 10x the real current.

ok... and this is a current sensor.

http://www.veris.com/Item/H940.aspx

100 bucks is insane btw... i buy them on ebay for like 30 bucks? i had no idea they were that much new or retail... maby go on amazon and find a comparable product... but veris makes good sensors. they are inside all the pump houses we design... they monitor one of the phases to the pumps and run the hour counters and indicator lights on the control panels.

the switches in these things are not designed for huge amp loads btw. this is why i reccomend you use another larger relay... i think the hawkeye i have is only like 5a... they are just not really meant to switch heavy compressor motors.

 

[Ignor_Amus]

Queequeg152, that's an elegant solution - thank you! Definitely could come in handy in some applications.

Do you feel this particular situation could be handled more easily by a simple DPDT relay? It could be wired so it provides juice to either the dehumidifier OR the exhaust fans.

The NC contacts can route power to the dehumidifier (as the default mode), and the coil can be triggered to switch power to the exhaust fans via the NO contacts. Sounds pretty easy-peasy to me, unless I'm not fully understanding the problem.

 

[Ignor_Amus]

Lazyman, here is an explanation:

NO = Normally Open contacts
NC = Normally Closed contacts.

The coil can be triggered by a manual switch, or by whatever controller you want.

Just make sure that whatever relay you use is properly rated for the voltage and amperage that you're going to run through it. (Overkill is good when selecting!)

This page will give you a good idea of what I'm talking about: http://www.electroschematics.com/9601/dpdt-switch-relay/ Theoe schematics are using 12V DC current as examples, but the theory is the same. Just look at the section labeled "Switch between 2 different Loads with DPDT switch".

 

[Ignor_Amus]

Yikes! I guess as a newbie, I can't go back and edit out my typo's? Bummer.

Plus I should have spent more time to find a better diagram for you, because the 12V DC stuff isn't relevant. (You're not going to be doing any polarity reversals or monitoring lights, etc.)

Hopefully you'll get the idea, and you should be able to wire up something yourself.

 

[queequeg152]

Queequeg152, that's an elegant solution - thank you! Definitely could come in handy in some applications.

Do you feel this particular situation could be handled more easily by a simple DPDT relay? It could be wired so it provides juice to either the dehumidifier OR the exhaust fans.

The NC contacts can route power to the dehumidifier (as the default mode), and the coil can be triggered to switch power to the exhaust fans via the NO contacts. Sounds pretty easy-peasy to me, unless I'm not fully understanding the problem.

actually yea lol... its sort of embarassing i didnt think of that.

yea i think thats actually a better/simpler solution, especially if you are using a thermostat to control either the dehumidifier or the exhaust fans.

you still might want to look into your dehumidifiers to make sure they have a built in short cycling prevention, if they do not, definatly get a delay on make/break relay and wire that in serial with the circuit that controls the dehuys.

 

[queequeg152]

and actually a relay would probably be a bit safer... relays 99.9% of the times either fail on or fail off... cheap contactors might fail ON more often than a sealed relay, but thats because they are generally open frame and get shit and scorching inside the contacts... even then though its not that common. most of the time they just fucking fall apart mechanically or the coil gets wrecked and shorts.

you dont need a double pole relay btw... a SPDT relay would work fine, you are just switching the hot legs, so unless your equipment is 240v, an SPDT will work fine.

 

[Lazyman]

Yeah I could probably build something, a SPDT relay sounded about right, just didn't know if they come in 120v 20A ratings or what. Was hoping there was something off the shelf, as an integrated 120VAC thermostat and 120v humidistat would be nice, but it seems such an animal doesn't exist. I have an old AIR 4 controller I can rewire with a SPDT relay, that might work.