How to control the speed of a 240v central heating pump at distance

Thread Starter

smurfy333

Joined Oct 18, 2015
8
Hello all

Just joined the site! Very good indeed it is. Anyway my question is below, oh and thanks for taking time to read it.

I have two central heating pumps in my house, first one is with the central heating boiler and the second one controls the flow from my log burner which has a small back boiler in it, for this instance I would like to control the speed of the pump off the log burner, the pump already has an in-built speed control and because this is under the floorboards of the first floor I have to run up and downstairs to keep controlling it, would I have to mod the pump I.e remove the speed control and move to a box next to the log burner so I can control the speed or would I set it to high and control with a pot next to the log burner.

I've come late into electronics and working on several projects which I'll be asking for help in the coming months if that's ok? So any help at all is very much appreciated.

Many thanks again in advance.
 

Alec_t

Joined Sep 17, 2013
10,355
Welcome to AAC!
I'd hazard a guess that the pump motor is a conventional induction one with speed selectable by switching stator windings. You won't get much speed reduction by varying the applied voltage with a pot (or other means), since speed is essentially governed by the number of stator poles and the mains frequency. The only way I see is, as you said, "to mod the pump I.e remove the speed control and move to a box next to the log burner".
 

Dodgydave

Joined Jun 22, 2012
8,373
Most central heating pumps like Grundfos have a 3speed switch selection, which selects a different winding in the motor, or puts a cap in series with the winding, might be best to remote wire the switch, or use a relay to replace the switch and remote wire it.
 
We would need to know a bit about the pump, but there is something called a VSD (Variable Speed Drive) that's used for induction motors. See: http://www.wolfautomation.com/products/38536/mini-variable-speed-drive-single-phase-25-to-1-hpbrweg-cfw100

This particular one has IR control and some other options. IR can be repeated.

Don't know if it's an appropriate solution.

Pump nameplate info would help. General location helps too because it gives us an idea of what electrical system were're working with and we can point to solutions on the side of the "big pond (Ocean)" that's more appropriate. The 240 VAC helps. Now how about more nameplate info, Model HP, type of motor?

It's helpful to repeat some of the info from the title in the body of the post. I forget the title info sometimes.
 

Thread Starter

smurfy333

Joined Oct 18, 2015
8
Why do you need to keep changing the speed of the pump? o_O
With a wood burner that has a boiler, You really need to control the speed to get the sweet spot, to fast and water doesn't heat up and to slow it will boil to quickly.
 

tcmtech

Joined Nov 4, 2013
2,808
With a wood burner that has a boiler, You really need to control the speed to get the sweet spot, to fast and water doesn't heat up and to slow it will boil to quickly.
I don't follow the logic being I have been heating my house off of a home built boiler for about 12 - 13 years now , I've also built several boilers for others too, and I have never had to adjust my pump speeds relating to its heat output or home heating load.
 

Thread Starter

smurfy333

Joined Oct 18, 2015
8
I don't follow the logic being I have been heating my house off of a home built boiler for about 12 - 13 years now , I've also built several boilers for others too, and I have never had to adjust my pump speeds relating to its heat output or home heating load.
Well done for you. I didn't realise you had the same setup as me!
 

GS3

Joined Sep 21, 2007
408
With a wood burner that has a boiler, You really need to control the speed to get the sweet spot, to fast and water doesn't heat up and to slow it will boil to quickly.
The water doesn't heat up but there is more water going through and more heat being carried away than with a slower pump. If your aim is hot water then yes, you need a slower pump but if your aim is space heating then you gain nothing and, in fact, you lose; a faster pump will carry more heat away.
 

Thread Starter

smurfy333

Joined Oct 18, 2015
8
Firstly, it's for heating, secondly I have 14 radiator over 3 floors, lastly, I have a small wood burner with small boiler, if you have the pump at full blast then forgive but I'm no expert hence the question, as soon as the water hits the boiler it's out again
 

GS3

Joined Sep 21, 2007
408
Firstly, it's for heating, secondly I have 14 radiator over 3 floors, lastly, I have a small wood burner with small boiler, if you have the pump at full blast then forgive but I'm no expert hence the question, as soon as the water hits the boiler it's out again
It is still carrying more heat than if it were hotter and slower flow. You are better off having a faster pump.

Car engines have a thermostat for this reason. When the motor is cold and you circulate water, even if the water does not reach high temperature it is still carrying away a lot of heat. Since you want the motor to heat up you slow the flow of water. The water gets hot because not so much heat is being taken to the radiator.
 
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