Johnward & VicVapour

[matt1e]

Heating is nothing more than a series of switches. There's noting complicated about it at all.

I dont think NTC's Opentherm & ebus are simple switches? in fact not switches at all. A 40 year old S plan is just switches - but things have moved on - honest.

That's wierd because I wire up loads of heating systems for a local plumbing firm, and it's always just switches.

Room stat = switch
Frost stat = switch
cylinder stat = switch
limit stat = switch
programmer = switch(es)
thermocouple = switch
NTC = switch
zone valve = switch

Yeah there might be some fancy electronics in there but all it really boils down to is lots of switches

If you think an NTC is a switch then you know nothing about electronics.

Course it is. It gets to a certain preset temperature and something either starts or stops. That's a switch.

Nope not a switch and agree with Dan too a thermocouple isn't a switch either
it's a bit like saying a photocell is a switch

Matt

A photocell is a switch just like all those other things are.

When it gets dark outside does it just kind of magic the lights on or does it switch them on?

Just because someone isn't physically pressing a button, it is still switching when the external stimuli it is desingned to operate with reaches a certain value.

What about a relay? When power is applied to it's coil does it switch something on or off?

With a photocell when light levels drop below 70 lux it switches something on. It's the same theory with all the other devices.

Look lots of photocell switches

RF I have read enough of your posts in the past to know you are no dimwit
Methinks you are just being slightly argumentative as I was the other night
most temp sensors (heatmisor devices excluded) are made up of just one component namely these

you can argue the fact as much as you like but they are not switches (and you know it methinks )

If It helps I have just ate humble pie too above (well sort of)

Matt

 

[Dan Robinson]

@BAS - still easy easy though

 

[matt1e]

ah this is where you are Dan I thought it was quiet over in plumbing

 

[ban-all-sheds]

@BAS - still easy easy though

What is?

To make a combi boiler which is as efficient as it could possibly be at providing heating AND as efficient as it could possibly be at providing instant hot water?

So are they all like that - there are none for example which don't work as well as they could at heating because they also have to do DHW?

 

[matt1e]

@BAS - still easy easy though

What is?

To make a combi boiler which is as efficient as it could possibly be at providing heating AND as efficient as it could possibly be at providing instant hot water?

So are they all like that - there are none for example which don't work as well as they could at heating because they also have to do DHW?

Bas they all work as well any other system boiler of the same spec for heating, its just they dont do both at the same time (or is that what you mean)

 

[ban-all-sheds]

No - I know that they don't do both at the same time, what I mean is do you end up with the best possible design for a CH boiler if you have to make it so that it can also deliver on-demand DHW, or do you end up with compromises somewhere?

You say "the same spec", but AFAIK you don't need 30kW± just for heating.

 

[Dan Robinson]

House I am in today has a calc of 37.2kW off rads. SW13. Pics going up now...

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Building inspector came round to see the job today.

Looked at the boiler and said how pretty it looked. then spent the next 30 minutes asking how to fix his diverter valve.


Guess I don't have to worry about getting it signed off. .

 

[matt1e]

No - I know that they don't do both at the same time, what I mean is do you end up with the best possible design for a CH boiler if you have to make it so that it can also deliver on-demand DHW, or do you end up with compromises somewhere?

You say "the same spec", but AFAIK you don't need 30kW± just for heating.

No you are right you don't but you can range rate most of them for central heating nowadays

 

[SimonH2]

No you are right you don't but you can range rate most of them for central heating nowadays

But will any range down from 30kW for DHW (combi) to under 2kW(max) for CH ?
If any do, will they still maintain their efficiency while doing it ?
Can they cope with the reduced flow rate required for the rads to be reasonably quiet, or do they need a fully open bypass (=high return temps, =non-condensing unless you keep the flow temp down) to keep the boiler happy ?

Those aren't hypothetical numbers, they are real numbers for a property.

 

[ecowarrior]

I think thats a design fault with the architect. Perhaps he should have speced a 3+6 KW elec boiler on a y plan with 3 going to the rads & 9 going to the cyl ( or what ever the cyl requires) IMO your flats requirement represents such a small and unusual requirement from a gas boiler that perhaps none have been designed ( or probably none can go that low) to service it? If it was a boiler with flow & return NTC cranked down to minimum (5kwish) the NTC's should cope without to much overshoot. I think some boilers advertise 1:10 ratio so that would give u 30 for DHW & 3ish for CH?

 

[SimonH2]

I think thats a design fault with the architect.

I'd avoid comment on that, but I strongly suspect there was no "design" to the heating - I imagine the plumber just used "rules of thumb" to guess at required rad sizes. In the development of 5 houses and 4 flats, I think they used the same boiler for everything (a Vokera Excel 80SP). I know the house on the end originally had one - and that's two floors, roof (only 4" insulation) and a whole gable end, vs the flat with only two external walls.

Perhaps he should have speced a 3+6 KW elec boiler

Electric

IMO your flats requirement represents such a small and unusual requirement from a gas boiler ...

I wouldn't be so sure these days. OK, it was probably unusual for the time these were built (18 years ago), but with modern insulation standards, many small properties are likely to be looking at similarly disparate requirements. The biggest issue being that having a combi for DHW is mutually exclusive with having a small capacity boiler. When eventually I do need to replace the boiler, I'll probably put a smaller one in - not that it's so much of an issue now with the thermal store.

 

[ban-all-sheds]

House I am in today has a calc of 37.2kW off rads.

Is that in order to achieve a quick response?

I don't know what my house needs, and it's nowhere near as large as that one, but even in the one in your photos I can't imagine how hot it would get with nearly 40 1-bar electric fires going all the time..

And if the heating isn't running all the time, then why not? Why have it so big that it has to go on and off, or modulate its output in some way?

As a rule of thumb, the easiest way to make an efficient machine is to design it so that it runs at a constant rate.

 

[Dan Robinson]

This place had 30 rads delivered today + the ground floor is UFH. It is big, and is being made bigger.

 

[ban-all-sheds]

So 37kW from the rads + UFH (barmy idea that stuff anyway).

Run it flat out 24 x 7 during the coldest design weather, and how hot will the house get?

If the answer is "too hot" then the heating system is "too big".

 

[RF Lighting]

UFH (barmy idea that stuff anyway).

Guess you've never seen a proper UFH system then?