Is room taking too long to warm up?

[garmcqui]

Hi all, i recently managed to get my Rapsberry Pi setup to automatically log room temperatures (target and actual) from our smart heating system (Evohome) and plot graphs on Plotly, which has led me to confirm what I've been feeling for a while now - the living room takes ages to warm up!

The following graph shows how the set temp (red trace) and actual room temp (blue trace) changed over the last 24h:


As
you can see, the target temperature changes from 10C to 21C at 5.30 am, but it is 8.30 before the room is nearing 21C, which seems long to me. Other rooms seem to heat up much quicker.

The radiator seems to get plenty warm, almost too warm to touch. Rad dimensions Are 1500mm X 300mm double (which according to spec, is rated at about 5000 BTU/h) but is under the window (see pic). The house is a new build, so should have good insulation, and the living room is 3.9m x 4.3m (ceiling standard height):



What do you think, am I being unreasonable to expect it to heat up quicker? Is the radiator sufficient for the room size?

Cheers

 

[hazetimesfive]

why you let your house get so cold.

 

[oldbutnotdead]

As above- 10 degrees is awful cold. Have you done a heat loss calc for the room (there's one here http://www.bestheating.com/btu-calculator). 3 hours to add 11 degrees C is not too shabby really, you might be better off having a higher night temperature set (it'll avoid lots of condensation problems to start with). This assumes you are actually in the UK rather than somewhere else with much lower average outside temperatures.

 

[Aquaheat]

You guys are reading the chart wrong. The house temp is 16.5C @ 05:30 and 21C @ 08:30

It is taking 3 hours for a 4.5C rise.

OP this is quite excessive. It should be in the region of 1.5Kw given off from the rad where as you should be looking at closer to 1.8Kw - 2Kw so it is a little undersized.

I would also look at the EvoHome HR92 position as your picture shows that it is in quite an enclosed position around a lot of media equipment can you be sure that this is not operating causing the rad to shut down during the warm up period?

I'd experiment with removing the head from the valve to start with and see if this increases warm up time.

Also how many are external walls and what is the temperature like outside during these tests?

Jon

 

[garmcqui]

Set temp is 10c overnight, basically just to ensure the boiler isn't on overnight (I presume most people don't keep the central heating on overnight?) but the rooms never get much below 15-16c.

Jon - I found the position of the HR92 to be poor, but I was limited as to where I would locate it without having to drain the system and swap the valves on the radiator. So I have a Y87RF room thermostat which does the temperature measurement, which I've found to be much more accurate.

I'd be happy to increase the rad size, but due to its location I reckon I'd be limited to a relatively small increase.

There are two external walls (modern cavity wall and dry lined though), room faces north so gets very little heat from the sun. I haven't done a heat loss calc, will do!

Cheers

 

[bhm1712]

Set temp is 10c overnight, basically just to ensure the boiler isn't on overnight (I presume most people don't keep the central heating on overnight?) but the rooms never get much below 15-16c.

Jon - I found the position of the HR92 to be poor, but I was limited as to where I would locate it without having to drain the system and swap the valves on the radiator. So I have a Y87RF room thermostat which does the temperature measurement, which I've found to be much more accurate.

I'd be happy to increase the rad size, but due to its location I reckon I'd be limited to a relatively small increase.

There are two external walls (modern cavity wall and dry lined though), room faces north so gets very little heat from the sun. I haven't done a heat loss calc, will do!

Cheers

I keep my heating on 24/7 and controlled to 20.0 degrees. This way, my system only ever needs to raise the temperature by a maximum of 1 degrees. (1 degree differential on the room stat) This way, my boiler spends about 3 hours within a 24 hour period on, and the rest off.

My gas bills are low as opposed to people's who have the heating on for a couple of hours in the morning and 5 or 6 hours in the evening bringing the house back up to an acceptable temperature again.

 

[bhm1712]

There's no need then for these ultra expensive and potty control systems like nest, evohome and hive to name but a few - which are absolute cobblers and false economy.

 

[garmcqui]

I'm not sure, but I think I read that this way of heating a house has been proven beyond reasonable doubt to be quite expensive.

 

[garmcqui]

Compared to before, we're currently saving about £25-30/mth on heating mate, plus the added flexibility of being able to amend schedules whilst out and about, plus the ability to monitor temperatures historically - all makes it worth it for me.

 

[bhm1712]

I'm not sure, but I think I read that this way of heating a house has been proven beyond reasonable doubt to be quite expensive.

How can it be more expensive when the boiler on periods are lower than that of heating it the "usual" way?! - by allowing the ambient temp to drop multiple degrees during the night and day time only to have to raise it back to an acceptable (20/21 degrees) again?

to say it's more expensive goes against the physics...

 

[bernardgreen]

How can it be more expensive when the boiler on periods are lower than that of heating it the "usual" way?

Letting the house cool down over night means the boiler is not firing up during the night. Keeping it warm during the night means the boiler is firing up during the night.

The question there for is :-

Is the amount of gas used to heat the house from over night cool to day time warm more or less than the gas used to keep the house warm over night.

 

[endecotp]

Say I have two leaky buckets.

I give one to bhm1712. He keeps it always full to the brim, with constant topping-up.
I give another to garmcqui. He fills it to the top, waits for it to empty, then fills it again.

Who uses the most water in the long term?

 

[Agile]

Your area is 16 sq metres and that should need less that 100W / sq m or 1.6 kW.

But your rad is rated at a flow temp of 70 C and that would not be possible to touch at all.

So you problem will be the rad temperature. The boiler may be more efficient with a low flow temp but that is at the expense of the rad outputs.


To know what is going on you would need to measure the flow and return temps using a contact thermometer.

Another problem you may have overlooked is that the curtain must NOT cover the rad otherwise the heat does not get into the room.

Tony Glazier

 

[Aquaheat]

I keep my heating on 24/7 and controlled to 20.0 degrees. This way, my system only ever needs to raise the temperature by a maximum of 1 degrees. (1 degree differential on the room stat) This way, my boiler spends about 3 hours within a 24 hour period on, and the rest off.

My gas bills are low as opposed to people's who have the heating on for a couple of hours in the morning and 5 or 6 hours in the evening bringing the house back up to an acceptable temperature again.

Let's assume that you are being truthful about the burn time of your boiler. (Which is very very unlikley)

In your example your boiler only burns for 8 minutes every hour to maintain a constant 20C +/- 1 totaling 3 hours in a 24 hour period.

If the OP was to set timer to ON 06:30/OFF 08:30 allowing a constant 30 minute warm up period and the 12 minutes ignition for the other 1 1/2 hours that's a total of 42 minutes of the boiler running.

Back on at 16:00 and off again at 22:00 again allowing a 30 minute warm up period and 44 minutes for the other 5 1/2 hours that's a total of 74 minutes

Total boiler ignition time in a 24 hour period is 116 minutes or 1 hour 56 minutes so a whole hour and 4 minutes less then your way saving a 1/3 on the energy usage.

All the above assumes a fixed Kw being used by the boiler.

Now add into the equation these supposed expensive pointless controls that will incorporate weather comp and open therm technology that will modulate the burner while running to adjust flow temperature and adjust the warm up period to take into account for ambient temperatures that saving will only increase further probably in the region of an additional 5 - 10%

All the above is obviously only a paperwork exercise and there are too many variables but you can see how wrong you are with your assumption that running 24/7 is a better way of doing it.

@garmcqui If you could get a 400mm x 1600mm in there that would push you up to about 2.1Kw

Jon

 

[bhm1712]

I suppose it all depends on how well the house is insulated and if the system controls are set up correctly.

Say I have two leaky buckets.

I give one to bhm1712. He keeps it always full to the brim, with constant topping-up.
I give another to garmcqui. He fills it to the top, waits for it to empty, then fills it again.

Who uses the most water in the long term?

You can't really use that analogy because by keeping a bucket brimmed you're wasting water by overflowing the bucket whereas once "I'm full to the brim" I stop adding the water. It's more like having a 1mm hole in the bottom of the bucket and re-adding the water once the level has dropped by 10mm, until it is full again instead of letting it empty and then filling it up from empty. Once again the analogy fails because going by that theory you use the same amount of water in total, but :

You also have to remember that allowing a boiler to remain off for extended periods of time allows all the system water to drop to ambient and so the boiler must again go to high modulation levels to reheat the water in the system from ambient to set point which also uses more gas.



The Gas useage and boiler on times I have speaks for itself when compared to the previous owners figures who ran the system in the "usual way". I am also not taking into consideration the repairs which were carried out on the system and finished a couple of weeks ago so my gas useage may have feel even further now.