# Identify/substitute Watson capacitor values

My ceiling fan is not spinning up properly any more. A quick google results in the solution "replace the capacitor." However, the values on the capacitor are not very explicit.

• Watson
• AC450V
• 0.5 + 0.8 +/- 5%
• T85

My guess: 450VAC, 0.5µF and 0.8µF with a tolerance of 5% and a temperature rating of 85 degrees.

Am I correct about the µF, or are these nF? What wire is connected to what µF?

It seems that I can't find this exact capacitor, nor easily find a different one with two wires with these values. Can I substitute this one capacitor for two separate capacitors, or is there some other way for me to obtain the correct type of capacitor?

Note: I'm located in The Netherlands (Europe), so e.g. eBay has limited availability.

Yes, those are the capacitances in microfarads. You can substitute two capacitors, however you would have to know the connection scheme. If you have a capacitance meter you can measure the leads and figure out which of the two is damaged (usually the capacitance drops from nominal due to the self-healing characteristic).

That is very much on the low end of the capacitance scale. You could replace the dual capacitor with 2x 1uF in series (0.5uF) and 2uF in series with 1.5uF (0.85uF). Four capacitors total. Easily available from Aliexpress.

Yep , your guesses are correct. Fan capacitors are typically around 1uF , smaller for low speed , larger for medium speed.

In your case you need a 0.5uF capacitor and a 0.8uF capacitor , both rated at 400VAC or better. The capacitors would normally be stocked as 0.47uF and 0.82uF , accuracy is not important. a 1uF capacitor would work in the fan OK as the medium speed.

You could also buy 3 capacitors of 0.47uF , and use two in parrallel for the 1uF.

Where to get small quantities is a bit of a problem as the postage cost would exceed the items cost, you must have some kind of hobbyist type electronics store other there? You've got your professional suppliers over there e.g. https://nl.farnell.com/ and https://nl.rs-online.com , I could look up suitable part numbers for you.

Here is a typical part https://nl.farnell.com/kemet/phe844rf6470mr06l2/cap-0-47-f-20-pp-radial/dp/2495765?ost=2495765 You would be looking for a polypropylene, or "PP", or "MKP", capacitors , at these voltages they are commonly called "safety Capacitors" , and will have "X1" or "X2" , harder to find them with long leads. And they would need more volume than your original capacitor.

As these are connected to a fan, you could probably use the cheaper polyester, or "PET", or "MKP" capacitors. (but that's probably what you have now!)

By the way, "Watson" isn't a real brand , just something the Chinese manufacturers stuck on the component. Buy a whole box full and they will write whatever you want on them.

The 305VAC X2 capacitors would be sufficient for 220v mains, e.g. https://nl.rs-online.com/web/p/polypropylene-film-capacitors/1248416/?sra=pstk , you have to buy these in packs of 10, (this is why I suggested earlier using 3 of same value) , part number 144-7768 is similar with longer leads. In the actual 440VAC rating 164-9608 has long leads (but is not a "safety capacitor".

Basically a X1 or X2 safety capacitor has inbuilt safety features that allow a 310VAC rated capacitor to be bolted across the 220v mains, (it has "fuses" that isolate parts of the capacitors should they fail) , to get a similar level of safety you would otherwise have to uprate to a 450VAC. A fan capacitor is in series with the fan, so the worst case failure scenario is the fan runs at full speed. Given so many X2 capacitors are used as EMC mains filters in all sorts of appliances, it is more economical to use X1 or X2 capacitors than the normal 450VAC rated capacitors.

• I tried looking it up myself at rs-online, but I'm unable to find exactly what I need, way too many options for me to understand. (As they say around here, couldn't see the forest because the trees are in the way). If you could find a suitable part that'd be great. Aug 30 '20 at 11:08
• OK standby , I have to look it up here on the Australian site, and give you the part number to look up.
– BobT
Aug 30 '20 at 11:12