On Sun, 24 Aug 2003 00:33:35 +0100, "IMM" wrote:


"Peter Parry" wrote in message


He has a Bachelor of Science in mechanical engineering and majored in
HVAC. Your qualifications are what exactly?

greater than that.

Go on - don't be shy - tell us.

With blown air systems the radiant temperature of all surfaces must
always be equal to or below the air temperature and for equivalent
levels of comfort higher, not lower, temperatures are required.

This is not accurate.

If you think it is inaccurate please explain

It is not accurate in his assumption comfort levels.

So you agree that with blown air systems the surface temperature of
interior surfaces will always be equal to or below air temperature?

The body is always
cooling. It is the rate of cooling that makes us feel hot or cold. Some
surfaces in line of sight of the body extract heat from the body more than
others. The surface type and colour also make a difference. Temperature of
the surface is just one aspect of MRT. If you read both authors, this is
said in a round about way.

Mean radiant temperature is simply the area weighted mean
temperature of all the objects surrounding the body. It will be
positive when surrounding objects are warmer than the average skin
temperature and negative when they are colder. It follows that hot
air systems, which cannot produce surface temperatures higher than
the air temperature will therefore require higher, not lower,
temperatures than radiant systems to achieve similar levels of
comfort. Radiant heat has a high MRT. Hot air has a lower MRT, it is
inescapable.

You can't. You don't understand MRT, and few actually do. It is regarded
as one of those things invented to explain something.

It is simply basic physics and physiology, nothing magic or
complicated about it.

Only in catalogue land. The great
advantage of slow reaction systems
is the controls can be really
simple _if_ the design is right in the
first place.

Nonsense!!! Do your physics make the concrete slab heat up faster or cool
faster?

no - which is why fancy controls are not usually needed.

Stop prattling on about physics you fool. No designer look at his O levels
physics book when designing a heating system.

If he doesn't understand the physics of heat loss and gain how then
does he design it?

Because your house is occupied most of the time.

Is it?

It s been a "fad" for the last 15 years
at least. (actually the last
2000 odd to be more precise)

It is a fad. The number installed systems at the mo is in single %age
figures. When the building boom really starts it will be insignificant in
installed systems.

Of course - because developers want the cheapest quickest and
simplest systems they can stuff in their little boxes. Quality is
not an issue.

Balls!!! Dream on. You have lived in army
houses.

Most of my houses were not army houses.

And you have experienced ?

Design and installation of 1000s of them.

and never lived with the consequences of any, like most plumbers.

I wasn't design/installed properly.

An assortment of far better qualified
people than you

They are not better qualified or experienced than me.

If you care to let us know your qualifications and experience I'll
compare them for you. I'm interested to know you consider yourself
to be better experienced and qualified in these matters than the
manufacturers senior designer is.

including engineers (not fitters) from
the manufacturers have said it is well
designed and installed.

Balls!! If it was designed and installed well the user would love it.

It was, he doesn't.

--
Peter Parry.
http://www.wpp.ltd.uk/