[gagibson]

I need some help. I have several baseboard heaters that I want to control with a regular digital - programmable thermostat. I understand that I need to install relays in the basement to turn the power on and off to the baseboards but I can't figure out what type of relays do you use? Normally open or Normally closed? I am using 240V Circuits with 30 AMP Breakers. I want it to work just like a furnace so I am assuming I need 24 Volt Coils on the relays - and a 24V Transformer. Any help you can provide would be awesome!

[hvac1000]

Usually baseboard heaters take special contactors.

See page 37 of the doc or page 95 W/R page for Lever-Temp products. A wiring diagram is included there.

http://www.white-rodgers.com/wrdhom/...ns/furnace.pdf

There are many different model available so here is just one example

http://www.white-rodgers.com/wrdhom/..._06_pg0286.pdf

[KISS]

I'm not sure of the reason to use the sequencer. It would be nice to know the wattage of each heater. Three of these should work.

SC-E05-24VAC

Here is the data sheet. Note that it's a 32 A resistive contactor, but it shows up as 25A. Use the resistive load ratings of 30 A or greater.

http://www.automationdirect.com/stat...fujimc9150.pdf

Here is the page.

SC-E05-24VAC Products

I think automation direct also has the enclosures with a mounting plate in the back. You have to drill and tap this for the transformer, a low voltage fuse holder and a 24 V transformer large enough to handle 3 contactors. An energy limiting transformer is the way to go, but any 240 V primary and 24 VAC secondary 40 VA or bigger.

It looks like it mounts on DIN rail too.

DIN terminals can be used.

Not cheap, but should work.

Contactors are generally normally open and are designed to switch high current loads.

I think you might be over your head.

[hvac1000]

I'm not sure of the reason to use the sequencer. It would be nice to know the wattage of each heater. three of these should work.

There are many reasons to use a listed and labeled item to control baseboard or any other heater.

As mentioned just before these are listed and labeled by UL and recognized as such. When you take a relay along with a transformer and toss it all in a metal box or try and cram it into the end cover of the baseboard heater you are in direct violation of the heaters listing. Since this setup was never tested for high temp use you run the risk of causing a fire so why anyone in there right mind would try to do that is beyond me.

If your home burns down the insurance inspector will not ding you for having improper equipment installed and thus voiding a part of your coverage. (It happens every day).

These units were designed by White Rodgers years ago (during the 60's) for the all electric homes that were sweeping the nation at the time. It seemed that there was no SAFE control setup for baseboard heat that met the minimal requirements.

The major complaint of using relays (NOISE) was eliminated. There is nothing worse than using a relay not designed for the HVAC business. While you are sitting there enjoying your wine and cheese the relay is banging on and off disturbing your friendly conversation even if it is with yourself. LOL

Another item it cured is (here it is again) the relays banging on and off in the sleeping areas of the home. Nothing like your kids waking you up to tell you of the strange noise in there bedroom which is being caused by the relay you installed.

Back then many heating and electric companies installed control boards/panels in the basement to try and get around the relay noise. This did not work to well since anytime you put a relay in a metal box the box magnifies the sound to start with and the cost of the extra control wire and feed lines were just cost prohibitive including labor. With these units (Silent Operator) the transformer is designed into the enclosure to simplify instillation.

So that is basically how these controls came to be. They are called Silent Operators for a reason and that is because you cannot hear them operate but just as important they take advantage of the heat anticipator built in the thermostat so you also have a Level Temp control built in. NOTE: set heat anticipator at .4A as instructed for a very smooth heat cycle with no over or under shoot that you will never get with a strait relay control.

If you know which controls you are going to use (part number) EBay has some once in a while cheap. Examples below

White Rodgers Level Temp Silent Operator 24A01G-2 - eBay (item 290338866862 end time Feb-06-10 16:00:16 PST)

White Rodgers Level Temp Silent Operator 24AO1G-3 - eBay (item 160393125837 end time Feb-06-10 19:37:02 PST)

24A05E-1 Level-Temp Silent Operator Low Voltage Control - eBay (item 230385100352 end time Feb-02-10 17:07:37 PST)

[KISS]

Makes sense:

Q: Explain this from the data sheet

NOTE: Use thermostat with a .2 A fixed heater,
or set adjustable heater in thermostat
at .2 A.

Does that mean you need to put a 24/.2 ohm, > 24*(0.2) (120 ohm 5 W) Watt resistor in series with the W wire of the thermostat to mimic the anticipator?

Resistor: Digi-Key - 45F120E-ND (Manufacturer - 45F120E)

[hvac1000]

A heater is an anticipator. Different engineers use different terms. Next time you get a chance take a old thermostat apart and have a look see. Today it is difficult to find a thermostst that does not have an adjustable anticipator/heater and the new digital units no longer have an adjustable anticipator/heater but use a series of fixed settings to allow various adjustments for different equipment. The new thermostat designs still follow the old tried and true anticipation series of so many cycles per hour but they are fixed instead of adjustable with a screw driver.

The true term used today is Heat Anticipator. But most people shorten it to anticipator.

Here is a note from class.