digital timer thc15a wiring

Thread Starter

Robert Sanders

Joined Apr 1, 2024
8
Hello.

I am having trouble with a THC15A digital timer. It seems so simple and I have reviewed all of the articles I can find on line. It seems there are several ways to hook up the timer or maybe just several versions and manufacturers. Mine is a Baomain.

The THC15A has 5 numbered terminals. If I look at the diagram supplied, Positive or Load goes to number one, Negative to number two. The diagram that came with it has Positive routed to number five, and the load to device going out on number four.

So I have a red wired running from one to five, Positive or Load. and I have a negative wire from number to to the device.

If the positive wire is in five, with the timer on, I get nothing if I plug a positive wire into three or four. Nothing

If I route the positive wire from one to four, then route the positive wire to the device in three, it is constantly on, no matter if the timer is on or not. If I route the positive wire to five, nothing.

Same thing if I route the positive wire from one to three. If the positive wire to the device is in four, constantly on. If that wire is in five, nothing.

I have conducted all of the above with Positive and Negative switched. Negative in One and Positive in two.

I am going to order another switch as I think I have run through all possible iterations. Attached are pictures that show what I have as instructions.
 

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Tonyr1084

Joined Sep 24, 2015
7,943
Welcome to AAC.

L & N are your main power in. The timer is just that. It switches the contacts between 3 & 4 and 4 & 5. Pin 3 is a normally closed contact and pin 5 is a normally open contact. Pin 4 is the common between those two. When the timer is at rest there is continuity between pins 3 & 4. When the timer is active there is continuity between pins 4 & 5. This is a simple single pole double throw switch. It's not a power supply. It doesn't provide power. It is rated for controlling voltages up to 240 VAC (Volts Alternating Current) at an amperage of at least 8 amps. I'm not sure what the 16(8)A,240VAC is saying. Perhaps it can control loads drawing up to 16 amps but I'm not going to be the one to say it can. You'll have to read the description further. But all this does is switch between 4&3 and 4&5. It's just a switch.
 

Tonyr1084

Joined Sep 24, 2015
7,943
This diagram:
Screenshot 2024-04-02 at 8.26.31 AM.png
Shows power from a breaker being routed to pin 5 which is the normal open (NO) pin. When the breaker is on the timer can turn something (assuming 240VAC) on at a programmed time. 240V is present at pin 5. which means the timer can only turn something on at a programmed time. You're not limited to using pin 5 as a power input. You could put it on pin 3 or 4. If you use pin 4 then pin 3 will keep something turned on until a programmed time shuts it off. When that programmed time expires whatever is connected to pin 3 will come back on.

You can switch between 3 & 5 with power being applied to pin 4. When active power will be present at pin 5. When inactive power will be present at pin 3. And you don't necessarily have to use it for 240VAC. You can use lower voltages depending on the ratings for lower powers. AC and DC switching is not the same. You can't switch 240VDC because you'll burn up the switch when it shuts off. That's another subject. Just mentioning that you can switch AC values up to 240 volts. In the document you posted I don't see anything about switching DC.
 

Thread Starter

Robert Sanders

Joined Apr 1, 2024
8
I understand it is not a power supply. I am running 12 Volts. I have attached the cables the way you are stating, but you don't mention the positive runner between terminal one and five. You seem to be saying that it should run into terminal 4. I am unable to get the continuity between 4 and 5 when the timer is active. I do get the continuous activity between 3 and 4. It is by design. Thanks for clearing that up.
 

Tonyr1084

Joined Sep 24, 2015
7,943
Again, pins 3, 4 & 5 constitute a switch. IF you are switching 240VAC then you need a jumper from pin 1 to 5 OR as the diagram shows, power coming from a breaker, which is a better option. The breaker protects the wiring down stream. If there's an electrical problem the breaker will shut off.

OK, you're switching 12 volts. Is that AC or DC? Again, that can become an issue. The reason why they show 240 going to pin 5 is so that when the timer is off no other line is active. You CAN wire that to pin 4. But then regardless of the state of the timer pin 3 or 5 will always be hot. Which can become a danger for electrical shock. But since you're switching 12 volts you definitely don't want to be running a jumper from pin 1 to ANY of the switch points. Not if you're controlling 12 volts.
 

Thread Starter

Robert Sanders

Joined Apr 1, 2024
8
T12 volts DC. I am running a couple of 12 volts pumps off of a small solar grid.
I have the waterfall plugged into 3 and the irrigation plugged into 5. 3 runs all the time. but when the timer goes active (little red light) the waterfall stays on. Irrigation that is routed to 5 never comes on. Should I try a new switch? Could be that my voltage is too low?
 

Tonyr1084

Joined Sep 24, 2015
7,943
Ok, Does it matter if positive is in 1 or 2? I have seen videos with Negative in 1 and positive in 2
Pins 1 & 2 are for 240 VAC ONLY! The timer won't operate on anything outside the rated voltages. (See Voltage Limit)
Screenshot 2024-04-02 at 8.52.14 AM.png
Apparently the timer is available in multiple voltages ranging from 12 volts (assuming AC only since they don't say DC) up to 240VAC. If you're switching 12 volts then you can order a 12V timer.

As I look at the data sheet I see it's rated to switch up to 16 amps at 250VAC. I don't understand "Lagging load: 10A/250VAC.
The lamp load is described as 2000 watts. With 12VAC that's 167 amps. DEFINITELY not for DC currents.
 

Tonyr1084

Joined Sep 24, 2015
7,943
T12 volts DC. I am running a couple of 12 volts pumps off of a small solar grid.
I have the waterfall plugged into 3 and the irrigation plugged into 5. 3 runs all the time. but when the timer goes active (little red light) the waterfall stays on. Irrigation that is routed to 5 never comes on. Should I try a new switch? Could be that my voltage is too low?
At this point it may be well worth it to post a schematic of how you have things wired. Pin 3 running all the time, if I understand correctly, the red light stays on when you expect it to shut off. I haven't an explanation for that. Not without a diagram.

I'd GUESS that pin 4 should be your power source. Pin 5 runs one pump and pin 3 runs the other. At no time should both be on. OR if my suspicions are correct, switching DC you might be switching more power than the switch can handle. How much current do your pumps draw? YouTube videos on switching high current DC. You'll see some shocking things (no pun intended). Even switching high current DC off - the current may continue to flow. The arcing can and will burn your switch box to ashes. Can burn the house down too. That's why fuses or breakers are highly advised.

Show us a diagram please.
 

Thread Starter

Robert Sanders

Joined Apr 1, 2024
8
I did order a 12 volt switch. it comes in tomorrow. but I still don't like how confused I am. This is all not in my house, I will add the fuses when I get it figured out.
 

Tonyr1084

Joined Sep 24, 2015
7,943
The unit you showed us is for 240VAC. If you take ANY power from that and try to control 12VDC you're going to blow something out. When you get the 12VDC unit (assuming it's DC) then yes, you can run the positive lead to pin 4. You'll find 12V between pin 3 and negative (or ground). When the relay program is active you'll find 12V between pin 5 and negative (or ground). You don't need to ground a 12 volt system, not unless you're running something that is highly sensitive to noise. But let's not get lost on the noise issue - it's a non-starter for this conversation. You don't need to ground the negative lead of the 12V.
 

Tonyr1084

Joined Sep 24, 2015
7,943
Here's what I got from your drawing:
Screenshot 2024-04-02 at 3.05.50 PM.pngYou said "Four 12V panels. Yeah, they can be around 15V in full direct sunlight. So the buck converter is definitely warranted. It will also keep voltages under control as the sun angle changes.

+12VDC goes to pin 1. Jumper from pin 1 to pin 4 brings power to the switching relay. Pin 3 powers the waterfall and pin 5 powers the pump. If this is purely a relay type switch then the jumper from 1 to 4 is right. if it's a solid state relay then there can be issues I'm not familiar with. Remember, you don't need to switch the positive side, you can switch the negative side. So power your pumps and ground them through the timer with the jumper moved from pin 1 to pin 2. Connect that jumper to pin 4 to provide the final pathway back to the pumps.
 
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