Compressor starters and the like?

[Alistair MacDonald]

Does anyone have any experience with compressors and starters for them? I am having a few issues with a dehumidifier and wondered if anyone could save me some reading. I appreciate the odds are against.

When powered up it starts fine once, but then will not start again until it has been left for a while. I don't know if this is the revise pressure or heat but my gut feeling tells me it is the former.

I have changed the starter for another lower impedance one and that does the same. I also tried running it on the secondary coil and using the primary as the starter as an experiment. This worked but I suspect it may not do so for long.

Has anyone any suggestions? Replacement starters are silly money as they are discontinued so it might be an case of simulating it with discreet components. Equally it could be the compressor on it's way out.

  Alistair

[Jon Davies]

Is the on/off cycle still the typical it has always been?

My fridge-freezer will exhibit the same issue you describe if I get a power cut (way oversensitive main RCD breaker!!!) whilst it is running, and then won't start, and the motor stall protection cuts it out.  I suspect the same in my case: back pressure causes the stall.

If the on/off cycle is now much shorter, it might not be enough time for the pressure to come down, hence the failure to start.  Might be worth checking the humidistat or whatever cycles the dehumidifier on and off.

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Cheers,

Jon.

[Alistair MacDonald]

Apart from the not starting it is behaving exactly the way it always has. I think it did this a few time for a week and then did it every time. It turns off when the air is not damp or when the grill is approaching freezing and that has always been somewhat random, so no change.

  Alistair

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Cheers,

Jon.

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[Alistair MacDonald]

I have just figured it is not back pressure. If the compressor is left powered but not turning for a long time it will not restart. If left unpowered for a long but shorter time it will restart. The power it is drawing when not turning is not a lot so it it not going to be a lot of heat, but this is probably what it is I guess.

  Alistair

[Jon Davies]

I'm a bit confused by the long but shorter time, but I guess you mean when it's powered off for slightly less time than when it is powered on, between typical compressor starting intervals :D

Do you think the heat might be affecting the magnetic field and weakening it enough to reduce the starting torque and stop the motor overcoming the initial mechanical resistance?  Perhaps there's an electrical fault meaning there's a not-so-quiescent current running through the coils...?

On Tue, 13 Mar 2018 at 13:47 Alistair MacDonald <alistair....@gmail.com> wrote:

I have just figured it is not back pressure. If the compressor is left powered but not turning for a long time it will not restart. If left unpowered for a long but shorter time it will restart. The power it is drawing when not turning is not a lot so it it not going to be a lot of heat, but this is probably what it is I guess.

  Alistair

On 11 March 2018 at 21:10, Alistair MacDonald <alistair....@gmail.com> wrote:

Apart from the not starting it is behaving exactly the way it always has. I think it did this a few time for a week and then did it every time. It turns off when the air is not damp or when the grill is approaching freezing and that has always been somewhat random, so no change.

  Alistair

On 11 March 2018 at 20:22, Jon Davies <jon.d...@gmail.com> wrote:

Is the on/off cycle still the typical it has always been?

My fridge-freezer will exhibit the same issue you describe if I get a power cut (way oversensitive main RCD breaker!!!) whilst it is running, and then won't start, and the motor stall protection cuts it out.  I suspect the same in my case: back pressure causes the stall.

If the on/off cycle is now much shorter, it might not be enough time for the pressure to come down, hence the failure to start.  Might be worth checking the humidistat or whatever cycles the dehumidifier on and off.

On Sun, 11 Mar 2018, 14:22 Alistair MacDonald, <alistair....@gmail.com> wrote:

Does anyone have any experience with compressors and starters for them? I am having a few issues with a dehumidifier and wondered if anyone could save me some reading. I appreciate the odds are against.

When powered up it starts fine once, but then will not start again until it has been left for a while. I don't know if this is the revise pressure or heat but my gut feeling tells me it is the former.

I have changed the starter for another lower impedance one and that does the same. I also tried running it on the secondary coil and using the primary as the starter as an experiment. This worked but I suspect it may not do so for long.

Has anyone any suggestions? Replacement starters are silly money as they are discontinued so it might be an case of simulating it with discreet components. Equally it could be the compressor on it's way out.

  Alistair

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Cheers,

Jon.

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Cheers,

Jon.

[Alistair MacDonald]

If I leave it unpowered for 10 minutes it will not start. If I leave it unpowered for about 30 minutes it will.

I am just not certain what it is. Nothing sounds all that plausible.

  Alistair

[David Pye]

Thermal cutout?

[Alistair MacDonald]

It never just stops on it's own. It just does not start. I have changed the starter so it is not a cutout on that.

  Alistair

Thermal cutout?

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Cheers,

Jon.

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Cheers,

Jon.

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