Heat cable questions (Seperation distances and heat generated).

Discussion in 'DIY Zone' started by -Adam-, Oct 21, 2019.

  1. -Adam-

    -Adam- Active Member

    Joined:
    Sep 9, 2019
    Messages:
    105
    Likes Received:
    41
    Gender:
    Male
    Location:
    Victoria
    Hi,

    I've got a number of questions for those who use heat cables please.

    Question 1: How close together are you comfortable with the heat cable being to each length?

    Question 2: When you first determine which wattage cable you will need do you calculate heat based on the wattage of the cable, or on the area and spacing of the cable?

    Question 3: What cable would you recommend to heat a 40x40cm tile?

    ... or would I be better off just going a heat mat to make things simpler even though they say that heat mats should only be used on glass viv's?






    Expanding on the questions above:

    The heat cable I have is Reptile one. In the instructions it says to have the cable no less than 5cm apart.

    However with my tests - I can not achieve the temperature required with the cable at this spacing so I'm not sure if I'm doing something wrong or whether their instructions are not practical?

    Do you follow the manufacturers recommendation and are you able to get sufficient heating - or is the recommendation more of a liability issue and impractical in real world scenarios?

    It seems from some photo's I've seen people put the cables much closer together but of course photo's can be deceptive with measurements so I wanted to check if I should bring them closer together or if I'm doing something wrong not to generate the required heat at 5cm spacing?

    In my situation it gets cold down here. (Inland victoria) - so maybe these recommendations are sufficient for warmer environments such as northern NSW and QLD?



    Next, I've found something interesting with the cable's wattage vs length.

    Reptile one have the following cables.

    15w - 2.0m
    25w - 4.5m
    60w - 7.5m
    100w - 12.0m

    Knowing that the heat is a direct product of the energy used - it seems that the 25w cable is actually the coolest of the lot when it comes from heat emitted over a particular length of cable.

    ie:

    15w = 7.5watts / meter
    25w = 5.5watts / meter
    60w = 8.0watts / meter
    100w = 8.3watts / meter

    (I'm trying to get the 25w one up to the high 30's with heat at present).

    While the 25w will give off more heat over the total length compared to the 15w - it seems as though the 25w one gives off less heat per any given area compared to the 15w if everything else is the same. (Spacing, etc).

    I'm sure it's not supposed to be this complicated to figure out which has me thinking I'm missing something trying to get my heat levels right.

    Thanks in advance.
     
  2. Melmy

    Melmy Not so new Member

    Joined:
    May 21, 2019
    Messages:
    79
    Likes Received:
    57
    Gender:
    Female
    Location:
    VIC
    If you search “heat tile” there are some great and thorough instructions which will get you sorted :)
     
  3. Sdaji

    Sdaji Almost Legendary

    Joined:
    Jun 28, 2004
    Messages:
    7,723
    Likes Received:
    980
    Location:
    Victoria
    I've never used heat cord with runs more then 5cm apart. I can't even recall seeing anyone else do it. When first using cords I tried some smaller ones but quickly settled on the 9m ones and don't use anything else. I do imagine this would be a hassle for people just wanting to heat one click clack or one small enclosure (good reason to keep at least a dozen snakes).

    And yep, it's a little weird that the wattage per unit length increases with the successively physically larger units. I'm not sure why they designed them that way but all manufacturers seem to stick with that same design.
     
  4. Melmy

    Melmy Not so new Member

    Joined:
    May 21, 2019
    Messages:
    79
    Likes Received:
    57
    Gender:
    Female
    Location:
    VIC
    Even more annoying is that there are a range of different lengths with the same wattage!
    25w works well for a 40cm tile with around 2-3cm spacing.
    Or just get a dozen snakes as Sdaji suggests ;)
     
  5. pythoninfinite

    pythoninfinite Subscriber Subscriber

    Joined:
    Aug 3, 2015
    Messages:
    993
    Likes Received:
    745
    I've used heat cords of all wattages, depending on application and enclosure size. If the 25W cable, spaced evenly on a 40cm tile, works well, I would use that. I have never observed a separation of 5cm, usually around 3cm, and had no overheating problems in 15 years of use. I do tend to be conservative with heating appliances - I try to use the minimum wattage needed to achieve the desired temperature, in case of any problems with thermostats, that way the potential to overheat is minimised.

    Jamie
     
    Melmy likes this.
  6. -Adam-

    -Adam- Active Member

    Joined:
    Sep 9, 2019
    Messages:
    105
    Likes Received:
    41
    Gender:
    Male
    Location:
    Victoria
    Thanks all,

    • I'll ignore the manufacturer instructions regarding separation distance. 3cm separation seems to be closer to the heat I require.
    • I'll work on the cable length required for the tile/space in question using 3cm separation as a guide:
    Working on a 3cm separation and 0.7mm cable length makes 3.7cm span per run - will be around 9 runs for a tile of that size (leaving separation around the left and right edges). Given 40cm in length plus 4cm give or take for the loop at the end to come back = 44cm per run. 44x9 = 3.96m = close to 4m required. 50cm allowance for getting some figures wrong means that the 25w. This all lines up perfectly with @Melmy & @pythoninfinite recommendations. Thanks for the confirmation! It makes it much easier when I can ignore the warning on the instructions. :)

    @Sdaji - I'm glad I'm not the only one confused by the length vs wattage. I understand the basics of heating elements and electronics - it seems either there's another variable at play or possibly different resistance in wire (which to me wouldn't make sense). Either way - the 25w at ~3cm separation should serve precisely what I need. Thanks!
     
  7. Sdaji

    Sdaji Almost Legendary

    Joined:
    Jun 28, 2004
    Messages:
    7,723
    Likes Received:
    980
    Location:
    Victoria

    I'm not sure why they design them to have higher wattage per unit length but the explanation of how they do it is simply by using an element with lower resistance per unit length.
     
  8. Blighty

    Blighty Not so new Member

    Joined:
    Mar 22, 2018
    Messages:
    82
    Likes Received:
    53
    Gender:
    Male
    Location:
    WA
    Oh, just be mindful when you order them that you confirm the heating length. I sell URS branded ones (from iPetz) and the heat length is marked with a blue stain/dot. For example, the 25W 4.3m Heat cord has approx 3.54m of it's length dedicated to heating. No idea about the other manufacturer's ones.
     
    -Adam- likes this.
  9. CF Constrictor

    CF Constrictor Not so new Member

    Joined:
    Jul 31, 2019
    Messages:
    49
    Likes Received:
    14
    Gender:
    Male
    Hi Adam
    I use a 50 watt , 7 metre heat cable , spaced 3 cm apart and run it through a standerd type incandecent light dimmer switch so desired temps are easily achieved all year round in an enclosure measuring 900 x 550 x 450mm.
    Hope that might be some use to you.
    Doug
     
    -Adam- likes this.

Share This Page