Heat cord inconsistency

[Karnyge]

Hey guys,
I recently changed over to heat cord, I made some groves in a sheet of MDF around 2cm apart wide enough and deep enough for the cord to sit flush with the board, not tight, perfect fit. I originally had a 2m 15w reptile one cord, and made the length of the board and grooves long enough to make 4 runs of the cable, I then placed aluminum tape over the cable, I made one groove a bit deeper and long enough so I could slide the thermostat probe underneath the heat cord. I had two 7l Stiema tubs siting on the tape which had dual thermometers to monitor the hot and cool ends, it was very difficult to maintain identical temps most of time, the tub on the left would be hotter than the tub on the right, sometimes it was hard to maintain a high enough temp in the right tub, I put this down to the the cable length.

While at SOFAR, I purchased a new heat cord, this time 25w 4m, I'm still getting inconsistencies, I've been testing a tub with two probes at the hot end, they have been degrees apart, Ive also tested with a heat gun some spots at the hot end are reading 35 while the thermometers read 32, obviously the heat gun may not be 100% accurate. I've now put a couple of tiles over the aluminum tape, the temps seem a bit more consistent, but when using the heat gun on the tiles they read different temps all over, ranging from 30 -37, I put this down to cool drafts etc. I have the thermostat set to 36 - 38 degrees. Any one have any ideas how to get more consistent temps across the board so I can run two click clacks on the same cord.

Cheers.

 

[GeckoJosh]

Try putting the thermostat probe inside the tub

 

[86JAP]

Try putting the thermostat probe inside the tub

+1

You want to regulate the temps in the tubs not under them.

 

[Karnyge]

+1

You want to regulate the temps in the tubs not under them.

I was trying to avoid putting the probe in the tub, as its a long metal one with a sharp end, is the heat different at the end of the cable compared to the beginning?

 

[86JAP]

It should be consistent all the way along, you can stretch it out and plug it in and check it at various points along the length to make sure. You should be able to run a file over the sharp end to smooth it off, if it is the type in thinking of the sensor part should be in the body of the probe just don't go crazy with the file.

 

[Rogue5861]

What sort of thermostat are you running? It will get pretty solid temps running a dimming or pulse thermostat. Having a heat soak works well but i think you have the cord to close to each other, most people run them every 40-50mm depending on how much heat they need.


Rick

 

[Karnyge]

What sort of thermostat are you running? It will get pretty solid temps running a dimming or pulse thermostat. Having a heat soak works well but i think you have the cord to close to each other, most people run them every 40-50mm depending on how much heat they need.


Rick

Can't remember the make now, no markings,

Sent from my HTC_PN071 using Tapatalk

 

[Rogue5861]

I would replace with a dimming or pulse thermostat, you should get a more stable temp.


Rick

 

[The_Geeza]

Throw it

 

[pharskie]

You can get decent dimming thermostats with separate light controls and day/night functions for less than 80 bucks.

 

[GeckoJosh]

Even one of the $10 ones from HongKong of Ebay would be better than that

 

[Karnyge]

it's worked well with the heat mat, just not for what I'm trying to achieve now, thanks for the help guys I'll have a look around for what was recommended.

cheers.

 

[AllThingsReptile]

Can't remember the make now, no markings,

Sent from my HTC_PN071 using Tapatalk

I had one of those, they're sold at almost every pet shop I've been to for $100+….
They don't work too great!

 

[Rogue5861]

I had one of those, they're sold at almost every pet shop I've been to for $100+….
They don't work too great!

They are a thermostat suited to a fridge, not for direct heating devices but ambient temperature control.


Rick

 

[Karnyge]

From memory I paid around 70

Sent from my HTC_PN071 using Tapatalk

 

[AllThingsReptile]

They are a thermostat suited to a fridge, not for direct heating devices but ambient temperature control.


Rick

fair enough, then its a bit stupid of petshops to sell and recommend them for use with heatmats, CHE's etc.

 

[Rogue5861]

Yep it really is stupid, especially the price they sell then for.


Rick

 

[Snake-Supplies]

I'd like to see (if you decide to go for another thermostat) how much things change in your enclosure and whether your "inconsistency'' disappears, and that the heat cord has a constant temperature throughout the cable, providing the only thing you change is the thermostat.

Dimming and pulse proportional thermostats do provide a more constant temperature, though that's not the problem in the question posted, the question I think is why the heat isn't a constant temp through the heat cord.

You say you have measure the temp all around with various thermometers.
Are they quality thermometers? Are they accurate?

I fail to see how the thermostat, changes the heat cord temp.

 

[Rogue5861]

I'd like to see (if you decide to go for another thermostat) how much things change in your enclosure and whether your "inconsistency'' disappears, and that the heat cord has a constant temperature throughout the cable, providing the only thing you change is the thermostat.

Dimming and pulse proportional thermostats do provide a more constant temperature, though that's not the problem in the question posted, the question I think is why the heat isn't a constant temp through the heat cord.

You say you have measure the temp all around with various thermometers.
Are they quality thermometers? Are they accurate?

I fail to see how the thermostat, changes the heat cord temp.

Due to it being an on/off thermostat the cord will heat an cool at different lenghts at different times. I have had variation in temps along cords i have but once running constantly they seem to heat up all over fine.


Rick

 

[Snake-Supplies]

Oh dear,
I look like a tosser!
I wrote that at work on my phone and was trying not to get caught so I didn't read it properly
Obviously my cut and pastes didn't work.
Should look more like this:

'd like to see (if you decide to go for another thermostat) how much things change in your enclosure and whether your "inconsistency'' disappears, and that the heat cord has a constant temperature throughout the cable, providing the only thing you change is the thermostat - regarding the comment about the cheap ebay thermostats you buy for under $15 as they are both the same on and off principal... and that I cannot see how a $10 Chinese thermostat, could be better than a $75 Australian made thermostat.

Dimming and pulse proportional thermostats do provide a more constant temperature, though that's not the problem in the question posted, the question I think is why the heat isn't a constant temp through the heat cord. Just saying what to buy does not give him the right answer, it's best to teach people why.

You say you have measure the temp all around with various thermometers.
Are they quality thermometers? Are they accurate?- regarding the different readings he's getting.

I fail to see how the thermostat, changes the heat cord temp. was meant to be cut and pasted to the top paragraph.