Aidan wrote in message
ups.com...
Dave Baker wrote:
So I dug out an old radiator valve, slapped it on the end of the vent in
the
loft and turned it off. It's been that way for years and hasn't made a
scrap
of difference to anything other than the loft is now dry.
With all due respect, you're daft.
I'm actually a rather competent engineer who was hoping for reasoned opinion
on the merits of this vent.
Take it off.
No thanks. As I say everything works very well as is.
So what purpose,
if any, was the vent really serving?
In normal operation it releases any air that gets into the system.
Typically dissoled oxygen in the boiler return wil be released from
solution when the water is haeted in the boiler and is discharged from
the open vent.
Firstly, the water in the boiler system always has an open vent path via the
fill point at the bottom of the tank in the loft. If water can get down that
I see no reason why dissolved oxygen can't get back up it.
Secondly, The vast bulk of the water in the system is in the radiators and
that's where the vast bulk of any dissolved oxygen will end up. There is no
way for bottom fed radiators to have this oxygen removed than by bleeding
from the valves at the top. A bleed valve at the top of the boiler system
would surely do the same rather than having to have a permanently open vent.
In the event of a control failure, it is a safety device; it releases
steam, prevents the system becoming over-pressurized and bursting. In
your system, such a failure would probably now cause the contents of
the heating system to be discharged into the loft and the boiler would
dry-fire to destruction.
Nonsense. The system isn't pressurised other than by the head of water from
the loft tank. The contents of the system can't be discharged into the loft
other than by the same pipe from the bottom of the loft tank which is
continuously filling it up anyway.
It was pumping over probably because it was piped incorrectly.
Possibly but it was certainly ok for many years and the only change made to
the system in 19 years was a new pump which was fitted by a Corgi plumber.
Now it's possible this was fitted to pump in the opposite direction from the
original pump but I can't instantly see how this would make a deal of
difference anyway. I'm open to suggestions as how it might. At present the
vent is on the return side of the pump so if anything I would think this
would give the least chance of pumping over.
Get
someone competent to fix that problem. Conversion to a sealed system
would be an improvement, if the boiler is suitable; if you'd like that
done, get someone competent to do that.
The boiler certainly isn't going to explode and anyway
there's a blow-off valve on the back of it.
I find your faith in a cheap safety valve to be touching.
They don't have to do anything in normal operation. If called upon to
operate in anger, a disturbing number fail to work. Many have been
dripping inconspicuously for years, the water evaporates from the hot
safety valve and the accumulation of limescale deposits concretes the
valve immovably shut. Have you tested the valve?
It's been checked, cleaned and the washer replaced a couple of times and is
fine. In any case the system is always vented to the bottom of the loft tank
as I have said.
The vent to the main part of the cylinder doesn't overflow of course
because
it isn't pumped but again I see no point to it other than maybe to let
any
air in the cylinder get out. However wouldn't the air be immediately
displaced out of a hot tap somewhere the first time the system was
filled if
there was no vent?
Kin 'ell! Is this a wind up? Leave it alone.
I have every intention of leaving it alone because it cause no problems as I
have made clear. Please try to confine yourself to the physics and
hydraulics of the issue rather than pontificating.
Immersion heater contacts frequently weld themselves together, so the
heater fails on. The open vent would then discharge steam. If you block
it, the steam will blow the contents of the cylinder into the storage
tank. If that discharge route is blocked, this happens;
There is no electric heater in the tank.
http://www.waterheaterblast.com
That is a small water heater (12 US gallons). Drivel loves posting that
link to promote his thermal stores, but someone proposes plugging the
vent on a domestic hot water storage system and he makes no comment; he
is a dangerous idiot.
Unvented water heaters are good, but they have at least 3 sequential
safety devices for each heating system. They are costly. A vented
cylinder cannot be converted.
--
Dave Baker
www.pumaracing.co.uk
*** Free account sponsored by SecureIX.com ***
*** Encrypt your Internet usage with a free VPN account from
http://www.SecureIX.com ***