Adjusting TRVs

In article , snipped-for-privacy@hotmail.com writes

Although TRVs are pretty crude devices, I don't think they're to blame in this case, it's just how our bodies perceive comfort level.

Consider a room with a radiator on one internal wall controlled by a TRV which is set to 22degrees. Say the opposite wall is external and it is not a particularly cold day. The surface of that wall might be 18degrees; lower than the room air temperature because it is external and is losing heat to the outside world. Sitting in the middle of the room you experience a balance between the two, probably not the mean of 20 but maybe you feel it is about 21degrees in the room.

Now say there is a cold snap. The external wall loses more heat and might have a surface temperature of say 14-16degrees. Sitting in the same place you experience a lower comfort level; you may think it is only 18 or 19 degrees, even though the air near the TRV is still controlled to 22. You feel colder so you turn up the TRV setting to compensate. The reverse happens when the temperature rises again.

An ideal heating system would compensate for this as the outside temperature changes but I don't imagine there are many in the real world that do.

The message from fred contains these words:

I am not a particular fan of TRVs (and have said so often enough in the past) because their very closeness to the radiator means they are influenced as much by the radiator temperature as by the room temperature.

If you control your living room with a room stat the need to adjust disappears at least for that room.

It has been mentioned occasionally that it is possible to get TRVs with remote sensors which would put TRVs almost on a par with a room stat (depending very much on where the sensor is sited) but I have never seen any such animal for sale.

Cue dIMM to snip drivel and say he has all his houses fitted out with them.

In article , Roger writes

Only to a degree I think (and probably to such a degree that you wouldn't normally notice the difference), the thermostat will only control the air temperature. I am saying that the comfort level (the perceived temperature) is influenced by cold (or hot) bodies in the room too, by radiation. Radiation will be less important when the temperature differences are less, but on a cold day will become more significant. Sitting near a cold external wall (or in the extreme a window) will feel cold, even though the circulating air temperature is as demanded.

Living in a house where the walls are 18" thick brings the difference between air temperature and comfort level sharply into focus ;-)

The message from fred contains these words:

I wouldn't know. All my external walls are 24" thick. :-)

I don't adjust my room stat from the time I turn the central heating on in early Autumn to when I turn it off in late spring (apart from when I am away for several days). What I do notice (as the digital temperature readout is constantly on) is that during the summer I tolerate (or even welcome) a lower room temperature than my thermostat settings. Incidentally my downstairs temperature settings are 19 C morning and evenings, 17 C through the day (I am usually at home part or all of the day) and a minimum of 13 C overnight. I find 17 C is just about acceptable sitting in front of the PC during the day but is a bit warm for housework.

In article , Roger writes

Ok, trumped then, but are you in bitter Scotland or just fluffy bunny, warm & cosy Englandshire :-?

Clearly more butch than me then, mine are set a bit higher and I turn the digital stat up a click on the most bitter of days.

Thanks for the alternate view.

I think its actually that they do not regulate the temperature in the room: They regulate the temperature of the air around the radiator.

If there is massive heatloss from a cold arae across the room, thenyou will need teh air arond teh radiotr several degrees higher t preserve the main body of teh room at a constant temperature. Al teh texts say don't put thermostats in places near herters. TRV's break that rle utterly.

They are better than nothng, but they are never a final correct and elegant solution. Crude bodges at best. They work better as the room insulation levels rise, which tends to equalise the temperature throughout the room as internal wall temps rise to meet the air temps inside.

They are lousy in older properties with draughts and cold walls.

The message from fred contains these words:

I was taught at school (long long ago) that in Summer Scotland is indeed cooler than England and the North of England cooler than the effete South but in Winter the isocheims (I had to get that out of a dictionary) run North-South with the coldest to the East.

I am on the East side of the Pennines but only at 535' above msl.

Probably a stupid point, but presumably the radiators are cold when you turn them up. Mrs Socks kept turning the valves up because she was cold, even though the radiator was pumping out max heat. I've explained how it all works now.

I'd probably describe my Victorian semi like that - not fully double glazed and solid outside walls.

But in the larger rooms, I've got more than one rad. Purely for convenience - I found it easier to site two or more small rads than one large one. And the cost difference when DIYing was modest.

FWIW, I found that mounting the TRVs horizontal gave slightly better control. As did balancing the system reasonably well with all TRVs fully open, and just relying on them to trim the temperatures slightly.