30kW System Boiler Choice

[DeltaT2]

yes... of course there are...all of them that take an out door sensor control modulation by calculating the optimum flow temperature, and hence the kw output...its pretty simple stuff...

what boilers do you fit Δ t? and with which controls?

None mate, I'm the CEO & Master Plumber. I don't get my hands dirty I leave that to wrench chimps like you. I employ a M&E Engineer to do all our design work & I just cash the big cheques.....

We won a job today, a Castle Lead Work job in the Highlands £250K & 40% Profit. Who needs to fanny around with WC & make buttons??

We also do Social Housing jobs, 6 rads & a combi, one day installs. There's also still good money at that. We'll fit any old sh.te the spec will permit.....

 

[ChrisR]

all of them that take an out door sensor control modulation by calculating the optimum flow temperature, and hence the kw output...its pretty simple stuff...

Too simple - that's why it doesn't work very well.
Open a window and...

And if a boiler modulates down, that does NOT make it oversized.
Sheesh.


The forum troll's at it again

 

[gaswizzard]

Great thread along with some great BS.

 

[chapeau]

That's not turning the problem around, it's setting a different problem.

I think we need to go back to the beginning.

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No heat loss calculation method that I know of takes into account the specific heat capacity of the building. All it considers is the maximum anticipated heat loss.

Beginning to me means using principles derived from physical laws. Happy to go there if you want..........

Maximum heat loss is directly related to the specific heat capacity of the building.

Consider two buildings, identical except one has a great bit inglenoook fireplace where the other has air. Raise both to 20C and they reach a steady state.

1) The inglenook house will have used more gas to get to 20C ( related to specific heat capacity)

2) Turn the heating off and graph heat loss (we can use room temperature as this gives a good indication) against time. The curves will be different (because one house has a different specific heat capacity)

Specific heat capacity works both ways, when heating up and cooling down.

 

[DeltaT2]

Within reason, no pre-gassed condensing boiler that modulates by WC controls can be over-sized. It's like all cars can travel at 10MPH or 40MPH, regardless of the size of engine.

 

[D_Hailsham]

Beginning to me means using principles derived from physical laws.

I was meaning going back to Simond's original assertion. You still haven't shown that he was wrong.

Maximum heat loss is directly related to the specific heat capacity of the building.

I agree. But the specific heat capacity, aka thermal mass, of a building is not taken into account when calculating the heating requirement.

A building with a high thermal mass will take longer to heat up from cold than a low TM, or require a greater heat input per minute to heat up in a shorter time. But the building will also take longer to cool down, so the heat required to maintain a constant temperature will be less than for a building with low thermal capacity.

 

[ALEC1]

I suspect thats where the savings are made...much like UFH...many people do comment that living with a decent weather comp system is like living with UFH...

others savings are probably made by lower standing losses, no over heating and programming...

Has any organisation ever tried to calculate the specific heat of the housing types in the UK...my own observation is that victorian houses in london actually are quite a good thermal store... the chimney breast mostly...

 

[ALEC1]

Δ T I am greatly reassured by your last post, the previous one made me think that you were so typical of our industry motivated by financial gain only with no real understanding of the technology..

now explain to me again please why you think compensation controls are a nonsense?

 

[Norcon]

now explain to me again please why you think compensation controls are a nonsense?

There nonsense in many small properties and in the small 3sq/m rooms that you advocate applying the technology too.

 

[ALEC1]

And the technical arguments against using internal compensation is?...

 

[ChrisR]

And the technical arguments against using internal compensation is?...

..not what Norcaon was referring to, which you know perfectly well. But as the the resident forum troll you had to come back with something silly of course.

 

[ALEC1]

Hi Chris...

No I don't know what he is getting at...compensation controls always call for the right amount of heat relative to set point and I can't see why you would not use internal compensation in small flats, or on any boiler for that matter...

The only coherent argument I have ever heard for on-off switching is that it is easy to understand, and thats not really an argument at all...just a knee jerk reaction from people who can't be bothered to "think" about how these things work.

 

[D_Hailsham]

The only coherent argument I have ever heard for on-off switching is that it is easy to understand, and thats not really an argument at all...just a knee jerk reaction from people who can't be bothered to "think" about how these things work, or even ask the simple question, why does the EU support the use of compensation controls but not the UK building regulations?

But modulating ones have to go into on-off mode if the required output is below the lower modulation level. The only difference is that standard controls regulate to a fixed, high, temperature and compensation controls vary the temperature.

UK building regulations do advocate compensation. See Domestic Building Compliance Guide 2010 Page 16 which says:

Where condensing boilers are fitted, systems should be designed so as to provide low primary system return temperatures, preferably less than 55 degC, which maximise condensing operation. Low temperature heat emitters such as underfloor heating and weather compensation are examples of techniques which provide low return water temperature.

 

[ALEC1]

Thanks D_H

Yes indeed modulating burners do go into on-off behaviour at low loads, but at low temperatures...which means that over heating is removed and comfort levels maintained with stable temperature...both adding too savings... (like cruise control on a car!)

But how can installers consider this technology if it is not generally available...(I am not expecting an answer to this as it is the manufacturers that decided things!)

and the whilst the spirit of the quote is correct in say UFH is a technique with the controls generally available in the UK the real benefits of UFH (lower operating temperatures) are designed out as almost every mixing valve needs a flow temp in excess of 70c to operate effectively...

Opentherm electronic controlled mixing valves operate in a different manner by floating the flow temperature to the floor while the boiler floats the flow temperature for the radiator circuit but these are not generally available

 

[freeoil]

i thought i was stubborn...this might lighten the load.
i knew a fella years ago that used calculate his rad size by the windows in the room.two 8"by4" windows in a living room would equal two 4"by 2" rads.no joke.
he was the first person to teach me how to do a lead soldered wiped joint and i am not talking about yorkshire fittings here i am talking lead pipe.no wonder the firm never let him work on his own.great hands no sense and probably dead and buried or a hundred and five.