What gives?

[tcianci]

Last year just for S&G's I plugged in one of those 1500 Watt oil filled radiators in the garage. Usually the garage is heated with a 25K BTU Beacon Morris hydronic unit heater. That little electric radiator would keep the place at 68-70 degrees once I got it up to temperature with the forced hot water.
Well, toward the end of the season the heater developed a leak and was losing oil so I finally canned it. This year I was looking through my stuff and pulled out a 1500 Watt Toastmaster ceramic heater. This unit can barely keep the place at 55-60. I know watts is watts but I'm wondering why such a big difference in temperature between the 2 units. I wish I still had the other one just so I could compare them apples to apples.

 

[rickairmedic]

TC the radiant oil filled heaters just plain work better . The good news is Homie Desperate still has them for less than $40.00 every day .

Rick

 

[yevangelis]

yeah maybe some engineer could explain exactly why but I'm pretty sure that a liquid based radiant heat is the most effective... radiant floor, oil filled, ole cast iron radiators, and steam etc..

this is my unlearnt upinion

 

[tcianci]

Ok, that's good to know. I thought I was missing some of my high school physics basics here. I do know that the oil filled heater has many more times the surface area of the ceramic heater and the oil is quite a thermal mass. but I wasn't prepared fror such a big difference in performance.
When my oil filled heater started l eaking I saw one on closeout (out of box unit) at the depot for 16 bucks but my typical stupidity kicked in and I passed on it

 

[djjsr]

Maybe it's colder outside?

 

[jonny o]

I have had a similar experience.

Last winter I borrowed one of those high-dollar infrared heaters and it held 50 degrees in my shop 24/7 and cycled on and off throughout the day.
Gave it back and tried a 15 dollar milkhouse heater. It does not shut off and barely holds 45ish for the same 1200-1500 watts.

I did all the math on watts, cost, cycles and such and came up with one thing: Although a watt is a watt, the high dollar heater moved a lot more air, actually cycling all of the air in the shop and warming up the items within? For some reason it was more effective.

Maybe you are faced with something similar? Your constant thermal mass may have effectively warmed up the items in your shop, as opposed to blowing air in a 10 foot loop?

Maybe just the most effective for your situation. Or maybe your shop is telling you that it feels safer with a radiator than having a red-hot element with the possibility of fumes and such. Either way, if you know what works, stick with it!

 

[EdT]

If it's a real ceramic element (no visible glowing coils) it's probably a PTC ceramic heater. PTC elements a a bit weird in that they have a critical temperature at which the resistance becomes, effectively, infinite. When that occurs, no heat is generated and the element cools off a bit and the resistance drops a bit and a little current flows and the heat /resistance goes back up and the heat stops and the cycle repeats. At room temp the resistance may be quite low and lots of current flows, but as it heats up the resistance increases and the heat output drops until it reaches some equilibrium as described above or associated with the rate at which heat is being pulled out of the device by the fan. I suspect that the heater is 1500 watts when the element is at room temp, but considerably less in operation hence it does not heat as well as the oil radiator which probably has a big wound heater like a hot water tank and it is probably on all the time. If you have an amp clamp, you could see how much power the ceramic is actually making after its warmed up. So, sometimes 1500 watts is not really 1500 watts; it's just something on a sticker required to meet UL or something.

 

[nehog]

I'm an engineer, and I can't explain it. But I think the effect is real too... I have two oil heaters and a forced air heater in the shop. The forced air heater seems to use more power, and provide less heat than the oil heaters! But the engineer in me says in the end a watt is a watt, and converted to heat at 100% efficiency (you can assume resistance heating is 100% efficient, or at least the same regardless of packaging) you should get the same number of BTUs.

I may try the experiment again this year and see if its true still...

 

[787B]

[...]the high dollar heater moved a lot more air

Ding, ding, ding!

A Watt is a Watt, but it's all about getting that heat spread around. Oil-filled radiator radiates it around. High-CFM fan-forced heaters move it around.

Little **** ceramic heaters don't move squat. The heat they put out heads straight for the ceiling in a narrow plume and stays there until it finds a way out. Fans can help move that heat around and improve the performance.

As for milkhouse heaters, I use one in my 70 sq-ft bathroom and it does a fine job. But I wouldn't use it in my 900 sq-ft garage as the flow is too low.