Extension doesn’t stay warm

JoeLowe

That’s just mean sticking the 5kw on to warm the room up quickly. I spend most of the day in the extension only as I work from home and don’t have the central heating on, but use a 5KW gas fire to warm the room.

It warms the room up in no time at all, not the heat disappears quickly as soon as it’s turned off. 

JoeLowe

KeithSussex said:

Has the heating load for the extension + adjoining room,  been accurately calculated ?
could use a heat loss calculator (free)  https://www.myson.co.uk/heat_loss_manager.htm  
If the extension is an open plan kitchen dining room, use living room in the heatloss calculator.
From the photo it looks a nice bright airy extension. If viewing as a potential buyer, seasonal heating / cooling would be low on my list of considerations.
Hope you get it sorted 

Radiators in the room add up to:
2 x 715 watts and 1 x 1073 watts

Heat Loss Calculator says should be around 3500 to 4000 watts.

That’s an easy fix and can get a plumber friend in swap / add a radiator.

However, still doesn’t stop the heat from disappearing once the hearing is switched off. 

Also will ask him to swap the thermostat to the kitchen so it’s goes off the coldest room. 

Jeepers_Creepers

I think the 'heat disappearing once the heating is off' is actually just a slight temp drop. That's why room stats need a small hysteresis to be effective - if the temp is allowed to drop by a single degree, it's usually very noticeable and not comfortable. I suspect something similar to that is all that's happening in your lovely extension.

If you didn't use the 5kW heater and relied solely on your CH, how quickly would the extension get to temp? Almost as quickly as the front room? Or does it not get to temp? If not, is that (a) because the rest of the house is 'satisfied', or (b) because even tho' the CH is going flat-out, your extension simply doesn't get up to temp?

(a) is simply a room stat issue - either move it to the ext and fit TRVs in the front room, or else tweak your front room rads down a tad to allow the rest of the house more 'boiler time'.

(b) is a rad-undersized issue in the ext (or they are not opened enough).

Do your front room rads have TRVs on them even if they are opened fully (as they should since the stat is in there)?

grumbler

JoeLowe said:

KeithSussex said:

Has the heating load for the extension + adjoining room,  been accurately calculated ?
could use a heat loss calculator (free)  https://www.myson.co.uk/heat_loss_manager.htm  
If the extension is an open plan kitchen dining room, use living room in the heatloss calculator.
From the photo it looks a nice bright airy extension. If viewing as a potential buyer, seasonal heating / cooling would be low on my list of considerations.
Hope you get it sorted 

Heat Loss Calculator says should be around 3500 to 4000 watts.
...
However, still doesn’t stop the heat from disappearing once the hearing is switched off. 

Disappearing heat is a norm. It's pure physics. That's why you need 3-4kW power to compensate the heat loss - in your case mainly though the windows and the door I guess.

Yes, moving the thermostat is a good idea. I hope your plumber suggest you a more flexible wireless one.

JoeLowe

Jeepers_Creepers said:

If you didn't use the 5kW heater and relied solely on your CH, how quickly would the extension get to temp? Almost as quickly as the front room? Or does it not get to temp? If not, is that (a) because the rest of the house is 'satisfied', or (b) because even tho' the CH is going flat-out, your extension simply doesn't get up to temp?

(a) is simply a room stat issue - either move it to the ext and fit TRVs in the front room, or else tweak your front room rads down a tad to allow the rest of the house more 'boiler time'.

(b) is a rad-undersized issue in the ext (or they are not opened enough).

Do your front room rads have TRVs on them even if they are opened fully (as they should since the stat is in there)?

The extension doesn’t get to temp as quick as as the other rooms and loses heat quicker. 

The heat loss calculator does shows that’s down to radiators being around 1500w short from what’s needed. I will get into this and have a look at what I can do. 

Have TRVs on them. 

Jeepers_Creepers

JoeLowe said:

The extension doesn’t get to temp as quick as as the other rooms and loses heat quicker. 

The heat loss calculator does shows that’s down to radiators being around 1500w short from what’s needed. I will get into this and have a look at what I can do. 

Have TRVs on them. 

There are TRVs on the front room rads too? What have they been set to? Usually the room with the stat doesn't also have TRVs as they'll fight eachother, (unless the TRVs are set to 'max' which means it's always open as they should be).

And do the ext's rads get as physically hot as the front room's?

See what the plumber suggests, but what I would personally try first is to move the stat into the ext room, tweak down the front room's lockshields to remove some of their priority, set the front room's TRVs to, I guess, 4 (since you like it cosy) and open the ext's room's TRVs to 'max' - 'cos that's where the stat will be now.

Set the room stat in the ext to whatever temp you want - again 22oC if that's how you like it. See how it all goes. If the front room still gets to temp far quicker than the ext, then you can tweak the FR's LS down a further teeny bit, and also open the EXT's LS up a teeny bit - ie adjust the 'balance' between the rooms.

The bottom line is, the stat will control the boiler, but it's now in the extension. Ergo the boiler will keep the flow coming until the ext is happy. Meanwhile, the front room will be controlling itself via the TRV.

JoeLowe

Not sure if there are TRV in the living room, will check in the morning. 

I think every radiator is currently set to max across the house. 

FreeBear

Jeepers_Creepers said: And do the ext's rads get as physically hot as the front room's?

The temperature of the water entering the radiator will have a major impact on the heat output, so it is worth measuring it.

Most radiators have a heat output (in BTUs or KW) based on a Delta T of 50° - If your room is at 20°C, and the water is at 70°C, the difference is the Delta T (in this case, 50°). Drop the water temperature by 10°C, and the heat output drops by 25%.

When purchasing radiators, you should be asking what the Delta T is for the quoted output - Some manufacturers use a ΔT of 60°...

Jeepers_Creepers

JoeLowe said:

Not sure if there are TRV in the living room, will check in the morning. 

I think every radiator is currently set to max across the house. 

I think you ideally need a fully-clued up plumber - not sure if 'old school' or 'hot off the press' is best! But someone to look at your whole system and how it's set up.

TRVs should be in all rooms other than the one that has the room stat. If the rads in the 'stat' room also have TRVs fitted, then these - and these only - should be set to 'max' so that they effectively remain open at all times (or else actually remove the TRV head!)

Rads should be sized appropriately for each room, obviously. Often, in practice, this is done on a 'ballpark' figure, and usually that's good enough. There may - possibly - be an issue with your ext room being underheated.

That's the start. Then comes the issue of balancing the rads so that they all supply heat to their respective rooms at around the same rate. Balancing is done via the lockshields, which are 'set' and then left alone. In general, rads closest to the boiler/pump will have their LSs closed off more than the ones further away. Balancing is a time-consuming process as each tweak has to be followed by a wait to allow the rad to readjust.

Finally, the rads in the 'stat' room are set - again via their LSs - to provide heat at a similar rate to the rest of the house's rooms. The actual temp in the 'stat' room is then governed by what the stat is set at. Obviously, when that room reaches its desired temp, the boiler shuts off and all the rads in the house stop being fed. If you find that bedrooms/study/dining/whatever rooms are not getting to their desired temps (as set on their respective TRVs) before the boiler shuts off because the 'stat' room has told it to, then it would suggest that the 'stat' room's rads are too 'hot' relative to the others; the stat room is heating up too quickly and therefore shutting off the boiler too soon. The system should be 'balanced' so that the comfy living areas heat up at the same rate as the cooler bedrooms and hallways etc.

The room with the stat should NOT also have working TRVs on their rads because the TRVs will do their own thing - going on and off depending on room temp - so will affect the room temp independently of the stat, so the stat's function will be compormised.

Jeepers_Creepers

When your system comes on in the morning and is firing away pipingly, are the rads in the EXT just as hot to the touch as the front room rads?