Circulation pump running too fast

[tomandsophie]

Instead of buying a new pump, could I just put a variable resistor in front of the current one to slow it down? It is just a regular Jabsco circulation pump - would it be damaged by putting a resistor in?

I want to get it down to a flow rate of around 3 litres/min. Currently it is something like 12 litres/min.

If this isn't realistic, does anybody have any recommendations for a (not too expensive) 12V circulation pump with a low flow rate?

 

p.s. I know I have discussed this before, some time ago, but last time there wasn't any distinct answer and eventually the thread was closed down because people were getting very argumentative.

Edited August 18, 2007 by tomandsophie

[DHutch]

Here?

 

http://www.canalworld.net/forums/index.php...irculation+pump

 

 

The thing is tom, you could slow your pump down using a resistor, or even a variable restistor, providing both where of a suitable size (ie, quite large).

- However, as this would have no benfit to you (as rather heatedly discused last time), there seems little point.

- Also, i wouldnt be supprised that if you would struggle to get a 12l/min pump to go as slow as 3l/min and still run properbly

- Depending on the pump you find it doesnt start, although it will keep running. (something you get with slowing pc fans down significatly)

 

 

 

Daniel

Edited August 18, 2007 by Dhutch

[John Orentas]

Always a very dodgy thing to do, putting a resistor on series with a motor, yes it will certainly give the slowing down effect but the trouble comes when you stop and try to restart it again.

 

You need a bit of circuitry to give it full voltage on start up. Ideally the way to control a DC motor is to 'chop' the supply, which effectively means switching it on and off at an optimum rate. Toy train, (sorry) model railway nerds use the technique to make the action of a loco's setting off look realistic. So perhaps model shops may be a starting point.

 

Oh dear is this an electrical topic, I fear I have trespassed.

[Scotty]

Theres an auction about to end on ebay for one that's 12v 4.3 litres/min £24 + £4 p+p

http://cgi.ebay.co.uk/12V-DIAPHRAGM-PUMP-O...oQQcmdZViewItem

if the link's not working try item no. 330155369753

 

hmm.. it's an on demand pump, so not really what you want

Edited August 18, 2007 by Scotty

[SoggyMoggies]

Is this to do with the problem with the solar heater? If so, one way you might be able to slow the pump down would be to use a timer circuit to give (say) a 5-second pulse every 20 seconds and use that to drive the pump via a relay. This would allow the pump to run flat out but only for a quarter of the time, thus giving an overall flow rate of around 3l/min.

[DHutch]

solar heater?

Heating circuit, backboiler, radiators, etc. I bealve

[tomandsophie]

Heating circuit, backboiler, radiators, etc. I bealve

 

Well, this is really about both pumps that we have running - back boiler one and solar panel one. Just interested to see what effect it will have to have a slower flow rate. I have had a lot of conflicting advice on whether or not it will make a difference so I guess it is best just to try it and see...

[Amicus]

If it's an impeller type of pump stick a gate valve in the line.

[ChrisPy]

my 12V jabsco circulation pump is installed as an injection pump, i.e. it bypasses the boiler and just gives a bit of a kick start to the convection circulation. Not the same as your case, but it suggests an option - make a bypass round the pump with an adjustable valve, pump runs full speed, flow is adjustable.

[tomandsophie]

Hmm, interesting. I might look into the valve option.

[smileypete]

Hi,

 

First try lots and lots of lagging on the cylinder and pipes, I'd put 4" on the cylinder and 2" on the pipes.

 

If you can't get thick lagging locally try these:

 

http://www.bes.co.uk/

 

Basically if there's not enough lagging the heat losses from pipes and calorifier will overwhelm the output from the panel on not-so-sunny days.

 

cheers,

Pete.

Edited August 18, 2007 by smileypete

[tomandsophie]

Pete, thanks for the advice. I've put loads of thick insulation on the calorifier. However, because the calorifier was installed early in the build, it is too tight against the bulkhead and the floor to be able to get the insulation all the way around it. I managed to get it around about 3/4 of it though, plus both ends, so it should make a difference.

I will get round to insulating the pipes tomorrow...

[chris w]

I have designed and built a 12v dimmer circuit which I use to control both lights and fans on the boat. It will handle about 200W so will easily control a 12v pump. You will have no problem with pump start-up as the circuit uses a technique known as pulse-width modulation (PWM) which will always hit the pump with the full voltage nor will you have any wasted heat as you would with a resistor. The circuit is over 90% efficient.

 

If you PM me I would be happy to send you the diagram if you feel that either you, or someone you know, could build it. You could then turn the speed knob and experiment at any pump speed from totally off to full 100% speed.

 

Chris

[pagan witch]

I don't recommend this as any kind of long term solution but if you just wanted to try the idea of reducing the flow to see if it would achieve your desired aim why not fit a valve and screw it down some to restrict the flow of water like that ?I'm pretty certain the pump wouldn't like this long term, but for a 'suck it and see' it would only come to a few qiud and can be easily 'uninstalled' by simply openeing the valve fully.If fortune is on your side and the pump is OK on it then it wouldn't take long to work out how many turns of the tap equate to the kind of flow rate you want and you would have a simply way of varying the flow to your hearts' content.Sorry everyone - should have read the numerous replies offering the same solution before I posted Yours in embarassment

[tomandsophie]

Here's another possible option. How about I try wiring my Jabsco pump directly to our solar panels? Then it would start up only when the sun is shining on the panels, thus only running when the water is being heated.

My only worries about this are:

1. The 'open circuit' voltage (i.e. before the charge controller) can be up to about 24v I think. Could this do the pump some damage?

2. Would the pump start properly?

[chris w]

Your solar panels will not provide enough current to start and run the motor.

 

Chris

[Semitrad]

Is it possible to remove any impeller blades?

[DHutch]

Your solar panels will not provide enough current to start and run the motor.

 

Chris

Some solor heating panels do have small photovoltaic pannels to run a ciruclation pump, just you would need very much smaller pump for that.

 

 

 

Daniel