Re: Ranco etc burned out?
Quote:
Originally Posted by
Yodawagon
Spyder robotics now has a room thermostat that is good for your situation. I think it needs a wall thermostat too though. Check their site.
Wow, thanks im pretty sure thats exactly what i need.
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Quote:
Originally Posted by
MarkS
I've had several Ranco's fail on me and I've lost animals because of it. I won't ever buy another one either.
Never again will i touch a ranco!
Re: Ranco etc burned out?
Quote:
Originally Posted by
spyderrobotics
Here is my 2 cents:
There is some confusion about ranco or any relay thermostat. I myself had to do quite a bit of research as we have some products entering this field. Here is a manual for the Ranco I found on line:
http://controltrends.org/wp-content/.../Ranco-ETC.pdf
The heating used with reptiles is resistive heating. That is what the oil filled heater is as well. You can see from this manual that the relay used is rated at 9.8 amps resistive which is 1176 watts (9.8 amps x 120 volts). So in this case a oil filled heater on high is more than the spec of the device. Medium should be fine as most of those heaters draw about 900 watts on medium.
Now the bigger story:
When the relay disengages it makes a huge arc across the contacts. I have run tests with relays doing this and each cycle you are wearing a little of the relay at a time and building up carbon on the contacts which increases resistance inline. Many of these relays are only rated at 30-50K operations resistive. So lets say your heating situation turns on the heater for 5 minutes and then cools for 5 minutes. Your cycle time is ten minutes. That is 144 cycles a day or 52,560 cycles per year. So in one years time you have used up rated life of those relays. High endurance relays last 100K cycles. So maybe 2 years life. Unfortunately relay based control is the best value for controlling oil filled heaters but you have to consider your control device as a consumable. BTW relays have two failure states. The relay can fail off (as in too high resistance due to carbon build up on the contacts) or it can fail on (high current welding of contacts together).
Solid state control is possible instead of relay control which does have the advantage of proportional control and no contacts to wear out but the problem is it generates alot of heat in the parts. I experimented with a couple of designs with aluminum enclosures using the whole enclosure as the heat sink and 1500 watts still got the enclosure up to a uncomfortable to the touch temp. Plus when all was said and done it would have been in the $250ish range for a single high output proportional thermostat which didn't seem sellable considering oil filled heater control isn't a big part of the market. :)
You can do some things to help prolong the life of a relay base thermostat. If the room is cold and you have excessive cycling consider using another oil filled heater on low as supplimental full time heat. Then the thermostat controlled one would be adding the final bump to your target temp. Or leave a few lights on in the room. You get the idea. The longer the periods are of on/off times the longer your relay thermostat life will be.
The power module we just came out with is also a consumable. The big advantage with it over a ranco is the ability to use the week scheduling for different temps and also because people can connect it to a internet based home thermostat so they can checkup on room temps.
We do have another full fledged thermostat coming out later this year for this purpose. This model has active line sensing and attempts to break the connection when the voltage in the ac sine wave is low which minimizes the arc. In my testing this took endurance relays that were shot at 100K and pushed them well above 300K+ and they were still in great condition. So the life will be much longer. We are also backing it with a second safety relay like in our other products plus many of the other advanced features of Herpstats. We are waiting for our parts supplies to catch up with the Herpstat 6 demand and then we will be working on the launch of that product.
So that is the skinny on relay based control. Hope that helps some.
Dion Brewington
Owner, Spyder Robotics
Until your new thermostat launches will the power module fit my needs?
Re: Ranco etc burned out?
Quote:
Originally Posted by
highqualityballz
Until your new thermostat launches will the power module fit my needs?
The power module will run a oil filled heater and was designed for that purpose. You will need to purchase a standard home thermostat and thermostat wire to connect the two from a local home improvement store. The wiring is fairly easy and the wiring instructions will be included with the home thermostat. :)
Re: Ranco etc burned out?
Quote:
Originally Posted by
spyderrobotics
Here is my 2 cents:
Now the bigger story:
When the relay disengages it makes a huge arc across the contacts. I have run tests with relays doing this and each cycle you are wearing a little of the relay at a time and building up carbon on the contacts which increases resistance inline.
Is this why it kept tripping my GFI? Would a proportional thermostat work with a GFI outlet?
Re: Ranco etc burned out?
Quote:
Originally Posted by
MarkS
Is this why it kept tripping my GFI? Would a proportional thermostat work with a GFI outlet?
This very well could be. Proportional thermostats usually work fine with GFI's. I've only come across one or two cases where there was an issue. If I remember right the person replaced the GFI with a new one of the same model and then it was fine. So there may be some tolerance differences. If you weren't already I would use a surge protector with a 2000+ joule rating in between the thermostat and wall outlet. The protectors have a mov cap that I suspect works both ways and may keep the relay arc from tripping the GFI.
