do normal heaters lose some efficiency over time???

[Magnum Man]

I have mostly various brands and sizes of digital heaters, with quartz glass tubes, & in the house I haven't noticed any issues, but outside in the Tilapia grow out tanks, where they are challenged, I'm seeing a difference with the heaters I'm using... last year I had a pair of 1200 watt heaters, but had problems with build up on the glass that effected their efficiency... I pulled them apart, & cleaned the glass tubes, over the winter, but bought a 2nd pair of 500 watt heaters, so that I could rotate them, & clean as needed,. during the growing season...

I started out this spring, with the 1200 watt heaters, and after 4-5 weeks, rotated the 500 watt heaters in, and soaked the 1200 watt heaters in vinegar, to clean them ( hoping if I didn't let the build up get as thick, I could just soak them, rather than disassembling them, and with a brush, they cleaned up nicely )... now its time to clean the 500 watt heaters, that, and the seasonal change has it dropping into the 40's - 50's over night, so a good time to rotate the bigger heaters back in... however I'm not noticing any additional warming from the 1200's over the 500's
... it appears as if I'm getting the equal or less heat from the 2 year old, but freshly cleaned 1200's, than I was from the dirty ( time to clean ) 500's... I was just wondering if anyone else has noticed a drop off of available heat, from your heaters over time???

 

[MaloK]

Yes, the heating element can degrade, leading to reduced heat output.

Your heaters should be considered as working in harsh conditions and would probably degrade faster. The crud accumulation can prevent heat dissipation and cause higher internal temperatures that slowly consume the element.

 

[Archerfish]

It is analogous to incandescent light bulbs in a multiple bulb fixture. One bulb burns out, you replace it and the new bulb is clearly brighter than the older bulbs.

 

[Magnum Man]

I guess all the more reason to buy bigger heaters than you think you would need???

...and a good reason to keep them clean... I had never had a buildup on my heaters before, & still not exactly sure why I'm seeing it, probably a combination of colder than normal room temperatures at times, so running for extended periods of time, more gunk in the water with as concentrated as the fish are in the tanks, & the fact that this is hard water, for the Tilapia, but I didn't expect it, & look for it last year, & the build up had gotten so thick on one of the heaters, that it actually broke the glass with the pressure between the plastic heat shield, and the glass... now this year, I'm checking them every month or so, & still getting quite a bit of build up, but not totally encasing the glass tubes, & putting pressure on it, like last year... I'll probably have to toss the 1200's after the abuse last year, & keep a battery of smaller ones, that I clean, maybe even as often as every 2 weeks, just to make sure I'm not increasing the internal temps, with build up on the tubes???

 

[Archerfish]

Well, I actually use a couple of heaters rather than one huge one for several reasons. To share the load so one large one isn't constantly running and wearing out fast, if a thermostat fails there is less risk of boiling the fish & better heating distribution. I usually replace heaters after five years. Might be excessive but in my opinion, five years is a reasonable lifespan. It is tough to actually calculate how much a heater degrades over time. You would have to measure the water temperature at the same ambient temperature and record the results over time.