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Size of Evaporation Coils vs. Refrigerant System.

08/01/2013 8:27 PM

Hi, I have 6 (six) air handlers, that haven't been stolen because just installed too high: 20 feet. The condenser units are gone and need to be replaced.

The system worked with R-22, but I;d like to switch to the latest standard and use the Lennox or AAO condenser that use a modern medium refrigeration gas/liquid.

I know the esters, oils and additives do not match well, but I want to clean the evaporators flawlessly and use them with the new condensers.

What about the size of the coils?

Thanks for your input. D

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#1

Re: size of evaporation coils vs. refrigerant sytem.

08/02/2013 12:27 AM

You might have to drop the condenser tonnage 10% or come close....but the distributor should have the statistics of different coils matched with the new condensers....they might work but just lose a little efficiency....with proper tx valves they will balance themselves...

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#2
In reply to #1

Re: size of evaporation coils vs. refrigerant sytem.

08/02/2013 1:42 AM

Thanks. D

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#3

Re: Size of Evaporation Coils vs. Refrigerant System.

08/02/2013 8:10 AM

have your installing contractor use a product like this before they triple evacuate and charge with your new refrigeranthttp://www51.honeywell.com/sm/genesolv/products-applications/acflush.html

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#4
In reply to #3

Re: Size of Evaporation Coils vs. Refrigerant System.

08/02/2013 9:23 AM

also.... if the question was, "can or will a coil designed originally for R-22 be used with refrigerant such as R 410A? the simple answer is yes it can be once its properly flushed. there was mention of expansion valves taking care of pressures. I 'm not going to agree with that 100% depending on where you are you might also have the option of using refrigerant 407 or a product like "Hotshot2" http://www.epa.gov/ozone/snap/refrigerants/lists/homeac.html you have to keep in mind that your evaporator was originally designed to operate at a running pressure around 60 PSI. although something like 410 can be adapted "to work" a 410 coil of modern construction and materials has a designed operating pressure closer to 100 PSI, * the exact numbers aren't my point, the point is your existing coil is a bit light to handle the new pressures but current wisdom says "it will work with a flush and a new metering device. " my suggestion is you scrap the coils and the metering devices and go with all new 410 across the board and not worry about future leaks from an old fatigued coil that's seeing regular pressures it was never designed to run at originally. I'm not saying it can't be modified but you did use the word "flawlessly" best of luck

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#5

Re: Size of Evaporation Coils vs. Refrigerant System.

08/03/2013 3:15 AM

Coil size is probably the least important thing to consider at this stage.

As Fredski points out,there will be an increase in operating PSI with a modern refrigerant.And as much as I would not worry about jumping up to 100 PSI from 60 (60???) some of the newer terianary blends are running much higher.300-400 PSI for some (as viewed from some charts).

The idea is...what condition are your evaps in? R-22 hasn't been installed in quite awhile.

Are the fins intact or or corroded (without looking I think we can all say 'Yes')? Even the best condensor package is a waste of time/money without the ability to match their performance @ the evap/AHU side.

Maybe this is an opportunity for some major technology upgrades.

H2O cooled condensors for domestic hot water generation (you could put these up high with the evaps)

VFD compressors & fans.

Staged compressor bank(s) in place of compressors for each AHU.Imagine 2 or 3 compressors in place of 6. Same with fans.

Food for thought I hope.

Jay

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#6
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Re: Size of Evaporation Coils vs. Refrigerant System.

08/03/2013 7:32 AM

They have collected some dust, but like brand new.

The building was in operation till one year ago and was built in 2008.

The office building is not a big deal for the A/C and has the ducts still in place.

For the production floor, I need to give each Clean room special attention (read- its own air handling - since EU and FDA are involved in the certifications, temperature and R.H. need to be controlled within narrow bands. even during the non productive hours.

The thermal load differs considerably: in production - up to 30 people and 2,500.00 Watts of lights, machinery loads etc.. against nothing at night and on holidays.

I thought of a chilled water system, but I need to re- use what is possible for budget reasons.

Do you have a link to the bank(s)? I considered water cooling too, but the roof is 25 feet high, flat and black!! More a condition to heat it up than be able to cool it down in this climate.

Using new water is expensive and it has too much calcium in it. And pumping is extra energy too. No well allowed.

Thank you for the feed back. It will keep my mind busy. D.

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#7
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Re: Size of Evaporation Coils vs. Refrigerant System.

08/03/2013 7:45 AM

The evaporator coils normally do not handle that pressure. The lines, pipes, tubing whatever, up to the expansion valve - spritz ventil - do, but the coil should be OK I guess. Do they really use special tubing, size and thickness adapted for each particular refrigerant? Need 480 (or 460) VAC 3 phase stuff with high (S)EER.

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#10
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Re: Size of Evaporation Coils vs. Refrigerant System.

08/03/2013 6:26 PM

an evaporator running 400 PS|I?? I'm running for the hills!

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#8

Re: Size of Evaporation Coils vs. Refrigerant System.

08/03/2013 1:18 PM

DVM I think you missed one part of FIX-IT'S post use the water to cool the coils and also make domestic hot water a good use of technology and funds. it could be a long term win-win.

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#9
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Re: Size of Evaporation Coils vs. Refrigerant System.

08/03/2013 6:11 PM

Re: Size of Evaporation Coils vs. Refrigerant System.

Thank you for pointing this out.

Except for the showers, the plant doesn't need hot water. We are working in a hot climate and a simple water solar panel with tank makes steamy hot water.

Problem is also time: the water based heat exchangers like they use in vessels do not come standard for on- the roof type system. In ships they make lots of hot water with the engine coolant, but here we talk of 90 degrees Celsius.

If there is no steady consumption, I find it a bad start to make something work within narrow process limits. More North, I should have considered this more. Perhaps I might consider a series coil water heat exchanger in the office A/C condensers.

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#11

Re: Size of Evaporation Coils vs. Refrigerant System.

08/03/2013 10:55 PM

You could use the old evap coils, but I wouldn't. The reason is that the new systems use much higher pressure. You risk leaks and since you need to change the TXV, why not just change the entire evap coil?

Yes, you can save some money trying to use the old R22 evap coils, but since it's a commercial application, reliability is important. Leaking refrigerant means a system not operating efficiently and possibly to the extent of not providing adequate cooling.

I've also read that it's recommended to change the lines as well. I don't think it's necessary if you completely clean them, but here's a website where they recommend it. Yoder-Stutzman.com/R410.html

I hope this helps.

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#12
In reply to #11

Re: Size of Evaporation Coils vs. Refrigerant System.

08/04/2013 1:13 AM

thank you so much.

In the mean time we have decided to only use the plenums (pleni) and not the air handlers anymore.

It is indeed a too high risk to get these re-instated.

There were in total 7 units, good for about 50 tons. Perhaps the opportunity to review everything and go for chilled water systems. 4 with one big evaporator for the offices (only chilled water will be circulating in it) and the other 3 to individual chiller units - like perhaps 8 pieces per 5 tons, distributed in the clean rooms.

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#13

Re: Size of Evaporation Coils vs. Refrigerant System.

08/04/2013 3:46 AM

Do you have a link to the bank(s)? I considered water cooling too, but the roof is 25 feet high, flat and black!! More a condition to heat it up than be able to cool it down in this climate.

Sorry D, no link. Banking or staging, is a typical feature I've seen used in larger systems (Trane boxcars come to mind) and is usually setup by the designer/engineer.

Another interesting point of the new 'blends' is that after a certain percentage of leakage (10-20 % ?) the system should be pumped down & recharged in order to keep the blended refrigerant balanced.This could be real troublesome for a retrofitted installation with unknown componants.

As for the H2O cooled condensors,your right about your DHW needs,this really wouldn't fit your application.Restaurants & motels are good candidates though.

Look forward to know what is finally decided upon.

Jay

P.S. 400# evap pressures ! DOH!

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#14

Re: Size of Evaporation Coils vs. Refrigerant System.

08/04/2013 3:22 PM

Really since the system is so old an you have to do so many modification's to meet the new code you come to a point where you really will never match up the efficiency standard of the system. (Meaning, your energy usage just makes it far easier to GO NEW!! ) an quit trying to get by on the cheap, it will save you aggravation an also matching system component's do give you the higher efficiency standards or S.E.E.R. for the system. But everyone try's too save a buck or two without giving the "big picture" a look at. An thats the economic angle of running the equipment as well as efficient electricity usage. But trying to match up equipment to a system designed for an entirely different refrigerant is not what the design engineer's had in mind. An those conversion's are truly used when you are trying too limp a system along...... if your trying too save money in the long run and recoup energy savings then there are other ways to make it cost effective to change to new equipment, thus, paying for the installation an avoiding the many hassles with trying to calibrate freon an parts that were not designed for long term use in a older system. Just a thought to consider my friend.

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#15
In reply to #14

Re: Size of Evaporation Coils vs. Refrigerant System.

09/09/2013 3:23 AM

What'd you do?

Did anyone explain your Hot Water could be instantly heated in cooling with some heat recovery as well, with existing off the shelf systems made for that?

Large2 ton to 75 ton systems are already ready for simply being the same used in restaurants today for only point of use dehumidifying and making HW.

Maritime/Nordic Heat Pumps, Water Furnace, Enertech/Hydron, Hydro-Temp (AR) all do not even need a ground loop tie-in to do this as strictly HW generators yielding "FREE" total and sensible cooling with any sizing 2 tons or 20 for say 1/2 of the averaged loads.

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