Whoops, posted this to a binary group, then copied it here without removing photos.
Here's the post again without the pictures, but links instead.
I bought a digital thermostat which is rated at 3 amps. Do you think I could run a 6A fanheater with it? I was going to upgrade the relay in it, but I've found that it already has an 8A relay. The only reason I can see for rating it as 3A is the circuit board tracks, or the connectors (see photos).
could run a 6A fanheater with it? =A0I was going to upgrade the relay in i= t, but I've found that it already has an 8A relay. =A0The only reason I can= see for rating it as 3A is the circuit board tracks, or the connectors (se= e photos).
Track ampacity can be solved by scraping off a narrow strip of the green stuff and adding a long track of solder on top. A more sure way to do it is to solder wires direct to teh relay pins, so you use your own wire and connectors rated to 6A+.
NT
run a 6A fanheater with it? I was going to upgrade the relay in it, but I've found that it already has an 8A relay. The only reason I can see for rating it as 3A is the circuit board tracks, or the connectors (see photos).
Is there some way to calculate the ampacity (I love that word, is it real?) of a circuit board track?
could run a 6A fanheater with it? I was going to upgrade the relay in it, but I've found that it already has an 8A relay. The only reason I can see for rating it as 3A is the circuit board tracks, or the connectors (see photos).
of a circuit board track?
I can measure it's resistance. And I can see it's length and width. And I can see how thick the circuitboard is and how much ventilation it has.
run a 6A fanheater with it? I was going to upgrade the relay in it, but I've found that it already has an 8A relay. The only reason I can see for rating it as 3A is the circuit board tracks, or the connectors (see photos).
The stat will be fitted onto a stone wall. It couldn't set fire to anything but itself.
k I could run a 6A fanheater with it? =A0I was going to upgrade the relay i= n it, but I've found that it already has an 8A relay. =A0The only reason I = can see for rating it as 3A is the circuit board tracks, or the connectors = (see photos).
thing but itself.
no carpet, no wood floor, no nearby newspaper etc? I'd use a relay with it.
NT
connector setup. That arrangement has a very, very small contact area which could lead to a resistive joint and overheating without putting a lot of load on it. The only thing in its favour is that the contact area could be high pressure, which would help a lot - at least until the contact pressure falls with age (I can't see a spring in there).
Also, the 8A rating of the relay is for a purely resistive load, not for a fan heater motor. Remember that the motor alone will draw at least 7x it's normal running current during startup. We normally work on 7x for something without a lot of inertia, like a pump, but fans can be much worse than this. The inductive rating of that relay is 3.5A according to the manufacturer (Omron) so it's goodbye relay contacts!
To switch a fan heater you'll need a small contactor, about 9A AC3 rated (the smallest size that I know of). These have double-break contacts so there is little arcing as they open.
The fan heater's motor is an inductive load. Arcing is therefore likely compared to the pure resistive load which is the element. An example of rating with resistive(inductive) is 8(3)A.
I would rather buy a unit with a 10(6A) rating, because fan heaters are a bit brutal on relay contacts when switched repeatedly via an external thermostat. Additionally any future fan heater might well be
8A re 2kW which is a little more common (although there are some 1.8kW & 3kW wall mounted units). Saves buying again in the future and might offer a little more contact life.It is not worth the risk in modifying a commodity item that is at most =A315 for a more suitable replacement. Simply return the thermostat under DSR, or sell on Ebay and buy another.
The motor will have an inductive element, but I really can't think of a more effective snubber than a low resistance heater element!!
could run a 6A fanheater with it? I was going to upgrade the relay in it, but I've found that it already has an 8A relay. The only reason I can see for rating it as 3A is the circuit board tracks, or the connectors (see photos).
but itself.
It's to heat a garage. There is nothing flammable within a metre of it.
As long as the elements remain in circuit. That is to say the fan heater's internal thermostat is turned to maximum, or it does not have one.
well that is of course if the motor is in parallel...
When those fork shaped connectors heat up from exxcess current, they lose springiness and deteriorate. Theres a flammable floor right under it. Its a truly barmy idea.
NT
What flammable floor?
Apart from switching 8 amps what else did you want it to do?
Be cheap. Be digital. And er.... I dunno. I was busy playing a computer game at the same time and got distracted.
You mean 'currently'. Stuff moves. And garages usually have more flammable stuff in them than anywhere else!
Whole idea is ludicrous. I wouldn't trust those sort of things to switch
1A with any reliability let alone a bloody fan heater, although my idea of a decent fan heater uses far nearer 13A and makes the plug top warm.That aside though, think of liability. What happens if, even though it's up to spec, if the fan heater decides to catch fire[1]? The insurance people poke through the remains and find a home brew bit of wiring...
Be better off with a fan heater with a froststat build in to it. At least if it goes horribly wrong you can say hand on heart you've not been playing silly buggers with it.
Scott (Captain)
[1] Leave a portable electric heating appliance to run unattended? Bwa-ha-ha-ha-ha!
Not this one. I store flammable liquids in my attic.
Why on earth not?
This one is 12A but it's on half power.
I don't do insurance.
I don't want it at frost-stat temperatures.
Yer only one higher.
You're one of those safety conscious folk aren't you? I've never heardof a fan heater spontaneously catching fire. Unless someone sticks a duvet on it or something daft.
pump etc. Hence you can drive more on a mostly resistive load.
I use a bog standard mechanical stat to control my workshop fan heater - I think that was rated as 10A resistive, and 3A inductive load similar to:
The flaw is that you probably can't measure the resistance accurately enough.
In theory you know that if you take the resistivity of copper (about 17 nOhms) and multiply by the tracks length, and then divide by its cross sectional area, it would equal your measured resistance. Hence you can work out the CSA from what you know...
Failing that you could assume it is a typical 35um thick track ;-)
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