Sealed system expansion vessel question(s)

[jaketabb]

Thanks for helping.

So a bigger than necessary vessel is OK, not dangerous or likely to cause any nusiance from my heating system? I am thinking a smaller one, would not be able to take up the volume of heated water and the pressure valve would open up??

Is there a standard size/charge pressure for domestic ?
If I were to under - charge it or over - charged it what would be the effects?

 

[kevplumb]

under charge it the system press would rise to much and blow the prv

Is there a standard size/charge pressure for domestic ?

.75 to 1.5 bar depends on the system volume

overcharge it (depending on how much) ain't a prob

 

[jackecole]

UNDER CHARGED VESSEL: your system pressure will read LOW on the pressure gauge as the low charge will not be able to force the water (when cooled down) back into the pipework/system - and you will top up, but when the water is heated in the system, there is not enough space for it to go and the PRV will discharge.

Average pressure charge is 0.5 bar

 

[doitall]

No, Undercharge and the system pressure will shoot up and discharge via the prv.

The system pressure is different to the pre-charge in the expansion vessel.

 

[kevplumb]

UNDER CHARGED VESSEL: your system pressure will read LOW on the pressure gauge as the low charge will not be able to force the water (when cooled down) back into the pipework/system - and you will top up, but when the water is heated in the system, there is not enough space for it to go and the PRV will discharge.

Average pressure charge is 0.5 bar

shoemenders

 

[jackecole]

yes if the system pressure is under charged from the start that will happen, BUT if the charge is lost naturally over time, what I wrote will happen

 

[kevplumb]

and this is relavent to the topic under discussion

 

[doitall]

yes if the system pressure is under charged from the start that will happen, BUT if the charge is lost naturally over time, what I wrote will happen

Shoemenders

 

[jackecole]

was just pointing out!! EXP vessels are very confusing little thingies!

Another point OP is: the MORE charge your vessel requires, eg 1.5 bar, the LARGER the vessel will have to be (when choosing gthe correct type). Eg a system with 75 litres of water requring just 0.5 bar pressure charge can use a smaller (slightly) vessel than a system of 75 litres water content requiring a 1.0 bar charge, etc

 

[kevplumb]

Another point OP is: the MORE charge your vessel requires, eg 1.5 bar, the LARGER the vessel will have to be (

quit while your losing bonny lad

 

[doitall]

I don't think you know how or why the expansion vessel is there or how it works.

 

[kevplumb]

yes i do

it's for the water te gann in like

 

[jaketabb]

Thanks for all your replies to my post!! Although I am fairly confused now after reading all the replies and contradictions!!

Can I ask a few last questions before ending this post please?

1)A slightly over sized Ex Vessel is OK? No side affects?

2) An undersized Ex Vessel will mean the pressure valve discahrges as not enough space for heated up water to expand into? Is that right?

3) An over charged Ex Vessel is OK as long as not pumped up way to high

4) An under charged vessel will mean the pressure valve will open when the water is heated up as there is not enough expansion space for it to be accomodated? And when cooled down the system will need to be re charged up again as the pressure gauge/dial will read low due to the discahrge?

5) The more pressure charge a vessel has, like 1 bar instead of 0.5 bar, then the vessel will have to be slightly bigger in size to cater for the less space for water due to extra air charge?

6) 0.5 bar is OK to charge up to as the highest radiator in my house is no way near 5 metres above the vessel?! And a standard size vessel (looking in screwfix and 8 litre vessel is smallest size) is OK for my 3 bedroom house?


Thanks for all your help

Best wishes

Jake

 

[kevplumb]

Thanks for all your replies to my post!! Although I am fairly confused now after reading all the replies and contradictions!!

Can I ask a few last questions before ending this post please?

1)A slightly over sized Ex Vessel is OK? No side affects?

2) An undersized Ex Vessel will mean the pressure valve discahrges as not enough space for heated up water to expand into? Is that right?

3) An over charged Ex Vessel is OK as long as not pumped up way to high

4) An under charged vessel will mean the pressure valve will open when the water is heated up as there is not enough expansion space for it to be accomodated? And when cooled down the system will need to be re charged up again as the pressure gauge/dial will read low due to the discahrge?

5) The more pressure charge a vessel has, like 1 bar instead of 0.5 bar, then the vessel will have to be slightly bigger in size to cater for the less space for water due to extra air charge?

6) 0.5 bar is OK to charge up to as the highest radiator in my house is no way near 5 metres above the vessel?! And a standard size vessel (looking in screwfix and 8 litre vessel is smallest size) is OK for my 3 bedroom house?


Thanks for all your help

Best wishes

Jake

1 yes

2 more or less


3 yup

4 yup

5 no

6 not relavent

but you have the gist

 

[jaketabb]

Thanks. The only reason I thought the more charge the vessel had then the larger size it would need to be is because i read a chart a system with 75 litres of water content with a 0.5 bar charge required only 6.3 litres of vessel and one with 1.0 bar charge required 8.2 litres of vessel!!