Why is my heating taking ages to get the house up to temperature?

[Mottie]

Just lately, my heating has been taking ages to get the house up to temperature. For example, this morning at 6.30 it was 17.9° and now at just gone 9.00, it’s only 19.5°. Temperature on the Hive room stat is set to 21.5°. I’m sure it didn’t used to take that long to warm the house up when it was first installed.

It's an 8 year old Vaillant EcoTEC plus 418 and I have a sealed heating system. System was powerflushed when the system was converted to a sealed one with the old boiler, two years previous to the new boiler being fitted and chemically flushed prior to installation of the current boiler plus it had inhibitor added and a filter fitted. I used to have it regulated down to 14/15Kw and a flow temp of 62°. Putting it back up to 18Kw with a flow temp of 70° seems to have made no difference. When it was first installed and set at max output, I could hear a definite 'roar' coming from the flue outside but again, I can’t remember hearing that lately. I missed a service last year but the year before, I was told that I should think about having a full strip down service with some seals replaced but I never got round to having that done. Is that right and do you think that would make a difference?

Any ideas?

 

[Wayners]

Don't burn yourself.
Be careful and sensible.
Grab the radiators with your hand tightly. Count to two. If you can hold tightly for more than two seconds without it becoming uncomfortable, you're radiators aren't hot enough. Turn the water temperature up.

 

[Johntheo5]

Just lately, my heating has been taking ages to get the house up to temperature. For example, this morning at 6.30 it was 17.9° and now at just gone 9.00, it’s only 19.5°. Temperature on the Hive room stat is set to 21.5°. I’m sure it didn’t used to take that long to warm the house up when it was first installed.

It's an 8 year old Vaillant EcoTEC plus 418 and I have a sealed heating system. System was powerflushed when the system was converted to a sealed one with the old boiler, two years previous to the new boiler being fitted and chemically flushed prior to installation of the current boiler plus it had inhibitor added and a filter fitted. I used to have it regulated down to 14/15Kw and a flow temp of 62°. Putting it back up to 18Kw with a flow temp of 70° seems to have made no difference. When it was first installed and set at max output, I could hear a definite 'roar' coming from the flue outside but again, I can’t remember hearing that lately. I missed a service last year but the year before, I was told that I should think about having a full strip down service with some seals replaced but I never got round to having that done. Is that right and do you think that would make a difference?

Any ideas?

Is the flow temperature reaching the now target temp of 70C?
If so, and the return temp is 60C, dT10C, then (at a 20C room temp) the rads will output 87.% of their T50 rating, if the return is 50C, dT20C then 74.8% of the T50 rating, if the return is only 40C, dT30C, then only 62.9% of the T50 rating.

 

[CountryFan]

Any changes recently, eg work on the boiler or additional radiators?

 

[Harry Bloomfield]

Putting it back up to 18Kw with a flow temp of 70° seems to have made no difference.

As above, are the radiator getting hot?

I have the same boiler, except open vented, and with the fancy Vaillant control system. -2C outdoors, heating set back to 14C overnight, and the indoor did almost fall to 14C, to trigger it. At 8am I nudged it up to 18C, by 9am it had just achieved the 18C.

 

[Mottie]

Any changes recently, eg work on the boiler or additional radiators?

No, none at all.

 

[Mottie]

As above, are the radiator getting hot?

Yes, too hot to keep my hand on for more than a couple of seconds. I can’t understand it.

 

[Mottie]

I’ll have to try seeing what’s happening with the temperature on the boiler control when I have the time. Boiler is in the loft.

 

[CountryFan]

No, none at all.

Yes, too hot to keep my hand on for more than a couple of seconds. I can’t understand it.

Based on this I would say perhaps a different heat loss or a weak/failing circulator

 

[danfre]

If your gas meter is under the stairs check that the lever is fully on.
When the boiler is cold you could turn on to max and do a gas rate using the meter to work out gas consumption

 

[Mottie]

If your gas meter is under the stairs check that the lever is fully on.
When the boiler is cold you could turn on to max and do a gas rate using the meter to work out gas consumption

Just checked. Fully on.

 

[ericmark]

Is it something daft like I found here where the thermostat seems to think I am not at home?

Every time something moves, like the door opening when I go to make coffee, it turns the heating on, and will stay on for around an hour, then return to away mode. First time I had the problem the local EE site had been damaged in the wind, after that I turned off geo-fencing. Since it detects me as I walk to thermostat, reading at the thermostat it seemed all OK, it was not until I looked at the app on my computer, did I realise it was switching off.

It seems some thermostats have anti-hysteresis software, this one did, and the result is it messes up the boiler's modulating software. I know I had to set my thermostats to oil, as it changes some re-start timings.

I also had a problem with this one, it would random loose radio link, so would fail to turn off, or on, but seemed random, and over time got worse.

I know you're using Hive, but you are pretty clued-up, so looking at something not quite so obvious. Here not so bad I can hear the boiler running, and it does not modulate, but with late mother's house, I did not have a clue if boiler running at minium or maximum or anywhere in between. My son had a problem with his first house, it ran A1 until he went on holiday, then after the heating had been turned off, it would not re-heat the house.

What was happening was one radiator had the lock shield wide open, while the TRV was regulating the flow, other radiators worked OK, but once allowed to go cold, the flow through that radiator was turning the boiler output down, so it was trying to heat the house one room at a time. And so much heat was going from the one heated room, it was not getting hot enough to cause the TRV to close, one warm day, and it caught up, and all rooms running again with no problem.

By time, I had moved here, I thought I knew how to set lock shield valves, but this micro bore, with non modulating boiler, seems to work very different. So here lock shield valves nearly wide open. To get rooms warm faster in this house, I set a sequence, so each TRV opens 10 minutes behind each other, so important rooms heated first. But never found I needed to do that until I moved here.

What does Hive tell you? This system has graphs I am sure Hive is the same, it shows when there was a demand, and how the room responded, both Wiser and Kasa do this, so I can see how well it has done. Nest is a bit useless, it shows energy history which shows how long it asked the boiler to run for, but not how long it actually ran for, or any temperature graphs, so all in all Nest is a bit like a chocolate fireguard. The Energenie TRV heads also do not show any graph, only target and current temperature. With is better than eqive TRV, which only shows target, but they were only £15 each, so can't really complain.

I was uncertain as to if to go with Hive or Wiser, I went with Wiser, but note Hive now is a whole range of thermostats, not just one, each with different features. So I have no idea what yours will show you?