Taking hours to heat the house

Lorian

61 can be good to keep the boiler condensing but may just be a bit too low. Do you have a thermometer you can measure the return temperature with? And maybe try 63c flow temp for a day which would be slightly less efficient but may help you hit your desired room temperatures. 

BUFF

Therese1 said:

The radiator temp on my boiler is 61° …is this too low? 

It may be too low for the sizes of your radiators.
Your boiler is 5 years old (so will be condensing which is why you want to run a lower flow temp for increased efficiency) but how old are your radiators? They may well have been sized for a system running higher flow temps.

macman

Did you draw the curtains upstairs before the evening? If not, it's just the warmer than-before-air in the bedrooms hitting the colder-than-usual outside walls and windows, which drops the air temp and causes water to condense and run down onto the window sills.

ariarnia

Chrysalis said:

So using smart meter data, I had water heating on for about 2 hours on Friday, sarahs mode says it is 15.6 KwH (central heating would be at least that, my boiler if I have CH on I have to also still heat water). 

15.6 (11.9) x 10.24p = £1.21

2000 watt heater on for 2 hours, and we will assume worst case scenario its on constantly not thermostat controlled.

4 x 33.02p = £1.32

maths look ok to you?

Thats best case gas against worst case electric.

--edit recalculated taking of normal pilot light daily usage.

Depressing figures, just 2 hours of heating per day over £30 extra per month on bill, the problem is if you start at 1-2 hours, it makes the unheated hours so much more difficult as body adjusts to the heated temperatures, so 2 hours quickly becomes 8 hours.  Reality is though the electric heater would be lower then that cost as thermostat would cycle the power.

(not for the op. just talking about relative heating costs)
 
i think that misses that the first couple of hours of gas are the most expensive. which that and the heat loss problem is why a low level of constant heat is said to be more efficient.

because the gas central heating also cycles using the thermostat and a wireless thermostat in the room with you should mean the gas central heating is only on to give the same amount of heat as the electric but using a cheaper fuel. 

we pay 3.5p for gas and 20p for electric (on a fix till march).

heating the hole house to 15 degrees all day (on a thermostat) 'cost' us 20kWh per day last month. then we could have 3 or 4 hours of logs on the stove heating it and the surrounding rooms to 20 in the evening vs needing to light the fire as soon as one of us gets up and keeping it going all day.

3.5*20 is 70p (for 24 hour background heat)
20*16 (8 hours of a 2kwh electric heater) is £3.20

at cap rates it would be 
10.3*20 = £2.06 (24 hours of 'not cold')
34*16 = £5.44 (8 hours of 'hot')

for full comparison we've worked out that we burn about 3kg of logs in an evening if we keep it going from dinner to bed time. that's about (very roughly) 15kwh of heat so about the equivalent of a 3kw electric heater. we can't price the logs as its a mix of free, bought ready to burn and bought cheap to self season for a couple of years. 

and we've spent time and money over the last few years sealing all the cracks and putting up thick curtains over all the doors and windows (door curtains do make a real difference) to make sure the space were heating are as insulated as possible without serious diy (which we'll be doing as and when now we bought the place from the landlord). 

ariarnia

Therese1 said:

Anyway, I switched the heating back on to see if this helped and it was still showing 15° and no more even after a few hours.  

HOWEVER! When I went upstairs to go to bed, every window up there (two bedrooms and bathroom) looked like I had been running a sauna!! Not just a bit of steam/condensation at the bottom….the whole of all of the windows!!  Neither bedroom rad was on higher than 1 (of 5).  

This suggests that the house is in fact heating….right??    Trouble is, with the Nest, because the heating is never getting to the requested temp 18°, it’s on constantly…..first time EVER my heating has been on for 9 hours …three times this week😵‍💫  

any other clues before I call out a plumber….or should it be a Nest specialist?? 

if the radiators feel hot then the house is heating (energy is getting in to the system). if the house feels cold then theres 2 possible reasons i can see. 

first is the house is starting from to cold. when we go away for a few days and turn off the heating then when we come home it can take 2 or 3 days before the house feels warm again. the heating has to chase out any damp in the air (damp air takes more energy to heat and sucks heat out of things it touches) and then to heat the actual bones of the house (not just make the air hot). it might be worth leaving the heating on for a couple of days even tho it will cost money just to get the house 'warm' then play around with how long you need the heating on to 'keep' that warmth. 

the second might be how quick the heat can escape. have you gone around and felt for drafts and cold spots? i mentioned above that we went around and OH used caulk sealant (in a little tube) to fill some little cracks under window sils and things like that. and he also replaced the door seals on our front and back upvc doors (it just pops out https://youtu.be/HXzc4U85xPU). also the condensation upstairs might be heat escaping from downstairs. on the lounge (which is the room we heat with the fire) we put up curtains over the door and replaced the lounge curtains with heavy winter curtains (before when we couldn't afford thermal curtains i safety pinned thin fleece blankets on the window side of the curtains to line them). we really focused on insulating that one room as a priority. that might be something you can maybe do then having the nest thermostat in that room with you and turn the rad up in that room while you keep them lower in the other rooms?

Therese1

BUFF said:

Therese1 said:

The radiator temp on my boiler is 61° …is this too low? 

It may be too low for the sizes of your radiators.
Your boiler is 5 years old (so will be condensing which is why you want to run a lower flow temp for increased efficiency) but how old are your radiators? They may well have been sized for a system running higher flow temps.

Aha, good point (though this is a new problem this year)….the radiators were put in when I first moved here 19yrs ago! I’ll put it up to 63 for a couple of days and see if it helps.  

Spies

My living room takes 1 hour per 1c (high ceiling) 

We are using 40-50kwh of gas a day at 10.3p/unit 

[Deleted User]

Aha, good point (though this is a new problem this year)….the radiators were put in when I first moved here 19yrs ago! I’ll put it up to 63 for a couple of days and see if it helps.  

Has the system even been drained; flushed and refilled with new inhibitor during that time? A radiator full of gas suggests that you have had both air and water in your heating system: this leads to internal radiator corrosion which generates sludge. This sludge can block radiators.

Another problem with old heating systems is an air/gas block in one or more of the vertical heating pipes: these can be difficult to shift. I have in the past connected a water hose to one of the radiator drains to push the airlock upwards.

A word of caution. Sludge can be a boiler killer so be wary of taking action that might cost you a lot of money. Boiler heat exchangers are not cheap. 

https://www.eskimodesign.co.uk/technical-resources/air-or-gas-in-radiators

grn99

Just wondering having read that, if the radiators are blazing hot? If so, are the lockshields are fully open and not balanced with water running through without any restriction to the flow at the lockshield end? In my experience that gave red hot radiators but not much heat in the room.

[Deleted User]

In my experience that gave red hot radiators but not much heat in the room.

I agree with your comment about the need for radiator balancing; however, if a 'red hot' radiator is not heating up a room then it means that the heat loss from the room exceeds the heat gain from the radiator. Either the room is poorly insulated or the radiator is under-sized for the room that it is in.