Why does my pump get noisy when rads are turned off?

[Last Triumph]

I have a standard gravity fed, traditional boiler CH system in my two story house.

In the winter when the rads are switched on, the pump opperates silently.

As the weather warms up and we start to turn rads of in various rooms, the more rads we turn off, the noiser the pump gets.

Now it is summer (ish!) all the rads are off and the pump is very noisy - almost as if by closing the rads is restricting flow and causing the pump to 'labour'.

If I use the CH controller to just pump the hot water for the tank isolating the rad system totally, it is just as noisy.

Can anybody explain this and offer a possible remedy.

I've bled the system and all the rads many time with no success if that is of any info?

 

[corgiman]

its getting nosiy cos you are reducing circulation and working the pump hard

 

[JohnD]

Now it is summer (ish!) all the rads are off and the pump is very noisy - almost as if by closing the rads is restricting flow

"almost?"

For a start, turn the pump speed down.

Then check that the wall stat is low enough that the pump does not run when heating is not required.

Haven't you got Thermostatic valves on most of the rads?

You can have a think about a bypass but this is not quite so easy.

 

[Last Triumph]

Now it is summer (ish!) all the rads are off and the pump is very noisy - almost as if by closing the rads is restricting flow

"almost?"

For a start, turn the pump speed down.

Then check that the wall stat is low enough that the pump does not run when heating is not required.

Haven't you got Thermostatic valves on most of the rads?

You can have a think about a bypass but this is not quite so easy.

I haven't got rad stats because the profiteers who built my modern (1991) cardboard / weetabix construction house built it to a price, erm, sorry, built it to a profit and used the cheapest and nastiest rad valves that could possibly be bought before the opening of China. The pipes that feed them come directly out of the wall at 45 degrees leaving absolutely zero room to pull them further out to re-make the olives and replace the valves. I would need to chisel out the plaster and cut the pipe to extend it and re-do it all afterwards - not worth it for rad stats.

The pump is on it's lowest setting already.

If the thermostat turns the pump off when it is warm enough, what circulates the hot water to my cylinder when I need hot water?

Having said all that, rad stats and / or thrmostat control or otherwise, why is my pump noisy when everyone elses isn't when they run hot water only?

Sorry if I sound dumb, I'm not a plumber and only have a very basic understanding of the heating system.

 

[Dan Robinson]

You'll need a differential by-pass fitted:

http://europe.hbc.honeywell.com/products/ecatdata/pg_du145.html

 

[Last Triumph]

That sounds exactly like what I need. Where does it fit?

If it is needed due to the inherent design of the system, why wasn't one installed when the house was built?

Ah yes, I forgot... sorry.

Still, at least with it being a new house all the walls are square, the beams equi-spaced, the floors level and the quality of workmanship up to scrath.....

 

[Dan Robinson]

After the pump outlet linking the flow and returns.

Back when your system was fitted they didn't use them - if they bothered with any by-pass it was a fixed by-pass - usually a gate valve.

If you have one then you can get a DU144 and replace directly (they're straight instead of angled).

 

[Last Triumph]

Ah.... on closer inspection of the pipework, I appear to have a bypass.

I was never sure what it did. I opened it fully once and all that happened was that my water didn't get hot.

Is it a case of trial and error to just crack it open enough to prevent the pump labouring but not enough to stop water flowing through the hot water tank?

 

[Dan Robinson]

eeeerrr, well its a start, but I would consider putting a differential one in - it'll self adjust to the conditions.

The trouble with the fixed one you have is that as soon as a rad is adjuste it changes the dynamic of the system.

 

[gas4you]

If the thermostat turns the pump off when it is warm enough, what circulates the hot water to my cylinder when I need hot water?

Your hot water cylinder is heated by gravity circulation as you stated in your first post.

This means is basically that hot water rises from the boiler and cold water falls to the boiler. Having your pump on could increase the time your hot water cylinder takes to heat up.

 

[Last Triumph]

Wow, this really is showing my ingnorance. I thought that the header tank in the loft was the gravity bit... I feel foolish amongst experts.

So, if I understand correctly, if I turn my wall thermostat down (which has been cleverly mounted in the cold and draughtly hall way by my front door) to a level which switchs the pump off, the boiler will still circulate water to my airing cupboard water cylindr by means of convection? (can the word convection be allpied to water as well as air?)

Thanks for all the help do far everyone.

 

[Dan Robinson]

Yep that sthe way it works.

Not very efficient, but reliable.

You could always get a wireless room thermostat.

http://content.honeywell.com/uk/homes/files/pag107.pdf

These are the dog's - appearance has been updated lately, Honeywell haven't released the new brochure though.

 

[Last Triumph]

Well I never knew that....

Is that standard practice in "normal, traditional, standard" systems from the last couple of decades then?

 

[Dan Robinson]

'tis indeed.

 

[namsag]

Hang on in original post Triumph says when he turns room stat down an HW on it is still as noisy . So it`s either a fully pumped system or the noise is not the pump.. 1991 new build system should be fully pumped.. Grundfos alpha pump could solve your problem as it adjusts it`s output depending on resistance of system ie amount of rads turned on or off.

Noise may just be a worn bearing or you may have a lot of cr#p in system