Dimmer Switch

[KWILParticipant @kwil]

Dave b

Have you seen the mess that some CH pumps have to circulate? Its more to do with lowered life of bearings before they actually stop.

[MuzzerParticipant @muzzer]

I have a Grundfos CH pump on my Bridgeport clone although it's the 3 speed version. I run mine on the high setting to get it primed quicker. As noted, you need to mount the inlet below the fluid level. Being paranoid, I have a plastic box under it (a shopping basket) in case it leaks, which of course it now hasn't.

These pumps are fine with a static head ie no flow. The only downside would be that it (and the fluid) would get warm after extended periods but why would you run the pump with zero flow anyway? And it wouldn't get very hot even then.

I simply vary the flow with the nozzle. If you want to get really clever you can download the flow characteristics for these pumps which show that they can develop a decent head but nothing too silly. Trying to vary the speed would seem rather pointless given the ease with which you can achieve the same outcome(!) with a simple tap. I'd post some pictures of my setup but there is very little to see…..

Merry

[Ed DuffnerParticipant @edduffner79357]

You used to be able to get dimmers for fluorescent lighting(inductive load). I wonder if these could be matched to a motor? In my ten years as an electrician I think I only fitted two of these units for lighting control and they were very expensive.

[MuzzerParticipant @muzzer]

Here's the flow characteristics for the Grundfos 15-50 pump in my system. BTW, it suggests you ensure at least 7.5% of the max flow as a minimum but as I said it's hardly critical. It can develop the best part of 5-6m head of water (suds) which was what I was checking when I found this.

[john fletcher 1Participant @johnfletcher1]

When I worked for BR we fitted dimmers to florescent lights in signal boxes, bascically, they kept the tube end cap heaters on and lowered the voltage via a transformer.I'm sure there is now a non repairable digital gadget full of 16 leg chips which dims lights much better. Regarding pole changing motors it might be easy to design them, but try sorting out the switching arangement when some thing goes faulty. I've recently been sorting a two speed motor on a Smart & Brown lathe with several inter locks. Fortunately a reader on this ME site sent me a copy of the maual, but the circuitdiagram left a bit to be desired.Please to say all is now working.Thank you Richard. John

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ian Phillips on 11/11/2013 18:18:

This is like bees not being able to fly but as they don't know that, they just carry on doing it.

Ian

.

I know it's off-topic, but Alan already has his answer; so what the heck.

This is fascinating.

MichaelG.

[Anonymous]

Posted by Bazyle on 11/11/2013 19:22:35:

Induction motors can be speed controlled by series resistors – my warm air central heating fan is doing that right now. However the motor is a version specifically designed fo rthis mode. Not all would work well and could overheat or something else bad.

Bazyle: I've racked my brain, but I still don't see how to speed control an induction motor with a series resistor? Could you explain in more detail please?

Regards,

Andrew

[Ian S CParticipant @iansc]

There is one way, it is sometimes used in fans to give two speeds, a choke (as used to be used for smoothing DC power supplies, looks like a transformer, but only one winding), with that in series the speed is dropped. Think (not sure) it's got something to do with altering phase angles or something like that. Ian S C

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Andrew Johnston on 12/11/2013 10:14:21:I've racked my brain, but I still don't see how to speed control an induction motor with a series resistor? Could you explain in more detail please?

I think the answer lies in the fact that the torque required to drive a fan drops off rapidly with decreasing speed (something like a square law?) so the motor can be run with a large degree of slip without stalling. Trying this with most normal loads won't work and the motor will rapidly stall.

Russell.

[Alan .204Participant @alan-204]

Thanks chaps I have sorted out what I will do with it now, that's all I wanted to know in the first place you reply's have been gratefully received, well nearly all of them, KWIL you seem to challenge what I do for a living in that you imply I may not know what I'm doing, so for the record the 15-50 pump does have a 5 metre head as mentioned and the 15-60 has a 6 metre head, this is what I work to when I design a new heating system for any one of my customers, if my comment to you about answering the question I asked in the first place and not confusing the issue has upset you then I'm sorry, may be next time keep the toys in the pram.

Regards to all Alan.

[RobonthemoorParticipant @robonthemoor]

Best debate I've ever read" Al""we will just put a valve on it.

rob

[Ian S CParticipant @iansc]

I did some experiments today. I used a 90W water pump from a washing machine, the only choke I have left was too big, and with it in series nothing happened, no rotation. Tried a transformer (230V : 36 V), tried the secondary first, and that worked OK, reduced speed by over 50%, it also reduces the torque by at least that (thumb and finger gripping the shaft), the system would do for a fan, but I doubt if it would be much use in a pump. I tried it with a 230V solenoid, and found similar results, but then I pulled the core out, and the speed changed over a range of 2 or 300rpm. I then put it all back in the junk box. Ian S C

[Ray LyonsParticipant @raylyons29267]

I have been running my suds system based on an old CH pump for 6 years without trouble. Flow adjustment is a small tap in the line to give from a mere trickle to a full blown wash. I didn't seen the need for complicated electrical circuits. Keep it simple, just switch on and it goes. (having said that it is bound to break down tomorrow)

Ray

[Alan .204Participant @alan-204]

Hi Ray it seems the dimmer switch is dead in the water and your are right keep things simple and it should be OK, just a couple of things I would like to ask if that's OK the first thing is do you run the pump through a 3 amp or 5 amp fuse like you would on a normal heating system 3 amp is used on gas boilers and 5 amp on oil firing boilers, second thing the tap you have on your circuit is it done like a bypass straight back to the tank to alter the flow or have you got one pipe from the pump direct to machine and also do you run on speed 1-2-3, some one said earlier on this thread about the need to run clean water only through the pump I can safely say that is not the case as those of you that have looked in the pipe work from an old heating system will all ready know, don't get me wrong you wouldn't want to pump anything much thicker than the soluble oil though.

Al.

[ChrisHParticipant @chrish]

Alan, At the risk of restating the obvious, a central heating pump is a centrifugal pump. As has been stated, they can, indeed should, be started against a shut valve, and then the discharge valve can be opened. The degree of opening determines the quantity of flow. You do not need to by-pass any flow back to the tank IMO unless the flow is very very small and the pump is in danger of overheating, which is extremely rare, and in which case the pump is grossly oversized! Use either a needle valve to control or preferably a ball valve – the cheaper, easier option – to control what flow you need. Please do not use a gate valve, they are useless other than for scrap – at sea we used to call them dimmo valves because they were such a dim idea.

Basically, this is what KWIL originally said but in more detail – keep it simple, it's best each time!

Chris

[Terry McCabeParticipant @terrymccabe]

Just as a matter of interest I forgot to switch off my Axminster coolant pump on my lathe and found it running after forty three hours. It seems to be none the worse so I have to say well done to Chinese manufacturing. I am just a satisfied customer, would not recommend using a circulation pump they can be touchy even on domestic heating and sieze if not in regular use.

[Ray LyonsParticipant @raylyons29267]

Hi Alan, I source most of my supplies from the car boot sale so it all has to be overhauled/modified before use. Never gave any thought to the fuse, just the standard 13amp in the plugtopand left the pump setting at max. I bought the pump for £3 which had 22mm connecting pipes, so that made it easier to connect. A 2 gal plastic container is used for the tank. I located the outlet about 2" from the bottom using a 15mm tank connector and then a 15mm flex with suitable connectors to the pump. On the pump discharge, the pipe is reduced to 10mm and a length of soft poly pipe goes from there to the lathe. I used the flexible "clicklok" system which came with a valve and nozzle to complete. To fit it in the lathe, a piece of scrap alloy bar is used about 1"x3/4" X4", drilled to make what I can only describe as an internal elbow. the holes were tapped to take a threaded spigot to which the poly tube is attached. The other end is threaded to take the valve, which I find can be controlled over quite a range of flow. My local £1 stall at the market have magnetic coat hooks which consist of a round magnet with a 3mm tapped spigot in the centre and supplied in packs of 2. Using a 3mm bolt the magnet is attached to the underside if the alloy bar which allows the coolant outlet to be positioned .

For the return to the tank, it is just a short length of garden hose feeding into a kitchen flour sieve to catch most of the crud. So far, I have not experienced any problems but after all this time, there must be a build up of gunge below the tank outlet which will have to be tackled eventually. For now, I prefer to leave as it is on the basis if it is not broken, why fix it.

Ray

[Ed DuffnerParticipant @edduffner79357]

With a running wattage of 50W it equates to 0.2083 amps at 240 volts. As it's a motor and probably an inductive load the rule of thumb used to be to multiply the running current by 1.8 to give an estimated start current and would then be 0.375 amps. So even a 2amp fuse should be ok to run the pump motor (I seem to remember a 2A fuse is the smallest amperage that will fit in a UK plug). If it's pumping a heavier fluid e.g. cutting oil, I imagine it might add a little to the start load due to effort required, but not much.

[jonathan heppelParticipant @jonathanheppel43280]

It's a bit late to say it but just going by the power rating and ignoring efficiency, that pump is a little smaller than a "proper" suds pump, so its flow may need no adjustment anyway.

[Alan .204Participant @alan-204]

Thanks for getting back to me Ray seems a good way to go with it so thanks again for the info, Jonathan that's a surprise I thought a proper suds pump would have a lot more go in it than a heating pump, you learn something every day. the chap that said the pump would need a valve that opens when the pump start's has baffled me a bit, can't think how many pumps I've changed and also fitted but never have i come across this vale he mentioned, sorry but if i go back a page to get your name i will lose everything I've just written.

Alan.

[David JuppParticipant @davidjupp51506]

I was talking about BIG centrifugal pumps (multi kW) where the electrical start up surge can be a major problem to cope with. By starting against a closed (or just cracked open) valve, the pump doesn't do much work so draws little power and motor can accelerate to full speed, without tripping out the supply. Then the valve is opened, flow increases, as does power draw.

A similar idea can be used in mines as an automatic control for sump pumps. A float is linked to the delivery valve, closes to prevent the pump from pumping the sump dry (and then air locking).

[Brian WarwickParticipant @brianwarwick88192]

Posted by KWIL on 11/11/2013 19:08:19:

Thank you Micheal G for your support,

NO is the correct answer.

in your opinion and of course that's the correct one

[jason udallParticipant @jasonudall57142]

Alan 204..at the risk of starting a flame war..

You indicate you specify and fit this species of pump for work..yet you ask what rating fuse.?

Kwil suggests a “plumbing ” solution..which might be simplest and at least readily tried..you dismiss this ( fine ).

Someone thought that the wattage of this pump is much lower than a “proper” suds pump , thus might not needs throttling down and you then seem to suggest that they are saying that its the other way round..

If you found yourself alone dealing with this I wouldn’t be suprised.

Edited By jason udall on 15/11/2013 14:46:06

[KWILParticipant @kwil]

Thank you Brian.

[Alan .204Participant @alan-204]

Posted by jason udall on 15/11/2013 14:42:39:
Alan 204..at the risk of starting a flame war..

You indicate you specify and fit this species of pump for work..yet you ask what rating fuse.? Kwil suggests a "plumbing " solution..which might be simplest and at least readily tried..you dismiss this ( fine ).
Someone thought that the wattage of this pump is much lower than a "proper" suds pump , thus might not needs throttling down and you then seem to suggest that they are saying that its the other way round..

If you found yourself alone dealing with this I wouldn't be suprised.

Edited By jason udall on 15/11/2013 14:46:06

Jason I don't know where to start with this so forgive me if I miss out something,yes I fit lot's and lot's of Grunfos pump's for me they are the best on the market so that's why I said what I said, this forum has helped me out a lot since I joined it but being a beginner it's difficult to be much use to the member's so I thought I would say which fuse we use on different systems my way of trying to be helpful, I asked what size fuse Ray has been using only because his pump is pumping coolant or even oil for all I know so thinking it will have a higher viscosity it may put more load on the pump and need a bigger fuse. at the beginning of this thread I asked a simple question, will a dimmer switch work on a heating pump to which Kwil answered in a way that would suggest I asked a different question he's still crying about that it seems, as for the rest of your reply I don't have a clue what your on about.

Maybe you and Kwil should get a room and forget about this thread.

Your's Alan, busy playing engineering on my own, it's more fun.

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