Pond pump speed control

[Tim Downie]

Is is possible to use a speed controller (like a light dimmer) with a small
pond pump?

I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit more
powerful than I need. The motor has a solid rotor that appears to be made
of a ferrite like material.

I know that speed controllers can cause overheating problems with some
motors but given that it's underwater with water bathing the rotor, I don't
imagine this would be a problem in this case.

Tim
--
Remove the obvious to reply by email.

[BigWallop]

"Tim Downie" > wrote in message
...
> Is is possible to use a speed controller (like a light dimmer) with a small
> pond pump?
>
> I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit more
> powerful than I need. The motor has a solid rotor that appears to be made
> of a ferrite like material.
>
> I know that speed controllers can cause overheating problems with some
> motors but given that it's underwater with water bathing the rotor, I don't
> imagine this would be a problem in this case.
>
> Tim
>

Unless you want to boil the water. It is simpler to install a restriction washer to
the outlet spout I would think. If the diameter of the spout is, say, 10 mm full
bore. Then placing a washer with a hole size of 5 mm should greatly reduce the output
from the spout.

Is the fancy head removable ? If it is, then put a small rubber washer with a smaller
hole on top before you put the head back on.


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[Mickey]

Get a smaller pump it may pay for itself in electricity.

"Tim Downie" > wrote in message
...
> Is is possible to use a speed controller (like a light dimmer) with a
> small
> pond pump?
>
> I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit more
> powerful than I need. The motor has a solid rotor that appears to be made
> of a ferrite like material.
>
> I know that speed controllers can cause overheating problems with some
> motors but given that it's underwater with water bathing the rotor, I
> don't
> imagine this would be a problem in this case.
>
> Tim
> --
> Remove the obvious to reply by email.
>

[Andy McKenzie]

"Mickey" > wrote in message
...
> Get a smaller pump it may pay for itself in electricity.
>
> "Tim Downie" > wrote in message
> ...
> > Is is possible to use a speed controller (like a light dimmer) with a
> > small
> > pond pump?
> >
> > I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit
more
> > powerful than I need. The motor has a solid rotor that appears to be
made
> > of a ferrite like material.
> >
> > I know that speed controllers can cause overheating problems with some
> > motors but given that it's underwater with water bathing the rotor, I
> > don't
> > imagine this would be a problem in this case.
> >

Quick calculation - 3000 l/hr pump takes 30 Watts - 1500l/hr pump takes 20
watts, so you save 10 watts switching to a smaller pump. 10 watts costs
about £5 assuming you run the pump 24*7, pumps cost £50, so you only save
money by changing the pump after 10 years!

Of course these numbers are almost certainly wrong!

I thought the best way to control the flow would be to bleed some water off
before the fountain/filter or whatever is taking too much water.

Andy

[Gale Pearce]

You can restrict the outflow side of the pump, but not the intake or you
will burn out your pump prematurely - I use a "ball valve" to reduce the
waterflow on my submersible pump on the line to my filter
Gale :~)
"Tim Downie" > wrote in message
...
> Is is possible to use a speed controller (like a light dimmer) with a
small
> pond pump?
>
> I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit more
> powerful than I need. The motor has a solid rotor that appears to be made
> of a ferrite like material.
>
> I know that speed controllers can cause overheating problems with some
> motors but given that it's underwater with water bathing the rotor, I
don't
> imagine this would be a problem in this case.
>
> Tim
> --
> Remove the obvious to reply by email.
>

Easy solution just screw a splitter onto it and divert the extra water to a
spitter or your water fall....MIKE
"Tim Downie" > wrote in message
...
> Is is possible to use a speed controller (like a light dimmer) with a
small
> pond pump?
>
> I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit more
> powerful than I need. The motor has a solid rotor that appears to be made
> of a ferrite like material.
>
> I know that speed controllers can cause overheating problems with some
> motors but given that it's underwater with water bathing the rotor, I
don't
> imagine this would be a problem in this case.
>
> Tim
> --
> Remove the obvious to reply by email.
>

[Benign Vanilla]

"Tim Downie" > wrote in message
...
> Is is possible to use a speed controller (like a light dimmer) with a
small
> pond pump?
>
> I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit more
> powerful than I need. The motor has a solid rotor that appears to be made
> of a ferrite like material.
>
> I know that speed controllers can cause overheating problems with some
> motors but given that it's underwater with water bathing the rotor, I
don't
> imagine this would be a problem in this case.

I'd suggest the following...

1. Get a new smaller pump, and sell this one on eBay. Your electric bill
will thank you.
2. Attach a short piece of hose, and a valve downstream from the pump. It's
not a problem to restrict the output of the pump. You don't want to restrict
the input.

BV.

[Ian Stirling]

In uk.d-i-y Benign Vanilla > wrote:
>
> "Tim Downie" > wrote in message
> ...
>> Is is possible to use a speed controller (like a light dimmer) with a
> small
>> pond pump?
>>
>> I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit more
>> powerful than I need. The motor has a solid rotor that appears to be made
>> of a ferrite like material.
>>
>> I know that speed controllers can cause overheating problems with some
>> motors but given that it's underwater with water bathing the rotor, I
> don't
>> imagine this would be a problem in this case.
>
> I'd suggest the following...
>
> 1. Get a new smaller pump, and sell this one on eBay. Your electric bill
> will thank you.

Pumps may use less than sticker ratings.
I have several 600W submersible pumps, that are (IIRC) 3000l/sec, from
lidl.
I stuck a meter on them, and they come out at around 360W.

[Geoff Beale]

BigWallop wrote:
>
> Unless you want to boil the water. It is simpler to install a
> restriction washer to the outlet spout I would think. If the
> diameter of the spout is, say, 10 mm full bore. Then placing a
> washer with a hole size of 5 mm should greatly reduce the output from
> the spout.
>
> Is the fancy head removable ? If it is, then put a small rubber
> washer with a smaller hole on top before you put the head back on.
>
>
> ---
> http://www.basecuritysystems.no-ip.com
>
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.688 / Virus Database: 449 - Release Date: 18/05/04

Rather than waste the pump's output by restricting it, run a "T" off the
output side and divert some of the flow to a home-made venturi (another
"T" with a restrictor on the long side and and an air intake tube into
the short side - you have to experiment a bit to get it right). This
will add valuable oxygenation to your pond and add a little more
movement to the water. Balance the flow between the two outputs with
ball valves on the hoses.
--
Geoff Beale
Extract digit to email.

[Ian Stirling]

In uk.d-i-y Tim Downie > wrote:
> Is is possible to use a speed controller (like a light dimmer) with a small
> pond pump?
>
> I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit more
> powerful than I need. The motor has a solid rotor that appears to be made
> of a ferrite like material.
>
> I know that speed controllers can cause overheating problems with some
> motors but given that it's underwater with water bathing the rotor, I don't
> imagine this would be a problem in this case.

In this case, simple speed controllers won't actually work, it'll stay at
a constant speed (3000RPM) until it stops working, and hums loudly.
Suitable speed controllers are going for around 40-50 quid on ebay.
Search on
inverter phase motor induction
on ebay, searching titles and descriptions.

[Tim Downie]

Gale Pearce wrote:
> You can restrict the outflow side of the pump, but not the intake or
> you will burn out your pump prematurely - I use a "ball valve" to
> reduce the waterflow on my submersible pump on the line to my filter
> Gale :~)

I've already got a restrictor and T-piece on the pump outlet so I can
control the output at present. Somehow it doesn't feel "right" to reduce
the flow this way. I can't help feeling that it's putting extra load on the
pump. As I have a reasonably hefty lamp dimmer kicking around, I was just
wondering if using a device like this would be more mechanically
"sympathetic" IYKWIM. (Probably complete nonsense I know).

Tim

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Remove the obvious to reply by email.

[John Laird]

On Fri, 21 May 2004 11:20:01 +0100, "Tim Downie"
> wrote:

>Is is possible to use a speed controller (like a light dimmer) with a small
>pond pump?
>
>I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit more
>powerful than I need. The motor has a solid rotor that appears to be made
>of a ferrite like material.
>
>I know that speed controllers can cause overheating problems with some
>motors but given that it's underwater with water bathing the rotor, I don't
>imagine this would be a problem in this case.

Pace "Home Improvement", there is no such concept to a man as "too much
power". What you need is more pond...

--
Too much month at the end of the money.

Mail john rather than nospam...

[Benign Vanilla]

"John Laird" > wrote in message
...
> On Fri, 21 May 2004 11:20:01 +0100, "Tim Downie"
> > wrote:
>
> >Is is possible to use a speed controller (like a light dimmer) with a
small
> >pond pump?
> >
> >I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit
more
> >powerful than I need. The motor has a solid rotor that appears to be
made
> >of a ferrite like material.
> >
> >I know that speed controllers can cause overheating problems with some
> >motors but given that it's underwater with water bathing the rotor, I
don't
> >imagine this would be a problem in this case.
>
> Pace "Home Improvement", there is no such concept to a man as "too much
> power". What you need is more pond...
>
> --
> Too much month at the end of the money.

Well put.

[Jeff Lowe]

"Tim Downie" > wrote in message
...
> Gale Pearce wrote:
> > You can restrict the outflow side of the pump, but not the intake or
> > you will burn out your pump prematurely - I use a "ball valve" to
> > reduce the waterflow on my submersible pump on the line to my filter
> > Gale :~)
>
> I've already got a restrictor and T-piece on the pump outlet so I can
> control the output at present. Somehow it doesn't feel "right" to reduce
> the flow this way. I can't help feeling that it's putting extra load on
the
> pump. As I have a reasonably hefty lamp dimmer kicking around, I was
just
> wondering if using a device like this would be more mechanically
> "sympathetic" IYKWIM. (Probably complete nonsense I know).

Since these are just turbine pumps, there is no difference as far as the
pump is concerned as to the location of the restriction on either the input
or output. I would not use a lamp dimmer since these are typically just
triacs and have a spiky output waveform which will cause motor heating,
however a variable speed control for a ceiling fan should work fine. One
other aspect to be aware of is that many pumps use either a fan or in the
case of submersibles, water to cool the motor. In this case any restriction
of flow, either by speed control, or by restriction may result in some
heating and should be watched.

Jeff Lowe

[Lurch]

On Fri, 21 May 2004 17:05:22 +0100, in uk.d-i-y "Tim Downie"
> strung together this:

>I've already got a restrictor and T-piece on the pump outlet so I can
>control the output at present. Somehow it doesn't feel "right" to reduce
>the flow this way.

If you read the instructions on most pumps that's how it's supposed to
be done. And under high pressure it probably would put additional
strain on the pump, but not really a concern at low pressures.
--

SJW
A.C.S. Ltd.

[Benign Vanilla]

"Jeff Lowe" > wrote in message
...
<snip>
> Since these are just turbine pumps, there is no difference as far as the
> pump is concerned as to the location of the restriction on either the
input
> or output.
<snip>

I have often wondered about that and assumed that by restricting the input
the pump would be able to empty the chamber faster then it could fill it
causes the chamber to be a mix of air and water, whereas if you restrict the
output, the chamber will retain more water and less air. Surely both ways
make the pump work a bit harder, but it seems to be restricting the output
is better for it then restricting the input.

BV.

[tg]

It is generally best never to restrict the input of a pump. I did not get to
see the original pump type, but many explicitly spell that out in their
directions as it does for my Sequence pump. Try to "reuse" the pump pressure
in other ways - redirect part to a filter/waterfall. Restricting the pump on
the output side is the same as adding head pressure due to vertical pump
height, fitting losses, change in pipe diameter etc... All reduce flow
rates.
Tim

"Benign Vanilla" > wrote in message
...
>
> "Jeff Lowe" > wrote in message
> ...
> <snip>
> > Since these are just turbine pumps, there is no difference as far as the
> > pump is concerned as to the location of the restriction on either the
> input
> > or output.
> <snip>
>
> I have often wondered about that and assumed that by restricting the input
> the pump would be able to empty the chamber faster then it could fill it
> causes the chamber to be a mix of air and water, whereas if you restrict
the
> output, the chamber will retain more water and less air. Surely both ways
> make the pump work a bit harder, but it seems to be restricting the output
> is better for it then restricting the input.
>
> BV.
>
>

[Ian Stirling]

In uk.d-i-y Jeff Lowe > wrote:
>
> "Tim Downie" > wrote in message
> ...
>> Gale Pearce wrote:
>> > You can restrict the outflow side of the pump, but not the intake or
>> > you will burn out your pump prematurely - I use a "ball valve" to
>> > reduce the waterflow on my submersible pump on the line to my filter
>> > Gale :~)
>>
>> I've already got a restrictor and T-piece on the pump outlet so I can
>> control the output at present. Somehow it doesn't feel "right" to reduce
>> the flow this way. I can't help feeling that it's putting extra load on
> the
>> pump. As I have a reasonably hefty lamp dimmer kicking around, I was
> just
>> wondering if using a device like this would be more mechanically
>> "sympathetic" IYKWIM. (Probably complete nonsense I know).
>
> Since these are just turbine pumps, there is no difference as far as the
> pump is concerned as to the location of the restriction on either the input
> or output. I would not use a lamp dimmer since these are typically just

Cavitation is a real concern if you put it on the input.
This does cause RAPID wear on the impeller.

[Jeff Lowe]

"Ian Stirling" > wrote in message
...
> In uk.d-i-y Jeff Lowe > wrote:
> >
> > "Tim Downie" > wrote in message
> > ...
> >> Gale Pearce wrote:
> >> > You can restrict the outflow side of the pump, but not the intake or
> >> > you will burn out your pump prematurely - I use a "ball valve" to
> >> > reduce the waterflow on my submersible pump on the line to my filter
> >> > Gale :~)
> >>
> >> I've already got a restrictor and T-piece on the pump outlet so I can
> >> control the output at present. Somehow it doesn't feel "right" to
reduce
> >> the flow this way. I can't help feeling that it's putting extra load
on
> > the
> >> pump. As I have a reasonably hefty lamp dimmer kicking around, I was
> > just
> >> wondering if using a device like this would be more mechanically
> >> "sympathetic" IYKWIM. (Probably complete nonsense I know).
> >
> > Since these are just turbine pumps, there is no difference as far as the
> > pump is concerned as to the location of the restriction on either the
input
> > or output. I would not use a lamp dimmer since these are typically just
>
> Cavitation is a real concern if you put it on the input.
> This does cause RAPID wear on the impeller.

Since we were talking about lamp dimmers I guess I assumed we were talking
fractional horsepower. I didn't think these capable of enough suction get
below water's vapor pressure at pond temperature. I mean that's 29" Hg. Of
course some ponds and pumps are bigger than others ;-)

Jeff

[Ian Stirling]

In uk.d-i-y Jeff Lowe > wrote:
> "Ian Stirling" > wrote in message
> ...
>> In uk.d-i-y Jeff Lowe > wrote:
>> >
>> > "Tim Downie" > wrote in message
>> > ...
>> >> Gale Pearce wrote:
>> >> > You can restrict the outflow side of the pump, but not the intake or
>> >> > you will burn out your pump prematurely - I use a "ball valve" to
>> >> > reduce the waterflow on my submersible pump on the line to my filter
>> >> > Gale :~)
>> >>
>> >> I've already got a restrictor and T-piece on the pump outlet so I can
>> >> control the output at present. Somehow it doesn't feel "right" to
> reduce
>> >> the flow this way. I can't help feeling that it's putting extra load
> on
>> > the
>> >> pump. As I have a reasonably hefty lamp dimmer kicking around, I was
>> > just
>> >> wondering if using a device like this would be more mechanically
>> >> "sympathetic" IYKWIM. (Probably complete nonsense I know).
>> >
>> > Since these are just turbine pumps, there is no difference as far as the
>> > pump is concerned as to the location of the restriction on either the
> input
>> > or output. I would not use a lamp dimmer since these are typically just
>>
>> Cavitation is a real concern if you put it on the input.
>> This does cause RAPID wear on the impeller.
>
> Since we were talking about lamp dimmers I guess I assumed we were talking
> fractional horsepower. I didn't think these capable of enough suction get
> below water's vapor pressure at pond temperature. I mean that's 29" Hg. Of
> course some ponds and pumps are bigger than others ;-)

That's not quite how it works.
The large amount of turbulence in the pump means that the pressure
varies quite a lot.
It's quite easy to get pressure locally to fall down below the vapour
pressure.
Then the bubbles collapse, and the rebound is VERY powerful.
This happens even to speedboat propellers ofr example.

[Mickey]

3000LPH pump = 49L
1500LPH pump = 49L

Using real numbers from Via Aqua pumps
3000 lph = 45 watts
1500 lph = 15 watts
30 watts x 24 hours = 720 watts perday
365 days x 720watts = 262800
262.8 kwatts x .5L (your pricing) = 131.4L
Pump pays for itself in 4.5 months @49L


How did you do your caculations?
10 watts per hour x 24 hours = 240 watts per day.
365 days x 240 = 87,600 watts
87.6 kwatts x .5L (your pricing) = 43.8l
Pump pays for itself in 13.2 months.

"Andy McKenzie" > wrote in message
...
> "Mickey" > wrote in message
> ...
>> Get a smaller pump it may pay for itself in electricity.
>>
>> "Tim Downie" > wrote in message
>> ...
>> > Is is possible to use a speed controller (like a light dimmer) with a
>> > small
>> > pond pump?
>> >
>> > I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit
> more
>> > powerful than I need. The motor has a solid rotor that appears to be
> made
>> > of a ferrite like material.
>> >
>> > I know that speed controllers can cause overheating problems with some
>> > motors but given that it's underwater with water bathing the rotor, I
>> > don't
>> > imagine this would be a problem in this case.
>> >
>
> Quick calculation - 3000 l/hr pump takes 30 Watts - 1500l/hr pump takes 20
> watts, so you save 10 watts switching to a smaller pump. 10 watts costs
> about £5 assuming you run the pump 24*7, pumps cost £50, so you only save
> money by changing the pump after 10 years!
>
> Of course these numbers are almost certainly wrong!
>
> I thought the best way to control the flow would be to bleed some water
> off
> before the fountain/filter or whatever is taking too much water.
>
> Andy
>
>

[Scott Mills]

"Geoff Beale" > wrote in message
...
>

> > Outgoing mail is certified Virus Free.
> > Checked by AVG anti-virus system (http://www.grisoft.com).
> > Version: 6.0.688 / Virus Database: 449 - Release Date: 18/05/04
>
> Rather than waste the pump's output by restricting it, run a "T" off the
> output side and divert some of the flow to a home-made venturi (another
> "T" with a restrictor on the long side and and an air intake tube into
> the short side - you have to experiment a bit to get it right). This
> will add valuable oxygenation to your pond and add a little more
> movement to the water. Balance the flow between the two outputs with
> ball valves on the hoses.



Nice idea, but I doubt he needs anymore oxygen being added to the pond if
there is a a reasonable amount of water movement at the surface. Indeed too
much disolved O2 is bad, as it reduces the waters ability to carry CO2 which
is needed for plant life. Often putting too much O2 in will simply cause
algee to thrive.

Scott

[Geoff Beale]

Scott Mills wrote:
> Nice idea, but I doubt he needs anymore oxygen being added to the
> pond if there is a a reasonable amount of water movement at the
> surface. Indeed too much disolved O2 is bad, as it reduces the waters
> ability to carry CO2 which is needed for plant life. Often putting
> too much O2 in will simply cause algee to thrive.
>
> Scott

The jet from a venturi is said to stabilize the level of oxygen and
prevent over-oxygenation. Adequate planting is the key to algae
control.
--
Geoff Beale
Extract digit to email.

[Andrew Burgess]

>Nice idea, but I doubt he needs anymore oxygen being added to the pond if
>there is a a reasonable amount of water movement at the surface. Indeed too
>much disolved O2 is bad, as it reduces the waters ability to carry CO2 which
>is needed for plant life.

The way I remember it is that surface agitation enables CO2 to reach
equilibrium with the atmosphere which is a low value. Without agitation it
tends to supersaturate (assuming CO2 producers like fish) which is better for
submersed plants, not a factor for plants with leaves in the air.

[HTH]

Ian Stirling wrote:

> In uk.d-i-y Tim Downie > wrote:
>
>>Is is possible to use a speed controller (like a light dimmer) with a small
>>pond pump?
>>
>>I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit more
>>powerful than I need. The motor has a solid rotor that appears to be made
>>of a ferrite like material.
>>
>>I know that speed controllers can cause overheating problems with some
>>motors but given that it's underwater with water bathing the rotor, I don't
>>imagine this would be a problem in this case.
>
>
> In this case, simple speed controllers won't actually work, it'll stay at
> a constant speed (3000RPM) until it stops working, and hums loudly.

I am not sure about the following and it would apply only to mag drive
pumps.

The pump works because the magnet is forced to follow the rotating
magnetic field. When the pump is "dimmed" the field becomes weak and
will be unable to force the magnet to stay ahead of it. As the rotating
field passes the magnet it will slightly demagnetize the magnet. In
time it will weaken the magnet to the point that the impeller will not
work at all.

The same thing happens when you restrict the output and it causes the
impeller to slow down. If the field is strong enough to keep the magnet
in sync with the rotating field even with the restriction then this is
not a problem. But I do not think it is alway the case.

HTH



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[Ian Stirling]

In uk.d-i-y HTH > wrote:
> Ian Stirling wrote:
>
>> In uk.d-i-y Tim Downie > wrote:
>>
>>>Is is possible to use a speed controller (like a light dimmer) with a small
>>>pond pump?
>>>
>>>I have a Bermuda 3000 (3000l/hr) submersible pump that's really a bit more
>>>powerful than I need. The motor has a solid rotor that appears to be made
>>>of a ferrite like material.
>>>
>>>I know that speed controllers can cause overheating problems with some
>>>motors but given that it's underwater with water bathing the rotor, I don't
>>>imagine this would be a problem in this case.
>>
>>
>> In this case, simple speed controllers won't actually work, it'll stay at
>> a constant speed (3000RPM) until it stops working, and hums loudly.
>
> I am not sure about the following and it would apply only to mag drive
> pumps.
>
> The pump works because the magnet is forced to follow the rotating
> magnetic field. When the pump is "dimmed" the field becomes weak and
> will be unable to force the magnet to stay ahead of it. As the rotating
> field passes the magnet it will slightly demagnetize the magnet. In
> time it will weaken the magnet to the point that the impeller will not
> work at all.

The case is similar to when the pump is just started, or the impeller
is stalled.
Magnets in general only demagnetise if you exceed the maximum field.
They generally do the first time it does, not over time.
So, probably not.

[Tim Downie]

"Ian Stirling" > wrote in message
...

> In this case, simple speed controllers won't actually work, it'll stay at
> a constant speed (3000RPM) until it stops working, and hums loudly.
> Suitable speed controllers are going for around 40-50 quid on ebay.
> Search on
> inverter phase motor induction
> on ebay, searching titles and descriptions.

Well, in the spirit of experimentation (and 4 glasses of wine) I decided I
just had to try it. The lamp dimmer, in the best traditions of DIY, was
scavenged from the next door neighbours bin. I wired it up, tested it with
a lamp and then plugged a smaller version of the same pump in to it.

As you said,initially no change and then just a sudden cessation of pumping.
Maybe a smaller pump will be the easiest option.

Cheers.

Tim

[Mike Patterson]

On Sat, 22 May 2004 22:51:30 +0100, "Tim Downie"
> wrote:

>
>"Ian Stirling" > wrote in message
...
>
>> In this case, simple speed controllers won't actually work, it'll stay at
>> a constant speed (3000RPM) until it stops working, and hums loudly.
>> Suitable speed controllers are going for around 40-50 quid on ebay.
>> Search on
>> inverter phase motor induction
>> on ebay, searching titles and descriptions.
>
>Well, in the spirit of experimentation (and 4 glasses of wine) I decided I
>just had to try it. The lamp dimmer, in the best traditions of DIY, was
>scavenged from the next door neighbours bin. I wired it up, tested it with
>a lamp and then plugged a smaller version of the same pump in to it.
>
>As you said,initially no change and then just a sudden cessation of pumping.
>Maybe a smaller pump will be the easiest option.
>
>Cheers.
>
>Tim
>
Lamp dimmers do ther job by chopping off the peaks of the power's sine
wave.

Run an electric motor through it and you're likely to get a fried
motor, assuming the dimmer doesn't overload and smoke first.

HTH, hope it's not too late for you. :-)
When you let the "go-smoke' out of electronics, they won't go anymore.

Mike


Mike Patterson
Please remove the spamtrap to email me.
"I always wanted to be somebody. I should have been more specific..."

[jammer]

On Fri, 21 May 2004 17:35:43 +0100, John Laird
> wrote:

>--
>Too much month at the end of the money.

I couldn't have said that better.

[Andrew Burgess]

>> In this case, simple speed controllers won't actually work, it'll stay at
>> a constant speed (3000RPM) until it stops working, and hums loudly.
>> Suitable speed controllers are going for around 40-50 quid on ebay.
>> Search on
>> inverter phase motor induction
>> on ebay, searching titles and descriptions.

>Well, in the spirit of experimentation (and 4 glasses of wine) I decided I
>just had to try it. The lamp dimmer, in the best traditions of DIY, was
>scavenged from the next door neighbours bin. I wired it up, tested it with
>a lamp and then plugged a smaller version of the same pump in to it.

I had the opposite result. I used a fan speed control which is just a
dimmer with a snubber to protect the triac. The speed changed just fine.
This was before I purchased the Kill-a-watt meter so I didn't measure
the energy usage.