under sized boiler ???

[AWheating]

Aw you mean have hot bath in a cold bathroom or a cold bath in a warm bathroom, electrical shower will fix that

:75:

LOL, if the cylinder is modern, it should keep warm for many, many hours. long enough for the heating to warm up

 

[Roger Welton]

Non issue in my eyes, as said just vary the timings slightly. We have the same at home boiler is currently range rated to 19kW with 15 rads (in 2 zones) and 300l unvented and we have never been cold or had no hot water.

 

[buckley plumb]

they used to say allow 2kw for the hw on vented cylinders do unvented cylinders realy need that much kw .

 

[cr0ft]

No, the modern unvented cylinders just have much more efficient heat exchangers so they can actually disperse more power into the water quicker. You could charge them with 2kw of heat from the boiler and for similar sized cylinders they would heat up in exactly the same time as an older vented one. Well a bit quicker actually due to better insulation but let's not split hairs!

 

[Whyme]

depends on the demand if its used by a few teenagers its gonna rob the heating regardless how long it heats or keeps the heat..i do like to learn and if 20kw can can heat a big house and big cylinder I'll be fitting smaller boilers in future.

 

[cr0ft]

Our cheap skate new home builders installed a Potterton Promax 15 SL 15KW system boiler onto our system. It has an unvented hot water cylinder with an 18.3KW heat exchanger. There are just under 15KW of radiators in our house.

You can get away with sizing a boiler to suit the heating requirement only in a house like Ray says. The rads will not be heated for the half hour or so a modern unvented cylinder takes to recharge, in practise it will hardly be noticed.

I caveat this with there are just 2 of us in the house and we use showers only most of the time.

Our house is a 5 bedroom detached house. I would say the boiler is undersized and when we change it I will fit a 24KW system boiler but it does the job.

 

[Nostrum]

There is no requirement to allow both the heating and hot water to be run at the same time under full load. Remember, the heat loss calculated will be at -1,-3 or whatever ie 1-2 weeks a year.

The rating of the coil is irrelevant really as long as heat up time complies with part L. In reality who's checking? How often will you need to heat the entire cylinder from cold?

if you are adding the coil size to the heat loss then your massively over sizing boilers.

Sounds like this boiler was sized perfectly which makes a change.

Also, who's to say the radiators aren't over sized? Sizing a boiler should be done by heat loss of the building not radiator sizes.

if they are running out of water, the cylinder is undersized not the boiler.

 

[Whyme]

Suppose its like everything, make do and change settings or get it changed..also being there and knowing if their bath people or shower, and when through the day are people using hw....

 

[Killy Bing]

the heating stops when hw is heating up.

Lockshield valve on the coil, balance it and job done?

 

[Whyme]

im assuming its balanced. i still believe it to be undersized but hay ho.