Hi experts,

I have what is probably a very simple question - I'm a newbie with
looking after central heating systems, being a new homeowner and having
grown up in a house with warm air vent heating (these radiator things
really are a new experience...).

To set the context, my boiler is on its last legs and received a "Not
to Current Standards" (NCS) warning from the gas engineer who recently
serviced it, on account of the flue position under an open porch - so
I'm the process of getting estimates for a replacement. In the
meantime, however, I'd like to do something about its kettling, which
has become very bad (the sound is actually more like knocking and
banging than kettling). As this is only a short term measure, I don't
want to descale and flush the system, because that would get done as
part of the new boiler installation. Reducing the temperature on the
boiler thermostat (it's now set at about 66 C) has improved but by no
means eradicated the problem. Also, I am absolutely sure there is no
air in the system (I've bled all the radiators, the radiators
themselves are not noisy, and they all heat up pretty evenly all over).

So, instead, what I've done is get hold of some Fernox noise reducer
and I've poured that into the expansion tank in my loft, as indicated
in the instructions on the bottle (which are really pretty brief). I'm
left wondering if this is all I need to do? Having been up in the loft
while the CH is running, it appears that nothing is moving up into the
expansion tank at all - the water in it is cold (and a little manky,
with one or two dead insects in it and cobwebs over the top), and the
pipes connecting it to the hot water tank are also cold - stone cold. I
checked the valve on the relevant pipework, and it's definitely open
all the way.

Now, perhaps this is normal if the system is running nicely and not
getting too hot? However, am I to expect that the Fernox additive will
get into the main part of the system simply via diffusion along the
pipework (as per standard chemistry/thermodynamics) - or should I drain
a little from the bottom of the system to draw what's in the expansion
tank down into the main part of the system? The instructions on the
Fernox didn't say anything about this, but it seems to me that it might
be necessary?

I also have two related questions:

1. Should the expansion tank and relevant associated pipework really
remain stone cold all the time, even when the CH has been running for a
while? Could there be some kind of blockage between the expansion tank
and the hot water tank? If so, what would be a good way of
investigating and correcting?

2. Should the expansion tank really be uncovered, so that the
afore-mentioned gunk and dead insects can end up in it? I appreciate
that the purpose of the tank is to allow the sytem to "breathe" in and
out as the CH water volume adjusts with its temperature - however,
presumably it would be OK to place some kind of non-airtight cover over
the tank?

Thanks very much, and apologies if these are very simple questions for
which the answers are obvious to most others!

Andy

Axeman wrote:
Hi experts,

No expert.... just plenty of practise recently :/


Now, perhaps this is normal if the system is running nicely and not
getting too hot? However, am I to expect that the Fernox additive will
get into the main part of the system simply via diffusion along the
pipework (as per standard chemistry/thermodynamics) - or should I drain
a little from the bottom of the system to draw what's in the expansion
tank down into the main part of the system? The instructions on the
Fernox didn't say anything about this, but it seems to me that it might
be necessary?

I'd tie up the ball-cock in the F&E tank, or turn the water mains off,
then drain 8-10 litres from the lowest drain point to draw the fernox
into the system, release the ball-cock (or restore mains pressure), to
refill as needed. Check the rads (bleed them)... but chances are they'll
be okay.



I also have two related questions:

1. Should the expansion tank and relevant associated pipework really
remain stone cold all the time, even when the CH has been running for a
while? Could there be some kind of blockage between the expansion tank
and the hot water tank? If so, what would be a good way of
investigating and correcting?

Ideally, yes, the F&E should be cold, although not unusual to get some
heat in there e.g. if you introduce air into the system. In my
experience (this morning) my F&E was cold.


2. Should the expansion tank really be uncovered, so that the
afore-mentioned gunk and dead insects can end up in it? I appreciate
that the purpose of the tank is to allow the sytem to "breathe" in and
out as the CH water volume adjusts with its temperature - however,
presumably it would be OK to place some kind of non-airtight cover over
the tank?


No. The F&E should be covered (and insulated). If you get any CH water
drawn up the expansion pipe expect that to bring some of the sludge from
the system with it

Thanks very much, and apologies if these are very simple questions for
which the answers are obvious to most others!

Andy

Thanks for the advice Mike, I'll drain a few litres from the expansion
tank as suggested (I'll scoop out some of the gunk first!). I'll also
get the expansion tank covered and lagged.

Thanks,

Andy

Axeman wrote:
Thanks for the advice Mike, I'll drain a few litres from the expansion
tank as suggested (I'll scoop out some of the gunk first!). I'll also
get the expansion tank covered and lagged.

Thanks,

Andy



Just to clarify... drain from the lowest drain point (downstairs
radiator, or boiler)... NOT from the expansion tank.

Yeah, take some paper towels or J-cloths with you into the attic... its
a pretty grim job, but better have the crap out of the system.


Mike

wonders how long he can last before unscrewing the newly installed
magnaclean to see how much crud that has picked up