My Nightmare Heating System

[Ferdinand]

7 hours ago, Hecateh said:

brilliant metaphor

 

can I share it?

 

 

Of course, though I thought it was a bit tortured, especially for the walrus.

 

 

Edited April 15, 2018 by Ferdinand

[SteamyTea]

kW, or kilowatt, is the power of the unit.

So if your 24 kW boiler is on for 1 hour, it has used 24 kWh of energy.

 

A watt (not a wot, or a Watt, he was the man it is named after) is a unit of power.  We use a capital W when abbreviating it but lower case w when writing it in full, watt.

Power is energy use with respect to time.  Often described as the rate of energy use.

Energy is measured in joule (not jewels, Joules was the man it is named after).  Like watts, we use a capital J when abbreviated and lower case when written in full.

A joule is the force needed to move 1 kg, 1 metre.  If we move that 1 kg, 1 metre in 1 second, then we have a watt.

 

So you could imagine starting with a large box of stones, each stone has a mass of 1 kg, and you have to move them 1 metre.  If you move 1 stone every second, you are delivering power at 1W, if you get some friends involved and move 24 thousand stones 1 metre every second, you are delivering at a rate of 24kW. Sweaty work and shows just how amazing electricity is.

 

So to recap, starting with energy, joules, delivered at a rate, we get watts.  J.s^-1 = W

Just to throw a bit more sums into it, there are 3600 seconds in 1 hour, so if you see energy use refereed to a MJ that is mega joules or million joules.  So 3.6 MJ is 1 kWh.

We really should sell energy by the MJ not the kWh as it would be a lot neater and easier to visualise.

 

[dpmiller]

3 hours ago, newhome said:

 

When I say switched off I mean the temps are set to be lower on the room stats during the times that I’m not here so the heating / boiler doesn’t come on. If there was a huge cold snap I guess it might have to come on even to maintain the lower temperature (which is 18 in the main living rooms rising to 20 when I’m physically here). When I return home the temperature is set at 20 so the boiler either comes on or not depending on whether the temperature has dropped below that value. So I guess it is autonomous, but I’m learning how to set it optimally as a 24kw electric boiler coming on all the time is a bit spendy. 

 

Does 24kw mean that it will use 24kw every hour it fires or something else? 

 

Remember that this is a thermal store system, so just because the house needs some heat doesn't mean that the boiler must come on. The boiler tops up the energy in the store so the cunning bit it to have this happen as little as possible and at the best time.

And isn't this boiler modulating? That means it won't be taking 24kW the whole time it's on anyway...

[newhome]

29 minutes ago, dpmiller said:

Remember that this is a thermal store system, so just because the house needs some heat doesn't mean that the boiler must come on. The boiler tops up the energy in the store so the cunning bit it to have this happen as little as possible and at the best time.

And isn't this boiler modulating? That means it won't be taking 24kW the whole time it's on anyway...

 

It seems to me that as soon as one of the rooms needs heat the boiler comes on. I’ve not yet seen any of the rooms showing ‘heating’ without the boiler firing although I haven’t looked at it obsessively for sure. I also haven’t seen the boiler at anything other than 24kw since the heating started working. It’s either 24kw or off. It can modulate however, I’m just not seeing it now. 

 

 

[Ferdinand]

50 minutes ago, newhome said:

 

It seems to me that as soon as one of the rooms needs heat the boiler comes on. I’ve not yet seen any of the rooms showing ‘heating’ without the boiler firing although I haven’t looked at it obsessively for sure. I also haven’t seen the boiler at anything other than 24kw since the heating started working. It’s either 24kw or off. It can modulate however, I’m just not seeing it now. 

 

 

 

In a place that size from cold it will take some time to heat the walls and foundations and so on before stabilising.

 

It could easily be a couple of weeks or more.

 

F

Edited April 15, 2018 by Ferdinand

[pulhamdown]

13 hours ago, newhome said:

 

I want to utilise the solar to heat the thermal store if I can during the day so I don’t want the electric boiler kicking in 24 x 7. My plan was to use it to heat rooms and water early in the morning, switch off at 7am when I leave for work if I go to the office, leave the solar to work during the day if it can, and then have the boiler switch on to heat up water and UFH ready for me to return in the evening. I’ve no idea if that’s a reasonable plan for this type of system tho! Very much at the learning stage! 

 

That's pretty much what we do.  Our house is near to passiv haus, and does retain any heat well. During the warmer months when the heating is not coming on,  just before taking a bath or shower, I turn off the boiler ( oil fired ) to allow the solar thermal to  heat up the water in the thermal store.  That usually lasts for two to three days, then I turn the boiler back on to top up the thermal store.  Works really well.

[A_L]

4 hours ago, newhome said:

 When I return home the temperature is set at 20 so the boiler either comes on or not depending on whether the temperature has dropped below that value. So I guess it is autonomous, but I’m learning how to set it optimally as a 24kw electric boiler coming on all the time is a bit spendy. 

 

Does 24kw mean that it will use 24kw every hour it fires or something else? 

 

53 minutes ago, newhome said:

It seems to me that as soon as one of the rooms needs heat the boiler comes on. I’ve not yet seen any of the rooms showing ‘heating’ without the boiler firing although I haven’t looked at it obsessively for sure. I also haven’t seen the boiler at anything other than 24kw since the heating started working. It’s either 24kw or off. It can modulate however, I’m just not seeing it now. 

 

Strictly speaking a 24kW boiler will use 24kWh every hour it is on, it is unusual for a electric boiler to modulate as its efficiency is unaffected by the on/off ratio. I do not how big you thermal store is (300l?) but it will only store about 10kWh of usable energy for the radiators and the boiler will tend to fire every time cool water from the radiators returns to the thermal store as its entry will be immediately below the heating elements and the sensor which controls them.

 

The size of your electricity bill is relatively unaffected by  the 24kW immersion as your heat loss from the tank will be a relatively minor 3kWh per day or so and this will provide background heat in the house anyway. The size of the bill is ultimately determined by the whole house heatloss and the mean average temperature you maintain.

[Nickfromwales]

If heating is called for, even for one room, the TS will take instruction from the lowest of the two cylinder thermostats eg 'winter mode'. The boiler will fire and go straight to max output as its trying to now heat the whole TS whilst heat is also being drawn out of it simultaneously. The reason the boiler sometimes lights and modulates quite quickly is that its in 'summer mode' ( DHW only ) and taking instruction from the upper cylinder stat, therefore the return temp gets up much much quicker and allows the boiler to drop its output accordingly, exactly how it should operate for the months of the year where space heating isn't required plus ST is generating too.  

If your drawing heat then the boiler is doing exactly what its been told to do eg replace it as quickly as it can, and as its not a gas boiler we don't need to worry about the temps of the return ( no need to maximise condensing efficiency therefore ). Another reason we've purposefully set the boiler to come on at full wallop at the first hint of duress is that the boiler is only 24kW and is, in my estimate, at least 50% undersized, so it needs to stay ahead of the curve to stand a chance of allowing the TS to do what its been asked to. In reality it should have had a ~35kW gas or oil boiler instead, or possibly the same electric boiler but its big brother ( 40KW iirc ) as the boiler thats there is definitely going to struggle if it gets dialled back from max. 

 

[Nickfromwales]

51 minutes ago, A_L said:

 

 

Strictly speaking a 24kW boiler will use 24kWh every hour it is on, it is unusual for a electric boiler to modulate as its efficiency is unaffected by the on/off ratio. I do not how big you thermal store is (300l?) but it will only store about 10kWh of usable energy for the radiators and the boiler will tend to fire every time cool water from the radiators returns to the thermal store as its entry will be immediately below the heating elements and the sensor which controls them.

 

The size of your electricity bill is relatively unaffected by  the 24kW immersion as your heat loss from the tank will be a relatively minor 3kWh per day or so and this will provide background heat in the house anyway. The size of the bill is ultimately determined by the whole house heatloss and the mean average temperature you maintain.

It's quite a clever boiler with 6 stage triac based heating output from 0 - 100%. It measures flow and return and indeed modulates quite ( if not too ) well. 

[SteamyTea]

7 minutes ago, Nickfromwales said:

It's quite a clever boiler with 6 stage triac based heating output from 0 - 100%. It measures flow and return and indeed modulates quite ( if not too ) well. 

So does it try and keep the temperature between the flow and return temperatures?  This may, or may not be what is wanted depending on how the load is varying.

[PeterW]

43 minutes ago, SteamyTea said:

So does it try and keep the temperature between the flow and return temperatures?  This may, or may not be what is wanted depending on how the load is varying.

 

19-20c on full chat at 24kw then modulates down to 16 then 8 when it gets closer. 

[jack]

7 hours ago, SteamyTea said:

 A joule is the force needed to move 1 kg, 1 metre.  If we move that 1 kg, 1 metre in 1 second, then we have a watt.

 

I suspect it's language choice, but this isn't quite right. The amount of energy required to move 1kg by 1m in 1 second could be anything. It could be zero in space (object moving at 1m/s), or around 10 joules against the earth's gravity.

 

From memory it takes 1 joule to accelerate 1kg by 1m/s2 (not against gravity).

[Nickfromwales]

35 minutes ago, jack said:

 

I suspect it's language choice, but this isn't quite right. The amount of energy required to move 1kg by 1m in 1 second could be anything. It could be zero in space (object moving at 1m/s), or around 10 joules against the earth's gravity.

 

From memory it takes 1 joule to accelerate 1kg by 1m/s2 (not against gravity).

Boffins corner for you two please?. 

I left school nearly two decades ago, and I'm not going back . 

 

[SteamyTea]

33 minutes ago, jack said:

accelerate

Yes.

Comes down to F = MA where force is mass times acceleration.  But to keep it simple initially, moving 1 kg, by 1 meter in 1 second, only, will use a watt of power

 

The example of an object moving in space is a tricky one for a number of reasons:

Space is curved

Space is expanding

Dark Mass

Dark Energy

Entropy is increasing

Time varies

[SteamyTea]

2 minutes ago, Nickfromwales said:

I left school nearly two decades ago

You lucky thing, I left 4 decades ago, and Jack, who knows, 16:55, just in time for Crackerjack!

Edited April 15, 2018 by SteamyTea

[jack]

13 minutes ago, SteamyTea said:

Yes.

Comes down to F = MA where force is mass times acceleration.  But to keep it simple initially, moving 1 kg, by 1 meter in 1 second, only, will use a watt of power

 

The example of an object moving in space is a tricky one for a number of reasons:

Space is curved

Space is expanding

Dark Mass

Dark Energy

Entropy is increasing

Time varies

 

So much irony. Thanks for the laugh.

[newhome]

5 hours ago, pulhamdown said:

That's pretty much what we do.  Our house is near to passiv haus, and does retain any heat well. During the warmer months when the heating is not coming on,  just before taking a bath or shower, I turn off the boiler ( oil fired ) to allow the solar thermal to  heat up the water in the thermal store.  That usually lasts for two to three days, then I turn the boiler back on to top up the thermal store.  Works really well.

 

Mine is certainly not passive sadly. And was cold in the fabric of the house as apart from 1 room I had no heating previously for at least a couple of years. I'm having trouble even seeing the solar thermal actually doing anything at present. How hot does yours heat your TS to? And what does the heat differential need to be between TS temp and the collectcr for the ST to actually heat the TS? From memory when the ST used to work many moons ago it used to take the TS temperature to about 40c (according to the one temp gauge about mid way up the TS). Never seemed to get hotter than that. 

 

 

[newhome]

1 hour ago, SteamyTea said:

You lucky thing, I left 4 decades ago, and Jack, who knows, 16:55, just in time for Crackerjack!

 

3.5 decades here!! Did physics A Level but don't remember any of it as hated every second of it. Chemistry and maths were more my thing, but actually physics could well have ended up being more useful for many more practical reasons. Should have paid more attention clearly . 

 

And I thought Crackerjack was at 5 'o clock?  I only remember Michael Aspel and Stewpot though 

 

 

[SteamyTea]

" All science is either physics or stamp collecting. " Ernest Rutherford

 

[newhome]

4 minutes ago, SteamyTea said:

" All science is either physics or stamp collecting. " Ernest Rutherford

 

 

A very ancient quote however. Can you really explain things like computer science, medicine, modern biology in terms of the principles of physics alone? Back in the day when Rutherford made that quote science may well have simply been data collection (biology certainly was) but things have evolved since then. 

 

And of course the biggest irony is that Rutherford was awarded the Nobel Prize for chemistry rather than physics .  

 

[jack]

Everything can be explained at a fundamental level by physics (although there's perhaps a metaphysical "what is physics" question that's worth addressing before committing one way or the other).

[SteamyTea]

Semi-conductors, which modern computers are made from, capitalise of quantum affects, so yes.

All of chemistry can be explained with physical processes, along with some statistics.

If physicists had been involved in the development of thalidomide, the problem would have been spotted and corrected a lot earlier.

[Nickfromwales]

5 hours ago, SteamyTea said:

So does it try and keep the temperature between the flow and return temperatures?  This may, or may not be what is wanted depending on how the load is varying.

Its a TS so there is no variable load. The boiler has one of two targets to attain. In DHW 'summer mode' we've set it to heat the top of the TS to 65 iirc so the boiler ( which is now a dumb box on the wall set to do as its told and nothing more ( practice differs slightly from the theory as its logic tells it to modulate as it hits the drop off point )) and therefore should just go at full wallop until that stat clicks to satisfied, where it should go into overrun and then standby. 

Likewise with the lower stat, just it takes longer to get there., but its set to a lower temp as its all UFH eg lower grade heat, plus we wanted the solar to have some input as soon as possible. A big kick in the C@@k is the DHW pump, when running, fires the spillover heat from the DHW PHE directly into the lower 1/4 of the TS ( even when in summer mode ) so lovely roasting hot water is forced into the TS and causes the swirling that gave us the previously posted temp readings of hotter in the middle than the top. 

Go fecking figure that design  I was half tempted to redirect that return back into the midriff but there weren't enough days in the window we both had. TBH we could have stayed there another 3-4 days yanking and tweaking, but it wasn't worth the "investment" as it will never be right without some serious 'material' alterations. 

Without picking this apart for its failings, it works, so a result afaic. But its still in the back of my head that we walked away without hitting 100% ( instead we left more than reasonably happy that we did what we could with what was there ).

In a PM I called it "polishing a turd", guess ill never make it to the parish council  "More tea, Vicar?" 

[Onoff]

3.5 decades...

 

So if a warm, draught free, airtight, MVHR equipped place is "passive"...my place must be Aggressive...

[Dreadnaught]

29 minutes ago, jack said:

Everything can be explained at a fundamental level by physics

 

Quantum uncertainty? Emergent complexity of biological systems?