Heat up time for cylinder?

[greenboy5]

Not so much a DIY question, but... is there a 'standard' time for a system boiler to heat an unvented cylinder? i.e. Kw per Litre? I want to be sure my boiler is working properly. (My boiler is 30Kw and I have a 250 l cylinder.) I should add my cylinder is not insulated, although I am considering buying a jacket if it will help.
Thanks

 

[JohnD]

if it isn't insulated it isn't up to modern standards so it might be quite slow. Modern ones have a calculated coil size.

A modern cylinder, in a modern installation, with a modern boiler, can heat up in 20 minutes. Obviously it has to be fully pumped

btw why on earth are you throwing money away with an uninsulated cylinder? and presumably uninsulated pipes too?

 

[greenboy5]

if it isn't insulated it isn't up to modern standards so it might be quite slow. Modern ones have a calculated coil size.

A modern cylinder, in a modern installation, with a modern boiler, can heat up in 20 minutes. Obviously it has to be fully pumped

btw why on earth are you throwing money away with an uninsulated cylinder? and presumably uninsulated pipes too?

Sorry - think I may have been dense here - I meant there is no external insulation around the cylinder. It is a modern one (I think) - a Telford Tempest installed only a few months ago - so I presume it has internal insulation...?

 

[Alfredo]

Follow this link. The heatup times table are on page 4.

Its downloadable so you can keep a copy.

http://www.telford-group.com/downloads/files/Installguide_tornado.pdf

Alfredo

 

[mysteryman]

The limiting factor in heat-up times with modern cylinders on a fully pumped system is often the heat transfer capacity of the heat exchanger coil. This is often much less than you might think. It should be at the very least 50% of the boiler output, and preferably more.

The other factor is the effectiveness of the cylinder thermostat or cylinder temperature sensor. This should be higher than the top of the coil - the old advice to fit it one third of the way up the cylinder was OK for gravity primaries. It needs to be in good contact with the cylinder wall or phial pocket, so that the controls respond quickly to rising water temperature.

 

[Biggles..]

Minutes = volume X temp rise / 14.3 X power input

Temp rise is difference between cold water and what ever cylinder stat is set at.

 

[45yearsagasman]

And don't forget to have your boiler set to at least deliver 70c as a minimum on the boiler stat.

 

[Ferpectionist]

The limiting factor in heat-up times with modern cylinders on a fully pumped system is often the heat transfer capacity of the heat exchanger coil. This is often much less than you might think. It should be at the very least 50% of the boiler output, and preferably more.

The other factor is the effectiveness of the cylinder thermostat or cylinder temperature sensor. This should be higher than the top of the coil - the old advice to fit it one third of the way up the cylinder was OK for gravity primaries. It needs to be in good contact with the cylinder wall or phial pocket, so that the controls respond quickly to rising water temperature.

The Tempest is stainless steel. If you want fast heatup and have the ability to downsize a cylinder then using a direct cylinder and have the a combi's water section is the most efficient.

1. Have a Surrey flange on a "direct" cylinder draw-off.
2. The DHW outlet of the combi to the Surrey.
3. The inlet of the combi teed into the cold fee or an available bottom tapping.
4. A Wilo bronze pump on on the combi inlet with non-return value in front.
5. Set the combi to 60C DHW.
6. Set the cylinder stat to under 60C.

The pump activates the combi section. Heat up is super rapid (plate heat exchangers are far more efficient than coils) as the hot water goes directly to the top of the cylinder. When the water cools in the cylinder the combi cuts in and pumps hot water to the top of the cylinder where it is needed. A 100 litre cylinder can perform like a 200 litre cylinder and when the cylinder is empty the combi gives enough to give a low flowrate of DHW. The Viessmann 222-F operates like this.

The cylinder can be switched out and only use the combi, by have a mo-mo valve on the cylinder inlet to stop water entering the cylinder, and of course fitting a cheap anti-vacuum valve on the cylinder.

It works out far cheaper. You buy a "direct" 90-100 direct cylinder, saving a wedge on a 200 indirect litre cylinder and bronze pump. Additional if you want, a mo-mo valve.

 

[Onetap]

water systems
george bramwell
morris mini
big burner
perfectionist

all your aliases

and i'm a troll

pi$$ of walter your a pest

You've missed a few, Kev. He's also known as Adam, IMM (International Man of Mystery), Dr. Evil, Drivel and others on the UK-DIY newsgroup which he has been trolling for years.

It is alleged by the resident troll hunters there that his name is, IIRC, John Burns-Curtis; he posted it, it's in the public domain.

He's an idiot.