30kW System Boiler Choice

[Tibbot]

From that, anyone would believe the people who've replied have a responsibility to you.

 

[MC2012]

 

[namsag]

Simond no not on drugs try reading up on what is required from Central heating .Then after that try reading up on your 9.5 degree statement

 

[D_Hailsham]

Simond no not on drugs try reading up on what is required from Central heating .Then after that try reading up on your 9.5 degree statement

I think it's you, Namsag, who should read Simond's example more carefully!

Outside temp = -2C
Inside temp = 21C
∴ Rise = 23C

If you need 30kW for a 23C rise, 15kW will give only 11.5C rise from -2C. So the room temperature will reach 9.5C.

 

[namsag]

Dont talk stupid the 30kw is to get it up to temp in ONE HOUR not the maximum temp that it will achieve when left on all day .
15 kw will get it higher than 9.5 when left on all day what is so hard to understand about that

 

[Ihavenojob]

Dan knows his stuff (as do most on the CC) so I would take heed.If it was down to me I would have a Vaillant,I like them.

 

[scoobydo123]

Just not a 4 series unless you like them to short cycle

 

[simond]

So using your logic, Namsag, a 5 kw boiler would take 6 hours to heat this house from outside temp of -2c.........


Yep, thought so. ha ha.

Heatloss calcs for MCS accredited systems now have to use CIBSE guide B. This is generally acknowleged to be the most accurate method and has to be used for FiT.

Suggest you shell out £100 for a copy.

Ps: to stroppy OP, the best one is the Vaillant new mkII ecotec 6 series, but size it scientifically, rather than eyeballing it.

 

[namsag]

No that is not how it works as well you should know .
You seem to struggle with what is required to get a room up to a rquired temp in the proper time . I am not here to educate you i dont have the time. try using google more selectively

 

[D_Hailsham]

No that is not how it works as well you should know .
You seem to struggle with what is required to get a room up to a required temp in the proper time . I am not here to educate you I don't have the time. try using google more selectively

Sorry, Mr N, but it's you who needs the education.

A house will only get warmer if the heat produced by the radiators (input) exceeds the heat lost through the walls (output). When the input equals the output the temperature cannot increase any further. The greater the difference between input and output, the faster the house will warm up.

The standard method is to size a system so it can heat up from -1c to 21C. This is done by calculating the heat loss when the inside is at 21C and outside -1C. Ignoring the time taken for the radiators to reach working temperature, initially the input will considerably exceed output, so the house will warm up quickly to begin with. As the house gets warmer the output will increase. However the input will stay constant, so the rate of heat up will reduce. Most systems are oversized by up to 15% to allow faster heating up and a safety margin for excessively cold weather.

My calculations are quite correct. If you need a 30kW boiler to maintain a temperature of 21C when it is -2C outside, a 15kW boiler will only be able to maintain a temperature of 9.5C, no matter how long you wait.

I don't know where you get the idea that a system is designed to provide a one hour warm up time.

 

[simond]

Trouble with forums is that you can easily make yourself look a fool. There's always the 'edit' button, Namsag.

 

[DeltaT2]

So using your logic, Namsag, a 5 kw boiler would take 6 hours to heat this house from outside temp of -2c.........


Yep, thought so. ha ha.

Heatloss calcs for MCS accredited systems now have to use CIBSE guide B. This is generally acknowleged to be the most accurate method and has to be used for FiT.

Suggest you shell out £100 for a copy.

Ps: to stroppy OP, the best one is the Vaillant new mkII ecotec 6 series, but size it scientifically, rather than eyeballing it.

With the greatest respect Simond, you're saying that like the MCS scheme is the Holy Grail..............

Have you read some of their drivel???!!! I mean, they even promoted ASHPs.................
C'mon??!!!

The OP going off in a strop is funny though, nearly as funny as saying all the great minds are housed in the combustion chamber pot.

 

[simond]

I don't dare write here what I think of the Government MCS scheme. If I did, they'd find a way of booting me off it.

However the CIBSE guide is about the most accurate heat calc method, if one wanted to be anal about it. Which I did!

 

[namsag]

D Halisham you seem to struggle along with Simond that central heating is not designed to only reach 21 degrees when its minus 1 outside strange yous both use the figure minus 2.
The rad sizing is to get it to 21 in a set time (this is not the maximum temp the house will get to) otherwise the heating could be on all day to eventually get it there , its in the old books that you wont find in your google search
So using your calculation in the winter of 2010 when it was minus 17 outside even with a 30kw boiler a house would only have got to only 5 degrees eh dont think so . Or in the worst places at minus 26 the houses would not have got above freezing
And you say an undersized boiler would have got it to around minus 7 well there is a thing called experience and i dont think anyone last year that i know attended any house because it was not even getting above minus and we have some seriously undersized boilers around.

Answer this in winter of 2010 did your own house heat up to perfectly ok

 

[scoobydo123]

Heatloss