[BLDG-SIM] Data source for cold water inlet temperatures

[Jason Glazer]

On 27 Feb 2003 at 13:22, Joe Huang wrote:

> Jason,
> 
> I have three thoughts on this :
> 
> 1) time delay in water temperatures compared to air
> temperatures. Have you tried comparing the inlet water
> temperatures to monthly average temperatures or degree-days
> from previous months ?   Assuming that the water pipes are
> underground, their temperatures might be closer to soil
> temperatures 1 meter or 2 meters down.  For those soil
> temperatures, the time lag from air temperatures would be 1
> month or 3 months, based on some foundation analysis work
> I've done recently.

I don't have any more data then the max, min and annual 
average inlet water temperature so I don't know the lag 
effects.  One to three months seems reasonable and matches 
my intuition.

> 
> 2) distance from where the water comes from. If the source
> is far away, the inlet water temperature will be a composite
> of the air (or soil) temperatures at the source and site.
> For example, water in San Francisco comes from the Sierras,
> so I would assume the water temperature would be
> significantly colder than San Francisco air or soil
> temperatures.  In your regressions, you might take those
> cities out or add in a second term for the air or soil
> temperatures at the water source.
> 

Sounds reasonable but I don't have any knowledge of the 
water sources.

> 3) there are a few places where the ground temperatures are
> significantly higher than air temperature due to geothermal
> sources. I don't know if any of the cities in the handbook
> falls in this category.
> 

I wonder of those places purposely bury their water pipes 
as deep as possible to take advantage of the "free water 
heater" affect?

> I would guess you should be able to get R2 much better than
> 0.4-0.6, more like 0.90 or so.  This is just purely a guess
> on my part.

Given the variation in water supply systems, I think many  
details would be needed to reach R2 of 0.90 but it is 
certainly possible. Unfortunately, I don't have the 
resources to do a survey of water supply systems.

> 
> Joe
> 
> ----- Original Message -----
> From: "Jason Glazer" <jglazer at gard.com>
> To: <BLDG-SIM at gard.com>
> Sent: Thursday, February 27, 2003 12:15 PM
> Subject: [BLDG-SIM] Data source for cold water inlet
> temperatures
> 
> 
> > I received many suggestions for data sources for cold
> > water inlet temperatures but the best was:
> >
> >   EPRI TR-100212, December 1992, "Commercial Water Heating
> >   Applications Handbook" by D.W. Abrams & Assoc.
> >
> > I did some analysis of that data with NCDC degree day and
> > average temperature data.  Generally, the conclusion I
> > came to is that average monthly and annual temperatures
> > are no better at predicting inlet temperature then heating
> > degree day data.  That is the not what I expected. The R2
> > (goodness of fit) that I was getting are in the 0.4 - 0.6
> > range, not very good but expected.  Here are the equations
> > I'm planning on using:
> >
> >   maximum inlet temp = -0.002860 * HDD + 87.8
> >
> >   average inlet temp = -0.003161 * HDD + 74.3
> >
> >   minimum inlet temp = -0.003135 * HDD + 59.3
> >
> > Where HDD is the annual heating degree days base 65.
> >
> > As you can see the slopes are about the same but the y-
> > intercepts are different.  For those who want to explore
> > the number some more, my spreadsheet is attached.
> >
> > Thanks to all who gave me references!
> >
> > Jason
> >
> >
> > On 23 Dec 2002 at 16:11, I wrote:
> >
> > > I'm looking for a data source for typical inlet water
> > > temperatures (water main temperature) for residential
> > > service water heaters for locations in the United
> > > States. This is roughly equivalent to the ground
> > > temperature at 6 to 8 feet depth. The temperature varies
> > > seasonally so knowing the average monthly value would be
> > > best.
> > >
> > > I am already aware of two sources of data that don't
> > > really help: Engineering Weather Data from NCDC has the
> > > 50 ft temperature and the map in the old ASHRAE Load
> > > Calculation Manual is for depths of 4 inches.
> > >
> > > Any leads would be appreciated.
> > >
> > > Jason
> > >

=========================================================
Jason Glazer, P.E.  jglazer AT gard DOT com  847 698 5686
GARD Analytics - http://www.gard.com/
1028 Busse Highway, Park Ridge, IL 60068
Building Energy Simulation and Analysis
Admin of BLDG-SIM list for building simulation users

======================================================
You received this e-mail because you are subscribed 
to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe 
from this mailing list send a blank message to 
BLDG-SIM-UNSUBSCRIBE at GARD.COM