|
Posted by Mo Hoaner on September 15, 2006, 7:40 am
>
>> I'm a electrician and a controls engineer that has been around this NG
>> for a couple of years. My business has gotten more into the management
>> of small/medium HVAC systems for existing industrial & commercial
>> clients. I've learned a great deal about how HVAC systems work from
>> the contributors here.
>
> Cool. Nice to meet you. BS EE here, so we can talk geek to geek.
> :-)
>
>> That said... I'm going to tell you that the majority of VS systems
>> out there today are 'dumb', and take very little feedback from the
>> real-world into consideration during operation.
>
> Poo.
Not. You are talking about a Ho Moaner system, not a commercial system
where you can dedicate a machine to do the monitoring and control of
multiple air handlers. Really... How many flow, temperature and pressure
sensors do you think they can hang on a system involving a tiny amount of
duct?
>> Airflow is a good example. It's usually extrapolated from a
>> computation of how much energy (amperage) the blower motor needs to
>> operate at X speed. This is done on-board at the motor... a
>> expensive-to-replace proposition that, as an engineer, I totally
>> disagree with.
>
> Agreed.
>
>> Some... better systems also will take readings from the
>> refrigeration circuit into consideration. Do a Google to learn more
>> about how a refrigeration circuit works. Sensors might measure line
>> temperatures or pressures at key points by which things like airflow
>> can be 'roughly' extrapolated.
>
> I figured that'd conceptually be a better way to do it than with
> circuitry on the fan alone.
There is. But it's a Ho Moaner system.....
>
>> Bottom line is... VS... by itself... does not gain you much
>> efficiency. How it effects the 'circuit' on the other hand... might
>> yield great cost savings. Remember, the biggest user of energy in
>> your system is the compressor and not the fan.
>
> It's not efficiency I'm after with VS I guess. The big selling point
> of it is comfort, quietness, and evenness of heat distribution, for me
> anyway. To have some air ciculating to even out the temperature in
> the house is why I'm considering it, though getting that benefit
> without having to run a motor full bore would also be welcome.
>
> Thanks for your response. I'll see if anyone can shed some light on
> why the Carrier dealer is steering me away from VS. Given that it's
> probably a decent markup item, I suspect there's got to be some truth
> to it. This dealer appeared to be the most clueful of the 3 outfits
> that were here, but I'm holding out hope that variations among how
> various manufacturers' VS works might also account for the differences
> in recommendations.
Because he's probably been doing this in the real world long enough that he
doesn't think it will make a difference in your case, and he doesn't want to
spend six months at the EE's house after installing the system. Or, maybe he
doesn't have much more of a clue how it works than the Frigidaire dealer who
knows how to set the dip switches.
>
> Best Regards,
> --
> Todd H.
> http://www.toddh.net/
| 
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap