Best way to heat 70's bungalow.

..Brian..

So we're in our second winter in this house, a late 70's ~1500sq ft bungalow. Oil fired central heating. Last year we had the cavity pumped and insulated the loft to 300mm. There is already double glazed windows. Most of the radiators were replaced and TRV's added. At the same time the heating controls were upgraded to a new digital one (as the old one actually caught fire!) but it doesn't seem to have a thermostat in it.

After all that, the house is frickin cold! The heating comes on for an hour in the morning and the house heats up, but then it cools down again really quickly and we have to go push a button on the heating controls to turn it back on for another hour. But the same thing happens, the heating spikes up and down, too hot or too cold.

How can I level this out? I presume with a thermostat. Do I need something like the NEST or will a basic one do? Will a thermostat take control of the heating and turn the boiler on and off as required to maintain a constant 20°C for example or how does it work? Will the TRV's effect it somehow?

Also who do I need to install it, a plumber or electrician? Thanks!

Dardania

You've done good so far with the TRVs. How are they set e.g. have you set them to a particular number in each room? If you're getting a spike of temperature when the boile ris on, it suggests some of the TRVs might be set too high...

The optimal solution is to have a programmable thermostat (not just a timeclock like it sounds you have) and on that programmable thermostat, you tell it you want the house a a particular temperature for a particular period of time (e.g. 19C between 7.30 and 8.30 am, and 20C between 5pm & 10pm)

That configuration of a programmable thermostat and TRVs should even out the temp in the house. An electrician should be able to fit this programmable stat - Nest would do, or if you don't need the advanced features of Nest, something like this would work: 

https://www.heatingcontrolsonline.co.uk/room-thermostats-c-21.html/programmable-thermostats-c-21_31.html/wireless-programmable-thermostats.html/danfoss-randall-tp5000sirf-wireless-programmable-room-stat-p-329.html?sort=p.price&order=ASC

I've linked to a wireless one - the thermostat should be located somewhere you live mainly in the house in a good central location (and you should switch the TRV there on fully to enable the thermostat achieve the control in that room rather than thermostat). And in every other rooms, the TRVs should prevent overheating

flashforward

What is the cause of this rapid heat + loss issue?

Seems like the op has done what he can re. insulation, and it works well as the house nearly overheats but what is causing the rapid loss? Or how can he go about finding the reason/ source?

Dardania

rapid heat is probably too high a boiler flow temperature + the TRVs set too high

Rapid heat loss is probably air tightness (or lack thereof)
Solution is stable heat input related to the heat loss - and heat loss can be reduced if air tightness is improved. But in either case (if airtightness is fixed or not) the heat input isn't adequately controlled now

..Brian..

Thanks for the replies. Coincidentally, the main room we live in (open plan kitchen / living room) didn't get new rads or TVRs so the thermostat wouldn't have that to compete with. What about the likes of dinner time though, when the oven and hob are going, the room can be warmer then just from cooking. Would that interfere with the thermostat enough to warrant locating it in another room?

At the moment the heating is programmed to come on for an hour in the morning and then throughout the day we just hit the boost button on the timeclock as required and that puts the heating on for an hour, but there's nothing to regulate the temperature. If I understand this correctly, the programmable thermostat will sense the ambient air temps and turn the boiler on and off as required to maintain a set temp?

The TRVs are all set pretty high in an attempt to get the rad hot so it will have more heat to retain after the heating turns back off and hour later. I'm sensing this isn't the way to go however. If I turn the TRVs down so that there isn't as high of a spike in temps, that will mean I'll have to have the heating on more often I'm guessing. Does the boiler burn the same amount of oil regardless of temps or what? As in, the same amount of oil will be burned regardless of what output settings I have the TRVs set to as they only cut off the supply of hot water to the rad? Or do I have this totally wrong?!

Dardania

Your sense is basically correct. To answer backwards, and in a stripped down version:

Your boiler sends out water at a particular temperature (say 80C) and expects to receive it back around a particular temperature (say 70C). That allows a loss of 10C to occur in your radiators, emitting heat. Depending on the age of the boiler, it will either
- switch the boiler off if the temperature returned is greater than 70C or it will keep running the boiler if the return temperature is less than 70C
- or if it's a more modern boiler will modulate it's oil consumption up and down to maintain the return temperature at 70C.
Either way, your boiler isn't automatically burning max oil whenever it is on - sometimes it's burning less oil, and sometimes it's burning no oil and just circulating water. That all depends on what way it receives water from the house.

So, with the TRVs, the idea is they maintain the room air temperature - you're meant to set them to a particular number depending on what temperature you want that room to be. On the TRVs in my house, they make suggestions e.g. setting II is for bedrooms, III for living spaces, IV for bathrooms (http://heating.danfoss.com/PCMPDF/013R9355_RAS_C2_CEN_VISXM202_.pdf ) - your TRVs may have different numbers, or correlations between numbers & room temperatures.
The TRVs will open or close depending upon whether the room is at the set temperature or not. The TRVs have nothing to do with regulating the surface temperature of the rad.

Taking the idea that the TRVs will open and close depending on whether their room is warm enough or not influences the temperature of the water returning to the boiler. If a load of TRVs are open and calling for heat (e.g. the rooms are cold), the boiler will receive return water from the radiators at a low temperature (as the radiators are dissipating the heat in the rooms. 
However, if the rooms are all relatively warm, and the TRVs are closed, the boiler will tend to receive water back from the radiator circuit at a higher temp (as there is not so much opportunity for radiators to dissipate that heat). Here, the boiler will reduce it's oil burner to match the demand, burning less oil. You mention that the main living space has no TRV - most of the heat will try to dissipate there if it can.

If you were to put thermostat in the living pace you refer to, yes as you say cooking etc. will influence it however you probably have a window open or an extract fan on, so it wouldn't be as detrimental an effect.

Regarding running boiler longer that just the boosting "pulses" you do at the moment, that is absolutely fine - the only area that would overheat is the main living space as no controls. I had a similar situation a few years ago where I fitted TRVs on every rad and a programmable thermostat in a relatives house (old 70s semi-d).He was decorating, and the programmable thermostat(wireless type) somehow disassociated itself from the hard wired receiver/switch (I suspect he dropped it and the batteries came out) - the hard wired switch which went into panic mode - it just switched the boiler on constantly. We only discovered this about 3 months later but no issue, as the boiler responded to the demand from the TRVs and stopped burning when it could.