A technical question

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"Steve" wrote in message
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Do not worry about it
Bye
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On 11/7/2011 11:24 AM, snipped-for-privacy@truthonly.com.Sword of Baal wrote:

The largest system I've ever worked on was at a university chiller plant, one of several for the campus complex and it had multiple 2K to 4K ton centrifugal chillers. The 4K ton R12 chillers were removed and replaced by a pair of 2K ton R134 units for each 4K ton unit. It was quite an experience that not many people have had to even see what's behind the walls and underground in large buildings and institutional complexes. I was involved in a retrofit of a large multistory nursing home where all outside units were replaced by several Trane screw compressors and the first indoor cooling tower in the area. It freed up a lot of space around the building. The largest reciprocating compressors I've dealt with were Carrier 5H60 units where I had to use my engine hoist to change out those units and 60 hp motors. With all the various large to small semi hermetic systems I've installed or repaired I still don't have what I consider that much experience. I haven't seen it all yet but I'm still looking.
I've worked on grocery store rack systems and large bakery refrigeration systems that used multiple variable capacity compressors and even some of different sizes so the smallest was able to maintain temps when there was a very low demand which gave me the idea of what I would do with a large two story house for HVAC and refrigeration serviced from one point. I learned about oil control dealing with rack systems in large commercial refrigeration systems and it's also where I learned to appreciate UV leak detection. Now I'm interested in variable speed inverter compressors that have appeared in recent years and would like to experiment with some of those. At one time I obtained a lot of used equipment from a salvage company that bought the systems from closed grocery stores and restaurants. The company resold a lot of equipment to grocery stores and businesses in the area but unfortunately the owner moved to another county so I no longer have easy access to all sorts of neat stuff. :-(
TDD
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"The Daring Dufas" wrote in message

Those Uni chillers were large, I wish I had manage to get some or that R12. Just a few bottles would have been nice.
My experience with centrifugal chillers is very low, how ever I have done a fair bit of work with screw compressors.
The largest recips I have worked on were using ammonia, mind you although it is a good refrigerant I am not that keen on it. Some of the screw compressors also I have worked on were using ammonia.
I tend to try and not work on ammonia systems if I can avoid it.
I saw in a refrigeration magazine a long time ago where in Japan they started up a system that had 48 ton of ammonia in it.............
-----------------------
Years ago I put together for my own use a self contained temprite beer cooling system.
I am not sure if they used temprites in the USA, they were in almost every hotel and bar here for instantly chilling draught beer. In Australia draught beer is the most served beer and drink in bars, almost every customer has a 'schooner' (15 oz glass size) of draught beer in front of them.
The temprites are being phase out now by glycol tank systems it seems.
Although a temprite can chill warm beer down, in most places the beer was stored in a cold room around 50 f and the final chilling was done under the bar by a temprite down to around 39 f.
Temprites were around 11 inches across and 15 inches high and connected to a refrigeration system external to the bar. The temperature of the temprite was controlled by a '750 valve' IE a suction pressure valve. Some temprites had 3 circuits in them for 3 different beers
If you are not familiar with temprites, they are a flooded system with a stainless steel coil in the refrigerant that instantly chills the beer. I have seen a 18 gallon (imperial) keg drained in 25 minutes though one of these and it chilled the warm beer down to 39 f. It was a free beer night at a construction camp.
Anyway my self contained temprite is sitting there with no R12 in it <sob>. Mind you these days I do not have keg parties, so it is not worth making it work again.
Things have change now there are no 18 gallon kegs, they are now 50 litres, or around 11 imperial gallons (around 13 US gallons)
I have not worked on bar equipment for many years now.
Just as side note. In New Zealand the bars used to have a large pressure tank in the cellar full of beer, this was filled by a 'milk' tanker full of beer which came around and filled it though a hose from the tanker.
I think they have now gone over to a keg system.
In UK in the sixties beer was stored in kegs and served at cellar temperatures (Supposedly around 56 f), their mild and bitter beers had no gas in them and those handles you see them pulling in English pubs (Beer engines) actually used suck the beer from the kegs. These days UK has gone over more to lager, which is served colder and with gas in it.
Different systems for different countries
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On 11/8/2011 2:06 PM, snipped-for-privacy@truthonly.com.Sword of Baal wrote:

A few years back a customer of mine wanted a system to measure the amount of beer flowing through his bar taps. We were looking at designing a system from scratch until I thought that someone must have already done this so I started searching the net. It turns out that such systems are common in Canada where there is a tax on virtually every drop of draught/draft beer and the bar owners have to keep very accurate inventory and sales records for the tax man. I don't know if he ever installed a system but it was a lot less work and money to purchase a ready made and fully developed system. ^_^
TDD
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"The Daring Dufas" wrote in message

Here they just tax the whole keg.
Tax on booze is high here.
Love it when in the USA and see your cheap prices of spirits.
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In some parts of Queensland, mainly in the older pubs they have a cold room behind the bar and beer taps though the wall of the cold room and the kegs are kept in the cold room and that is how the cool their beer.
Is there some sort of main way the cool draft beer in the USA?
As I have said that here draft is the main beer sold.
I sort have the idea in the US that draft is considered an inferior beer. That is not the case here.
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On Thu, 10 Nov 2011 10:54:47 +1000, < snipped-for-privacy@truthonly.com.Sword of Baal> wrote:>

    50 % of which is tax.

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On 11/07/2011 12:09 AM, The Daring Dufas wrote:

Generally different refrigerants work better for different temp ranges. Also, one condensing unit will not be as efficient for BOTH people-space cooling and food refrigeration. You want to make the refrigerant go through the smallest temperature change throughout the cycle for best efficiency.
Jon
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On 11/15/2011 3:30 PM, Jon Elson wrote:

It was a mental exercise that may have lead to an interesting experiment in the real world. You may know of the existence of single condenser AC systems that have several evaporator/air handlers in different rooms of a house. I've worked on systems in restaurants that used a single refrigerant for air conditioning, small refrigeration and walk-in coolers. The refrigerant was R-22 and with certain adjustments and considerations, worked very well. Some day, after winning the lottery or getting an inheritance from a deceased unknown relative, I suppose I'll get to try my ideas for a single point refrigeration and AC system. ^_^
TDD
TDD
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The Coast Guard ships that I have been stationed on used R22 in multi box refrigeration systems... 1 freeze box and 1 refrigeration box..... both operated from the same system. Cleaning seawater side of shell and tube condensers sucked.
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On 11/15/2011 9:14 PM, Steve wrote:

I've worked on a lot of water cooled ice machines that used city water and the things worked very well but around here, the price of water and sewer has gone sky high so folks have gotten away from water cooled condensing units.
TDD
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"The Daring Dufas" wrote in message

The coast guard ship multi system would have almost the same back (suction) pressure if the refrigerator box had a freezer compartment in it, even if they did not it would still be quite similar, IE say 10 PSI for R22 for the freezer, and depending on the type and size of the coil in the refrigeration box it could be up to say 20 PSI.
This is quite different when you put an air conditioning system in the same system where the suction pressure could go up to 70 or 80 PSI depending of course on the entering air and the size of the evaporator. Even if you run the A/C refrigerant temperature down to around freezing say around 57 PSI there is still too bigger difference between the two systems. You could of course put a huge compressor in and use back pressure valves but that would be quite expensive to install and run.
When the air conditioning was turned on the and calling for cooling the rest of the system would get no cooling. On a hot day the A/C would want to be cooling all the time.
It is not a system I would install.

I am surprised that they allow water to be used like that.
Carrier used to make a couple of real nice evaporative condensers, I used them on many occasions.
I think they were models 9B2 and 9B3 and they handled around 6 ton and 10 ton from memory. They had twin centrifugal scroll fans and a head pressure controlled water valve, which discharged water into the bottom of the fan scrolls.
The fans threw the water onto the copper condensing coils, the excess water draining back into the scrolls, so it was not a 100% loss system, as the water valve only opened when the fans were short of water. There were no water pumps in the system, the fans did all the work.
The water boards frowned on them as they thought they used too much water. They are no longer made.
I used these in Sydney where the design conditions were 90 DB 73 WB, up here in the tropics the wet bulb is too high for them to work well.
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On 11/19/2011 3:40 PM, snipped-for-privacy@truthonly.com.Sword of Baal wrote:

We still have cooling towers around here for larger installations. One I did a lot of work on was a bowling alley that had two open drive Carrier 5H60 compressors and a cooling tower. I was always replacing bearings, shafts and motors on the darn thing because it dated back to the late 1950's or early 1960's. Of course the hospital complexes in the area all use cooling towers and chilled water. The university hospital is about to build their own steam plant because the power company which once had many steam customers downtown is closing their plant soon because most downtown buildings don't use steam heat anymore. The South Side of town has been taken over by the university hospital system, numerous research facilities and a number of other hospitals. There are chilled water and steam distribution complexes everywhere to service the large buildings. I suppose the new university steam plant will become the supplier for the hospital monster that ate South Side. The economy of the city shifted from steel production to hospitals, medical and scientific research.
TDD
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On 11/15/2011 09:14 PM, Steve wrote:

OK, this requires the suction side of the compressor to be at the evaporator pressure for the freezer, much lower than the refrigerator. There must be some kind of proportioning system like solenoid valves or maybe proportioning valves to regulate refrigerant to the refrigerator evaporator, or it would get too cold, or raise suction pressure so the freezer box won't get cold enough.
Anyway, not a very efficient system, but maybe better than having two whole systems.
Jon
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THAT EXPLAINS IT ALL

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"Grumpy" wrote in message

It explains why you stuck your nose in with no ability to answer the question.
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You still dont get it! no one can gave you that answer because!
It depends on many factors such as? Size of Condenser, Evaporator, Heat you are looking to get out of system, Thermal Expansion Valves are set for best super heat, regardless if unit is in heat or cooling mode and head can run from 200 to 350
Depend on ambient Temperature and Humidifies. And you are not EE you are dumb ass otherwise you would not be asking a such stupid question like that!!!! (The end)
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"grumpy" wrote in message

The Snow white mixed you up your name is dopey.
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On 11/06/2011 11:04 PM, snipped-for-privacy@truthonly.com.Sword of Baal wrote:

This is a hot-air heat pump system, or something else? Best efficiency seems to be to run the condenser fan so the outlet air temp is as low as you can stand, and still think it is "heat" rather than "cold wind". If you slow the fan down, the air picks up more heat, but the compressor head pressure goes up, too. Throttling the suction reduces effective compressor displacement, but in a lossy way, also making the HP input increase. So, the most efficient way to lower head pressure is to keep removing the heat from the condenser as fast as possible, and not throttle the suction or the evaporator with a TXV.
Jon
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"Jon Elson" wrote in message of Baal wrote:

Thank your for your input.
Basically it is an air conditioning system located in the tropics in a home servicing 3 rooms, a computer room and 2 bed rooms
From a domestic point of view there is a fairly high indoor load in one bedroom (a 50 inch Plasma TV set, a hi Fi surround system and computer etc) and the computer room with quite a bit of stuff in it. The second bedroom is not that often used but also has some electrical load, a 30 inch TV, hi fi surround system and 2 computers.
As it is located in the topics the heating side is not the primary concern, but the cooling is the main use.
Design conditions are here 35 c DB 27 WB. (95 DB 80 WB) inside conditions around 25 c (77 f summer) 24 c (75 f winter) Actually I get a bit heavy handed with my design and use slightly higher numbers to ensure a good result. I have never had a client complain the system works too well :-)
It is a 2.5 ton system with a larger than required condenser to ensure the head pressure is kept fairly low. The system is on R22 and has a discharge pressure electronic speed control on the two outdoor fans to keep the head pressure low, around 190-240 PSI. The fan control is set for 200 PSI. The higher head pressure will only be there on quite hot days.
Highest recorded temperature in the city by the ocean was 40 c (104 f) but as I am on the outskirts of town inland it gets a bit warmer. I have seen it up to 40 c (104 f) once, that was not when the 40 c high was in the city, that was many years ago.
The rooms are individually controlled by 3 thermostats that each can turn on cooling or heating, but only heating or cooling can run at any one time.
The thermostat also opens a damper allowing air into the room in use. So there can be one, two or three rooms drawing air when required.
Usually during the day the computer room is used by one or two persons, sometime one bedroom is also in use during the day but the system should allow all 3 rooms to be cooled, but on a maximum day some loss of conditions can occur if all 3 rooms are calling for cooling, but that would be a rare occurrence.
The indoor and outdoor coils are fed by TX valves and there is a extra R22 in the receiver if it is required.
There are electric elements in the duct and can be used if required to help with the conditions if the humidistat calls in cooling overriding the thermostats, but they are not set up for normal heating but can be switched in if the reverse cycle fails. The humidistat is set fairly high to reduce running costs.
The humidistat is only in one bedroom, as the internal load in the computer room should ensure that the cooling runs long enough to reduce the humidity
I may fit a humidifier later, time will tell on that.
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Heating is mainly going to be used in one bedroom, sometimes the second bedroom but not often, and rarely in the computer room, although all three could be called into operation if required at one time.
Seeing the system can only have one room getting air into it when running on heating the air over the indoor coil shall be reduced, hence I will control the head pressure by controlling the outdoor fans should it get too high. Hence the question about the best head pressure.
The fact there are reasonably high indoor loads in two rooms Plus some indoor load in the second bedroom if it is in use coupled with the fact that heating is not often requite many days in this area means that the heating is a secondary consideration.
A few early mornings a year get down to 11 c (52 f) in the last 9 years twice I have seen it drop early morning to 9 c (48 f). During the day it usually gets up around 27 c (80 f) so homes do not get freezing cold as they would in the snow country.
Now getting back to heating.
In theory the correct amount of heat to keep the correct temperature would be the same as the heat loss once the room is at design temperature.
This meaning you would have the plant heating all the time. Now a hot and cold deck could do this but I cannot see what that would be a practical solution here.
Then we come to a reverse cycle system so in this case with one room requiting heating if we keep it working at maximum efficiency then we would get quick short hot burst of air to get the room up to temperature, with a certain amount of over shoot with the very hot air in the duct.
Hence I was looking for a reasonable amount of heat at a reasonable cost and keeping the room at a fairly constant temperature with a reasonable time heating system running.
I intend to put a couple of pressure switched in to turn on the other rooms when the system is heating should the head pressure get too high with only one room actually turned on. There will be a couple of other pressure switches to override the thermostats if the suction pressure gets too low on cooling turning on other rooms to bring it up.
I have also a 3 speed fan motor on the supply air which I can automatically switch if required.
I am a firm believer that air conditioning should not be felt or heard, so the system should be quiet, no drafts felt and the correct temperature being held within the design conditions.
Hence I use fairly large internally insulated ducts as the main ducts to ensure quiet running with correct size outlets.
Here on this system the 6 ton is operational, the 2.5 ton has the ductwork in and that is operational, the condensing unit is on my work bench requiring me to pipe it up and some of the house pipework is completed.
No have never done cheap house installs, mine have been superior ones by people who wanted a good job done and were prepared to pay for them and mainly did commercial and industrial stuff.
===================== While on heating I have a 6 ton system but I am using electric elements to heat this area, as it will not be needing heating very often, so running economy is not a problem.
Besides that as the 6 ton system was originally designs to have 2 fan coil units I do not like the idea of using it on reverse cycle.
The control is by a Barber Colman time proportional thermostat. They turn on the elements for a short time when only a small amount of heat us required then switch them off again, the element does not have time to get to full heat, just warming the air.
After a time it switched back on again and the element has not fully cooled down, so the air is still being warmed as it switched back on. In essence there is a supply of warm air being supplied all the time to the area when required.
If the room temperature falls then the heating period is longer and the off period is less so as to try and keep the correct amount of heat flowing into the conditioned space.
Should it get cold enough in the room the elements stay on all the time.
It gives a pretty good control.
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BTW in the 2.5 ton system there are return air vents in each of the three rooms.
There are 2 fresh air systems one of each system that have fans in them to bring in fresh are when required, the smaller system with bring in fresh air when the outside air is cool enough instead of running cooling.
The fresh air system and their fans are installed.
They can be locked on if required, other wise they are on a timer that turns them on once the system is running for short periods.
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