Is it good practice to fit a switch to manually control a Grundfos pump?

[Nikynooz]

Hi - first time poster.

We have a wood fired boiler stove that heats a tank of water and four radiators. (Charnwood country 8b)
The grundfos pump is controlled by a thermostat on the HW tank - when the water in the tank is warm enough the pump sends water to the rads.
The system works well but the tank and pump are in the corner of a bedroom and it's annoyingly noisy when we are trying to sleep. (most of the noise is from the pressurised water in the pipes - the pump is pretty quiet)

I want to fit a switch so we can manually turn the pump off at night - similar to a cooker switch.
Is this a good idea? Anything I should be concerned about?

Thanks in advance for any advice,

Nick.

 

[SpecialK]

Fit a timer that stops the pump coming on at night?

 

[bernardgreen]

Pumping water around the radiators may be essential to remove heat from the wood fired boiler as the fuel burns out.

 

[Johntheo5]

What will dump the heat then, boiler is running all night.

 

[Jackrae]

If your pipework is noisy it could be that the pump is pushing the water too fast around the circuit. You could try reducing the pump speed (presuming it has speed control) whilst ensuring it is still capable of dumping the boiler's maximim fire rate.

 

[Exedon]

Better control would be 2 pipe stats
One on return that runs pump when return hot enough (back end protection) this could be switched.
Second pipe stat on flow wired to switch at say 75c to run pump and disapate heat, this requires permanent live
So at night pump would only run when really needed

 

[oldbutnotdead]

What sort of noise are you getting? If it's air bubbles rattling round then bleed them out. As above, have a look at the pump speed setting, try altering it (in the daytime when you can keep an eye on temperatures).
If the noise is kettling (the water temp is above 80° or so) you need to look at how you are fuelling overnight and maybe reduce the burn rate a bit.
If the thing is kettling then turning the pump off will increase the noise as the water in the backboiler will start to boil.

 

[Nikynooz]

Thanks all for your wise words. The stove is only fuelled during the day - and heats a large vented water tank. The noise is only annoying because the house is in a very quiet part of the scottish highlands and we can hear the noise above the silence. I think the only potential danger is someone switching the pump off when the stove is fired up.

 

[oldbutnotdead]

A properly designed system can boil dry without risk of injury. If you aren't adding heat at night, convection (and the heatloss radiator that should be on the gravity circuit) should take care of residual heat in the firebox.
Question re the thermostat on the cylinder that controls the heating pump- is it measuring the temperature of the tank contents (either a probe into tank or strapped to the outside) or is it measuring the gravity circuit temperature (so strapped to one of the feed or return pipes coming up from the woodburner).

 

[Nikynooz]

Hi Oldbutnotdead - thanks for your help -The stat is on the outside of the new and quite large HW tank that we fitted as part of the project.
When the system was first installed we only had two relatively small rads in our upstairs bedrooms and the hot water in the tank and those rads got extremely hot if the stove was properly fired up. I was not involved in the original install and have recently added two new larger rads in our downstairs living area. We only get heat to the rads once the tank is warm enough.

 

[Johntheo5]

That's a bit unusual as normally a pipestat is installed on the stove flow pipe set maybe to start the circ pump at65C which will cut out at - 55C .