I am getting TRVs put on my 25 rad central heating system.... The plumber
is putting in Drayton TRV-4's on most of the rads, aswell as power-flushing
whilst it is drained.
Wondered whether it is worthwhile spending the extra £300 he has quoted to
replace the remaining existing valve on each rad with a new lockshield.
Is it worthwhile replacing the other valve on each rad when you install
TRVs?? I personally dont think it is as you open the lockshield fully
anyway and dont use it at all. The only downside might be is if you ever
come to remove a radiator and the lockshield is leaking - you'd have to
drain the system down again?
Wasnt going to bother but wished to check others thoughts.
I can't see any practical benefit other than what you have already
mentioned. If they work then leave them. £300 seems an awful lot just to
replace valves but I suppose there might be a stuck olive or two. Wickes
do a pack of five 15mm valves for £9.29 or so. So you could do my
standard semi for less than £15 in parts plus labour.
You will pay for your sins. If you have already paid, please disregard
While you are having what appears to be a fairly major ch overhaul, I would
And if you are fitting decent TRVs like Draytons, go for a decent l/s like
You don't say how old the system is, but if it is any age at all and needs
power flushing, there is obviously a degree of crud in the system.
This can deposit in the valve bodies (as these are a point of max
restriction in the heating ciruit) and can lead to poor valve performance
and in the worst case blockage. Power flushing is not a cure all and the
efficiency of this method of cleaning can be reduced by intricate pipe
routing which slows the water velocity.
It would be interesting to ask for a (small) radiator to be removed after
the power flushing (before new valves are fitted), particularly an
end-of-line rad, and tipped up/manually flushed into a bowl. Make sure you
are there to see the results yourself. This would give a fair indication of
the effectiveness of the clean. Easy job and not much to ask if you are
paying £100s for the flushing.
These recommendations are not hearsay or guess work, as I have recently
overhauled a heating system in a 1970s property which had been suffering
pump over issues and was therefore pretty cruddy.
If you intend to stay in the property, consider fitting MagnaClean or Boiler
Buddy filters to keep crud at bay.
Also consider the controllability of the current system and whether it could
be easily improved.
That's an interesting comment in your final sentence and I find it a little
baffling. Can you enlighten me? !
I fitted TRV's to all my radiators last autumn (bar the hall radiator where
the roomstat is located). AIUI, radiators without TRVs are balanced so that
each radiator supplies sufficient heat for the room in question. A TRV
equipped rad will, of course, heat the room up to the required temp as set
on the valve, and then shut down. I'm baffled as to why balancing should be
necessary on such a set-up. I've been using my new system, with the
lock-shield valves fully open, throughout the winter and have found a
dramatic improvement over past winters. Temperatures in each room have
remained far more stable and constant without any need to be constantly
adjusting the room stat.
I'm genuinely intrigued by your comment and would appreciate your comments.
TRVs really only come into operation as each room reaches its control
temperature and they start to close down. Until then your system behaves
just like they aren't there and you need to balance the outputs of the
radiators to ensure than the house heats up evenly. If you don't do that
then you risk having the room closest the boiler with the largest radiator
stealing all the heat until that room reaches temperature (and the TRV
closes down) then the next nearest with the next largest radiator and so on
until the most distant room with the smallest radiator finally gets some
heat. The house will eventually get warm throughout but it is not the most
efficient or quickest way of going about it. In the worst case, a large rad
that is close to the boiler and wide open will raise the temperature of the
return flow higher than it should making a modulating boiler turn itself down
or a less sophisticated boiler start cycling. This will result in longer warm
up time or poor control.
Think of TRVs as devices to stop rooms becoming overheated, not as
It may be that your system has a pretty neutral balance to start with so
the extremes above do not apply or it may be that your previous balance
settings were throttling the system flow and slowing warm up. The latter
was certainly the case on my system on my first attempt at balancing and
opening it up a little and following the balancing procedure on the uk.d-i-y
faq site improved matters.
To balance a TRV system, open the TRVs fully and follow the procedure
on the uk.d-i-y faq then set your desired control temperature on the TRVs
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