Help with temperature control relay

Thread Starter

Phil Hunnictt

Joined Jul 2, 2019
7
I am looking for a way to put freeze protection on my new variable speed control pool pump. The pump has a connection, where it provides 5 vdc, and looks for a completed circuit any of the input wires. So basically, I just need a switch that is triggered at a temperature near freezing.

I am looking at this temperature controller from Amazon.

https://www.amazon.com/Inkbird-All-Purpose-Temperature-Controller-ITC-1000/dp/B00OXPE8U6?pf_rd_p=0fc3f2c4-3ed5-4d11-9995-8d7c82394713&pd_rd_wg=R906C&pf_rd_r=6MPEBQSNRGK5ZN4RCC1D&ref_=pd_gw_cr_simh&pd_rd_w=wLSas&pd_rd_r=b57e0bfc-d340-4727-9e27-f8e487c61648

My question is, if the controller uses a 120 VAC supply, do the relays need 120 VAC to operate?

If I wire 120 VAC to the power input only, and wire the 5vdc circuit from the pump to the relay, will the relay close when triggered by the temperature?

I guess the simplified question is, if I wire 120 VAC to the input only, will the relays open and close with nothing attached to the pins.
 

AnalogKid

Joined Aug 1, 2013
8,305
Consider figure 3.3 on page 5. The relay action is completely independent of the power source. The relays will change state when the controller setpoints are reached. The relays are rated *up to* the values in the datasheet. They will handle anything less, such as 120 Vac to the controller and 5 Vdc on the relay contacts.

Note: Someone will point out that relay contacts intended for medium current AC sometimes do not perform well with low current DC loads. AC relay contacts assume some arcing when the contacts open, burning off an oxidation layer (the contacts often have some silver in them). "Proper" relay contacts for low voltage / low current DC are gold plated because there is not enough energy to make an arc. My opinion is that since the critical state for you is going from closed to open, the contacts should be fine in your application.

ak
 

Thread Starter

Phil Hunnictt

Joined Jul 2, 2019
7
Consider figure 3.3 on page 5. The relay action is completely independent of the power source. The relays will change state when the controller setpoints are reached. The relays are rated *up to* the values in the datasheet. They will handle anything less, such as 120 Vac to the controller and 5 Vdc on the relay contacts.

Note: Someone will point out that relay contacts intended for medium current AC sometimes do not perform well with low current DC loads. AC relay contacts assume some arcing when the contacts open, burning off an oxidation layer (the contacts often have some silver in them). "Proper" relay contacts for low voltage / low current DC are gold plated because there is not enough energy to make an arc. My opinion is that since the critical state for you is going from closed to open, the contacts should be fine in your application.

ak
Thank you so much, in your opinion, would this be the best solution for my application?
 

Thread Starter

Phil Hunnictt

Joined Jul 2, 2019
7
Thanks, but I would really like to circulate the water, to ensure there is still not a cold spot somewhere in the reservoir.
 

Thread Starter

Phil Hunnictt

Joined Jul 2, 2019
7
Consider figure 3.3 on page 5. The relay action is completely independent of the power source. The relays will change state when the controller setpoints are reached. The relays are rated *up to* the values in the datasheet. They will handle anything less, such as 120 Vac to the controller and 5 Vdc on the relay contacts.

Note: Someone will point out that relay contacts intended for medium current AC sometimes do not perform well with low current DC loads. AC relay contacts assume some arcing when the contacts open, burning off an oxidation layer (the contacts often have some silver in them). "Proper" relay contacts for low voltage / low current DC are gold plated because there is not enough energy to make an arc. My opinion is that since the critical state for you is going from closed to open, the contacts should be fine in your application.

ak
What document are you referring to that contains figure 3.3 on page 5?
 

Thread Starter

Phil Hunnictt

Joined Jul 2, 2019
7
If the water is circulating why do you need freeze protection? Where do you live?
The circulation of the water is the freeze protection. The temperature controller will trip the relay when the temperature dips below the set temperature. The pool pump controller will then start the pump when it sees the 5vdc from the relay.
 

SamR

Joined Mar 19, 2019
1,806
It's a panel mount device. Requires 120VAC operating power. Not weatherproof so needs a protective enclosure. No external sensor so for outside temp control must be mounted outside. Has 2 10A/250VAC rated contact outputs. 1 for cool, 1 for heat. So will need external wiring to another device. Lots of layers to this onion. The heat tape has 1 plug. Internal thermostat to energize heating wrap with no external connection needed Weather resistant.
 

SamR

Joined Mar 19, 2019
1,806
Or just use the AC output contacts to drive another AC relay w/ DC rated contacts for 5VDC if that is what your pump needs to turn it on. Try and remember KISS.
 

Reloadron

Joined Jan 15, 2015
5,120
I would first try it with the contacts it has. Then if you have problems just do as SamR suggest in post #14,

Something I am not seeing and may have missed in the data sheet is what value of NTC Thermistor to use as a sensor? NTC just means Negative Temperature Coefficient which is well and fine but they normally have a resistance called out at 25 degrees C for example 1K or 10K or 100K Ohms. You also want a sheath material since you will want submersible. So there are some things to work with depending on the environment you will use it in. Maybe I just overlooked that in the manual?

Ron
 

Reloadron

Joined Jan 15, 2015
5,120
Well, the odds are you can make it work or if needed fabricate something from it. :) As long as it shows up with something.

Ron
 
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