Heat output of a range rated appliance

[PullerGas]

Be it electric or gas there are two basic ways to control a boiler output, one is the analogue control the other is digital the latter using a mark/space ratio, however with electric that mark/space can be a rather short time, possibly seconds or even shorter, however with gas, the time is a lot longer, so with gas one has to be careful not to use a unit which is too big. There is it seems a minimum flame height. So where possible the gas boiler should be controlled by the return water temperature and only when the flame is at a minimum setting should the electric control take over.

I was taught the wall thermostat is there to turn off the heating when no longer required, it is not there to control the room temperature. To control room temperature with a wet system you need to measure the temperature very close to the radiator and measure both air and water temperature the latter used to compensate for the air temperature being measured close to the source.

As an industrial electrician I have been required to heat all sorts, wax, steel, and rooms. Using not only gas and electric but also oil and solid fuel, one of my jobs was to write the software to control the heaters and reduce the hysteresis to a minimum. Using solid state contactors easy enough with electric heaters the time between each pulse can be short, but using heat pumps one has to allow the pressure to equalise before a restart, so using inverters and altering motor speed instead of simple on/off works better, like gas there is a limit minimum and maximum speed.

I have tried many times to design the system. And straight from Uni out came the slide rule to work it all out. However quickly I realised too many variables, it actually works better looking at the task, and saying this is similar to the job I did at xxxx but half or twice the size so it will likely need a heating unit of xKW, one considers the last one proved too big, or too small.

In the main we have to use units of 3kW, 6kW, 12kW etc, working out it needs 4.25kW is rather pointless if you can't buy a 4.25kW unit, one uses experience, you look at the room, and you say to ones self 3kW will be too small think it with need a 6kW, yes you could work it all out, but why?

If you buy a car to get to work, you don't work out what size of engine is required to get you to work in 1 hour, you use experience, and you say I'll have that one, you have considered all the pros and cons but you have not worked out the engine size, even with wagons you clearly have to satisfy the so many BHP per ton rules, but you look at reliability more than engine size.

Yawn!!...........Really?? Amazing!!

 

[bernardgreen]

yes you could work it all out, but why?

Because that is what the training tells you is the approved method. Education and experience are also needed

And straight from Uni out came the slide rule to work it all out.

Same with first project circuit designers. They produced precise values for the resistors in their design. None of which were standard values. and some did not consider the effect of resistors having tolerances and seldom being exactly ( 1% ) the resistor that they were labelled with.

 

[ericmark]

I will admit new build yes, needs to be worked out, after that point look at the fuel bills, that is more accurate.

 

[picasso]

If a thermostat is not used to control room temp why is it adjustable ? why not just have a big red switch saying ON/OFF ?

 

[bernardgreen]

I will admit new build yes, needs to be worked out, after that point look at the fuel bills, that is more accurate.

The difficulty is that the new build is a building and not yet a home with people living in it and therefore the calculations ( estimates ) can only be worked out based on the building and cannot include any life style factors because the future occupants and their lifestyle is unknown.

The "calculations" do sometimes include some consideration of the affect of an "average" or "typical" people / person living in the property but defining the "average" or "typical" occupancy life style is seldom accurate in reality. Hence the system that is best for one new build house and it's occupant may be the worse for the identical new build next door but with a different type of occupancy.

 

[bernardgreen]

If a thermostat is not used to control room temp why is it adjustable ? why not just have a big red switch saying ON/OFF ?

Because there may not be a person in the room able to operate the big red switch. Or maybe they have fainted in excessive heat or are unable to think straight due to hypothermia.

 

[PullerGas]

Because there may not be a person in the room able to operate the big red switch. Or maybe they have fainted in excessive heat or are unable to think straight due to hypothermia.

Drivel & complete drivel Berny boy. Any building will have a heat-loss calc done, where the system will heat the building to counteract the heat loss through the fabric of the construction. Turn it up too 28 if you want missus, but the system is only designed to heat it too 21!!

Also there's a large degree of +&- on analogical thermostats anyway, so not an exact science by any stretch of the imagination!!

Leave the heating to the Heating Engineers, not the Google Warriors!!

 

[aptsys]

Turn it up too 28 if you want missus, but the system is only designed to heat it too 21!!

That's a bit old fashioned. You can design for whatever you like - the calculations may be tailored for individual requirements, where the bathroom may be designed for a degree or two warmer, and the kitchen lower etc.

 

[bernardgreen]

the calculations may be tailored for individual requirements,

That is true when fitting a new system in an old house, but not necesarily true for a new build unless the house has been bought off plan and the prospective owner has put his or her requirements to the heating designer.

 

[muggles]

If a boiler is range rated. What information is require to work out the heat output of the appliance on a given installation?

Heat input and appliance efficiency

 

[bernardgreen]

Heat input and appliance efficiency

Actual efficiency and not the marketing figures of greater than 100%

 

[PullerGas]

That's a bit old fashioned. You can design for whatever you like - the calculations may be tailored for individual requirements, where the bathroom may be designed for a degree or two warmer, and the kitchen lower etc.

Get real, how many Architecturally designed gaffs are built in this country. You don't live in the real world!!
The vast majority of houses are built by National Builders, like it or lump it!!
The beard stroking Google Warriors are dangerous & out of touch, this forum has gone to the dogs & DaftDIYers are not getting proper advice from professionals, like my good self.

 

[PullerGas]

That is true when fitting a new system in an old house, but not necesarily true for a new build unless the house has been bought off plan and the prospective owner has put his or her requirements to the heating designer.

La la land!!

 

[AGAS]

he only asked about calculating the output FFS , jeezs

 

[aptsys]

Get real, how many Architecturally designed gaffs are built in this country. You don't live in the real world!!
The vast majority of houses are built by National Builders, like it or lump it!!
The beard stroking Google Warriors are dangerous & out of touch, this forum has gone to the dogs & DaftDIYers are not getting proper advice from professionals, like my good self.

I don't deal with the mass produced cheap housing estates. They just fit whatever parts are cheapest which will just about do the job.