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Motor start capacitor - value ?



 
 
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  #1  
Old September 10th 09, 12:45 PM posted to uk.d-i-y
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Posts: 164
Default Motor start capacitor - value ?

Have acquired an old pedestal drill with a
British Houston Thompson single phase 1/4hp motor
marked KF TD3205 type BS 2408

The motor start capacitor needs replacing but it has no visible markings
on it due to several paint coatings !

With capacitor removed the motor will run with a hand start and I can
hear what I assume is a centrifugal switch clicking on spin up and spin
down.

Any advice on what size capacitor to buy and try ?
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  #2  
Old September 10th 09, 03:44 PM posted to uk.d-i-y
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Posts: 18,600
Default Motor start capacitor - value ?

robert wrote:
Have acquired an old pedestal drill with a
British Houston Thompson single phase 1/4hp motor
marked KF TD3205 type BS 2408

The motor start capacitor needs replacing but it has no visible markings
on it due to several paint coatings !

With capacitor removed the motor will run with a hand start and I can
hear what I assume is a centrifugal switch clicking on spin up and spin
down.

Any advice on what size capacitor to buy and try ?



IIRC about 2.2uF 450V DC or 250v AC is the approved sort of size. For
a sport of one horsepower motor thing.


  #3  
Old September 10th 09, 04:02 PM posted to uk.d-i-y
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Posts: 177
Default Motor start capacitor - value ?

On 10 Sep, 14:44, The Natural Philosopher
wrote:
robert wrote:
Have acquired an old pedestal drill with a
British Houston Thompson single phase 1/4hp motor
marked KF TD3205 type BS 2408


The motor start capacitor needs replacing but it has no visible markings
on it *due to several paint coatings !


With capacitor removed the motor will run with a hand start and I can
hear what I assume is a centrifugal switch clicking on spin up and spin
down.


Any advice on what size capacitor to buy and try ?


* IIRC about 2.2uF 450V DC or 250v AC is the approved sort of size. For
a sport of one horsepower motor thing.


Go to a company that does motor rewinding as a supplier (Yellow Pages)
- and of course they will be able to tell you anyway.

Rob
  #4  
Old September 10th 09, 09:59 PM posted to uk.d-i-y
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Posts: 18,600
Default Motor start capacitor - value ?

John Rumm wrote:
The Natural Philosopher wrote:
robert wrote:
Have acquired an old pedestal drill with a
British Houston Thompson single phase 1/4hp motor
marked KF TD3205 type BS 2408

The motor start capacitor needs replacing but it has no visible
markings on it due to several paint coatings !

With capacitor removed the motor will run with a hand start and I can
hear what I assume is a centrifugal switch clicking on spin up and
spin down.

Any advice on what size capacitor to buy and try ?



IIRC about 2.2uF 450V DC or 250v AC is the approved sort of size. For
a sport of one horsepower motor thing.


There seems to be quit a variation. The one on my 1hp dust collector was
100uF:

http://www.internode.co.uk/SIP/DSCN5328.JPG

bloody eck. Thats biog that is. I did have one lying round on me desk,
but it got 'tidied up'.

It isn't that critical., Its just to 'nudge' the motor in the right
direction. Too small and the motor wont start or may start
backwards..that's all.

http://www.remco.co.uk/products/capa...stud_mount.htm

i'll be buggered everything from 1 to 100uF seems to be available.
  #5  
Old September 10th 09, 10:53 PM posted to uk.d-i-y
external usenet poster
 
Posts: 754
Default Motor start capacitor - value ?

On 10 Sep, 11:45, robert wrote:
Have acquired an old pedestal drill with a
British Houston Thompson single phase 1/4hp motor
marked KF TD3205 type BS 2408

The motor start capacitor needs replacing but it has no visible markings
on it *due to several paint coatings !

With capacitor removed the motor will run with a hand start and I can
hear what I assume is a centrifugal switch clicking on spin up and spin
down.

Any advice on what size capacitor to buy and try ?


A 70 watt burner motor takes a 4 microfarad. Multiplying up a 1/4 hp
should be about 187 watts so try as a beginning 11 or 12 microfarad.
Make sure any cap you try is rated for mains ac. if it helps you could
use 3 of the burner motor caps in parallel. I got mine from Farnell
Components a few years ago
  #6  
Old September 10th 09, 11:47 PM posted to uk.d-i-y
external usenet poster
 
Posts: 3,574
Default Motor start capacitor - value ?

On Sep 10, 9:53*pm, cynic wrote:
On 10 Sep, 11:45, robert wrote:

Have acquired an old pedestal drill with a
British Houston Thompson single phase 1/4hp motor
marked KF TD3205 type BS 2408


The motor start capacitor needs replacing but it has no visible markings
on it *due to several paint coatings !


With capacitor removed the motor will run with a hand start and I can
hear what I assume is a centrifugal switch clicking on spin up and spin
down.


Any advice on what size capacitor to buy and try ?


A 70 watt burner motor takes a 4 microfarad. Multiplying up a 1/4 hp
should be about 187 watts so try as a beginning 11 or 12 microfarad.
Make sure any cap you try is rated for mains ac. if it helps you could
use 3 of the burner motor caps in parallel. I got mine from Farnell
Components a few years ago


IIRC motor caps need to be rated to higher than mains voltage, typ
600v.


NT
  #7  
Old September 10th 09, 11:51 PM posted to uk.d-i-y
external usenet poster
 
Posts: 339
Default Motor start capacitor - value ?


"The Natural Philosopher" wrote in message
...
John Rumm wrote:
The Natural Philosopher wrote:
robert wrote:
Have acquired an old pedestal drill with a
British Houston Thompson single phase 1/4hp motor
marked KF TD3205 type BS 2408

The motor start capacitor needs replacing but it has no visible
markings on it due to several paint coatings !

With capacitor removed the motor will run with a hand start and I can
hear what I assume is a centrifugal switch clicking on spin up and spin
down.

Any advice on what size capacitor to buy and try ?


IIRC about 2.2uF 450V DC or 250v AC is the approved sort of size. For a
sport of one horsepower motor thing.


There seems to be quit a variation. The one on my 1hp dust collector was
100uF:

http://www.internode.co.uk/SIP/DSCN5328.JPG

bloody eck. Thats biog that is. I did have one lying round on me desk, but
it got 'tidied up'.

It isn't that critical., Its just to 'nudge' the motor in the right
direction. Too small and the motor wont start or may start
backwards..that's all.

http://www.remco.co.uk/products/capa...stud_mount.htm

i'll be buggered everything from 1 to 100uF seems to be available.


I would suggest to the OP, that he probably won't go far wrong in choosing a
replacement cap of the same size or volume, assuming that the voltage rating
is the same of course.

It depends on the capacitor construction, it's age, but generally for motor
start capacitors, the value and voltage rating determine the size/volume.


  #8  
Old September 11th 09, 09:35 AM posted to uk.d-i-y
external usenet poster
 
Posts: 177
Default Motor start capacitor - value ?

On 10 Sep, 22:51, "Fredxx" wrote:
"The Natural Philosopher" wrote in ...



John Rumm wrote:
The Natural Philosopher wrote:
robert wrote:
Have acquired an old pedestal drill with a
British Houston Thompson single phase 1/4hp motor
marked KF TD3205 type BS 2408


The motor start capacitor needs replacing but it has no visible
markings on it *due to several paint coatings !


With capacitor removed the motor will run with a hand start and I can
hear what I assume is a centrifugal switch clicking on spin up and spin
down.


Any advice on what size capacitor to buy and try ?


*IIRC about 2.2uF 450V DC or 250v AC is the approved sort of size. For a
sport of one horsepower motor thing.


There seems to be quit a variation. The one on my 1hp dust collector was
100uF:


http://www.internode.co.uk/SIP/DSCN5328.JPG


bloody eck. Thats biog that is. I did have one lying round on me desk, but
it got 'tidied up'.


It isn't that critical., Its just to 'nudge' the motor in the right
direction. Too small and the motor wont start or may start
backwards..that's all.


http://www.remco.co.uk/products/capa...pacitors_stud_...


i'll be buggered everything from 1 to 100uF seems to be available.


I would suggest to the OP, that he probably won't go far wrong in choosing a
replacement cap of the same size or volume, assuming that the voltage rating
is the same of course.

It depends on the capacitor construction, it's age, but generally for motor
start capacitors, the value and voltage rating determine the size/volume.


Same physical size/volume doesn't apply as modern capacitors are very
much smaller for the same capacitance and voltage rating.
  #9  
Old September 11th 09, 11:28 AM posted to uk.d-i-y
external usenet poster
 
Posts: 888
Default Motor start capacitor - value ?

On Thu, 10 Sep 2009 14:44:09 +0100, The Natural Philosopher wrote:

robert wrote:


Any advice on what size capacitor to buy and try ?



IIRC about 2.2uF 450V DC or 250v AC is the approved sort of size. For
a sport of one horsepower motor thing.


You'll find these in pre-loved (skip grade) central heating circulators
(pumps)



--
John Stumbles -- http://yaph.co.uk

What do you mean, talking about it isn't oral sex?
  #10  
Old September 11th 09, 09:44 PM posted to uk.d-i-y
external usenet poster
 
Posts: 3,864
Default Motor start capacitor - value ?

In message , YAPH
writes
On Thu, 10 Sep 2009 14:44:09 +0100, The Natural Philosopher wrote:

robert wrote:


Any advice on what size capacitor to buy and try ?



IIRC about 2.2uF 450V DC or 250v AC is the approved sort of size. For
a sport of one horsepower motor thing.


You'll find these in pre-loved (skip grade) central heating circulators
(pumps)

Although the capacitor might well be the reason why the pump is in the
skip ...

--
geoff
 




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