Central heating pump

[Badger76]

Hi all,

Can anyone tell me what I should set my central heating pump at 1, 2, or 3. I have 10 radiators on ground floor and 4 first floor up, I have it set at 2 just now rads are hot but the house is not that hot I have correct rad size in all rooms.

 

[MickyP10]

Think it's more involved than that but try no. three and see what happens. Were they hot before? Is the pump like for like? Do the rads need bleeding/balancing? Boiler temp, etc...

 

[Armo74]

If all the rads are hot but the rooms feel cold i would be questioning the rad sizes.
How do you know they are sized correctly?

 

[Badger76]

Put new heating in last year always thought it was a bit cold, system is balanced and there is no air in rads, boiler temp is ok the rads get hot.

 

[Badger76]

I took size of rooms and gave then to plump centre they told me they were correct size for room.

 

[Armo74]

Insufficient insulation and undersized rads= cold house.
Did you fit the heating yourself?
If the rooms have always been cold since the installation I would calculate the heat loss again and see if the rads are sized correctly.

 

[Badger76]

If I move the pump to three will it make any hotter heating was fitted with a company cavity wall insulation done and some of the rads are bigger than they should be.

 

[MickyP10]

Try it!

 

[Galoka]

I took size of rooms and gave then to plump centre they told me they were correct size for room.

There is rather more to it than just room size to do the sizing properly, if you want to check, this site came up on a recent tread and seems pretty good.

http://www.starsapp.co.uk/

AS well as the rads being the right size, the pipe runs need to be able to carry enough water to each rad. Though in a typical domestic situation, 22mm pipe for the 'main' runs and 15mm to the rads will work fine.

Increasing the pump speed will probably help if the rads aren't getting enough water so they aren't putting out all the heat they could. If however they are then you need to look at the sizing again.

Do all rooms not get hot enough? is the room stat kicking in? are the TRV's closing down?

 

[Badger76]

At the temp outside just now the rooms get hot but when it gets cold I need to top up the heating with a wood burner.

The trvs are all working ok, the whole heating system works perfect with the only exception of the house not being as hot as it should when it gets very cold outside.

 

[Galoka]

Ah, I see. Well it might well be that the system can't put out enough heat when colder outside.

Some of the pro heating engineers around here should be more up on current practice, but when I did the design for the CH in my last house (1997) ISTR that the suggested external design temp was -1C - so if it gets much below that it the system might struggle to keep the house warm. I think I used a lower minimum design temp , maybe -5C

 

[Agile]

The typical design in the UK is for -1 C outside.

But the calculators usually include about 10% extra power to assist with warming up from cold and when its is colder outside.

Tony

 

[Badger76]

I am going to set the pump at 3 will let everyone know how I get on.

 

[Agile]

For most installations "2" is the best setting.

You need to measure the flow and return temps of each rad before fiddling with pump speeds.

The heat output depends on the flow temp from the boiler. Turn that up a little after balancing the rads if that is needed.

Tony