Capacitors

  • Thread starter The Medway Handyman
  • Start date

T

The Medway Handyman

Hi All

I have an acquaintance who is trying to repair a Bosch pressure washer.

The faulty component appears to be a capacitor rated at 25uF. Not sure if
it's a start or run capacitor. Maplins stock the same make but only in 20uF
or 30uF.

Can either of these be used instead - and which one?

TIA

--
Dave
The Medway Handyman
www.medwayhandyman.co.uk
01634 717930
07850 597257
 
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F

Fred

The Medway Handyman said:
Hi All

I have an acquaintance who is trying to repair a Bosch pressure washer.

The faulty component appears to be a capacitor rated at 25uF. Not sure if
it's a start or run capacitor. Maplins stock the same make but only in
20uF or 30uF.

Can either of these be used instead - and which one?

TIA
Probably - yes as all these devices have a wide tolerance. To be on the
safe side I'd use 20uF in parallel with a 5 or 4.7uF.

Do make sure you use the correct type!
 
P

Paul Herber

Probably - yes as all these devices have a wide tolerance. To be on the
safe side I'd use 20uF in parallel with a 5 or 4.7uF.

Do make sure you use the correct type!
and voltage rating.
 
T

The Medway Handyman

Fred said:
Probably - yes as all these devices have a wide tolerance. To be on
the safe side I'd use 20uF in parallel with a 5 or 4.7uF.

Do make sure you use the correct type!
Thanks Fred. How would I identify the correct type? What am I looking for?


--
Dave
The Medway Handyman
www.medwayhandyman.co.uk
01634 717930
07850 597257
 
J

John Weston

The Medway Handyman, in article <YLl5g.62322$wl.42372
@text.news.blueyonder.co.uk>, says...
Hi All

I have an acquaintance who is trying to repair a Bosch pressure washer.

The faulty component appears to be a capacitor rated at 25uF. Not sure if
it's a start or run capacitor. Maplins stock the same make but only in 20uF
or 30uF.

Can either of these be used instead - and which one?

TIA
It's probably a motor run capacitor and so is designed for the
specific motor windings of the motor. If you go for a lower
value, the motor may not even run. If you go too big, it may
run unevenly due to an unbalanced rotational field or result
in a lower motor life, due to the higher current = heat. If
you look in CPC or RS components, etc, you should find the
correct value.

I'd experiment with other values if you have them available,
to check the fault is the capacitor, but if you are buying
one, get the right one. The voltage rating can be higher but
the capacitance should be as close as possible.

AFAIR, If it is a motor start capacitor, there will be a
second run capacitor, often in the same case (look for 4
terminals), and some form of contact that opens when the motor
is up-to-speed. Given the application, I don't think it is a
dedicated start capacitor, even in a Bosch :) Start
capacitors are less critical and you can normally use one of
higher capacitance without a problem.
 
R

raden

The Medway said:
Hi All

I have an acquaintance who is trying to repair a Bosch pressure washer.

The faulty component appears to be a capacitor rated at 25uF.
Not sure if
it's a start or run capacitor.
Sounds a bit high to me
 
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T

The Natural Philosopher

The said:
Hi All

I have an acquaintance who is trying to repair a Bosch pressure washer.

The faulty component appears to be a capacitor rated at 25uF. Not sure if
it's a start or run capacitor. Maplins stock the same make but only in 20uF
or 30uF.

Can either of these be used instead - and which one?

TIA
Either. Needs to be 400v AC rated
 
T

The3rd Earl Of Derby

The said:
Hi All

I have an acquaintance who is trying to repair a Bosch pressure
washer.

The faulty component appears to be a capacitor rated at 25uF. Not
sure if it's a start or run capacitor. Maplins stock the same make
but only in 20uF or 30uF.

Can either of these be used instead - and which one?

TIA
Is it yellow and squarish in shape? if so my guess is its a spark
suppressor cap and 30uF will suffice.
 
R

robgraham

That sounds unlikely with the size of capacitance given. Spark
suppression capacitors require a low ESR to absorb the RF and a
capacitor of 25uF is not going to have that typically. Spark
suppressors are normally in the 0.1uF range - further I doubt that
pressure washers use universal motors so there are no sparks to
suppress.

I converted a 2kw motor from a broken pressure washer to run my
circular saw some time back. In doing so I had to replace the timer
capacitor and the start/run capacitors. The timer capacitor in my case
was in an electronic circuit and was small - the start/run capacitors
were like the ones shown in the Maplin advert and were of that physical
size, voltage and tolerance. If it is a timer capacitor it is most
likely to be electrolytic and have a tolerance in the order of 50% or
more, so any of the values given will do.

The Maplin site has a website http://www.lcrcapacitors.co.uk/ - see
if that gives any guidance on the accuracy requirement of start/run
caps. As pressure washers are run for quite short periods I wouldn't
have thought that a slight change would have made much difference and I
would go for the 30uF.

Rob
 
D

Dave Plowman (News)

Is it yellow and squarish in shape? if so my guess is its a spark
suppressor cap and 30uF will suffice.
Sounds a bit big to me for RF suppression. The range of these tends to be
about 0.01 - 1µF.
 
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T

The Natural Philosopher

The3rd said:
Is it yellow and squarish in shape? if so my guess is its a spark
suppressor cap and 30uF will suffice.
well its always nice to see complete and utter ignorance displayed on
the forum isn't it?
 
R

raden

The Natural said:
well its always nice to see complete and utter ignorance displayed on
the forum isn't it?
What forum ?

it's a newsgroup
 
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T

The Natural Philosopher

raden said:
What forum ?

it's a newsgroup
Whatever. I switch between usenet and other web based discussion areas
so much. sometimes I forget which one I'm in.
 

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