Weather Compensating Settings

[Jackrae]

Dare I say that a straight line is a curve of infinite radius

 

[vulcancontinental]

Dare I say that a straight line is a curve of infinite radius

As you dared to say that may I dare say how infinately subtle our heating curve is then.

 

[D_Hailsham]

I'm sure most will see the obvious floors in the document without even getting to the claims of WC giving a 20% reduction in your annual fuel bill.

Apart from the 20% saving, which seems to assume a room stat with a very wide differential between off and on, I can't see any flaws in the document; or are you questioning the whole basis of weather compensation?

I was intrigued to see the curve incorporated in our boiler PCB is not a curve it's linear. When compared against the Open Therm curve, which is a curve, it is very close.

I assume, always dangerous, that the OT curves would be the same whereas manufacturers curves may differ.

I didn't know OT produced curves. The only version of the OT Protocol available on the Net is version 2.2 from Feb 2003; and there are no curves in it. Are WC curves now included in the latest version? If so, how have they been calculated?

Why is the relationship between external temp and water temperature not a linear one?

 

[vulcancontinental]

ve no input into OT, it just is to me but I can compare others to it.

Heat loss is not linear because rate of loss changes as temperature difference between inside and outside widens or narrows.

 

[Biggles..]

The view man document contains some slight technical errors and some unsustained figures/quotes etc.
The line isn't quite linear with OT as it takes into account a few other variables from within, Vaillant doesn't even need an internal ref temp for their WC.
Some of the old AQ style controllers used compensation/optimisation based on straight lines.

VC- as I've always said, and inline with scores of other building service documents, WC will only offer 2-3% against an already efficient system, from my own figures on my own heating it actually gave an increase of around 15%, made for uncomfortable cold areas due to varying convector styles and was happily disabled!

I'm quite surprised that your company is continuing with OT, that said I guess it fits the budget to bring in a protocol rather than like the big boys develop their own, that said with the merger, will you be adopting the Bus system used by your parent company?

 

[Dan Robinson]

You presume much Mr Clarke .

 

[D_Hailsham]

I've no input into OT, it just is to me but I can compare others to it.

After I posted my last reply I realized that you could have been talking about your own OT controller. So I looked them up; and found no reference to the curve. Can you confirm which boiler and controller you were talking about.

Heat loss is not linear because rate of loss changes as temperature difference between inside and outside widens or narrows.

I have to disagree with you about that.

All heatloss calculators assume that there is a linear relationship between temperature difference and heat loss. So if 22kW is required for -1C outside and 21C indoors (1kW per degree) then 11kW is required for 10C outside and 21C inside.

Maybe the curve compensates for non-linearity in radiator output as flow temp reduces, particularly with constant flow from a fixed speed pump.

 

[vulcancontinental]

The view man document contains some slight technical errors and some unsustained figures/quotes etc.
The line isn't quite linear with OT as it takes into account a few other variables from within, Vaillant doesn't even need an internal ref temp for their WC.
Some of the old AQ style controllers used compensation/optimisation based on straight lines.

VC- as I've always said, and inline with scores of other building service documents, WC will only offer 2-3% against an already efficient system, from my own figures on my own heating it actually gave an increase of around 15%, made for uncomfortable cold areas due to varying convector styles and was happily disabled!

I'm quite surprised that your company is continuing with OT, that said I guess it fits the budget to bring in a protocol rather than like the big boys develop their own, that said with the merger, will you be adopting the Bus system used by your parent company?

I've had AQ WC for years with an internal sensor. TBH the system was cheaper but I think the comnfort is worth it if it wasn't. I think you're right about the 2%. When companies make outlandish statements it puts me off.

OT is here I think to stay with the big boys on the block using it.

There is no merger and it stopped some time ago, I thought most knew unless you know more, you always seem to have your ear to the ground.

Veissmanns consultants insisted the Riello name was dropped in Italy and no way would the family go for that so that was that. I was dissapointed but we just started a Veissmann guy who said don't be.

I believe km and ebus are bastardised versions of OT and originally thought it churlish of the two to opt out but I can see their point, they don't want something interfering with their onboard software.

The new gizmo, kept away from plebs like me who will have to explain it, looks like it will start to exploit OT more fully rather than just the basic boiler control OT often offers.

 

[vulcancontinental]

I've no input into OT, it just is to me but I can compare others to it.

After I posted my last reply I realized that you could have been talking about your own OT controller. So I looked them up; and found no reference to the curve. Can you confirm which boiler and controller you were talking about.

Heat loss is not linear because rate of loss changes as temperature difference between inside and outside widens or narrows.

I have to disagree with you about that.

All heatloss calculators assume that there is a linear relationship between temperature difference and heat loss. So if 22kW is required for -1C outside and 21C indoors (1kW per degree) then 11kW is required for 10C outside and 21C inside.

Maybe the curve compensates for non-linearity in radiator output as flow temp reduces, particularly with constant flow from a fixed speed pump.

If you can find the instruction booklet for our 711 OT unit online the curve is reproduced in there. If you look at any of the current range of boilers with the exception of the Mynute VHE, 35HE or Linea One they will show you the onboard curve.

 

[D_Hailsham]

If you can find the instruction booklet for our 711 OT unit online the curve is reproduced in there. If you look at any of the current range of boilers with the exception of the Mynute VHE, 35HE or Linea One they will show you the onboard curve.

Can't find the 711; did you mean the 611? If you did, there are no curves in the online manuals. The same goes for all the boilers I looked at.

Can you provide a few links?

 

[vulcancontinental]

If you can find the instruction booklet for our 711 OT unit online the curve is reproduced in there. If you look at any of the current range of boilers with the exception of the Mynute VHE, 35HE or Linea One they will show you the onboard curve.

Can't find the 711; did you mean the 611? If you did, there are no curves in the online manuals. The same goes for all the boilers I looked at.

Can you provide a few links?

The 611 is our older unit made by Thebens who also sold it to Veissmann and to Ideal. The 711 is a different unit, made by another manufacturer and I looked at our site but it's not listed.
I don't have a photogragh of the boklet or a scan at home.

If you look at our website and at the Vision C or Verve or Unica i install instructions you will see the onboard curve, standard across our boilers.

 

[D_Hailsham]

If you look at our website and at the Vision C or Verve or Unica i install instructions you will see the onboard curve, standard across our boilers.

Thanks.

The equation, e.g. in the Verve Manual, produces a straight line. Whereas those shown in other manufacturers' literature are frequently curved lines. What determines this and how is the curve calculated? Or are the curved lines artistic licence?

There is an error in the chart showing the curves for the Verve. The curve labels are all ten time bigger than they should be, i.e: 40 should be 4; 20 should be 2; etc. The other two boilers you mentioned are correct.

 

[vulcancontinental]

If you look at our website and at the Vision C or Verve or Unica i install instructions you will see the onboard curve, standard across our boilers.

Thanks.

The equation, e.g. in the Verve Manual, produces a straight line. Whereas those shown in other manufacturers' literature are frequently curved lines. What determines this and how is the curve calculated? Or are the curved lines artistic licence?

There is an error in the chart showing the curves for the Verve. The curve labels are all ten time bigger than they should be, i.e: 40 should be 4; 20 should be 2; etc. The other two boilers you mentioned are correct.

Well spotted about the error, it was the first time they'd published it and a long time ago so I'd forgotten about that

No, the curves are not artistic license but you didn't agree with my opinion although you seemed to confirm it a little later.

Heat transfer is faster (or slower) the greater or lesser the temperature difference. Therefore as the delta T between inside ond out narrows the line is not linear. Well, that's how it was taught to me.

The difference is slight and affected in real life by hundreds of other factors uniquue to different properties and uses so not as important to the end user but much more important to a mathematician.

 

[Biggles..]

As said it becomes a curve due to rate being applied to the calculation/software

 

[D_Hailsham]

Heat transfer is faster (or slower) the greater or lesser the temperature difference. Therefore as the delta T between inside and out narrows the line is not linear. Well, that's how it was taught to me.

I have to disagree with that.

Heat loss is directly proportional to the difference in temperature between inside and outside. If you double (or halve) the delta, you double (or halve) the heat loss (transfer). So the radiator output will also double or halve. It is therefore a linear relationship.

Stelrad Stars will confirm what I am saying.