Reddit mentions: The best furnace replacement relays

Hvac guy came out today for $75 to check out the unit, and said that the fan motor bearings were bad and the motor was heating up and needs to be replaced, and that it has caused the contactor to go bad which he said was a potential fire hazard. Said it would be 500 for him to replace so I'm going to replace them myself.

I found the parts on amazon for about $130 total on amazon motor and contactor, but I will call the part stores locally tommorow which I imagine will be higher priced. Fan removed from the motor very easily which I was glad because the videos I watched showed that some can be very hard to take off.

Thankfully I have a spare window unit to use until it the AC is working again.

> Would a 220v controller still be under the router speed controller category?

I don't think they make commonly available 220v router speed controllers. I think they were referring to purpose built controllers. The SSR style voltage regulators aren't that expensive. Something like this with this pot and some kind of box, and some 10ga wires, and you have a controller. You can add a volt/ammeter, and switches, etc. Shouldn't cost more than $30. I posted a link to a kit above as well.

You can also use the Chinese SCR voltage regulators, lots of people use them for this purpose. Something like this or this. The second one has a fan, which will help it run cooler.

OK. Head on over to /r/homeautomation and /r/smarthome, and they can help you decide on what setup would work for you.

You will need a relay similar to this for the interface:

https://www.amazon.com/Honeywell-RA89A1074-Switching-Relay-24V/dp/B008HOV67M

Most timers will accumulate error, which will mean that your "6AM" will become 6:05, then 6:10 as the days/weeks/years pass. Would that be a problem?

If so, using the mains as a timing reference is one solution. The alternative is something that gets a time signal which corrects any drift.

The mains timing solution is pretty simple. You buy two plug in mains timer adapters. You may be able to buy those from your local dollar store. eg "DollarTree". They have a mains socket which is switched on and off by the adapter. You set the time and how long (eg by moving pegs).

Plug a 5A 12v output wallwart into one adapter and set it to switch the socket on at 6AM and off at 6:15, then on at 8PM and off at 8:15.

Buy a 120vac two pole change over relay. Wire the coil of that to a mains plug and and plug that into a second timer adapter. Set that timer to switch on once a day at 7:45PM and off again at 8:30.


Now, you run the output wires from the 12v output wallwart to the centre contacts of the relay. You connect the actuator wires to the "normally open" relay contacts. You take two wires from those contacts, swap them over and connect them to the remaining, "normally closed" relay contacts.

Job done. How it works is simple. When 6AM happens, the first timer switches the wallwart on, which supplies 12v to the actuator, via the relay normally closed contacts. At 6:15, the 12v switches off again.

In the evening, the second timer sends power to the relay coil. So the relay joins the centre contacts to the normally open ones. When the first time puts power on, a few minutes later, it goes direct to the actuator and not via the swapped over wires. So the actuator runs in the opposite direction. A few minutes later, the wall wart is switched off. A few minutes later, the relay is switched off.

I'll leave you to find the time switch adapters - relays like this https://www.amazon.com/YC-GP-DPDT-2-Power-Relay-Heavy-Duty-Listed/dp/B00SFYWO02/ref=sr_1_2?ie=UTF8&qid=1499093996&sr=8-2&keywords=120v+two+pole+relay

don't need soldering and have an insulated cover.

So one like this or this work? Whats the difference between the two?

I once had a place replace one of these at a 3x markup from the price on Amazon. They didn't offer extra support, warranty, or anything else. I'm cool with a bit of a markup, but if anything, I would expect they should be able to source these parts cheaper than I can get them for on Amazon. Why isn't that the case?

something like this could work.

https://www.amazon.com/Omron-Electronics-B3SL-1002P-Switch-Tactile/dp/B008BT6JOS

just check measurements.

As long as the relay is optically isolated and rated for that much voltage, sure. And nothing line oriented connects to the pi side.

Here's an example. https://www.amazon.com/Opto-isolated-Optocoupler-Capability-Optimus-Electric/dp/B071JQ95GN

Not a MOSFET, this DC-DC SSR. I have it bolted to the frame for heat dissipation, but no forced cooling on it atm. I do have 2 fans on the RAMPS board