Posted by *geogeek* on January 27, 2006, 3:04 pm

I'd like to track the number of btus that enter my house through my

solar hot water system daily. Besides recording the change in

temperature each day and doing a little math, what are my options? I

use a Tekmar 155 controller. This units gives me delta T hours, which

I don't think is very useful (am I wrong?)....

Any help or advice would be greatly appreciated.

Posted by *Ecnerwal* on January 27, 2006, 11:27 pm

*> I'd like to track the number of btus that enter my house through my*

*> solar hot water system daily. Besides recording the change in*

*> temperature each day and doing a little math, what are my options? I*

*> use a Tekmar 155 controller. This units gives me delta T hours, which*

*> I don't think is very useful (am I wrong?)....*

*> *

*> Any help or advice would be greatly appreciated.*

I that's hours of pumping times (average temperature difference while

pumping) all you need to figure out (might be difficult, might not,

depending on collector loop design) is how much water moves per hour

while the pump pumps (for ease of BTUs, you want to know how many

_pounds_ of water), and you're there - multiply (delta T hour) by

(pounds per hour), you have BTUs (if the delta T in in Farenheit -

otherwise one more unit conversion).

--

Cats, coffee, chocolate...vices to live by

Posted by *Mitch Dickson* on January 29, 2006, 3:35 pm

*> --*

*> Cats, coffee, chocolate...vices to live by*

I love cats myself. Want my new cat Burgou recipe? It starts, "Shoot 6

cats".........................

Mitch :)

Posted by *Steve Shantz* on January 28, 2006, 4:45 pm

geogeek wrote:

*> I'd like to track the number of btus that enter my house through my*

*> solar hot water system daily. Besides recording the change in*

*> temperature each day and doing a little math, what are my options? I*

*> use a Tekmar 155 controller. This units gives me delta T hours, which*

*> I don't think is very useful (am I wrong?)....*

*> Any help or advice would be greatly appreciated.*

An accurate measurement of flow rate is one of the biggest problems

here. If you have an AC pump connected to a differential controller,

you could make a fairly educated guess as to your flow rate. If you

know the amount of time the pump is on, and the Delta T, BTU/hr is a

straightforward calculation:

Pumping Time per day (minutes) x Gallons per minute x 8.77 lb per

gallon x Delta T (degrees F) x 0.87 BTU/lb F = BTU per day

The density and specific heat factors are for 50% propylene glycol. If

you are pumping water, the density is 8, and specific heat is 1.0

However, if you have a DC pump powered by solar panels (as is my

system), an accurate estimation of flow rate and pumping time is

impossible. A flow meter is the only way around this problem. I have

yet to find a good inexpensive one. If anybody knows of one, please

let me know.

One of my goals it to see if I can get a PIC controller, interface it

to temperature sensors and a flow meter, and voila... BTUs / day.

Steve

Posted by *schooner* on January 28, 2006, 7:49 pm

Check out the OneWire temp sensors if your looking for a simple solution.

geogeek wrote:

*> I'd like to track the number of btus that enter my house through my*

*> solar hot water system daily. Besides recording the change in*

*> temperature each day and doing a little math, what are my options? I*

*> use a Tekmar 155 controller. This units gives me delta T hours, which*

*> I don't think is very useful (am I wrong?)....*

*> Any help or advice would be greatly appreciated.*

An accurate measurement of flow rate is one of the biggest problems

here. If you have an AC pump connected to a differential controller,

you could make a fairly educated guess as to your flow rate. If you

know the amount of time the pump is on, and the Delta T, BTU/hr is a

straightforward calculation:

Pumping Time per day (minutes) x Gallons per minute x 8.77 lb per

gallon x Delta T (degrees F) x 0.87 BTU/lb °F = BTU per day

The density and specific heat factors are for 50% propylene glycol. If

you are pumping water, the density is 8, and specific heat is 1.0

However, if you have a DC pump powered by solar panels (as is my

system), an accurate estimation of flow rate and pumping time is

impossible. A flow meter is the only way around this problem. I have

yet to find a good inexpensive one. If anybody knows of one, please

let me know.

One of my goals it to see if I can get a PIC controller, interface it

to temperature sensors and a flow meter, and voila... BTUs / day.

Steve

> I'd like to track the number of btus that enter my house through my> solar hot water system daily. Besides recording the change in> temperature each day and doing a little math, what are my options? I> use a Tekmar 155 controller. This units gives me delta T hours, which> I don't think is very useful (am I wrong?)....>> Any help or advice would be greatly appreciated.