I moved to a new place and I don't understand the relationship between the boiler heat dial, the heat dials on the radiators and the thermostat. Which dial overrides which, or do they all work in tandem somehow?
I am in UK if that makes a difference.
The thermostat on the wall controls "demand". This is connected to your boiler controller. The knob on your boiler looks like your heat curve. You set it hotter for colder temperatures and it compensates for the bigger difference. The knob on your radiator is a thermostatic valve. It is purely mechanical and it opens when temperature goes below the setpoint. Similar in principal to the thermostat on a car engine (but water flows when it's cold instead of warm).
leave the knob on the boiler alone, this is the temperature that the boiler heats the water to
set the thermostat temperature to what you think will be comfortable, this is the temperature that the boiler turns on and off at
the radiator valve controls if hot water from the boiler gets into that radiator or not
the radiator nearest the thermostat should not have a valve on it, if it does the valve should be set to 5 or maximum (if this rad were off but the thermostat was turning the boiler on the boiler would be cycling for no reason)
the radiator valves should be set according to the room and its use, guidelines are something like bathroom=max, living areas slightly less, sleeping areas slightly less, unoccupied rooms less, if you are away on holiday put them all on snowflake.
if all the rooms are cold, but the radiator valves are all open and the boiler is running (determined by the thermostat) then bump up the boiler knob. that particular boiler is a wosterbosh? should have green led display tells you the loop temperature, old old houses had high loops like 70ish, modern regs require something mental like 55, the lower the loop temp the bigger the radiators you need to heat the room because the transfer takes longer.
you can look up bleeding radiators if you are new to that too basically the water rusts the rads from the inside out producing hydrogen gas which gets trapped in the rads and makes them less effective, a little valve on each rad at the top lets the gas out.
if a rad is cold at the top and hot at the bottom it needs bled. if its hot at the top and cold at the bottom it might be full of sludge.
if some rads are hotter than others you can look up balancing but its a really tedious process where you play with a different valve on the opposite end of the radiator to get the flow in them the same (rads further from the boiler get less flow because pipe resistance, upstairs are worse)
Max is around 30C (or even more, depends on the manufacturer), overkill for a bath.
boiler heat should always be at maximum unless you have a moronic child who will lean on the hot radiator until it burns them.
From a thermodynamic perspective, the heater loop works "more efficiently" when the boiler is running as hot as is safely feasible. The boiler itself will be consuming more real power, but the rest of the system can work at a lower flowrate load to achieve the same output of heat. This is from a basic principle: A hot object radiates heat into a colder area (until equilibrium is reached). An even hotter object radiates even more heat more easily into that area.
Thus, hot boiler working fluid needs less flow to provide the radiators with the heatload needed to transmit the same amount of heating into an area. This is more "thermodynamically efficient", despite the boiler itself consuming more power to sustain a higher temperature.
To put it in (easy, not necessarily realistic) numbers:
Pretend a 60C source liquid requires 4m^2 of radiator surface area and 20LPM of flowrate to heat a 20m^2 room from 18 to 21C.
That same system at 80C liquid would do the same with 10LPM.
Keeping the boiler maximum hot allows for better demand change handling, but is wasteful, because most people just want to set a house temp and forget about it.
A boiler-heater system that is balanced well i.e. all rooms are recieving the amount of heat you desire, only needs to have the radiator valves adjusted when for example you are cooking in the kitchen and don't need as much heat from the boiler system at that time. Everything else and every other situation is just a matter of patience as temps adjust to demand load.
This is true in terms of thermodynamics but not how high efficiency boilers work.
In a high efficiency boiler the return water is preheated right when it enters the boiler by running along the top of the boiler where it receives heat from the flame that could not be taken up by the outgoing water.
When you make the outgoing water hotter, the return water will be hotter too and take up less of this residual heat. So when you put the temperature lower and the flow higher the house will heat up slower but more efficiently (after accounting for the energy needed to increase the flow rate). Also the tubes will be less hot so less heat is wasted into the walls. The advice is to put it on the lowest setting that will still heat up the house fast enough (the less insulated the house is, the higher the temperature has to be). The difference can be some £500-700 per year for modern units in well insulated houses
absolutely moronic
don't agree with him
high temp heating is not thermodynamically efficient, for the very reason you already stated in your post (you need more heat to heat the house - > worse ratio of heat inputted into living spaces to heat wasted in gas burned in boiler - >lower thermodynamic efficiency)
the gains in the pump power are negligible next to the losses
this is the basic pitfall of optimization
OPs boiler is a condensing boiler, which became mandatory in 2005.
the boiler is most efficient when the flue gas is able to be condensed in a heat exchanger to preheat the return flow.
if the return temp is around 60 degrees or so the boiler can only be around 75 percent efficient, as the return temp drops to around 55 the boiler can condense and efficiency can reach around 85, at something like 45 degrees we can hit 90+% efficiency.
>In a high efficiency boiler the return water is preheated right when it enters the boiler by running along the top of the boiler where it receives heat from the flame that could not be taken up by the outgoing water.
correct, but the reason we call them condenser boilers is because there is a phase change occurring where a knee in the efficiency curve occurs, the relationship is not linear.
combi boilers have different temperature settings for CH and HW. 30c in HW is certainly well below limits to prevent legionella. fit a thermostatic mixer at the bath if scalding water is an issue, this is already a requirement in public buildings afaik. certainly schools and hospitals.
also true, rate of energy loss increases with temperature differential (inside to outside), the colder you can stand the house being the more efficient it is.
without an indoor thermostat the boiler will cycle unnecessarily, in a hot house it will start up, burn gas, pump water, for no reason before determining that the return is hot enough and shutting down for a few minutes and restarting the process again. thats why an internal thermostat is required and the rad nearest should be fully open.
outdoor temp is absolutely required for things like air source heat pump because it is so pathetic at generating heat and cannot cope with demand changes.
r u tarded
30C is the temperature the radiator valve is trying to achieve if set to max, it's a thermostatic valve
which is way too high and in most setups unreachable anyway
apologies, i see now that the post referred to the setting of the bathroom radiator trv, i read it as a moron post confusing heating a bathroom CH with filling a bath HW settings.
i am not any kind of heating engineer, i only remembered from winter prep a few weeks ago that bathroom was highest setting of all the rooms and have confused this for being the highest setting available on the trv.
my trv manual (pic) suggests the second highest setting for bathroom.
i can only suggest anons consult the documentation for their particular trvs for guidance
danvos is the biggest shit btw,
most expensive thermostat, valve gets stuck all the time, proprietary valve-thermostat connector instead of just a thread, hard to turn.
It's mot just about the losses through the walls, the boiler is less efficient too.
WTF is a boiler? Phoenix bro here.
https://www.worcester-bosch.co.uk/products/boilers/explained
do you have a outdoor temperature meter?
if not you should look to adding one then you can throw the middle thermostat out. the boiler then adjusts to the outdoor temperature and the radiators get 30° to 90°C if its freaking cold.
then you remove all radiator thermostats (just to make sure there 100% open and not stuck.)
then you put a thermometer in every room and turn down the boiler so long in small steps till the coolest room gets to cold for you're feelings.
then but this wont work with all radiators, you use a Allen key to throttle the flow rate on the radiators in the hot rooms until all rooms have the same temperature (bathroom a bit warmer etc.)
then you can try to lower the setting on the boiler even more. then you install the thermostat knobs on the radiators again and set them to the desired room temperature.
this way the boiler only makes so much heat the rooms need, the radiators caps only close if you cook bake something to avoid overheating.
in many old building the boiler is oversized and runs really hot (energy was cheap and no boiler installer wanted complaints about it being to cold) the boiler runs and after a short time the radiators close and the flow rate goes down, then the boiler reaches its temperature quickly and shuts off and cycles like that many times a day, wasting most heat to warm the chimney.
btw i miss the old days before the war when my workplace still ran the radiators at fixed 90°C all day the nice radiant heat was great but it would make you poor if you still heat like this at home.
>l ran the radiators at fixed 90°C all day the nice radiant heat was great but it would make you poor
being poor is nothing when you have been boiled alive