Speed control of Central Heating Circulator

Hi guys, title says it all really.

I want to control the speed of a central heating pump somewhere slower than normal.

Q1. What sort of motor is in a domestic central heating pump (UK 50Hz single phase ).

Q2. Is it controllable from an Inverter? These usually run shaded pole or Capacitor run/start type motors.

Q3. Does anyone have any suitable circuit diagrams for a speed controller, fixed speed would do. I'm guessing the speed is controlled by the frequency.

TIA

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Terminal_Crazy

Mitch - 1995 Z28 LT1 M6          terminal_crazy@sand-hill.freeserve.co.uk
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Reply to
Terminal Crazy
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What is it you mean by "heating pump"? If it's a "heat pump" (i.e., a reversible "air conditioner"), then the compressor motor shouldn't be messed with, period. If you're simply talking about the blower that circulates the air, then we'd need to know what kind of motor is driving it. I guess it's kind of hard to control an induction motor that wasn't designed for electronic speed control.

Good Luck! Rich

Reply to
Rich Grise

Cetral Heating Hot water circulator such as CirculatingPumps CP53

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The only info i have so far is it's a "drum motor design" whatever that means. It does come with 3 selectable speeds similar to most domestic pumps.

Thanks

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Terminal_Crazy

Mitch - 1995 Z28 LT1 M6          terminal_crazy@sand-hill.freeserve.co.uk
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Terminal Crazy

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Ok, fair enough, but what is it you want to accomplish that it can't already?

Thanks, Rich

Reply to
Rich Grise

I'd like to run it at a slower speed than it currently does.

I could throttle it back but that would be inneficient.

I have a large 200,000 BTU Oil fired boiler which heats the house. I have also linked in a 30-40,000 BTU Multifuel stove heating the system. Just using gravity circulation the boiler/pipework can get noisy/hot. with the pump running it removes the water too fast. Very likely the pump is way too big for the section it's serving. Rather than replace the pump, I was wondering if I can control its speed. Most inverters seem to do Capacitor run/start motors or shaded pole, but i don't know what type of motor this uses.

Ideally, if I can control the speed, I can control the temperature of the water circulation within limits.

Is it possible the speed can be reduced ?

Thanks

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Terminal_Crazy

Mitch - 1995 Z28 LT1 M6          terminal_crazy@sand-hill.freeserve.co.uk
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Terminal Crazy

have you thought about using a zone valve? You can employ them to do bypass of hot water delivery. They come in a variety of combinations just depends on how you want to divert the water. Simply let the water that isn't be used go back to the tank..

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Something to look at..

Reply to
Jamie

Terminal Crazy Inscribed thus:

Why not just use a restrictor valve. Pump continues to run but the flow is reduced.

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Best Regards:
                     Baron.
Reply to
Baron

That raises the backpressure, could stall (and overheat) a pump motor.

The other way is to have a valved shunt, so the water flows in the heating system and also through a second, parallel, loop (like a short circuit). The pump still puts out the same number of gallons per second, but the house pipes only see part of the flow.

Reply to
whit3rd

Probably a split phase induction motor (especially if quiet running) there should be a "boilerplate" on it somewhere that says.

assuming it's hydronic central heating and a centrifugal pump simply reducing the voltage may be enough as the torque will reduce proportionate to the speed, if it's a displacement pump trying that may overheat the motor.

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?? 100% natural
Reply to
Jasen Betts

whit3rd Inscribed thus:

I can see the advantages of that method. I do use a restrictor valve on my system, but its only a two radiator loop.

I did a quick test by closing the valve completely, the pump, at its slowest setting still runs, but you are right it does labour somewhat. I didn't run it like that long enough to see if it got too hot. Oddly if I set it to the highest speed, it doesn't seem to labour at all.

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Best Regards:
                     Baron.
Reply to
Baron

Is it a centrifugal pump? In a vacuum cleaner, when you block the hose, and it goes "Woooeeeee," speeding up, and it sounds like it's laboring terribly, did you know that the current draw decreases? That's because when a centrifugal pump isn't moving any fluid, there is no load, because no work is done, so the motor speeds up because of the reduced load.

Cheers! Rich

Reply to
Rich Grise

You most likely are talking about units that employ a universal motor..

They like to spin out of control when the load is removed but serve as a great motor for vacuums..

I do think he is using a drum motor for that application.

Reply to
Jamie

Rich Grise Inscribed thus:

As far as I know it is a centrifugal pump. The inlet feeds the centre of the impellor and the outlet is at the edge. Its also a capacitor start/run motor with three speeds. I assume tapped windings.

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Best Regards:
                     Baron.
Reply to
Baron

It'd be worth checking, because, as I said, a centrifugal pump wouldn't be harmed by sticking a restrictor valve in the line, as someone else suggested.

Cheers! Rich

Reply to
Rich Grise

as long as you don't get cavitation it won't be harmed.

if it's tapped windings reducing the supply voltage is probably harmless too.

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?? 100% natural
Reply to
Jasen Betts

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