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Central Heating - how to make things more efficient (Read 2876 times)

James Malloch

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We’re in a 3 bed house which stays pretty warm, but it’s a 100 year old terrace so still costs a fair bit to heat.

We use:

- Dining Room for breakfast
- 2 small bedrooms for working 9-5
- Dining Room/Living Room in the evening.

Our thermostat (digital but not smart) is on the upstairs landing which, given all the doors are generally closed, means the heating is often triggered. We could turn the thermostat down but we find it hard to get a happy medium where it’s on when we need it. Especially day-to-day depending on the outside temperature.

So I’ve been wondering about whether to get some kind of smarter system in.

Either a smart thermostat which we can put in our office which gets hotter was faster than the rest of the house, and then move down at the end of the day. Or some of the smart radiator valves which turn individual radiators on/off based on whatever temperatures you set them at for different times of day. Or even a combination of both.

Given that prices are due to rise and I prefer being warm, any thoughts or advice on setting things up to work more efficiently would be welcome.

dunnyg

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We used to have a thermostat that you could move, that worked well for us combined with turning some radiators on and off.

It was there when we turned up so no idea on costs etc.

spidermonkey09

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I have a similar situation and think to a certain extent this is part of the issue with old houses. Ours is a Hive and is pretty smart but I'm unconvinced it makes much difference compared to a normal system.

I am the same as you and hate being cold. I just have ours on a standard morning and evening setup and give it a 2 hour boost if its particularly cold during the day. For me a more low tech manual solution is way more likely to work in an old house with weird draughts everywhere.

sdm

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We used to have a thermostat that you could move, that worked well for us combined with turning some radiators on and off.

It was there when we turned up so no idea on costs etc.

That's what I have in my 3 bed Victorian terrace. I also didn't buy the moveable thermostat.

I use:
- Kitchen/breakfast room for breakfast and occasional WFH
- living room/boardroom in the evenings and early mornings (wanting it to be cool when training
- 1/2 bedrooms overnight

I looked a while back at whether it made sense to install a Tado/Hive/Nest etc system, primarily for geofencing as my schedule can be a bit erratic. My conclusion (before energy prices started rising) was that the savings would never outweigh the cost. I also have privacy/security concerns with Hive/Nest and I find the Tado valves are loud enough to wake me up when I stay in houses with them.

I've stuck with the wireless thermostat with radiators in each room turned higher/lower and then I occasionally move the thermostat or change the temperature if required. Mostly, this is restricted to turning down the heating for a bit before a board session.

SamT

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Problem is with a thermostat controlling your whole system is that its only valid for that one condition in that one location.

Wireless TRVs (thermostatic radiator valves) are a possible solution to easily 'zoning' your home.  Not 'that' expensive and relatively easy for a plumber, or competent DIY'er to replace.

Its faily widly accepted that TRVs don't actually function that well (i.e. acurately measure the temp of a room and turn on / off at the desired temperature).  But at least these give you the option to program them individually so you can have bedrooms on in the morning, but not in the evening, and living room only on in the evening etc etc.

https://theevohomeshop.co.uk/

« Last Edit: March 01, 2022, 10:05:55 pm by SamT »

Potash

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I have smart TRV in my place.

I am generally positive.

They fitted into the existing TRVs with no need for a plumber.

They generally are within a degree or two of the room temperature (apart from one room which is about four out).

I can set the house up with individual room temperature and time profiles to heat bedrooms only first and last thing, office when I'm in it. Some rooms on frost protection only etc.

None of that increases function over what constantly changing manual TRV settings could achieve. But who wants to spend all their time adjusting radiators.

The room heat on demand function is good and replaces the thermostat in one place issue. I need to get a plumber in to put a bypass valve on the boiler and an extra TRV on the bypass radiator to get the most out of this.

I'm sure it would work better with a modulating boiler.

The negative side is that the Hive app is shit. I spec large commercial BMS systems at work though so my expectations might be too high.

wasbeen

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If you have a condensing gas boiler, it is worth considering turning down the flow temperature on the boiler. Condensing boilers only work at peak efficiency if the return temperature is below 45 degrees C, this would normally correspond to a flow temperature around 50-60 degrees.

Typically they are set-up to operate with a flow temperature of 80 degrees and return at 60 degrees. At these temperatures the boiler is not condensing. This can be clearly seen as as a plume of steam coming out. This will knock the efficiency back by around 10%.

If you reduce the temperature, you may need to have the heating on a little longer. Depending on how your radiators are sized, you may struggle to get up to temperature on very cold days. From our own experience, it has not been a problem at all, as the house is much better insulated than when the heating system was installed.

https://www.theheatinghub.co.uk/articles/turn-down-the-boiler-flow-temperature

The other big thing is to turn off all the radiators upstairs completely apart from the bathroom. Obviously you may run in to problems if you are working from home. In order to control damp, you may need to have good extractor fan and/or a dehumidifier.
« Last Edit: March 02, 2022, 08:30:35 am by wasbeen »

dr_botnik

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Have you considered underfloor heating? Less energy, not mega difficult to install (you could probably do most of it, just need a sparky to wire it up)

SamT

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Have you considered underfloor heating? Less energy, not mega difficult to install (you could probably do most of it, just need a sparky to wire it up)

Really????  - I'm never sure why people assume underfloor is 'more efficient' or uses less energy.

Heat in needs to equal heat out.  i.e. if you want a room to remain at a certian temperature, you have to put the same amount of heat in, to match the heat being lost.  Only improving insulation can alter this equation.

However, there is a difference with "effectiveness".  i.e. how the human occupant 'feels' in the room. single location 'hot' radiators can create draughts, whereas a lower temp over a larger area can feel more steady state if that makes sense.

Potash

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Low temperature hot water underfloor heating generally works with lower temperature flow and return f&r water temperatures.

As detailed up thread, if you have a condensing boiler AND you set it to run with a low f&r water temperature it will operate in condensing mode. Condensing mode is more efficient as it recovers the latent energy from the water created by the combustion of gas.

(there are some condensing boilers which use the supply combustion air to condense the flue gases & therefore give you condensing efficiencies at high temperatures)

If you have a heat pump the efficiency you will get out of the heat pump varies with the difference in temperature between the source temperature (outside, underground etc) and the f&r water temperature. If you drop the water temperature you have a smaller difference and get higher efficiencies.

Electric underfloor heating is 100% efficient but as electricity is expensive this means you still pay a lot.

Paul B

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I recorded my energy use in the last house (obv. different years) which was a very draughty end terrace with the heating on morning and evening and then left on entirely. I was surprised that the difference wasn't huge whereas the latter was a lot more comfortable.

However, there is a difference with "effectiveness".  i.e. how the human occupant 'feels' in the room. single location 'hot' radiators can create draughts, whereas a lower temp over a larger area can feel more steady state if that makes sense.

This. My current place has underfloor. Again, once we turn it on, it's on. The difficulty we have currently is heating the office where we both WFH but two people, two laptops and a greyhound actually seems to keep it fairly warm!

Potash

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There is a difference between the air temperature and the "experienced" temperature. The experienced temperature is generally called the operative temperature and is determined from the air temperature, the air speed, and the radiant temperature.

This is all also captured by the Predicted Mean Vote PMV & Predicted People Dissatisfied PPD metric.

In summary, if the radiant temperature is much lower than the air temperature you will feel cold despite the air temperature being acceptable. This is observed within large glazed office areas where people feel cold adjacent to the full height windows despite it being 22 degrees in the room.

Conversely if you have high radiant temperatures in a space you feel warm despite low air temperatures. My living room feels warm at an air temp of 15 degrees due to a wood burning stove getting the radiant temperature really high.

Potash

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edit.

PPD percentage people dissatisfied

James Malloch

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Thanks for all the responses - and sorry for my late reply!

I’m going to go for the Hive Heating System in the first instance and see what difference that makes. My dad got it last year and was saying how it’s saved them quite a bit already. Once we’re away on our trip the number of rooms in use will drop (and especially 9-5 as the guy moving away doesn’t WFH) so I think this will keep things in check initially.

We might add 1/2 of the smart radiator valves too but will have another think about that.

Has anyone installed the HIVE active heating system themselves? Is it a pain (we already have an external thermostat that would be being replaced) to do or is it a quick/easy job?

Potash

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I have installed this.

The smart TRVs fit onto the base body of existing mechanical TRVs.

The smart TRV fitted onto our existing mechanical TRVs with no issue. They all took a little while to calibrate but all bar two radiators got sorted.

One radiator TRV clearly had issues with green gunge and signs of leakage. The Hive smart TRV failed to calibrate on this radiator. A second radiator also failed to calibrate and work with the smart valve regardless of which smart valve I used so I assume this one is also a bit duff. I have quotes for a plumber to replace the mechanical TRV base units but have yet to do it.

My wife wired in the hive thermostat after watching youtube and her background is child psychology.

 

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