120V circuit control with ELK relays

[signal15]

On the 8 port output expander with relays, it appears the relays can switch 120V. According to the docs, 10A @ 125 VAC. Is anyone doing this?

I am putting in 3 more pumps for my in floor heating, and I don't want to spend another $350 for a pump controller. The only thing the pump controller does is detect whether the thermostat is calling for heat or not (via an open or closed circuit), and then turn on the main pump, and the pump for the zone that is calling for heat. The pumps only take 0.48 amps each, well below the rated max.

What I'm concerned about is three things:
- Does building code typically allow low voltage and line voltage in the same box?
- How to enclose the relay board so no one sticks their fingers in it and gets zapped with line voltage
- Can running line voltage through them cause interference or problems with the ELK itself? Are the relays properly isolated to make sure there is no power draining back into the system?

I'm looking at using a ELK-M1XOVR with a single RS-485 wire run to the pump manifold panel.

 

[AceCannon]

Cool. So you are going to wire the thermostat into 1 or more Elk input zones?

Will a separate relay be needed for this, given most t-stat's 24vac power?

 

[gatchel]

I always use a separate relay to control anything over 12 or 24 volts.

I am not an electrician.....

I believe that if you want to bring low voltage wire into the same enclosure as the high voltage the wires they all need to have the same voltage and temperature ratings....I think. Check your local code for clarification.

I usually run a control voltage from the elk relays (12vdc) to a cube relay in a separate junction box or nema enclosure and place the cube relay there with the high voltage switching done there also.

 

[Digger]

Going off memory the NEC requires that power limited and non powered limited wiring be seperated by at least a 1/4 inch. Seperated can also mean a barrier. Several alarm mfgs are using heat shrink tubing or double insulated wire on their battery leads that are not power limited (low voltage so not a shock hazard but enough power to be a fire hazard) as a barrier.

My opinion is that the ELK-M1OVR minimizes accidental contact with high voltage by design. The type of terminal block and the layout of the board really minimizes the exposure of casual contact.

I would make sure that the board is mounted securely in the enclosure and that the enclosure is properly grounded. I would also route and secure the wiring so that it is not easily damaged.

One of the best things to use is a good dose of common sense and I am sure you are already doing that.

 

[signal15]

Cool. So you are going to wire the thermostat into 1 or more Elk input zones?

Will a separate relay be needed for this, given most t-stat's 24vac power?

My t-stats are Aube thermostats, and they are powered off 2 AA batteries. No 24VAC required, they just close the circuit when they call for heat. So I am going to run them into an input zone on the ELK, and do something like:

WHENEVER GARAGE HEAT BECOMES SECURE
	 THEN TURN ON MAIN PUMP
	 THEN TURN ON GARAGE PUMP

I will have to figure out a way to shut them off though. If two zones are calling for heat and one of them shuts off, I need to make sure that the main pump does not get shut off since it would still be required for the other zone. I'll probably have to implement a counter that counts the number of zones calling for heat and then increment/decrement it appropriately and only shut off the main pump when it's zero. Shouldn't be too hard.

Technically, I could use temp probes and actually have the ELK do everything. But my thermostats dynamically learn the thermal mass of the substrate and turn the system on every 20 minutes, varying the amount of time it stays on to keep the temperature more constant. Otherwise, your temperature shoots way past your target temp because you've heated the floor too hot and it's continuing to radiate heat into the room even though the pumps are off. I think the scripting on the ELK does not have enough features to be able to replicate this functionality. If it could, and if the M1XEP had an XHTML interface, I could control it all through my Polycom phone screens in each room. That would rock.

I'll probably get one of these cases to mount the pump control stuff in:
http://www.par-metal.com/product-ttp-20series.php

 

[ano]

Don't do it. Very bad idea. Control the load with a solidstate relay mounted near the pump and use the Elk to control the solidstate relay. A regular relay works also, but solidstate is better. You will have low-voltage and high-voltage both in the box by your pump, and the electrical code gets tricky there, but its possible, and make sure any in-wall low-voltage wires are rated for in-wall.

Solidstate relays look like this Solidstate switch

Most have a pretty wide control range, but you want 12V most likely.

 

[BraveSirRobbin]

You might also want to look at "Relay in a Box" solutions. I know WayneW uses them and they may be a good fit for this application.

 

[Ira]

You might also want to look at "Relay in a Box" solutions. I know WayneW uses them and they may be a good fit for this application.

I use them, too. Very convenient and not that expensive.

I've purchased several of them from this place.

Here is the manufacturer's website (Functional Devices). They manufacture a lot more types of relays than what is shown on the original link, and a lot of other stuff.

Ira

 

[BraveSirRobbin]

Also note that they are "UL Listed"!

 

[signal15]

Would an output expander have enough power to drive these, or would I need the output expander with relays and a separate power supply to trigger the solid-state relays?

 

[Ira]

Would an output expander have enough power to drive these, or would I need the output expander with relays and a separate power supply to trigger the solid-state relays?

For the "relay-in-a-box", if you go to the manufacturer's website and click on the various models, it will give you all the specs you can use. The RIBU1C is probably the most "typical" one. It can be either N/O or N/C. According to the website, it draws 15mA at 12Vdc and is rated at 10 amps resistive. There are dozens of different models for different coil voltages, contact ratings, with and without manual override switches, contact types, configurations, duty cycle, etc.

They also have similar relays that are not "in-a-box", i.e., they can be panel mounted or track mounted. They have pilot relays, power relays, optoisolated relays, etc.

Their product line is pretty interesting for HA stuff, even though that's not the business they are in.

I'm not affiliated with them in any way, but I do use their products.

Ira