HA20C Installation Help Needed

I really hit a series of road blocks today while TRYING to install an HA20C light switch, mostly caused by my brain’s inability to properly translate the rewiring diagrams that accompany this Intermatic dimmer. This should have been SO EASY, considering it’s just a typical 3-way light setup – two switches (with the HA20C in the ‘hot’ box), and a single light. Nothing unusual!

I won’t rehash my many tribulations/bumblings here, but here’s the final problem…

The HA20C works perfectly, but when I flip the remote switch (a standard 3-way, wired according to the diagram!), nothing happens. Light stays ON or light stays OFF, governed solely by the HA20C.

What gives? Might I have a faulty unit?

I’ve tried to include my wiring setup below…
(ppppbbbt…nope, inserting a Picasa “table link” didn’t work)

…but just in case, here’s a hard link:

MANY THANKS for guidance or troubleshooting tips here, and apologies to poor Anthony240 whom I bombarded with questions of this nature all day!!

  • LS

It looks like your travelers are not hooked up correctly on the second switch. You should have a hot into the HA2OC and two travelers out which go to the traveler connections on the second switch. Then the hot goes out of the second switch to the hot side of the light.

Remember, my second switch is not a HA20C, but just a standard 3-way – Intermatic’s wiring diagram says you can use either a plain single-pole light switch or 3-way switch as the remote for the HA20C.


According to their instructions, I wired the RED traveler to the 3-way’s COMMON (dark) terminal, and the BLACK traveler (from the HA’s BLUE lead) to one of the 3-way’s other terminals.

Honestly, I’m beginning to think I somehow fried my HA20C in the process of installing it.

UPDATE: Okay, this is weird. After two days of not fiddling with the setup at all, the remote (standard 3-way) switch suddenly started working! A member of the household flipped it this morning, and lo and behold, the dining room lights came on. I was stunned!

Granted, it may STOP working any minute now, but for now, at least the situation has improved. Although I must add that the light came on by itself last night, to my chagrin. (I’ll therefore probably move this HA20C to duty on our porch light, which is a single-switch setup.) FYI, Vera has nothing to do with all this, since I never paired the HA20C with her.

I doubt enough fellow MCV members use HA20C dimmers in their setups to care about this topic, so this will be my final post on the subject. Had to share my amazement that – left alone – a digital device can sometimes decide to behave differently!

I have several of the HA14’s which are the lower wattage version. My first attempt to intstall them didn’t go so well until I figured out that what I thought my wiring was doing was not really what it was doing.

In the HA14 three way setup, it is correct that the second switch only needs to be a two way as I have one set up exactly that way. Your diagram is correct if your red (traveller) is connected to the common on the three way. You need to be certain that the blue lead connects all the way to the load and not through the second switch. This is different than for a normal 3-way mechanical set-up. I have never had an issue with one of these turning on by themself.

For anyone tuning in, and for the benefit of future HA20C users, I spoke with Intermatic customer support (815-675-7000) at length about this problem, and “Dan” there knew of this issue.

He said I should trade out the 3-way switch with another (brand new!) 3-way or 2-way switch which may have a better chance at transmitting the low-voltage signal which the HA20C uses to “sense” the remote switch’s position. I will try that and report my results below soon.

NOTE: The couple of 3-way switches I already tried in this application are less than 3 years old, but “Dan” insisted that some switches – and sometimes poor electrical connections – cause this issue, which is one of the hardest to troubleshoot. His recommendation of trying out another inexpensive switch, and also checking all my wire nut connections, makes practical sense.

Final verdict: SUCCESS! Swapping out the 3-way switch for a brand new 69-cent 2-way switch solved the problem, exactly as the Intermatic tech suggested it might. His theory of the HA20C’s “sensing signal” being unable to pass through the bulkier 3-way switch made sense, although neither of us really could say what type of signal it IS (RF? low-voltage?).

Looking at the diagram above, you will note that as long as the controlled light is ON, the blue traveler leg of the 2-way switch is HOT (110V). Flipping the 2-way switch must therefore energize the red traveler wire, however momentarily, while the HA20C proceeds to dim the light down to an OFF state. So, the HA20C must also use a signal or “continuity” to sense when the switch is flipped again, to know it’s time to turn the light back ON. It’s an ingenious design in my opinion.

I hope my experiences here help out future installers of this (now discontinued) dimmer switch!!

Gotta love those $0.69 switches! That’s how I got mine to work too. Mine also worked with my conventional 3-way, but it wasn’t doing anything so I swapped it out.

Wow, wish I would have seen this thread when you posted it. I had the same issue and tech support was great in helping me figure it all out. They basically said it’s wired up like their timers.

WOW! Yesterday I spent hours trying to figure out why my HA20 wouldn’t work. I have multiple HA20s so I was even able to swap them out to make sure it wasn’t the switch. For the first two hours I cursed the electricians who wired my house because they didn’t use the properly colored wires and clearly they must have wired something wrong. Then I grabbed the multimeter and was able to identify the hot wire in the hot box and the common wire in the other box. Alas, after another 3+ hours I couldn’t get these damn things to work and I “knew” that I was wiring it “correctly.” I even had the instructions right in front of me, but since I knew how 3-way switches worked, my mind couldn’t see the clearly labeled “Not used” traveler on the 3-way switch. The part that really gets me upset is that I have had one of these installed in a 3-way scenario for six months which I thought was working properly so I used it’s wiring as confirmation that I’m doing everything the same way. It wasn’t until this morning that my wife told me that the remote 3-way switch never worked.

All I had to do was forget what I knew about 3-way switches and take the time to really read the diagram.

If I am understanding things correctly then these switches need to be installed in the hot box. (Which was also part of my problem) That’s kind of a bummer since I prefer to have dimmer controls in the box that is not the hot box.

what is sounds like is that carbon which forms on the switch contacts is interfering with the signal from the Ha-20. In a new switch this will not be an issue. With a normal 120v incandescent load this would not be an issue also. You cannot get away from the carbon.

@Markbean, just to ultra-clarify … YES, the HA20C must be installed in the ‘hot’ box, since it (literally) “carries the load” for the lighting circuit. Every other switch (if any) in a 3-way or n-way setup simply reports back to the HA.

Finding which box has the ‘hot’ lead may not be a trivial matter – even for a seasoned electrician, I suppose – but at least it’s an unambiguous process. In my case, I got lucky!

@Zmistro, thanks for the clarification about carbon build-up on switches … something I hadn’t anticipated in such a ‘young’ switch (about 3 years old).

Well I would never had thought that the carbon would be a problem either. However if a new switch cured the problem and no wires were changed then that is the only cause I could think of.