House takes ages to heat up

[clayton]

I have a 3 bed detached house with 12 radiators, the boiler is a British gas 330+ that was serviced this year and a new pump fitted. I have also flushed the system with sentinal x400 and x800, all the radiators are new.

This morning at 8am the Nest app had the house tempreture at 13 now at 12.27 its showing 17.5 this seems an age to heat the house.

The boiler seems to be running fine, the thermostat is set at 70 but currently showing 67.

Should the system take this long to heat up ?

Thanks.

 

[CBW]

I would have thought if it’s 67 at the boiler, then the radiators should be heating the house quicker than you describe. Has the system been balanced? Are the radiators hot to touch? Are both flow and return valves definitely open?

 

[stem]

If the house hasn't been heated for a while, allowed to get really cold, or the heating has previously only been on for brief intermittent periods of time, it can take some time to heat up the fabric of the property and its contents. Also, you don't tell us much about the house other than it's "a 3 bed detached house" that could be a sprawling Victorian villa with a draughty cellar, huge single glazed bay windows, open chimneys, solid walls, thin loft insulation and high ceilings etc., or a modern, super insulated property with half the internal volume to heat.

Assuming that you haven't been away for the last week and not had the heating on, then the bottom line is simply that heat is escaping from the property nearly as fast as you are putting it back in. So the first step is to identify first if it's the heating, or the property that is at fault. If the radiators get hot to the touch, then the boiler and heating system can do no more as it stands. On the other hand, if the radiators are only warm to the touch, or have cold spots, then something is amiss and investigation is required.

If the radiators are hot, then the next question is, are there enough and are they big enough for the size of the room they are located in? If you are not sure, you can use this table to find out the recommended BTU's requirement.....

.....and then compare the requirements with the actual BTU figures for the size of radiators you have. You probably won't know that, but online radiator sales webpages will give you the BTU output for radiators of the same specification.

It could be a matter of improving the insulation of the property to keep the heat in. Think of it as being like a bucket with a hole in letting water escape, you can either turn the tap up and let more water in, or fill the hole and stop it escaping. In the same way your heating may be doing it's job and putting the heat in, but the house could be leaking it out almost as fast.

 

[clayton]

Well I poped out for ten minutes only to return and find the heating off and an error F22 Dry on the display, its been running all day.

 

[BlueLoo]

Ooh.

Low flow?
Would explain the poor heating.

Plumber time.

 

[Ihavenojob]

Get the engineer to check the boiler has been set for the correct output. The 330+ can be range rated from 10 to 30 Kw. It may be rated too high, and the boiler can't clear the heat quickly enough with a smallish system.

 

[clayton]

Get the engineer to check the boiler has been set for the correct output. The 330+ can be range rated from 10 to 30 Kw. It may be rated too high, and the boiler can't clear the heat quickly enough with a smallish system.

The boiler was gas rated to 20kw before it was serviced, My plumber cant get out to me for a couple of weeks so will have to wait.

 

[Dereekoo]

Put pump speed at 3 and see if that helps

 

[ericmark]

Has the system been balanced?

That would seem likely problem. Son did the same, with TRV heads once the system is hot the TRV's will control flow so will work OK, but warming up hot water returns to boiler so boiler thinks the house is already warm.

If house cold and boiler output is hot and return is cold then boiler fault, but if return is hot then radiator setting are wrong.

What I did with a large house to speed up warming is to use programmable TRV heads, so radiators are heated in the sequence that we use the rooms. but only 15 minutes between each radiator once hot they stay hot.

 

[bhm1712]

Did British Gas install that boiler? We have the same boiler (installed a good many years ago) and when they installed it they did not fit an automatic bypass to the system. For the first few weeks they were back and forwards to our house to clear the same fault but it always came back. All barring one radiator had a TRV and when they all closed down, the single small radiator and low flow through it was not enough to dissipate heat from the boilers cooling water and when the motorised zone valve closed once the stat was satisfied the pump overrun started and there was nowhere for the water to flow too…

it was me who pointed out to them that the installation manual for the boiler states that an auto bypass must be fitted. They quickly fitted one and the problem went away. I also spent many hours balancing the system as they left all lock shield valves fully open so some radiators never got very hot and took ages to heat the room.

 

[clayton]

Still trying to sort this issue with the boiler taking ages to heat the house. I've done a video running the boiler from 9c to 67c it took 5 hrs to reach this tempreture, I've edited the video down to just over 4 minutes
Once at 60c it seems to takes its time getting any warmer. Taking 5 hrs to get upto 65c is this normal for a boiler am I worring about nothing ?

POI's are
12.05 boiler turns off
12.49 boiler at 60c
13.12 61c
13.29 62c
14.12 63c
14.33 64c
15.00 65c

 

[snb]

You need to check D0 in settings. My guess this has been down rated too much. Let us know what it was set at. If anything below 18 then increase to that. If above then increase by 4

 

[DP]

Strongly suggest you carry out multiple flushes to remove residual X800 from the installation else you will need to replace pump after pump

When carrying out any chemical cleanse, it is very important to carry out thorough flush to remove the muck that chemicals suspend in the system water. A simple draindown is not sufficient

I would be looking at getting proper service as detailed in the manual

Also, turn hot water zone off and then see if radiators work better
Check the differential between the two pipe at top of the boiler.

 

[JohnD]

you say the boiler flow is around 60C

Are the radiators fully hot? All over? Top, bottom, middle and sides?

Are they big enough? Give us an example or room size and rad size please.

Did you see @stem post 3rd December?

 

[ericmark]

As I said before son had same problem, and all down to lock shield valves not being set.

If boilers had a gauge built in showing output it would be easy, but in the main they don't, you know it is running, but not a clue if 10 kW or 30 kW output or anywhere between.

My boiler (oil) is easy, it has a fixed output, so if running it is producing 20 kW if not 0 kW and so I have a good idea how hard it is working by the sound it makes when running.

Your boiler (gas) has a variable output, so it may be running but no idea if 10 kW or 30 kW or anywhere in between, so you need to ensure the water is cooled by the radiators to a point where the boiler is giving full output when the home is cold. So you want the water to cool in each radiator around 15°C between input and output of the radiator, maybe more.

I am an electrician not a heating engineer, so I don't have his array of tools, and I will admit to measure the incoming pipe temperature and outgoing pipe temperature is not easy without a differential thermometer. I tried a aim and read thermometer and the reading varied too much.

So I closed each lock shield valve starting closest to boiler waited for feed and return pipes to go cold then opened lock shield ¼ turn at a time with some time between each adjustment, until one pipe got just a little warm, then moved to next radiator, this is far from perfect, but a good start.

TRV heads take time to open and close, mine exercise to stop TRV's sticking mid day every Saturday and it takes around 4 minutes to open/close and return to setting, if the flow in the radiator is too high, radiator can get stinking hot before the TRV can adjust flow. But I have four Energenie MiHome TRV heads which report to the PC target and current temperature, so by moving the heads radiator to radiator I can monitor performance and fine adjust the lock shield valve.

The process is simple, target under current assuming target has not just dropped, close lock shield a tad, the reverse not quite so simple as target over current may just need more time, but if regular then open a tad. Once the lock shield is set even with a mechanical wax TRV head the rooms do keep to temperature set.

In mothers house with gas modulating boiler before setting living room radiator tended to be stinking hot or cold, after setting it seemed to stay warm all the time but not stinking hot, this resulted in when sun came through bay windows the room still went up in temperature, but radiator cooled quicker, so maximum temperature when set to 20°C did hit 32°C in the sun, but after setting 24°C maximum, rooms where sun did not cause a temperature raise were within 1°C of the setting, it really did work well.

Only down side was the Energenie Mihome TRV heads have a rather OTT anti-hysteresis software built in, so would set to 22°C at 7 am and 20°C at 8 am to get room warm quicker. Makes like the Drayton Wiser claim to have built in algorithms to counter this problem and work out how long it takes to heat the room.

In theory the installer should set the lock shield valves before he leaves, part of the commissioning, but with parents house although the firm specialised in fitting central heating, they seemed to use cheap labour and a few proper engineers and so many errors made, including the system never being commissioned.

Every lock shield valve had been left wide open.