Central heating pump settings/noise

benson1980

Hi all,

After a bit of advice on the above. We have a 5 bed house- 16 radiators. Sealed CH with system boiler/hot water cylinder. In our airing cupboard we have our Grundfos pump which is a 15/60 130 model.

When we moved in the speed was set at 3. When we had our new (unvented) hot water cylinder installed in the summer we explained to our plumber that we found the system in general a bit noisy he reduced the speed to 2 which dramatically improved things- I'd say the noise on 3 is just a constant humming sound predominantly in the vicinity of the larger flow and return pipes under the floorboards rather than the pump itself being noisy. However, now the weather is getting a bit colder and we are using our CH more I've noticed it doesn't seem to get all of the radiators hot and last night for instance it was running for several hours and there were some rads that were still luke warm. 

I guess my main question was for this size system, is it likely going to be the case that we are just going to need the higher setting? Is there anything else we can tweak, or potentially look at a different pump? There does seem to be quite a large jump between speed/noise of setting 2 versus setting 3, so not sure if a pump with some more speed options perhaps would make a difference?

I do need to re-balance the system at some point, which is probably worth mentioning. There's no air locks/radiators all bled, and we had our system power flushed as well in the summer and a magnetic filter installed.

Bendy_House

Full marks for a perfect description of the issue!

It's hard to be certain whether the third speed is actually needed, or if it's more a case of the system needing a bit more balancing. From my very limited experience, I'd say that '3' is very rarely required on a well set up system, even one as large as yours, so I'd hope that you would be able to get to a point where it isn't. (But, very limited experience here, espec on large systems).

There's another aspect to this, tho', and its that your system MIGHT actually benefit from the faster speed when it heats up from cold, as ALL your rads will be screaming for hot water. As the rooms heat up, tho', water demand will/should reduce significantly, likely to the speed equiv of a '1' or even less. So, the ultimate solution - even IF balancing helps - could be to go for a Smart pump with auto adjustment. These very cleverly monitor the water flow resistance, and adjust the flow to suit. As rad TRVs shut off, resistance will increase, and the pump will back off. If you open up a demand for DHW, the pump will increase in response. Apart from less wear and noise, it could also provide a useful saving on leccy running costs.

If you have a manual pump running on '3' and half the rads have shut off, then you will almost certainly have 'increased' noise.

So, yes, balance the system at some point, but I'd also seriously consider a pump swap.

I 'think' that these may even be a Build Reg requirement on new systems?

Apodemus

Is it possible that as part of the summer works, the plumber also turned down the flow temperature on your boiler?  Also possible that there is an optimum combination of flow rate and flow temperature and that with the pump at '2' you will need to increase the boiler temp to deliver sufficient heat to the furthest radiators. 

benson1980

Bendy_House said:

So, yes, balance the system at some point, but I'd also seriously consider a pump swap.

Ah ok. Interesting. Would it potentially be one like this that I would want, and is this easy to DIY potentially? Looks like there's just two big connecting 'nuts' on the pipework, unscrew (drain system first obviously), put new one on hoping Grundfos have stuck to standard dimensions, wire as per old one? Or is it more complicated?

https://www.anchorpumps.com/grundfos-alpha1-l-15-40-130-domestic-circulator-240v-1-connections-3?gclid=Cj0KCQiAg_KbBhDLARIsANx7wAxbK6tvxF_dYVXzPdbaUOpngN_yf-wsUQM9667yRVPuxdwdKL2vo1UaAhZjEALw_wcB

Edit: or this one maybe?

https://www.anchorpumps.com/grundfos-alpha2-25-60-130mm-domestic-circulator-pump-with-auto-adapt-240volt?gclid=Cj0KCQiAg_KbBhDLARIsANx7wAyK_ts4AuOXgXyaARIYwmvCJvS0Xri-UizB4RDs2K6ZMewfzbYIUa4aAnWvEALw_wcB

Apodemus said:

Is it possible that as part of the summer works, the plumber also turned down the flow temperature on your boiler?  Also possible that there is an optimum combination of flow rate and flow temperature and that with the pump at '2' you will need to increase the boiler temp to deliver sufficient heat to the furthest radiators. 

Thanks- yes he did indeed. He turned the flow temp down to 55 which barely got the radiators warm. I've had a fiddle with it this morning and even turning it up to 65 and pump setting at 2 it just doesn't seem powerful enough to heat up all the rads. At soon as it's on 3, all the rads get piping hot, quickly, and at a lower flow temp (around 58).

Bendy_House

Hi Benson.

Yes, that's the sort of pumps I meant. I'd need to look at these two and see how they differ - and why the large price difference! 

The good news is that it's entirely DIYable as they should be a standard fit. Also, there's every chance your existing pump will have isolating valves either side of it, so need to even drain down!

I'd wait for confirmation from an actual plumber on here (or elsewhere) before choosing a pump. Don't even be restricted to Grundfos, even tho' they are reputable. There's DAB, Wilo and others.

Good call by Apod re boiler setting. I'd imagine, tho', that it isn't the 'cause' of your issue. The output temp you set your boiler at should be pretty independent of the flow rate. If the furthest away rads are colder than the nearest, then that suggests an imbalance, end of. I'm pretty sure.

Any option of adding a weather compensator to your boiler? 

Bendy_House

Make and model of boiler?

benson1980

Not sure about weather compensator/never heard of them- will have to look into that. It's a Vaillant Ecotec 428...

Bendy_House

Weather comp is (usually) an outdoor temp sensor which tells the boiler how hot to get in order to heat the house. Saves having to manually turn the boiler temp control up and down manually for the energy savings (the cooler the boiler, the more efficient it runs). The instructions for your boiler should mention it, perhaps under the 'electrical connections' part.

benson1980

After a bit more research I ended up buying a lowara ecorcirc which has a speed dial which I can gradually turn up, rather than just three settings. It also has that ‘smart’ feature so can give that a go as well. 

Bendy_House

benson1980 said:

After a bit more research I ended up buying a lowara ecorcirc which has a speed dial which I can gradually turn up, rather than just three settings. It also has that ‘smart’ feature so can give that a go as well. 

Never heard of it! The 'smart' feature is the important one, as you ideally want the pump responding to the changing demand. 

Please report back

Bendy_House

Are you DIYing?