Shower pump question

Hi

My father-in-law has just installed a Stuart Turner pump which he's had lying around (indoors) for about 4 years. He's plumbed in the hot and cold feeds and outlets, and the wiring has been done by (or checked by) a sparks.

When he turns the water on, both the hot and cold flow through the pump and out of his shower head, but the pump only makes a humming noise and gets hot (apparently).

He removed it today for inspection and noticed that, upon removing either end cover (to access the impeller bit), that it seems to be stiffer than would be expected when trying to turn. I had expected the motor to spin freely, but then, what do I know!?

And, as an aside, how do the flow sensors work? They just seem to be sealed plastic boxes on the end of a wire.

Ta.

Reply to
Grumps
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It could be working normally. It depends how hot it gets and how stiff the impellors are to turn. He needs to compare his pump with another to know.

Reply to
Rednadnerb

Please ignore my last post.

Reply to
Rednadnerb

Both of the pumps that I have had, have turned completely freely, as you would expect. Just a hum and getting very hot, would indicate that it is stalled. the sensors are magnets in a holder that is *just* too heavy to float. As the water starts to flow upwards through the chambers, the magnet holders are carried up on the flow. Located by the side of each of the chamber upper limits, is a reed switch. When the magnet comes up parallel to the reed, it closes, switching on the electronic speed control circuitry for the pump motor. The reed switches are in a low voltage part of the circuit.

Arfa

Reply to
Arfa Daily

They use magnetic flow switches like wot you describe on diesel fired hot water pressure washers. You can test them by passing a magnet next to them - you can usually hear the reed switch make.

If the pump has been lying around for a while it could just be crudded up. If left with water in it, could just be stuck with a bit of limescale.

Reply to
The Medway Handyman

Thanks (both).

The pump has not been installed since purchased 4 years ago, so there shouldn't be any crud.

I'll have a word with S-T and see what to do next. May have to strip it completely (if possible).

Reply to
Grumps

It is an induction motor with a start capacitor, they have a shelf life of about 3 to 4 years IIRC (if not used), and give the symptoms you describe, take the numbers off it and try RS for an equivalent.

I have just been through this with a oil burner motor, if you flicked the switch on an off a couple of times it would sometimes start. I first of all thought it was the motor bearings, but dragging the old grey cells, electrical theory from 30 years ago, this was the cheaper option! Our local heating engineer who I know, diagnosis , 'new motor needed gov' Motor £100+, (no chance) start capacitor from local oil spares emporium £23.., RS £4 internet, £1.40!! ( but you had to order 10!!) replaced the capacitor... sorted.

Des

Des

Reply to
Dieseldes

Thanks. That's interesting. And a dead cap would cause the motor to feel stiff to turn?

That'd be great if it was a simple as that. I had another cap problem recently where a sub-woofer power supply had gone bad. The manufacturer wanted £116 to mend it. It was sorted with a 9p cap from Farnell.

Reply to
Grumps

snip.

They are harder to to turn than a brushed moter (magnetic force and all that... hence the need for the capacitor!!) with the oil pump attached my one was almost impossible to turn with fingers.

a quick Google brought up this

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will probably be around 4uf 400V called Motor run capacitors.

My original one didn't have bolt end but a junior hacksaw soon sorted that ..these give you an idea of whats available

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they are so cheap and if left unused they have a short shelf life, it makes sense before any major strip down to replace it first. use the KISS principle.

Des

Reply to
Dieseldes

It should spin quite freely when switched off.

The cap died on my lawnmower (induction motor). In this case, it gradually died over two seasons, and was taking longer and longer to spin up, eventually not doing so at all. If you turned it on and then gave the blade a spin by hand, it would spin up to full speed, in either direction. Mindful of retaining all my fingers, I decided this was not a good long term proposition, and replaced the capacitor.

I have some equipment which has an induction motor with a run capacitor, and it also has electric breaking. I haven't investigated in detail, but I think it does the breaking by shorting out the capacitor (effectively driving both windings from same phase), so it may be that a shorted capacitor will tend to lock the rotor. It makes quite a significant hum noise whilst the electric breaking is applied, even when the rotor has stopped turning.

CPC is quite a good source of mains motor start/run capacitors.

Reply to
Andrew Gabriel

Shelf life of the start capacitor should be a /lot/ longer than that. However, on something of that size I'd expect the capacitor to be in use continuously as a phase shifter. Failure (or of the centrifugal switch) would possibly give the symptoms described.

Reply to
<me9

Have you shares in a company making capacitors. I've been in the electronics/electrical trade for over 40 years and haven't heard such drivel.

Electrolytic capacitors (which are polarised and unsuitable for use on AC) may need re-forming if unused for some time. Motor run capacitors are of a completely different construction.

Reply to
<me9

It would appear (it's not my pump), that the seals had stuck solid. S-T suggest that a shower pump is run at least once every 4 weeks, not once in 4 years! Anyway, with a bit of playing, the motor now spins free. Problem is, water dribbles our from the seals now. Maybe they've been dislodged by my father-in-law's playing, or maybe they've just had it! And they're not cheap to replace either. £17 each.

Do all induction motors have a centrifugal switch?

Reply to
Grumps

No. Only those with a start capacitor. Induction motors with a run capacitor (or multi-phase supply) or with shaded poles don't have one.

Reply to
Andrew Gabriel

No. Some (most small ones) have the phase shifted winding permanently powered.

Reply to
<me9

In t'olden days I worked for the Warwick Pump & Engineering Co, one of the early pressure washer manufacturers in the UK and they used Brook Thompson motors.

They had a start and a run capacitor and a centrifugal switch to chamge from one to the other. Constant cause of breakdowns, they got damp or mucky & wouldn't switch. I rather thought it would be done electronically in some way these days? Are they still commonly used?

Reply to
The Medway Handyman

I'm not absolutely convinced that that's true. The first pump that I had was a 'cheapo' - about 70 quid at the time, as I recall - light intermittent duty job, and the current one is a more expensive - about £110 I think - unit rated for continuous operation. They both came from different stables, but are constructed similarly. That's a motor in the middle and an impeller chamber unit at each end. Both had (have) speed control electronics in an enclosure on top. Now the thing is, I'm in the electronics business, so when I look at the control board, I basically understand what I am seeing, and it is nothing more or less than a perfectly bog-standard triac-based phase angle speed controller, which would suggest that it is a perfectly ordinary universal motor with brushgear. Also, induction motors are pretty near silent, but all the add-on shower pumps that I've heard, sound like a brush motor when running. My original one, which did stirling service over a number of years, used every day, failed in a way that suggested that the brushes had plain worn out. I think I still have it laying around somewhere. I'll have to see if it will come to bits, and take a look at exactly what motor type it is.

Arfa

Reply to
Arfa Daily

Thanks for the info. In this case, the Stuart Turner pump has an induction motor ( see page 10

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) with no centrifugal switch.

Reply to
Grumps

Interesting. So presumably pretty quiet, but no facility for adjusting the amount of boost that it provides ? In some installations, I could see that that might be a bit of a disadvantage. Although induction motors are long-lived compared to brush types, I'm not sure that would actually be much of an advantage, as the bearings would probably be wearing out on either type, first. Was it particularly expensive ? Looks as though it might be ...

Arfa

Reply to
Arfa Daily

It is currently very quiet as the seals have, er, well, sealed themselves tight; it doesn't run! I believe it was about £150-ish.

Reply to
Grumps

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