HVAC Question

[Scrambled]

Hi everyone-

I have a question about my HVAC system. Last year or so, I installed a RCS TR 40 and two TR 16 t-stat controllers. I was playing around in the attic and I removed one of the TR-16s and am in the process of installing a RCS 4 zone controller. I am wanting a method where I can monitor whether the compressor is running, the fan is running, and or the emergency heat strips are turned on.

The RCS controllers have relays that turn the compressor on, the fan on, and also controll the heat strips.

I think the voltage is 24 volts AC. I have not confirmed this with my multi-meter, but that is what I think.

Does anyone know of a way to get 24 volts AC into either an Elk or an Ocelot?


Thanks


steve

 

[WayneW]

I love Relay-In-A-Box from Functional Devices. I use a bunch of them for HVAC and pool system interface since both use 24VAC. 24VAC relays are not a common hobbyist item.

RIBU1C Enclosed Relay 10 Amp SPDT with 10-30 Vac/dc/120 Vac Coil
http://www.functionaldevices.com/pdf/RIBU1C.pdf
check eBay ($10 for buy it now) or a distributor.

 

[Timoh]

Just realized that I missed the explanation of my diagram!!!! I guess it didn't copy paste or something...

Here's the explanation...
A capacitor at point "B" and the secu16 input at point "A" looking for ~4.8vdc as "on". What size should the capacitor be? Or would I need to use the circuit to switch a transistor and wire that into the secu16.

24ac
|
|
\/
~
| B
|
\
/
\ 10k
/
\
|
|
| A
|
\
/
\ 2.5k
/
\
|
|
|
Gnd

 

[Timoh]

I was pretty close...
Guy over on the ADI users board filled in the blanks...

I've done a similar circuit to convert the ac voltage output of a homemade current draw sensor to a dc signal. It should work fine, as long as you filter the voltage well enough to produce a steady dc output. something around 10uF should be good. You might also need to divide the voltage a bit more then what your circuit would do as it is. A fully rectified and filtered 24 vac input should produce about 34 vdc. To get about 5 volts, you need to drop the voltage to about 1/7th of the full input voltage. If you replace the 10k resistor by a 15k unit, and the 2.5k with a 2.2k, then you would be close to a 5 volt output or a bit less, on the safe side.

 

[politics123]

How about an easier solution? Just get a CR around the fan motor wiring which detects the fan being on?

 

[Scrambled]

Thanks everyone for the input.

I think I am going to install the relays. I don't really want to add more clutter, but I think by doing this there is a less of a chance of breaking something expensive.

I will add a post and let everyone know how this turns out.

Thanks

Steve

 

[Timoh]

How about an easier solution? Just get a CR around the fan motor wiring which detects the fan being on?

You would still need to rectify and smooth it to a nice stable DC voltage and then divide it so you get an appropriate voltage that can be read by the ocelot.

A straight CR would have a voltage that would cycle with AC or the revs of the motor depending where you put it.

Tim

 

[politics123]

How about an easier solution? Just get a CR around the fan motor wiring which detects the fan being on?

You would still need to rectify and smooth it to a nice stable DC voltage and then divide it so you get an appropriate voltage that can be read by the ocelot.

A straight CR would have a voltage that would cycle with AC or the revs of the motor depending where you put it.

Tim

Hmm... My Humidifier has a CR that wraps around the fan motor. It's a pretty simple normally open relay. In an ELK, just configure it as a NO zone, right? Can be wired in 30 seconds, no risk to expensive HVAC gear, and it only costs about $20.

http://www.amazon.com/Aprilaire-24V-Sensin...0/dp/B000K1BDIC

 

[Timoh]

How about an easier solution? Just get a CR around the fan motor wiring which detects the fan being on?

You would still need to rectify and smooth it to a nice stable DC voltage and then divide it so you get an appropriate voltage that can be read by the ocelot.

A straight CR would have a voltage that would cycle with AC or the revs of the motor depending where you put it.

Tim

Hmm... My Humidifier has a CR that wraps around the fan motor. It's a pretty simple normally open relay. In an ELK, just configure it as a NO zone, right? Can be wired in 30 seconds, no risk to expensive HVAC gear, and it only costs about $20.

http://www.amazon.com/Aprilaire-24V-Sensin...0/dp/B000K1BDIC

You are correct.

CR-magnetics make all sorts of coils and sensors. The ones I was thinking of was *just* the coil. But they do make one that has some embedded relays that are NO or NC. Those would work.

Tim

 

[Scrambled]

OK Now time for Question #2

I thought about starting a new thread, but since this question is about my HVAC I decided to ask it here.

I have all of my RCS T-stats connected to a hub. This hub uses RS-485 as the protocol for transmitting and receiving between the hub and my ELK M1 serial adapter.

When I want to use the RCS program that connects my PC to the HUB, I have to unwire the ELK serial adapter, and then connect another adapter to the wires. At this point I can monitor all of the T-stats and make any necessary changes. Then I have to change adapters to connect the Elk back up.


My question is Can I connect the Elk and the computer adapter to the RS-485 at the same time, and not let the smoke out?



Steve

 

[FrankMc]

Hi Steve

RS485 comms usually has one Master connected to several slaves...What your suggesting (i think) is connecting 2 masters to several slaves....not sure if any damage will occur but odd behaviour at the least , would occur ....

Maybe a solution would be to have a toggle switch which operates a double pole changeover relay...could use a 12v dc relay fed from your elk system

Connect the 2 rs485 cables from the hub to the common connections of the relay and say connect the elk adaptor to the n/c connections of the relay and connect the pc adaptor for the rcs software to the n/o contacts..........

So with the toggle switch in the off position the relay is de energised and the rs485 comms from the hub is connected to the elk adaptor...Then when the Toggle switch on = relay on = rs 485 comms from the hub is connected to the pc adaptor...Just the flick of a switch to change selection....

Hope that makes some sense
Frank

 

[Scrambled]

Frank-

That is a good idea. I never thought about installing a relay.

Do you or anyone else know if the Elk wil go nuts or just ignore the XSP when it is disconnected?

Is there any chance of damaging the XSP from using a relay?



thanks


Steve

 

[FrankMc]

Hi Steve

Dont have an Elk so cant say for sure....What happens when you currently disconnect the elk interface to connect your pc interface for your thermostats ???....Maybe you need to disable it using the Elk software before disconnecting ????...Of course switching the comms when doing a download to the Elk would cause huge problems...

Dont think switching the comms would damage the elk interface.....Ask over in the Security section maybe Spanky will help...

HTH
Frank