I have a two zone RFH system in place to heat the basement and main floor of a 16’x 26’ addition to our ranch on the shores of Georgian Bay. For now I have a 3000 W electric water heater to carry the load. (I know, I know, the water heater was cheap, and it was DIY, as opposed to the gas heater which was 4x as expensive.) I have two wall thermostats which call for 24 volts, and 2 zone valves. The pump is 110 Volts. What should the rating be on the 24 Volt transformer to power the relay, to turn on the pump I see 24 Volt transformers for sale at HD for $15.00 CDN. They seem to be replacement transformers for “Waite†Humidifiers. The heating wholesale out let wants to sell me a 24 Volt transformer and base for about $60.00. Should I bite the bullet and buy the higher price spread, or will the inexpensive option work. And what is the ideal temperature to set the thermostat on the HWH. The addition has a gas fireplace for a quick warm up.
Cheers,
BigEr
Replies
A relay usually only takes a few watts of power to operate, so most any transformer (of the proper voltage) should work. Doorbell transformers are usually 120VAC in / 24VAC out and are rated at 20 or 50 watts, one of those would probably work. Just make sure your relay requires 24VAC, not DC.
What voltage are your valves - you don't need to run them on 24 volts, do you?
Edited to add: You can probably take the make and model number of your relay and find a data sheet for it online, then you can tell for sure what it requires. Many manufacturers have that sort of info available on their websites these days.
Edited 11/4/2004 8:01 pm ET by Stuart
Ahoy Stuart,
Thanx for your input. The zone valves are Honeywell V8043. They indeed are 24Volt models, and draw 6 watts. If both loops call for heat, then 12 watts. I'll find the draw of the relay, (to turn the pump on) as well. I guess the load on the secondary side is light. I'm trying to rationalize the difference between the 15.00 transformer, and the 60.00 transformer.
Erwin
So if both valves open, that's 12 watts, plus another couple (for guesstimating, say 8 watts) for the relay, you have 20 watts. Take that times 125% to allow for overloading and you have about 25 watts minimum required.
There are all kinds of transformers that will work, I did a little searching and found a suitable transformer at this website for $16.
http://homesecuritystore.com/ezStore123/DTProductZoom.asp?productID=1069