Proportional vs Non-Proportional question

[ted1025]

okay I've done some reading on here about the topic of proportional vs non-proportional(on/off) and understand the concept of both of them.

I need a t-stat so I'm looking into the Herpstat which I can use either pro or non-pro.

Whoever has a Herpstat, what do you use?

I ask because right in the manual, I looked it up online, under the Non-pro heating it states "This floating method avoids unnecessary wear on the heating system."

What does that mean?? Using pro will wear out the heat tape faster?? the flexwatt tape I'm using will last longer if I use non-pro? the actual t-stat will last longer?

thanks!

[2kdime]

I use a Herpstat Pro.

Non-proportional thermostats switch on heaters or devices on at full power and then cut power off completely once it reaches your set temperature.

Proportional thermostats adjust the amount of power so that your device will almost always be on, just at a very low level to maintain your temps.

Proportional stats/proportional mode on the Herpstats are better for your heating/cooling devices.

[ted1025]

I use a Herpstat Pro.

Non-proportional thermostats switch on heaters or devices on at full power and then cut power off completely once it reaches your set temperature.

Proportional thermostats adjust the amount of power so that your device will almost always be on, just at a very low level to maintain your temps.

Proportional stats/proportional mode on the Herpstats are better for your heating/cooling devices.

Hey, thanks for the reply. Not being rude, but I knew the specifics of how each mode worked. I'm asking why is it stated that running Non-pro avoids unneccesary wear on the heating system...

Like does running Pro mode wear out your stuff faster and people know this but they still prefer this method anyway?

[PythonWallace]

I would think that that only applies to light bulbs or actual heaters. Flexwatt should hold up fine, either way. It basically means that something like a light bulb will last a very long time (longer than the number of hours you are supposed to be able to get out of it) if you are running it constantly at a dimmed (proportional) level, while if you turn it on and off 40x per day at full power, it will likely burn out a lot quicker. I'd imagine space heaters and such would be the same, but if you are using something as simply constructed as Flexwatt, it probably won't matter as far as the life of the heat tape is concerned, but it's still better to use the proportional setting if you have it. It just stays more consistent than on/off, and I'm pretty sure that it uses a lot less electricity to run it at a low wattage non-stop than it takes to turn it on to full power all the time.

[DustinB]

As far as I know they both function the same, just the pro has a few more features and 4 probes. How many snakes do you have or plan to have? If you only have one or 2 then you only need a herpstat or herpstat II.

"Nonproportional Mode (Heating)
Heat is applied until the temperature exceeds 88.5°F.
Temperature is allowed to drop to 88.0°F before heat is reapplied. This floating method avoids
unnecessary wear on the heating system."

I think this is just saying that it doesn't allow it to get too hot or too cold, it maintains a fairly close temp to not have so much expansion and contraction on the elements of a heating pad, but with this mod it's fairly useless if you buy this t-stat. Not many people buy this to use it as an on/off style.

[spyderrobotics]

Proportional is always better if you can use it. Non-proportional is really just there for a backup in case the proportional doesn't work out. Say you use a ceramic heat emmitter. Most will work great on proportional. Some though will emmit a faint noise as the power is dimmed. So if that is a nuisance you can switch to non-proportional where no dimming occurs. With the non-proportional control of a Herpstat it will help extend life longer than a standard relay based thermostat for heating devices that may be sensitive. The reason is it detects the zero crossing of the AC sine wave each half cycle and would turn the triac on at that point. Without getting too technical just think of this example. Most of us have had an experience where we turn on a light switch in our house at some point and had the light bulb flash for a second and then burn out. The reason is because the filiment was worn but you happened to turn power on when the AC was at its highest voltage (AC swings between 120v and zero constantly) and the abrupt power shot the bulb. With zero crossing detection its turning on voltage while its still low so its less harsh. Any proportional thermostat in proportional mode can still turn the power on when its half way through the wave at 120vac (which is basically 50% power output). However, since it doesn't spend the majority of its time there its still better than a relay based thermostat. Again, the longevity of the heating device is a minor concern. Most will probably never see a difference. The nuisance of certain ceramic heat emmiters (some metal rack systems will also have a noise due to the resonance of the metal holder the heat tape sits on) is really why I wrote it into the code.

Hope that helps!

Dion Brewington
Owner, Spyder Robotics

[ted1025]

Thanks everyone for the replies, I get it now. Herpstat is on the way!