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HVAC Discussions - Heating, ventilation and air conditioning.
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Posted by mona anderson on November 8, 2006, 10:48 am
hi everyone, I'm new in the business (just got my EPA type I and II licenses)
and have
a request from a customer for a manuscript storage area with a need for a
humidistat
control. temperature does not matter as it's year-round cool due to a high
altitude
but the area gets rain 5 days out of 7 and humidity control is difficult
as the documents are stored in an area with irregular electric service, we've
already
created a generator and solar (with inverters and battery banks) backup system
which
is instantly activated if there is a power loss.
I have a couple very promising mini-splits on hand which have the ability to run
blower at very low speeds and the systems would be started in series (relays
already
installed) with a 5 min delay to minimize instant on power surge
the humidistat control I'm looking for would have to be a fairly simple piece of
24v
controller, it can have the usual 5% accuracy but would have to have at least
some of
these capabilities
maximum 52% relative humidity with ability to turn off at a lower value or range
no reheat system
ability to set minimum and max for relative humidity
all the controls I've looked at so far have a range of 6 or 8% and don't have
any
adjustment capability
when the new visionpro iaq became available I was hoping it would allow me a way
to
program only based on humidity range but it's also limited in this
the ideal control would monitor indoor humidity (not temperature) and turn on
first
system when 53% is detected but have the ability to shut down when humidity is
dropped
to 49-50%.
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Posted by AKS on November 8, 2006, 5:06 pm
There are systems that can control Relative Humidity's
with in 3 or 4% with out any problems however you are
looking at big bucks I work on systems that control
temperature plus and minus 1/2 Deg. F. and like wise
Relative Humidity's plus and minus 1%. for example
70 Deg. F. and 36% RH. Once you start to control RH
the cost of instrumentation goes up quickly.
I would suggest that you have talk to you customer
If he want that type control let me know I will point
you in right direction.
Good luck from Dido
www.cas-environ.com
show/hide quoted text
> hi everyone, I'm new in the business (just got my EPA type I and II
> licenses) and have a request from a customer for a manuscript storage area
> with a need for a humidistat control. temperature does not matter as it's
> year-round cool due to a high altitude but the area gets rain 5 days out
> of 7 and humidity control is difficult
> as the documents are stored in an area with irregular electric service,
> we've already created a generator and solar (with inverters and battery
> banks) backup system which is instantly activated if there is a power
> loss.
> I have a couple very promising mini-splits on hand which have the ability
> to run blower at very low speeds and the systems would be started in
> series (relays already installed) with a 5 min delay to minimize instant
> on power surge
> the humidistat control I'm looking for would have to be a fairly simple
> piece of 24v controller, it can have the usual 5% accuracy but would have
> to have at least some of these capabilities
> maximum 52% relative humidity with ability to turn off at a lower value or
> range
> no reheat system
> ability to set minimum and max for relative humidity
> all the controls I've looked at so far have a range of 6 or 8% and don't
> have any adjustment capability
> when the new visionpro iaq became available I was hoping it would allow me
> a way to program only based on humidity range but it's also limited in
> this
> the ideal control would monitor indoor humidity (not temperature) and turn
> on first system when 53% is detected but have the ability to shut down
> when humidity is dropped to 49-50%.
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Posted by mona anderson on November 8, 2006, 9:37 pm
AKS wrote:
show/hide quoted text
> There are systems that can control Relative Humidity's
> with in 3 or 4% with out any problems
just checking to be sure you and I are writing about the same thing. I am *not*
concerned over the accuracy of the RH measurement. what I *am* interested in is
finding a control that will operate within a very narrow range. all of the plus
$100
humidistats on the market have the ability to set value for RH within +/-1%.
that *is
not* what I am writing about.
when a humidistat opens 24v due to a humidity rise, it typically does not do it
in a
range of 1% despite the setpoint value. thus, the control may be programmed to
40% and
it will not activate at 41% but will likely do so at 44% or 45%.
similarly it will not close the 24v at 39% but will likely do so at 36% to 37%
if you have a control in mind that can do better than this, please post a link
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Posted by AKS on November 9, 2006, 7:27 pm
show/hide quoted text
> AKS wrote:
>> There are systems that can control Relative Humidity's
>> with in 3 or 4% with out any problems
> just checking to be sure you and I are writing about the same thing. I am
> *not* concerned over the accuracy of the RH measurement. what I *am*
> interested in is finding a control that will operate within a very narrow
> range. all of the plus $100 humidistats on the market have the ability to
> set value for RH within +/-1%. that *is not* what I am writing about.
Yes we are talking about same thing
control I am talking about will turn on and off with in 1%
and even with in less then that
Proportional controllers will turn on and off in some cases
with in plus and minus 1/10 of % but system is not cheap
Dido
show/hide quoted text
> when a humidistat opens 24v due to a humidity rise, it typically does not
> do it in a range of 1% despite the setpoint value. thus, the control may
> be programmed to 40% and it will not activate at 41% but will likely do so
> at 44% or 45%.
> similarly it will not close the 24v at 39% but will likely do so at 36% to
> 37%
> if you have a control in mind that can do better than this, please post a
> link
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> licenses) and have a request from a customer for a manuscript storage area
> with a need for a humidistat control. temperature does not matter as it's
> year-round cool due to a high altitude but the area gets rain 5 days out
> of 7 and humidity control is difficult
> as the documents are stored in an area with irregular electric service,
> we've already created a generator and solar (with inverters and battery
> banks) backup system which is instantly activated if there is a power
> loss.
> I have a couple very promising mini-splits on hand which have the ability
> to run blower at very low speeds and the systems would be started in
> series (relays already installed) with a 5 min delay to minimize instant
> on power surge
> the humidistat control I'm looking for would have to be a fairly simple
> piece of 24v controller, it can have the usual 5% accuracy but would have
> to have at least some of these capabilities
> maximum 52% relative humidity with ability to turn off at a lower value or
> range
> no reheat system
> ability to set minimum and max for relative humidity
> all the controls I've looked at so far have a range of 6 or 8% and don't
> have any adjustment capability
> when the new visionpro iaq became available I was hoping it would allow me
> a way to program only based on humidity range but it's also limited in
> this
> the ideal control would monitor indoor humidity (not temperature) and turn
> on first system when 53% is detected but have the ability to shut down
> when humidity is dropped to 49-50%.