internal temperature conditions 4

[skyhooks1]

we all know what internal temperature control conditions are, i.e 24degC +-2 etc, but where is it stated that 24 deg.C is the design temperature and that +-2 deg.C is the control range.

 

[jherbert]

ic, I have clearer picture of the question.

Since the glazing was *known* at the time of
deisgn/installion therefore has no bearing,
unless it was changed?

It is real simple:

The designer (contractor?) failed to provide
adequate cooling to overcome the solar load
at the specified design day, easy enough to
argue using ashrae.

Why bother trying to complicate your case
with tolerance issue? The system tolerance
has no bearing on the real issue, the system
is not failing by 0.25 deg is it?

It will be way to complex, your argue +/-2 deg C,
I would counter with instrument tolerance...too messy.
measured where?

In CIBSE air temperature is not even the criteria
for comfort, which would help you case on a sunny
day.

cheers,

 

[IRstuff]

I think you're barking up the wrong a/c.

Unless the specification says something to the effect of:

"nominal temperature of 24º with an uncertainty of ±2º"

there is no technical basis for assuming that interpretation. Even as written, it would still be ambiguous whether the tolerance represents the total uncertainty or something like a 1-[σ] tolerance.

The fact that you've gotten different answers suggests that there is no commonly accepted interpretation for your specification. And, unless there's a statutory or contract requirement, the specification cannot be superceded.

TTFN

 

[jherbert]

I agree with IRstuff

I feel if you open that line of enquiry
you would allow the opposition to argue
tolerance mean't floor to ceiling or
day to night, and twenty other excuses.

It would cause confusion, making
your case *appear* weak.

cheers,

 

[MintJulep]

Skyhook,

The +/- 2 thing is definately too weak to try to base your case on.

It seems clear that the contractor did not calculate the cooling load in accordance with recognized practices. Does the contractor have an PE on staff? You may even have the opportunity to argue that the contractor performed "engineering" without being and engineer.

It also sounds like the spec provided by the consultant is ambiguous.

 

[imok2]

Skyhook
This is a typical standard practice statement taken from Honeywell Gray Manual
"Properly applied automatic controls ensure that a correctly designed HVAC system will maintain a comfortable environment and perform economically under a wide range of operating conditions. Automatic controls regulate HVAC system output in response to varying indoor and outdoor conditions to maintain general comfort conditions in office areas and provide narrow temperature and humidity limits where required in production areas for product quality".I'm sure you can find much more to bolster your case
Roger

 

[BravoCompany]

ASHRAE prescribes recommendations for human comfort based on dry bulb temperature, relative humidity and radiation. They basically outline an envelope within a set of givens. I believe it’s all spelled out in the Fundamentals.

The real question here is what exactly was the contractor's contractual obligation to the client and did he meet those obligations? I am not clear on this based your description so far. What were the conditions of the contract? Was performance criteria assigned? These are the questions that would come up in a court of law.

One last side note, have you run cooling load calculations to identify what the design capacity should have been? Forget any calculations the contractor may or may not have done. This action alone could easily demonstrate quantitatively the deficiency of the cooling system, however, the contractor may not have been under obligation to provide a system to maintain set point if it was not written in the contract documents.

 

[lilliput1]

Require them to submit the heating & cooling load calculation as evidence. They are required to have one otherwize they have not engineered the system.

 

[skyhooks1]

hi everyone,
just to let everyone know who commented on this forum that we have won the case, the approach we took was to highlight the fact that the developer did not comply with the specification and therefore not fulfilling their contract. the court agreed with this and now is required to rectify the problem. i'm think this is where the fun starts, tring to get the developer to install something that is correct and fixes the problem should be interesting in itself, but at the end of the day the developer didn't build the building to spec and cut corners to improve profit.

'in your face you penny pinching ba**ards'

thanks again to everyone for thei comments.

cheers
mark.

 

[friartuck]

Seems like a good lawyer is needed here.

CIBSE Guides are just that and I would suggest that the ASHRAE guides are the same.

The specification will be the key, although the client will have reasonable expectations that the work will be carried out by a suitably competent person.etc.

I have appeared as an expert witness on design faults and the only winner is the legal team..so its best to resolve the problem amicably.

An expert witness would look at the clients initial brief and the specification.

Also, what temperature has been specified, i.e. is it 'air dry bulb', environmental, 'resultant' etc. There are many thermal indexes to choose from.

Drapes

 

[paulkeating]

I'm all for simplifying things when it comes to clients ..... remember, they see things from a different perspective so, much and all as that may annoy us engineers, it's something we need to always bear in mind.

So, in my view, it is not a matter of what the system was sized for (because the sizing is merely an intermediate step between A (client saying "please design me a system") and B (you delivering a system). Focussing on how it was sized is missing the point.

Also, be VERY careful not to confuse CONTROL range and PERFORMANCE range. If the temperature sensor "kicks in" at say 25, the room will continue to rise in temperature "for a while", in other words there won't be an IMMEDIATE response felt at the point of control.

The room might have some inertia in it so even though the sensor/stat has kicked in at 25, the room inertia might be greater than the "thump" of the cooling system and so the room might get to 26 before it stops heating and starts to cool down.

I'd be asking - how is it performing? If it performs such that the room oscillates between 26 and some temperature below 26, then I'd say you've met the hardest part of the 24 +- 2 degC. The system should be capable of getting the room to 24 for "most of the time", (and so I would size the system based on 24 deg C internal absolute, then ADD soem % or whatever to account for inertia).

Any help ??

Paul K

PS - Jeez Billy Q, with an intellect like yours, maybe you should come work for me ..... (private joke, apologies to others, I'll post my CONSIDERED response later).

PS Billy, please send cheque in the amount of $895 + GST for Civic dampers ordered H x W instead of W x H .....