Grundfos 15 60 pump switch setting with Ideal Icos HE 24

GadgetDaddy · 30 Apr 2010

Hiya Guys,
Please help a numpty...!

I have had some jip with the above system recently, no hot water although CH working fine anyhow to cut a long story short the Mrs had turned down the thermostat on the hotwater tank months ago to 30c as she thought the water was too hot.....DOH....!, so since the weather got warmer the temp must of been ok so the system not firing up, after much reading researching resetting of the system I discovered that little gem....so Ive set the stat to 60c based on reading more articles, but along my journey I discovered the GF 15 60 pump and noticing the switch setting on the side and it intrigued me as to whether its on the correct setting as our boiler was changed about 4 years ago and I dont know if the setting its on is for the old boiler (hope this makes sense).

Its in the middle at the mo and these are the figures which relate to the switch setting I think

0.17 40
0.30 65
0.44 95

cheers lads

Agile · 30 Apr 2010

Middle is fine!

I dont know where you are getting those figures though.

Tony

GadgetDaddy · 30 Apr 2010

thanks for the reply mate, the figures are on the front of the pump
they also show up on pg 5 of the manual here

http://www.screwfix.com/sfd/i/cat/pdfs/01/p3983301.pdf

cheers

ianniann · 30 Apr 2010

The correct setting is the lowest one that gives you an adequate flow of hot water around your radiators. It even says so in the manual

Without knowing a few more details, the best advice is probably to leave it where it is. Some boilers won't be happy if you turn the pump down too low, although generally if all the radiators get suitably warm then there shouldn't be a problem.

GadgetDaddy · 30 Apr 2010

i saw that line in the manual and was trying to word a question around it without success, would you suggest trying it on a lower speed?

what are the pros/cons of the lower speed?

tia

ianniann · 30 Apr 2010

Pros of a low pump setting:
- low power usage, which can be a noticeable percentage of the cost if the boiler is ticking over with low heat requirements;
- lower noise;
- lower wear and tear on the pump;
- improved temperature drop on the return, which newer boilers prefer.

Cons:
- too low and heat won't be removed from the boiler quickly enough causing problems;
- too low and the pump may not be able to force water to the higher radiators;
- too low and radiators at the end of the system may not get hot enough, although this should really be fixed by radiator balancing.

New condensing boilers are typically specified for a 20C temperature drop, which is achieved by correct radiator sizing and balancing in combination with the correct pump speed setting. More expensive boilers have modulating pumps which can cope with variable loads from TRVs, which I'm assuming you don't have.

GadgetDaddy · 30 Apr 2010

thanks for the comprehensive reply ianniann, I think unless someone knows these two bits of equipment and advises otherwise then its staying on setting 2, i dont want to under or over power the system

Agile · 1 May 2010

There is another "Con" that can be added to that list !

If the pump is getting a little sticky then leaving it on setting "1" will sometimes not provide enough starting torque to get it to start to turn !

Tony

GadgetDaddy · 1 May 2010

thanks for that "gotcha" agile

ianniann · 1 May 2010

I wouldn't worry too much about trying the lowest setting, it isn't likely to blow up. If it doesn't work at all then most likely the pump is half dead anyway.

If it runs, then you can check the heat flow through your radiators. If the highest ones don't get hot at all then turn it back to 2. If the radiators furthest from the boiler are only warm while the closest ones are hot then you should balance the radiators and see if you can balance them all out to nicely warm with a 20C drop across them. Again, if the best you can do is hot at the input (and maybe the top) of each radiator and cold over a good part of the radiator then the pump is too slow on that setting. Running like this briefly isn't going to hurt anything.

If you don't want to mess about, then the current setting is only costing you maybe an extra ten quid a year in electricity and a hard to quantify but not huge amount of gas from running the boiler at a slightly less efficient level of condensing.

GadgetDaddy · 3 May 2010

thanks once again ianniann for your detailed and informed opinion, gives me more confidence changing the settings and testing it

diynot

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Grundfos 15 60 pump switch setting with Ideal Icos HE 24

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