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Does a PWM fan controller reduce the electricity used?


eid

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1 minute ago, WotEver said:

The thermostat question seems to be a different question though?

Only outside my head!

 

What I meant to say, was: do I need to use the thermostat option to reduce electricity use, or does the PWM do that anyway?

 

Thank you for your help :)

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2 minutes ago, eid said:

Only outside my head!

 

What I meant to say, was: do I need to use the thermostat option to reduce electricity use, or does the PWM do that anyway?

 

Thank you for your help :)

Well, a thermostat is to control the heat circulation rather than electricity use. It runs the pump to distribute heat either because the boat needs heating up or because the water is getting too hot and needs to be circulated to cool it. As a by-product obviously if the pump is turned off then it’ll be using no power. 

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I am not sure heat transferred is proportional to fluid flow. Thus, a pump turning on/off wouldn't act as a thermostat (it would transfer the same amount of heat, either by warming up an amount of water a bit, or warming up say half the amount of water, by twice as much, if it flowed through the hex at half the speed.

 

I guess a thermostat would need to blend the flow of water through a hex and bypassed water, to be able to actually regulate the temperature of that water, given a fixed heating source  - or have some way of controlling the heat output of whatever is heating the water itself, eg controlling the gas flow of a gas burner or something like that. But I'm assuming the heat source is the engine.

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34 minutes ago, Paul C said:

I am not sure heat transferred is proportional to fluid flow. Thus, a pump turning on/off wouldn't act as a thermostat (it would transfer the same amount of heat, either by warming up an amount of water a bit, or warming up say half the amount of water, by twice as much, if it flowed through the hex at half the speed.

 

I guess a thermostat would need to blend the flow of water through a hex and bypassed water, to be able to actually regulate the temperature of that water, given a fixed heating source  - or have some way of controlling the heat output of whatever is heating the water itself, eg controlling the gas flow of a gas burner or something like that. But I'm assuming the heat source is the engine.

The heat source is a diesel heater. I have found (partially due to the advice in this thread) that the PWM controller, which controls the speed at which the water is pumped through the heat source, fulfils all my requirements : reduce pump noise, reduce electricity use, increase heat transferred to radiators.

 

I think the thermostatic control would achieve a similar effect, though I haven't tested it.

 

My unscientific take on this is that if the water is pumped too quickly through the system, the (minimally) heated water is cooled too much by the ambient temperature to retain its heat. I suspect this isn't the correct explanation, as it doesn't stand up even to my questions. However, my experience shows that full flow water through the heat source does not heat the radiators at all, whereas slowed flow does, a lot.

 

 

 

 

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I have a PWM controler connected to my central heating pump to slow the water going through my lockgate works fine , I have it set as slow as it will go , radiators get nice and hot now , before they where  cold as the water was going through the boiler to quick

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8 hours ago, eid said:

My unscientific take on this is that if the water is pumped too quickly through the system, the (minimally) heated water is cooled too much by the ambient temperature to retain its heat. 

If you think about this for a moment you’ll see the flaw in the logic. 

 

The water isn’t supposed to retain its heat. It’s supposed to give it up to the ambient air; that’s how central heating works ;)

 

If the water travels through the heater too fast then the heater won’t be raising the water temperature by much but the same amount of heat is being generated...

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18 minutes ago, Robbo said:

Can we have a link to one of these PWM controllers, I’m interested in one.

Google for “12v pwm pump controller”. Loads about, depends on the current rating of your pump as to which is suitable. 

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27 minutes ago, WotEver said:

If you think about this for a moment you’ll see the flaw in the logic. 

 

The water isn’t supposed to retain its heat. It’s supposed to give it up to the ambient air; that’s how central heating works ;)

 

If the water travels through the heater too fast then the heater won’t be raising the water temperature by much but the same amount of heat is being generated...

Yes, that makes sense ?

20 minutes ago, Robbo said:

Can we have a link to one of these PWM controllers, I’m interested in one.

This is the one I have:

 

https://www.kemo-electronic.de/en/Transformer-Dimmer/Controller/Modules/M171-PWM-Power-control-9-28-V-DC-max-10-A.php

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