Boiler not heating all of the RADS

A good point and one I forgot to mention. Also, whilst TRVs have to contend with the self heating effect due to their proximity to the heat source they're controlling, they're a reasonable alternative to the use of expensive remote temperature sensors in each room wired to individual solenoid operated valves to obtain improved temperature control. TRVs may be a compromise solution but at least they *are* a (more affordable, if less than perfect) solution.

The main problem with TRVs being that it requires the user to keep fine tuning their settings over several days to set the room temperature to a reasonable approximation of what is deemed to be comfortable for each particular room or heating space. They don't offer the simplicity and instant gratification that a more sophisticated remote thermostat controller (calibrated in actual degrees C or F) is able to provide the user. Such sophistication costs money which may not necessarily offer a return on investment (especially in a house full of 'knob twiddlers').

I can confidently say from experience that TRVs are not at all a replacement for a room stat. I explained why earlier.

NT

Thing is no room stat ever can cope with cool spots in the average room. Unless you have some form of forced air circulation. So the TRV - especially if more than one rad in a room - can do just about as good a job.

Most of use inherit a system that was pre-installed, either by a previous owner or a spec builder. They are normally planned for least installation cost.

Andy

Hence my 'caveat' :-)

Mind you, when the installer has no choice but to use a rad distribution manifold on each floor, placing the manifold blocks to minimise installation costs usually works in favour of balancing the flows for each radiator on their given floor. However, this still leaves some variations in the balance of flows going from the main flow/return manifolds serving each floor manifold.

In our case, on account of the DHW tank's location which dictated the location of the pump and the 3 way mid position valve, this placed the main manifold in the void between the ground floor ceiling space and the

1st floor which isn't too far from midway between the ground and 2nd floor radiator circuits. I guess the LSVs were throttling the 1st floor rads the most to balance the floor manifold flows. Mind you, with only three rads on the 2nd floor and 5 rads each on the ground and 1st floors, leaving the LSVs wide open on the ground and slightly more remote 2nd floor rads would probably be about right once the 1st floor rad LSVs had been adjusted.

Mind you having successfully removed the back bedroom rad last weekend to allow the plasterer to re-plaster the room including sorting out the crumbling plaster behind the rad, I'm encouraged to repeat the exercise with the remaining 11 rads (the heated towel rail is a recent replacement a mere 6 or 7 years ago) just to flush out the sludge which must have settled to the bottom of each rad as I discovered with the one I had been

*forced* to remove.

I collected very clean water from that rad which only started showing a hint of blackness when it was down to the dregs. Said water was recycled back to the header tank after tying up the ballcock and bailing it out to a dry state. The ballcock remains tied up for the time being until I drain down my next rad for flushing out.

I plan on collecting the rad water for re-cycling back to the header tank before refitting the back bedroom rad to minimise diluting with fresh untreated mains water. I'm also planning on buying another five litres of Fernox inhibitor[1] ready for when I re-fit the last two rads so as to maximise the strength of inhibitor getting into the system and minimise squandering inhibitor[2] on a header tankful of water to a minimum.

[1] I lost about half of the 22 quid's worth I'd refreshed the system with just 6 months prior to our 'Bull in a China Shop' builder hammering a nail through a CH pipe running under the 1st floor bathroom we were having revamped around 18 months ago. This 'accident' was despite my warnings for him to take care to avoid damaging the pipework, the presence of which I'd alerted him to.

His plumber repaired the pipe using some sort of speedfit/pushfit coupling which, TBH, I'm not entirely sure can be regarded as a reliable alternative to a good old fashioned soldered Yorkshire joint. Anyway, I've been meaning to freshen up the now diluted inhibitor and now seems to be an excellent opportunity to kill two birds with one stone (give each rad its very first flush out in over thirty years and bring the inhibitor back up to strength).

[1] I know it's considered a good idea to give the header tank a dose of inhibitor to reduce bacterial growth notwithstanding that the anti- oxidant component will be consumed in pretty short order but I plan to hold back a quarter litre to add as a final measured dose rather than just leave it to chance.