Is my Suprima 40L too small

[ZeeCC]

Hi all

I moved into a house which has an un-vented central heating system/hot water tank system but the house has 14 radiators and some never get so hot that you cannot keep your hands on them. Is the boiler too small?

Cheers

David

 

[D_Hailsham]

It might be, then it might not. It all depends on how big the rads are.

1. What temperature do you set the room stat to?
2. How long does it take for the house to reach the set temperature in the morning?
3. Does it have difficulty maintaining the temperature?

If you want a ballpark figure as to the size boiler you need for your size and construction house., use the Recommended boiler size at:

http://www.sedbuk.com/

 

[ZeeCC]

It might be, then it might not. It all depends on how big the rads are.

1. What temperature do you set the room stat to?
2. How long does it take for the house to reach the set temperature in the morning?
3. Does it have difficulty maintaining the temperature?

If you want a ballpark figure as to the size boiler you need for your size and construction house., use the Recommended boiler size at:

http://www.sedbuk.com/

Thanks for the reply. I suppose my question is vague as I know very little about central heating and I wonder how such small boiler can heat up a 4 beds detached house efficiently. It does stuggle a bit in the corridor and 1 bedroom where the radiators are not that hot and overall upstairs radiators are not as hot as downstairs anyway. Maybe bleeding might help.

Cheers

David

 

[gas4you]

On the face of it it does sound too small, but then it makes a difference whether you have 14 small rads or large doubles etc.

You need to measure each rad and find a manufacturers catalogue to add all the heat outputs together, then add 3 or 4 Kw for the cylinder.

Your boiler is 12Kw approx, at a guess I would estimate you need about 18Kw minimum.

 

[baxpoti]

From your post, putting in a 'bigger' boiler would not resolve the problem of what is probably a poorly designed installation, undersized pipework and an unbalanced system (probably full of air and no inhibitor).

 

[bengasman]

sounds like baxpoti is right, whole system needs redesigning and modernising. time to get a pro in

 

[Agile]

It probably only needs balancing!

Look in FAQ on this site for details of how to do it.

It might also be rather sludged up but try balancing first.

Tony

 

[Meldrew's mate]

First check the pump is set to speed 2 or 3 (out of 3)

Try this simple test.
1. Turn boiler temperature setting to about half way.
2. Turn on CH but not HW
3. Turn roomstat right up high
4. Does the boiler ever stop burning (flame out, green lamp flashing slowly?
5. Do ANY of the rads get properly hot?

If the answer to 4 is YES then it,s large enough FOR THE LOAD WHICH IS APPLIED TO IT. Your next job is to balance the system to ensure even load to each radiator - see DIYnot guide. If the answer to 4 is NO and the burner has been running for over an hour then the boiler is NOT large enough.

Turn down the lockshield valve on each HOT radiator (usually the upstairs and small rads) gradually until the temperature difference between flow and return ends is about 12C - leave 10 mins between adjustments to stabilise. Once done all rads on a properly, or even vaguely designed system should improve their outputs, then redo the test 1 - 5.

Finally, check that all this good intentioned bleeding hasn't dropped the system pressure too low - for a two storey house about 1 bar is sufficient.
This method should keep you occupied for a couple of evenings during the advert breaks.

 

[stardanny]

Boiler may be too small for 14 radiators, but what about the pump? It may be set to low speed, you can check the radiator close to boiler may get hot than the rest of radiators.