36.6kw boiler and central heating pump speed

[dormermike]

Hi

I have looked into this by searching but asking the question too to see what the general feedback is.

I have a largish bungalow (dormer, approx 210sqm) with a ideal mexico 2 36kw boiler with open vented y-plan system. Stat in living room and TRV's on all rads (except a bypass rad).

On pump speed setting 2, I found the boiler would often fire for a very short period quite frequently and didnt seem long enough to possibly contribute any heat to the rads. I suspect this was because the water inside the boiler would get upto temp (setting 5 of 6) before the heat could be shifted away from the boiler so experimented by turning up to setting 3 and sure enough boiler seems to stay on longer, and rads get very hot very quickly.

I should add that on setting 2, all the rads got hot except for one which is the furthest I think, and on setting 3 this rad is definately hotter.

So, is it OK to leave pump on setting 3? I think the system is working better, but guess i'll know for sure when my bills arrive (if they are hugely increased i'll put it back to 2!! haha).

One thing I wonder is, would setting 2 work better if all the lockshields except for that one rad were throttled back a bit.. worth a try?

Thanks
Mike

 

[Agile]

You can leave it on "3" but it will be more noisy and use more power.

BUT it should not be necessary!

I suspect that your boiler is grossly over rated for your house.

How long ago was it fitted? Who chose that size?

Have you done a whole house heat loss calculation?

That size can heat a 10 bed house!

Tony

 

[dormermike]

Boiler was here when we moved in. Did a heatloss calc ages ago and it wasn't wildly off, lots of large rooms etc

Anyway, no plans to change boiler.

I guess my assumption is plausible then, heat not being removed quick enough on setting 2?

Cheers

 

[dcawkwell]

The boiler needs setting to it's minimum burner setting
so that it will heat for longer and cycle less.


Depends how many radiators you have but I would say that the system needs balancing better see the online help here about balancing to
improve the heating of radiators.

 

[Agile]

Mike listen to this!

If the boiler can heat up the rads quickly then its over powered, probably quite seriously.

Most of those older boilers can be set to a heat output of about 60% - 100% of the rated power. Yours is obviously set higher than necessary and thats inefficient when its cycling.

When its 10 C outside you need the boiler set so that once its reached the normal room temperature of 21 C the boiler is running about 50% of the time!

Tony

 

[CBF]

i don't think the question can really be answered at the moment because you haven't told us the make & model of the pump ?

 

[Agile]

Its a Grunfos 15-60 pump!

 

[dormermike]

Yeah its a grundfos not sure of rating, can check tomorrow as I can't get to the pump at moment.

I have had a Corgi chap look at the system, had it serviced last winter. I mentioned range rating at the time and was told not possible. Actually the response I had was probably not dissimilar had I asked him to split atoms on my dining room table.

Regarding the dial on the front, the flow temperature, can you help me understand why a low setting rather than high would help? Surely higher means longer burn duration to get water up to temp?
Edit: or is that not what is meant by "burner setting"?

Thanks all.

 

[CBF]

unless it's a small system or has a design fault ie incorrect feed & vent i always run a 15/60 on no 3

 

[Dan Robinson]

Can you upload a picture of the boiler's data badge?

 

[dormermike]

Can you upload a picture of the boiler's data badge?

Here you go - thanks

Untitled

• dormermike
• 22 Oct 2012
• 1

 

[dormermike]

Pump says "15-60 130" on the front of it.

 

[dormermike]

Can you upload a picture of the boiler's data badge?

Here you go - thanks

Untitled

• dormermike
• 22 Oct 2012
• 1

So is it a 36.6kw and can the jet be downsized? Thanks

 

[D_Hailsham]

Untitled

• dormermike
• 22 Oct 2012
• 1

The boiler can be range-rated!

Click on the pic to enlarge it and you will see the three possible settings: Min, Mid and Max. There should be an arrow on the left pointing to the current setting. Below that it shows the burner settings.

 

[D_Hailsham]

Before changing the boiler output you need to use the Whole House Boiler Size Calculator to find out how large a boiler you really need. This will tell you which setting the boiler should be on.