Ultratherm on on/off thermostats

[hungba]

Hi, I was wondering if anyone has experience with Ultratherm type heat pads on an on/off thermostat?

I have decided to use a thermostat that I bought that is on/off because it is industrial strength and should have much lower chance of failing. I have noticed that Ultratherm type heat pads I have, DO reach the desired temperatures, but it takes quite a while, like 30 mins before it is fully heat up. I want to use them because I tried them on full blast no thermostat and they were not hot enough to melt the tubs or anything. It would make the snake quite unconfortable but I don't think it would kill it in case any accident happens.

Now, the problem I see is, what if the thermostat is set to switch off and on at a certain temperature, and when the heat goes down, it turns the heat pad on, but it takes quite a while for the heat pad to FULLY heat up (although it starts heating up immediately a little bit). So, will that cause the temperature to fall MUCH LOWER, even though the thermostat has already turned the heat pad on?

For example, if the thermostat was set to turn on when temps from to 87F, and turn off at 89F. The temperature falls to 87F, and the thermostat turns the heat pad on. But it takes a while for the heat pad to get to full heat, so the temp falls to 86, 85, 84 etc... before it starts going back up? Or will the 'beginning heat" be enough to stop the temp from falling?

I have some flexwatt too, but haven't tested it yet. I hear it heats up faster but I don't know for sure.

Anyone with experience?

[RichL]

If it takes that long to heat up, i would think that it would drop a bit more like you listed.. The on/off thermostat should be fine, I would probably use the flexwatt instead though.

My $.02

[kitedemon]

On/offs have the tendency to have a lot of throw. There seem to be a lot of variables like probe response and materials ambient temps. What I have found though lots of testing (hydrofarm and johnson) in cool room temps this is made worse and with thin wall materials worse again (tubs) especially when the heat is attached to the tub directly (peel and stick) Usually the problem is over heating as the probe is often slower to respond than the tub is to heat and the temp shoots far past the set point before the unit shuts power down.

I have an ultratherm and understand what you are saying they are designed to heat slowly and not reach as hot as a regular pad. The thing that would be a problem is if the ultratherm cools faster then the probe. In that case the temp would drop below the set point and enclosure temps with it. I don't know if this would happen or not I don't believe that the pad would drop faster or slower than the probe so I'd guess they would read close to the same so you will only loose the 1-4ºF depending on the unit and when the kick on point is in relationship to the set point.

If you do find a problem you might try (if the ultratherm has enough power to manage it) attaching the pad to glass this will heat and transfer to the enclosure (unless you are using a tank then it is already done) but as glass cools much more slowly the loss will be minimalized. I works on the top end so I figure it will work on the low end too.

On/off units do not have the accuracy or proportional units so there is often probe error tossed into the mix as well. In my experience I have had the same number of on off failures as proportional ones (one each) the on off failed open full power and the proportional safety circuit shut off the unit so it went cold. I actually believe that proportional units although more complex may have a slightly higher failure rate but also have a lower rate of over heating due to the safety systems built into most units. In either case a failsafe is IMO not an optional tool but a necessary one. It prevents damage from a failure. The most common cause of failure of any T-stat is probe being pulled away from the heat usually that is by human error. No single T-stat is safe with out a failsafe in this case.

[hungba]

In either case a failsafe is IMO not an optional tool but a necessary one. It prevents damage from a failure. The most common cause of failure of any T-stat is probe being pulled away from the heat usually that is by human error. No single T-stat is safe with out a failsafe in this case.

Can you please tell me what you mean by failsafe? Is it a special feature on t-stats? Or something you plug it in?

[hungba]

If it takes that long to heat up, i would think that it would drop a bit more like you listed.. The on/off thermostat should be fine, I would probably use the flexwatt instead though.

My $.02

The thing I like about the UTH pads over the flexwatt is that I have tested them and they do get hot enough and above, and I have tried running them full blast all night and while they do get hot to the point the snake can be very unconfortable if the t-stat fails, they do not melt the tubs nor start a fire. My friend said I should get something hotter as the weather is only slightly cool now and he said that I should get something that will be hot enough when the weather gets a little cooler but not cold enough to warrant heating the room yet.

Also I like them because they not only are more sturdy with heavier plastic laminating, but they also come with a free protective cover, that has aluminium on the bottom and plastic sheet on top to prevent scratching. THey are a lot more expensive though, more than 10 times the cost of the flexwatt almost.

I don't like the fact that they are all separate wires though, which is messy and also if one pad fails and your t-stat isn't monitoring that one, then...

I don't know if the flexwatt will as I haven't tested it yet. Actually I am not living in the USA and everything is different. When I say flexwatt it is the same product but manufactured by a korean company. It is 67W/M which works out to be about 20W/foot for 11 inch wide, so about the same as flexwatt.

What I don't understand is that if you calculate it the wattage/size area it isn't that much higher than the UTH, the UTH is 15cm X 28cm which is about half the size of the 11 inch flexwatt per foot. It is 7W. So, that size of the flexwatt would be 10W or so. How much hotter is 10W over 7W for the same size??? Yet, I am scared of flexwatt from all the stories I read online and warnings etc., but it's only 3W over the power of the Ultratherm type heat pad, which I have tested and is no where NEAR the ability to cause any real danger.

The UTHs do have a rheostat attached to them though, but I turned them up to full blast. I wonder if even at full blast, that the rheostat somehow decreases the temps/wattage a little bit?

[kitedemon]

Ultra therms are safer than flexwatt generally the temp I get off maxed out flexwatt is 160+ (I stopped it as there is not point in allowing it to continue it is hotter than my animals can handle. The 17 inch flexwatt is lower voltage but it only hits 85-88 which isn't warm enough.

A fail safe is a secondary t-stat that the primary is regulated by.


Hosted on Fotki


Many proportional designs have feed back circuits so if a probe stops working it will shut down the power to that heater rather than on offs where it will try to hit the target temp on a dead probe. They also have circuits that run checks internally and will also shut down if there is an issue found that is not to say they cannot fail they can and do, but it is to say that some of the failures have built in safety.

[hungba]

Do they usually use a cheaper model for the failsafe and the good one as the normal one? So you use the normal Tstat to set the temp to where you want it and you use the other one to set it higher so that if it fails at least it won't go above a certain point?

I have heard of using a rheostat as a failsafe, if the thermostat fails, the rheostat will stop it from going too high.

Ultra therms are safer than flexwatt generally the temp I get off maxed out flexwatt is 160+ (I stopped it as there is not point in allowing it to continue it is hotter than my animals can handle. The 17 inch flexwatt is lower voltage but it only hits 85-88 which isn't warm enough.

A fail safe is a secondary t-stat that the primary is regulated by.


Hosted on Fotki


Many proportional designs have feed back circuits so if a probe stops working it will shut down the power to that heater rather than on offs where it will try to hit the target temp on a dead probe. They also have circuits that run checks internally and will also shut down if there is an issue found that is not to say they cannot fail they can and do, but it is to say that some of the failures have built in safety.

[kitedemon]

Yes that is the idea it is set to a max operating temp. I use 100ºF mostly because I run my enclosures in cool rooms and the primary t-stat probe interior mounted (cool room with unstable temps again) the uth often will read directly 96-7 at 100 the interior temp at the highest (warmest room temp I have recorded) is 98 and 93 at the lowest room temp Both are inside a reasonable range not stellar but tolerable for a few days at longest I am ever away for. If the pad hits over 100º the secondary (must be an on/off type) will kill the power to the primary one and allow the pad to cool when it dips below the proscribed set point it will power up the secondary and start again.

Yes a cheaper design is fine for a failsafe I have Johnson and a hydrofarm or two for this purpose.



Rheostats as a failsafe do not make much sense to me unless the room temps are stable if the room temps changes so does the temp at a given power. Say at 40% power @ 70º a given pad is 90º out put but at 80º 40% power it is likely to be 100º or even more my experiences tell more due the thermal loss dynamics. The same is true on the low side 40% power gives you 80 at a room temp of 60º so if used as a fail safe it relies on the climate control of the room to work too. Say a oil heater fails the rheostat may drop the max temp to where the T-stat cannot work properly, failure or no failure. That system only works on the high end and only if the room does not change. To me a safety system should be as versatile as possible.