You send reminders

Eugene Silberstein 3

You can go to www.dupont.com and search for pressure-enthalpy charts. They, at first glance, appear to be sheets of paper that have been put in front of a 2-year old wielding a pack of crayons. This chart provides all of the information you will ever need as far as the refrigerant properties go.

As far as the formulas go, they are very hard to come by and very confusing at best. AS I mentioned, these charts are most often used as design tools by system designers and engineers. By system designers, I do not mean the gentlemen that determine what system to put in your house. I am referring to the engineers who determine how many feet of tubing are needed in the condenser coil, what size tubing to use... You know, the guys who actually engineer the machines.

A number of books have some elementary information regarding p-h charts, but I have not found the information in one, easy-to-read and understand place.

The neat thing about these charts is that you can calculate and determine the:

Net refrigeration effect of the system

Total heat of rejection

Heat of work

Heat of compression

Compression ratio

Mass flow rate per ton

Mass flow rate of the sytem

Theoretical horsepower per ton of the system

Coefficient of performance

Capacity of the compressor

Capacity of the evaporator

Capacity of the condenser

System EER

Cool, huh?

Sit tight Jeff, there will be one available in the near future (Sept-Oct) that, in my humble opinion, will answer all of your questions.

Jeff Lawrence_24

You even give them a deal!

And they still call you, in a panic because the air conditioning went out.

The highs here today and tomorrow are forecast not to get over 86 degrees with a 60% or better chance of rain, so it won't be that bad.

I sent out service reminders in the spring that tells my customers that the summer is coming and it's time to get their systems serviced. Quite a few of my customers have their AC systems checked out and they get a higher priority if they do have a problem. Then there are the people that never have the systems serviced (or even change the air filters). They are the ones that need it RIGHT NOW!

Yes Ma'am, we'll have someone there as soon as possible, but it may not be until late today or Monday, unless you want Saturday service.

Yes Ma'am, Saturday service does cost more.

Yes Ma'am, I know, but there are a lot of people in the same condition.

Yes Ma'am, we'll be out as soon as we can, thank you.


Customers. You gotta love them.

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Constantin

Beautiful pictures...

... though you may want to downsize them a bit. One of them reminds me of a post I saw at HVAC-Talk years ago where an enterprising HO discovered that she could recycle her filter media simply by flipping it inside the AH every month. Needless to say, her evaporator looked like a lint magnet.

How does the industry approach preventative maintenance (PM) at homes where the equipment has been left to its own devices vs. homes where the PM has been done religiously? Do you guys automatically go to a T&M basis of getting the coils, etc. cleaned or does a "dirty" system cleaning cost the same as a "not-so-dirty" one?

I for one would not relish the need to pull blower wheels, wash HX's, etc. when normal maintenance would have had me do nothing more than replace a filter, check the system pressures, etc.

Steamhead

Think

there's anything primordial growing on those?

bigugh_4

Indeed there is

Used to clean them as we all have, Learned to wear a good dust mask as other peoples dust makes for bad company! (oppossed to "other peoples beer" that is the best brand!) Oh remove the blower and take it to a car wash for squirting. take out the motor and give the blower the bath it sorrley needs. Air blast the motor clean. remember to oil the motors with 20W non-detergent motor oil. Sanitary gloves, like a surgeon wears are cheap and worth the cost. there are many kinds of them, you may be allergic to one kind or another, so do not give up.
Oh and try not to scratch your nose while doing this unpleasaant task, as it makes for a dirty upper lip, and a guarenteed cold in three days!

ScottMP

Oh

" We clean the filters all the time ".

" Oh No we don't have cats ".

I feel your pain Jeff.

Scott

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jeff_51

oooooh so familiar

been in the 90's here for the last three weeks and they wonder why there 30 yr old ac unit isn't working better. at best a seer6.5 but oh no, we can't replace it. Shouldn't it be good for awhile yet? Can't you just keep coming back and fixing it? And why does it cost so much. Looked at a furnace once, it had been slowly using more and more gas and not heating as well. The first thing I ascked was, "when did you last change the filter?" You got it, "what filter?" It had NEVER been changed in over twenty years. Took almost an hour to dig everything out. YIKES. I'm ure you all have similar storys.

Jeff Lawrence_24

Gary

It's nice to have you back!

I actually cleaned this one in the parking lot by my van and did wear gloves.

Here's the after picture. The funny thing about this one was the evap coil was fairly clean.

Jeff

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Eugene Silberstein 3

Very Nice Before and After

Nice work Jeff.

I would keep a copy of those pictures in your truck to show your customers (both present and future) the importance of routine maintenance.

How's John making out with the book?

Eugene Silberstein 3

Hit 'em where it hurts

Jeff,

One of my favorite topics in all of air conditioning is pressure-enthalpy. Typically, the p-h chart and all of the things it has to offer are used exclusively by design engineers and the like.

When I see a system that is completely fouled, as in the case of the one that you were referencing, I plot the system on a pressure-enthlpy chart and calculate the various sytem parameters, including system capacity and EER.

After the repair/cleaning/maintenance is complete, I repeat the calculations and plots.

It's really neat to see the difference and also provide a graphical representation of the system to the customer before and after your work has been performed.

"Gee, no wonder my system hasn't been cooling my house properly", or "That explains the high electricity bills over the past three summers". Gotta love the business.

Jeff Lawrence_24

I never thought of that.

I've seen the P/T charts, but never (that I recall) any P/E charts, as I recall.

How can I get a P/E chart and the formulas?

Thanks Gene.

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Eugene Silberstein 3

Pics

Jeff,

Any other cool a/c pics you have would be appreciated.

Eugene