Wednesday 1 February 2012

Central Heating twiddles

 So recently I've been noticing that the heating in the house is on what seems like a lot of time, the radiators aren't always as hot as I'd expect and generally the house is a bit chilly. Now this is during the coldest time of year where I live in the UK, so temperatures outside are dropping to 1 or 2oC overnight and during the mornings not getting far beyond that. With everyone in the house out during the day I'm unsure what it goes to during this time, but on evenings/overnight is when we notice it. So I started to watch how the heating was setup and then started tinkering!

We use a gas-fired central boiler (not combi), that has timed on/off schedules for heating and hot water. The hot water/heating switch is done by changing the valve setting from the pump circulation (i.e. when hot water is set to on it will divert some/all of the heating hot water circulation into the hot water tank). So my first observation is that when heating and hot water are on at the same time then surely this will halve the efficiency of doing one or the other jobs quickly.

Radiators in each of the rooms, the majority have TRV (Thermostatic Radiator Valve)'s fitted on them, and have a 0-6 scale for setting the desired temperature. Most of these are set to maximum all the time. Only two radiators do not have TRV's, these are both in the living room/dining room (It's one large area, no partition walls, etc). This is also where the temperature room thermostat is located.

There is a single room thermostat in the dining room, this is a digital/electronic temperature sensor running off two AAA batteries (annoying when they run out), that switches the heating circulation on and off depending on the ambient temperature.

The other little niggle is that the house is quite open-plan. The downstairs is a large living room/dining room, open to the staircase, and obviously up to the upstairs landing. Therefore the majority of heat (in my limited knowledge) will escape straight upstairs to the top of the stairs! Not ideal.

So, my first steps were to change the heating programmer, to get different on/off times for the heating and hot water cycles, and to prioritise heating by only switching hot water on after I've giving the heating a chance to warm the place up. So I opted for 3 on/off sequences during the day. First one for when we get up on a morning, on 5am-8am heating only. Then for when we get home, 3am-9pm. Then one to keep the chill off at 10pm-11pm. I went for hot water going on once daily from 4pm-8pm. So that seems to keep the heating happily running and not letting the house get too cold, as I think that was an initial problem, the house dipping way too cold, so taking the heating too long to warm back up.

The room thermostat was then set to 20.5oC as that seemed a reasonable temperature that is warm but not boiling. This I think might not be helping things, as I think this might need to be higher, but more on that later.

I then attacked the radiators and the TRV's, as I know I had one of these fail in the kitchen and jam closed, so that TRV was removed, so that radiator is just on full all the time. A few of the radiators needed bleeding, so did that for a few days to make sure we didn't have any problems with air in the system. I then turned ALL TRV's down so they weren't sitting on maximum. This was because a few websites I had read stated that running a TRV at maximum is bad for the valve and heating system (can't find the quote to cite now, if you know please comment/post back!). Then went round each of the rooms and changed the TRV depending on if the room should be hot/warm/cold, the majority of bedrooms I set on 5 (one off maximum), bathrooms a little below that and thought I'd leave it at that.

Unfortunately the heating still wasn't really doing what I wanted, the children were complaining of a cold bedroom during the night/morning, our master bedroom got red-hot at night and early mornings, and the rest of the house was warm! So that didn't quite work it seems. My next discovery were the next generation of programmable TRV's. These you can set times/dates and temperatures and the unit will vary that individual radiator based on this. I thought this would be ideal for the master bedroom, as during the day/early evening it was pointlessly heating the room. So I purchased a programmable TRV from a heating/electronics firm in the UK (I'm not going to name them here, as I found their service SHOCKING, it took 2 devices and me piecing the working parts from the two together to get a single working TRV. Not impressed!).

I ordered "Radio energy-saver regulator" which is a german-manufactured device that simply plugs into your standard TRV fitting, so no draining the system, etc, just unscrew the old TRV top off and this on. You program it either via its LCD screen, or you can also use the USB computer programmer, which I chose. You then set what time-periods to use, temperatures and set it going. This has made a huge difference to the master bedroom, although some further tweaks to the schedule are needed as at the moment its like living in the antarctic! But that could also be due to the overall heating turning off too soon. Obviously the TRV will only heat the radiator up when three conditions are now met. The main heating timer is on, the downstairs thermostat is set to heat and the programmable TRV decides that its schedule and room temperature say it needs to heat. Unfortunately it has no control over the first two conditions, so therefore if the sequences aren't matched, then this fails, and I suspect this is where I'm going wrong at the moment. I'm setting the TRV schedule to warm the room before we retire to the bedroom, but at this time the rest of the house is warm enough, so the thermostat on the heating has cut out, so although our TRV wants to heat the room, it can't as the heating isn't firing. So more tweaking is needed here!


And thats about where I'm up to. I need to do some more tweaking with programs and temperatures to get things right, but I'm happy that I have much more control and I believe I can see where the problems are on the system now!

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