Expansion vessel size large system

[slide]

Have seen many differing formulas for this.

My system volume is 1417 litres
My static head is 11 metres
PRV set at three bar

One calculation I found said it should be 145 litres... can you imagine?
Another said 50, which seems more realistic!

Cheers

 

[happyflyer]

That one hell of a system over 300 gallons, how big are the boilers

 

[newcastle phill]

Wow thats one mutha of a system.
Almost 1.5 tonne of water...

Whats it in......2 bed semi

 

[happyflyer]

http://www.bssindustrial.co.uk/uploads/docs/589.pdf

Its a two up and two down office block

 

[Ermintrude]

150 sounds reasonable

 

[slide]

Total 92kW. Cast iron/column rads.....

 

[Ermintrude]

So 150l then . Some expansion going to occur don't want the gaskets flexing on the groundfloor cos plant rooms on roof and fitted with 12l vessel?

 

[newcastle phill]

http://www.bssindustrial.co.uk/uploads/docs/589.pdf

Its a two up and two down office block

Now it makes sense

 

[Ermintrude]

That one hell of a system over 300 gallons, how big are the boilers

Cdi classic 24kw

 

[bright spark]

A rule of thumb from an expansion vessel/pressurisation unit pump supplier I was told to go by if your stuck on a Commercial job is 1 litre per kW once it's not a high temp heating system. Then go up to d next size up. In your case 100litres.
Should do ye. Did I read ye have d system pressure is set at 3 bar. Maybe I read it wrong, that's a bit too high for 2 storey block. 1.5 bar should be plenty

 

[Worcester]

The (Domestic - I know) Heating Design guide says @ PRV 3bar and 1.5bar initial charge = 0.156 * 1417 = 221 Litres

We regularly install 100 litre expansion vessels on systems with a 500 litre buffer tank.

Your expansion factor at 70° Average temperature is 2.2%, and the minimum recommended is 3% .

150 Litres is what I'd go for.

 

[Nostrum]

150 is about right, as a rule of thumb I work on 10%.

 

[happyflyer]

System water content = 1500 ltrs
Maximum water temperature = 80°C
Maximum allow working pressure = 3 barg – 0.3 barg
Initial system pressure = 10 mtr static = 1 barg + 0.3 barg


Expansion vessel efficiency = 3.7 – 2.3 = 0.38/3.7


Vessel size = 1500 + 10% X 0.03 = 49 / 0.38


130 ltr

nearest heating vessel. 150 ltres

Bet he's done it by now

BTW Expansion vessels are cheap if you fit one too big what the hell, if you fit one too small you will end up fitting another one along side it and you will look daft

 

[happyflyer]

Slide just slid away and did it without us, nice