central heating problem

[andymort]

hoping somebody may be able to help me with a problem on my vented heating system ...

to cut a long story short

i have relocated my hot water cylinder and pump in the attic (to liberate space on the landing ... airing cupboard)

in order to do this I have lifted both the storage tank and the central heating expansion tank about 1.5m in order to provide the necessary head on the hot water cylinder and keep the expansion tank above the pump ... maintaining a positive presuure throughout all the system.

the problem i have is that my system is continuously filling up with air, rads require bleeding and the system is noisy (assume it is the air)

i think i am drawing air in through the vent to the expansion tank when the pump starts ... the length of the vent pipe is less than it was originally and i do get overflow from the expanion tank which seems to coincide with the pump starting

i have overcome the problem by selecting a lower speed on the pump, unfortunately at a lower speed i do not seem to be able to balance the system such that all the rads heat up ... no matter how much i try.

currently in the 22mm vent line there is a simple air separator (vessel)

i was wondering there was anything available that i could put in the vent line which would allow the vent to perform its required function but prevent the air being drawn in

i was looking at mechanical air vents/separators and backflow prevention products ...

any help would be much appreciated
_________________
enthusiastic but an amateur

[HSP]

any reason why you can convert to a sealed system incorporating an expansion vessel and filling loop??
_________________
Dont cha wish your bouyfriend was a plumber like me !!!

[andymort]

i don't know is the simple answer ... how does this work ?

looking at a schematic (found on the net) it appears the system is pressurised (gauge fitted) ... i guess with the main components being fitted in the attic i would not have access to the gauge to confirm the system is operating correctly

if the system requires topping up how would i know, and then how would i know when to stop filling ?

i am will to try anything that will solve the problem !
_________________
enthusiastic but an amateur

[andymort]

think i've done it but not in a conventional way ...

firstly i dropped the vent into the expansion tank, below the water level. This solved the air problem, pump speed increased ... all the rads nice and hot.

but ... water was drawn out of the tank, through the vent, and replenished up from the system, causing it to heat up like a rad

i have now fitted a non return check valve in the vent ... which seems to have done the trick

i'm not a pro so not really sure if this "solution" will introduce any other problems ... ?

comments/advice much appreciated
_________________
enthusiastic but an amateur

[mark6266]

what you have done is very bad pratice no valves should be fitted on the vent pipe ! I to agree with the first answer but for future reference (rule of thumb) your header tank must be at least 1 meter above the highest point in the system . i think you should call a pro in to convert to a sealed system also you can buy convertion kits for around £70 for one of the smaller ones . get the pro the tell you the size you need then buy it and pay the feller to fit it you will have a happy customer and be able to sleep at night and a lesson learnt . i wish you well but PLEASE dont fit any valves on a vent pipe ever (that is school boy stuff in plumbing you know)
regards mark (allinplumbing@fsmail.net)

[andymort]

all back to normal now ... thanks for the advice

i have also introduced the feed from the header tank into the system between the vent and the pump suction (as recomended in many "system design" sites)

this has stopped the air being drawn in and i can run my pump on the middle speed setting ... all the rads now heat up

the vent is now back to as it should be ... no obstructions

thanks again

am
_________________
enthusiastic but an amateur