I'm trying to help a mate with his old but trusty Kew electric steam cleaner / pressure washer. He was using it a couple of days ago when it just stopped (completely).
I've had a look over it and think I may have stumbled across what could be the problem but would like the advice of the panel please.
If you press the motor contactor down manually the motor seems to run ok. However, it doesn't seem to want to power up via the main off-cold-hot rotary switch. I've checked (stripped, clean and re-assembled) the switch and it looks like it's now working (again) as per the design sheet (there were a couple of contacts that were h/r on my DMM).
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out all the extra bits (mostly to do with the hot / steam side of things) it looks like we have 6 wires going to the motor, 4 larger wires (two going to the switched side of the contactor / OLP and two to the power but elsewhere / big cap?) and two finer wires that seem to be in series with the contactor coil (coil ~ 600 ohm). CA
3-16.
http://dl.dr Kew 2.2kW 50Hz 1 Phase Typ 6150660-84 ? 0.97 66uF 450 VDB ls K1.F IP54 S1 VDE 0530/72
But not sure that would help. What would help would be the schematic but of course there isn't one.
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any advice gratefully welcomed please. Do these AC motors typically need more than 4 wires and if not what are this thinner pair for?
They could be thermistor overload sensors. However, these would normally have a relatively low resistance (a few hundred Ohms) at room temperature. You say they are o/c?
Thermal switch ought to be normally closed for *failure to safety* reasons.
Motor start centrifugal should be closed when stationary.
Yup, o/c (even on my 20kohm range) across the pair and against all other motor connectors and ground.
I did think of that one and the motor does start ok even though these wires don't seem to be carrying anything and couldn't see how they would do anything of use if they 'cut in' at revs.
Thanks anyway .. two heads are often better than one .. ;-)
Almost certainly some form of over-temperature device, I'd say. Either PTC thermistor (ceramic or polymer type) or thermal fuse ('microtemp' etc., sometimes self-resetting and sometimes one-shot). If you're lucky the device might be replaceable, given sufficient stripping down of the motor, but more likely it will be embedded in the windings. In the latter case you're stuffed, unless you want to re-engineer the protection with an external device (a Klixon type thermal switch, etc).
You've checked that the contactor coil isn't o/c, presumably?
Centrifugal switches are generally only found on older motors. Anything modern enough to have built-in thermal protection will almost certainly be of the capacitor-run type.
That's good then (as it could be bypassed, at least for a test).
Ok.
The 'control box' sits on top of the motor and forms the lid to the top of the motor and it's junction box etc. We lifted the box a bit but couldn't take it far nor see very much (other than the stator winding etc).
That was a thought (had it been a failed thermal device etc). If we do get it going again (by bypassing said failed thermal trip) I'll get him to monitor the worst case motor temp and see if we can rig a replacement.
Yes, at about 600 ohms. I couldn't see any mention of what it should be on the datasheet (it's a CA 3-16).
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>>> Motor start centrifugal should be closed when stationary.
My mate things this could be 25+ years old but I'm guessing you mean older than that?
Yup, this is such (I tested the cap the best I could with my DMM by just putting it on K ohms and applying it to the cap both ways and seeing it 'conduct' then go o/c).
There are numerous leads coming off the temperature control board to the numerous interlocks to manage the diesel boiler, fuel lever, fuel pump, water temp and gawd knows what else. It also has two 12V relays whose outputs are in series and also manage power to a subset of this plant. I've measured the relay coils (~200 ohms) and tested that the n/o connections actually make when the relays are actuated manually.
The 12 way switch has 12 or so red wires coming off it making tracing out all the wiring pretty mechanical.
The Off-On-Hot switch has a momentary action between Off and On that triggers the motor run contactor and that is then held in by a contact pair on the contactor itself.
So, we have:
Live - main switch - intermediate action switch pair in parallel with self hold switch on top of contactor (latter with manual override button) - mystery wire to and from motor - contactor coil - main switch - neutral.
Sticking the meter on 600V AC and measuring around (hands off when powered up) shows 240V across mystery wires to motor (so through contactor coil).
Maybe if we do get it running again I'll get a big sheet of paper and draw it all out!
Apparently these were / are pretty good bits of kit the fact that it has lasted as long as it has (25+ years) reflect that.
I know /my/ Kew Hobby pressure washer is smaller than my Lincoln Mig welder but nearly as heavy! ;-)
Check (it's also very quiet and free running etc).
Understood.
There is.
Understood.
Or in this case, inhibiting (even cold) startup?
Basically it looks like this. There is a main switch that directly powers the motor start contactor (assuming this wire pair that go to the motor should be a short cct 'over temperature device of some sort). You can also electro mechanically activate the contactor by pressing the button on the top. Neither work atm because (I think) this light wire pair going into the motor being o/c.
For hot you move the main switch to position 2 and then that activates a PCB with a 12V psu powering some logic and a pair of relays whose mains voltage n/o contacts are wired in series to provide power to . The relays are presumably activated to enable the 'Hot' function and would fail safe (o/c) should any of the interlock criteria you reference not be met.The 4 pins on this bit of the board they are laid out as:
Pin 1 - 240V in (though a fuse to TXfmr AND directly (?) to the relay contacts then to output on Pin4 if both relays are activated. Pins 2 and 3 are neutrals (in / out).
I've not observed 240 on this board as yet but it's neutral is definitely connected (I've measured 240 on other parts with that as a neutral).
Also on the same (temperature control knob / led gauge) board are probably about 5 pairs of wires (presumably inputs to the board as they are connected via low wattage resistors) that go off to the likes of the diesel tank, fuel pump, something in the output hose connector (pressure switch?) and probably others. As yet I've not seen this powered up and would only be on when the main switch is on the 'Hot' position (and presumably the main contactor on).
Not that I have seen as yet and outside this mystery wire pair going into the motor, nothing that would stop the contactor pulling in and the motor running. ;-(
There is a follow up now and that is my mate is going to look at a second hand model the same as his and if it looks like it's a runner, buy it. Some parts do seem to be available but at a price so he could use the working one as both a reference and supply or recipient of spare parts.
I've also suggested he buy a multimeter and will show him how to use it. ;-)
Is that what they call a single spiral of boiler 'tubing'? This has such but I don't think he any issues with the hot side, when it's running. ;-)
Of course but I'm not sure any of that would be (is) in play for the cold / simple circuit.
When I first started investigating it I pressed the contactor manually and the motor span up and was quickly going to enter it's header tank. ;-)
It turns out it was (and the one I eluded to). ;-)
This may well have such things and he told me there is a manual delay the operator must apply when going from hot to cold (one assumes to purge the heat from the boiler etc).
Understood but there didn't (in this case) seem to be such a thing.
I'm sure it has. Luckily it turned out to be what we feel could be a motor overtemperature device and since that was replaced with a straight linking wire the machine is running 100% again . We were able to get pretty close to that decision after getting the schematic for the main rotary switch and then marking the 12 red wires with their numbers. At least then I was able to map out enough of the cct to work out what should make the motor run contactor pull in and everything pointed to said failed (o/c) device. My mate being able to locate and buy a second, working near-identical machine today gave him both functional cover, a test / comparison platform and a load of spares. ;-)
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