Contents
Interior
The oscillating base (KFH660) and main housing are each held together by four T15 “security” screws. Remove them to get inside; all internal screws have plain Phillips #2 heads.
The rear housing has just one difference between the KFH600/610 and KFH660: KFH600/610 have a barrier (indicated by the overlaid red rectangle) to prevent finger access to live parts, which is omitted from the KFH660 as there it would block the wires from getting to the base; mounting posts for the cord clamp and tip-over switch, as well as the cord entry hole, are still present even though unused.
Wiring
These are the internal connecting wires; all are ample for their respective loads:
| Item | Colour | Style | Rated VAC | Rated T (°C) | Conductor size | Loading |
| Main active | Brown | UL AWM 1015 | 600 | 90/105* | 16AWG (1.31mm2) | 10A |
| Main neutral | Blue | |||||
| Front heating element | Yellow | UL AWM 1015 | 600 | 90/105* | 18AWG (0.82mm2) | 5A |
| Rear heating element | Red | UL AWM 1015 | 600 | 90/105* | 18AWG (0.82mm2) | 5A |
| Fan motor | Black | UL AWM 1015 | 600 | 90/105* | 22AWG (0.33mm2) | ≈0.1A |
| Synchronous motor | Black | UL AWM 1015 | 600 | 90/105* | 24AWG (0.2mm2) | <0.1A |
| Neon indicator | White | UL AWM 1007 | 300 | 80 | 22AWG (0.33mm2) | <1mA |
*Although the rating given by UL is 105°C, as with any thermoplastic PVC rated >90°C the full temperature is only applicable for a limited time (maybe 20,000 hours in total, or an average of up to 500 hours per annum as permitted for the Australian V‑90HT grade). Continuous use (which a heater like this qualifies as, for the purpose of this rule) is still limited to 90°C, to prevent plastic flow.
Wire routing is done quite safely, with the fan motor leads tucked into a secure channel (on the back of the heater frame); the fan shroud segregates the other wires (where they run up the left-hand side) from the heating elements and impeller. The wires are also guided by a “P”-clamp near where they go to the controls, except that the incoming neutral is left out of this (at least in the KFH660) due to being a bit short (why Kambrook even put the thermostat in neutral in the first place isn’t clear, as this only seems to complicate the wiring harness and also leave the elements live while the switch is on but thermostat off).
Silicone boots insulate a majority of the internal “blade” receptacles. The “cup”-style crimp connectors are sheathed in braided fiberglass sleeves, for fire protection in case they go bad and overheat. (Even though only the main neutral one actually bears the load of the heater proper!)
I (temporarily) removed the sleeve from my KFH660’s neutral connector to inspect, and the crimp indent appears satisfactory.
Controls
The rotary power switch is a Changzhou Jinhe Electrics XK2 type, quite standard apart from the reversed rotation direction; the given rating is 250V 15A/125V 26A, although none of its contacts are loaded above 5A in this application. As designated by their terminal numbers, contact 1 is for the rear element, contact 2 for the front element, and contact 3 for the neon+fan(+oscillation); contact 4 is not installed. Curiously, the slightly-newer KFH600’s switch is less stiff than that of my KFH660.
I do remember that the KFH200 actually had a mica piece between the switch and panel (presumably to stop it from burning through the panel in the event of burn-out), although that switch was of a very different design (but actually had a steel front, funnily enough). Perhaps this was later judged “overkill”, although I can’t say it was a bad idea.
The thermostat (not in KFH600/KFH700) is also very much standard fare; it bears the markings “YWS”, “XWX-WK” and “WK-03”. As far as I can tell from searching (though I couldn’t find a proper website), these are manufactured by “Forever Great Technology Co., Ltd.” It’s VDE rated for 250V 16A.
Its mounting screws are a tad over-long (at least in the KFH610/660), so I ended up placing washers (≈0.9mm thick) under the screw heads in my unit.
Heater assembly
The two heating elements are of the prevalent form, with half-power using the front-most of the two (as seems to be the norm in fan heaters with 2 power settings).
Here are their parameters:
| Identified | Measured | Calculated (power at 240V) | |||||
| Alloy | Wire diameter | Cold resistance | Cold power | (estimated hot power) | Length | Surface load | |
| Front | FeCrAl | 0.5mm (0.196mm2) | 48.2Ω | 1195W | 1172W | 6.81m | 10.96W/cm2 |
| Rear | 49.3Ω | 1168W | 1145W | 6.97m | 10.46W/cm2 | ||
| (combined) | 24.4Ω | 2363W | 2317W | ||||
Hot power estimation is based on a 2% resistance increase, as specified for Kanthal AF or Kanthal D wires at 400°C.
Adding the rated 20W of the fan motor, overall power of the heater falls within 3% of the nominal.
I’ve calculated the lengths for Kanthal AF wire; if Kanthal D, then it will be about 3% longer. End terminals appear to be the usual nickel-plated steel (with its usual weakness to moist dust).
The thermal cut-out is a Klixon TH10CA061, which trips at 75±5°C and is rated for 30,000 switching cycles at 250V 13A. The thermal fuse is a Microtemp G4A with TF=158°C (probably to prevent nuisance failure with age).
Kambrook have made sure to dedicate each rivet to connecting conductive parts or mounting them to the frame (not both in the same place); some cheapies I’ve seen aren’t so careful about that, which could lead to connection failure if the plastic creeps under pressure.
Fan
A basic 2-blade impeller (about 155mm diameter stamped out of 0.4mm steel with a black powder-coating (?)) is driven by a conventional shaded-pole motor, made by Shenzhen Zhaoli Motor. Here’s the nearest equivalent they list; they suggest a lifespan of 5,000–10,000 hours, although without stating the conditions.
Instead of mounting directly to the rear casing, the motor is mounted to the heater frame, which four self-tapping screws then secure to the casing. This is probably done for easier assembly, and also sidesteps the usual requirement of having to cover the screw heads (or recess them deeply) for supplementary insulation.
Unfortunately, the casing design does nothing to protect the back bearing from dust, so use in a dusty environment is likely to shorten the lifespan.
If you’re confident to go inside the heater, however, then you could add a dust shield like this one I made from a strip of rigid PVC (cut from packaging); plasticized PVC will be too soft, and other plastic types are usually flammable unless specifically treated with fire-retardant (so not recommended here). However, I recommend wearing gloves (preferably powder-free) while handling the heater assembly, as perspiration can shorten the life of heating elements.
The KFH600’s (and no doubt KFH610) fan neutral connection is made with a piggyback receptacle plugged onto the heater common tab, and the neon lamp has a receptacle plugged onto the piggyback tab. Unfortunately, this particular piggyback receptacle is quite a poor design (looking something like a cross between the “Economy” and “Commercial” lines from TE), and was in rather loose contact (yet still took immense force to unplug). The wire end was also solder-dipped before crimping, which I understand to not be a great practice either (how bad it will be depends on the hardness of whatever solder is used, but I’d prefer not to risk it with any type of solder here).
At least, since it’s only in the fan circuit, the low current prevents it from posing a serious hazard; I wouldn’t be as forgiving in the heat circuit.
My KFH660 uses a decent piggyback receptacle in this location (the wire it’s fitted to is identical in type, although it goes to a cup connector with the neon+fan wires; the piggyback tab is then used by the oscillation motor), so I suspect that the poor one was selected by Shenzhen Zhaoli Motor (and not by Kambrook themselves).
Neon indicator
The neon bulb is quite small (3.7mm diameter by 9.2mm long), but thankfully has a sensible 510kΩ (±5%, carbon film, 0.25W judging by size) series resistor. My unit hasn’t noticeably darkened from when it was new.
Oscillation
This is done using a standard synchronous motor (model TYJ50-8A7 from Foshan Shunde Hengxing Micro Motor) with a rated speed of 2.5rpm at 50Hz (1,200:1 reduction).
Timing the back-and-forth cycles confirms this (24 seconds per cycle, 12 each way).
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