Single heat pump runs with Two air handler ?

Hi All:
I have two Carrier Air Conditionning system (each 3.5Ton) cooling my 2100sq ft home which I knew is more than my need. Well it comes like this when I bought this single story rancher house. Both the systems are more then 10 years old and needs to be replaced. Both air handlers are 3.5 tons (Carrier brand) with R-22 charge. I am thinking to replace just the out door units with single 3.5 - 4 tons heat pump (R-22 Type) and run it with both existing air handlers by splitting the in and out line at the heat pump and running upto both air handlers. I just need to know if any up and down side with this setup. I don't wanna throw lot of money in it because my house is old. Any suggestions will be appreciated. Thanks... Awsome
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I got news for you sport.... unless you have 20ft ceilings throughout the house, and over 1,000sqft of single glazed glass, the chances are pretty damn good that all you *NEED* is 3 - 3.5 tons for the whole home. 2nd, they don't make R22 heat pumps anymore, 3rd, R22 refrigerant is going the way of the dodo bird in a really quick hurry. http://www.epa.gov/ozone/title6/phaseout/hcfc.html You no longer have the choice of replacing *just* the outside unit, you have to replace both inside and outside. What you are proposing with yout existing system will not work.
This is what will work.... Call a licensed, insured, Master Technician. Have him do a complete room-by-room Manual J heat load/loss calculation on the home Also a Manual D ductwork calculation. Sit down with the tech and look at your options for a new system and new ductwork. Sign the contract for him to design and install the new system in your home. After the city building inspector signs off on it, pay the man,
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My guess, is that you won't find any installers or techs who are willing to do such a thing. More trouble than benefit.
I'd get a professional service, including coil cleaning. Might buy some time. I've had enough success with coil cleaning, to reccomend it to everyone. To the regulars on this list, I sound like a broken record, I'm sure.
Christopher A. Young Learn more about Jesus www.lds.org .
Hi All:
I have two Carrier Air Conditionning system (each 3.5Ton) cooling my 2100sq ft home which I knew is more than my need. Well it comes like this when I bought this single story rancher house. Both the systems are more then 10 years old and needs to be replaced. Both air handlers are 3.5 tons (Carrier brand) with R-22 charge. I am thinking to replace just the out door units with single 3.5 - 4 tons heat pump (R-22 Type) and run it with both existing air handlers by splitting the in and out line at the heat pump and running upto both air handlers. I just need to know if any up and down side with this setup. I don't wanna throw lot of money in it because my house is old. Any suggestions will be appreciated. Thanks... Awsome
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I agree that you need a Professional to come out and perform an accurate Cooling Load Estimate using a detailed form, so he can properly determine what you need in capacity. While its common to see One A/C unit serving multiple Air Handling Units in a commercial application, it isnt for residential . There are some very critical considerations to doing such a set up, particularly the suction line which has to be sized very accurately for proper oil return . The liquid line is less critical . Have a Professional come out and think along the lines of tieing in all the ductwork to one NEW Air Handling Unit with balancing dampers in the all the branch ducts....hooked up to a new Heat Pump Unit. Have him accurately size the system and perhaps your requirement will be either a 4 or 5 ton cooling load . If you dont already have a functioning roof mounted attic fan , get one because it will reduce the attic temps and thus the indoor spaces while making your roof deck last longer (theoretically) .
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"Awsome" wrote in message
Hi All:

--------------------------
A lot of systems use capillaries to control the flow of refrigerant and as such are balance charged. IE they need exactly the correct amount of refrigerant in the system to make it operate correctly. If this is the case it would be difficult of using 2 fan coil systems on a single condensing unit.
It is possible to do if the system have TX valves and the condensing unit has a receiver and uses a TV valve to control the amount of refrigerant entering the outdoor coil on reverse cycle.
It still would not be a simple job.
---------------
Cooling only
If the fan coils have TX valves and solenoids fitted it is not that difficult, but again if I was installing it I would like to see a receiver in the condensing unit to ensure there was enough refrigerant for the operating fan coil unit, as there would be some left in the second system. Receivers hold extra refrigerant.
As there also could be a problem with oil return I would consider an oil separator in the condensing unit. Much attention would need to be given to the pipework to ensure proper oil return even with an oil separator fitted. A surge tank on the main suction line could also be considered to stop flood back on start up.
If the system has a receiver then pump down could be considered. IE when the system is about to shut down the solenoid coil closes and the refrigerant is pumped into the receiver to attempt to stop a refrigerant and oil problems on start up, the compressor then shut down on the low pressure control.
-----------
Reverse Cycle
Over the last 50 years in the trade I have seen many larger systems that were just a single 10 hp and up spilt systems made by larger air conditioning companies (One fan coil & one condensing unit) that had problems with reverse cycle, so personally I would not attempt a one off multiple fan coil system on a single condensing unit.
Too many possible problems
In my home I designed a single condensing unit (6 ton)s to have two fan coil units, one has been installed, but I have abandoned the idea of the second, as I decide against having the extensions build.
In my case I am using electric elements for heating in that system. Mind you I am living in the tropics and heating is not a big issue here.
Because of possible problems I would not consider reverse cycle in this instance. The smaller system here, yet to be completed will be reverse cycle (2.5 HP) a singe fan coil unit and single condensing unit
For the work you want done it would need someone who has much experience in dealing with this sort of a system, not someone who simply installs single split systems.
================================= For the more technically minded.
The Fisher Library in Sydney University NSW
One of the systems had 6 x 5H 120 Carrier Compressors (125 HP each) there were connected together as a single condensing system.
These compressors have internal unloading.
The system used the refrigerant system to both heating and cooling.
The whole system consisted on many zones, each having a heating a cooling coil in that zone.
The system was designed to allow either one, or both of both coils to be operated at the same time for temperature and humidity control in each zone.
There was a outdoor condensing coil and a outdoor balancing coil in case the system got out of balance with either heating or cooling. A very large slop pot to catch any liquid return.
When I last saw it after 2 years, they were still straightening out problems..............
One of the reasons I would not like to design a multiple fan coil system on reverse cycle.
================================= On saying all of that I do not get involved with smaller domestic system nor for that matter domestic systems hardly at all but larger commercial and industrial system, so there may be more advanced systems out there now that I am unaware of.
I would be interested to know of any multiple fan coil unit systems with one condenser, where you could run two fan coil units at the same time, one on reverse heating and one of cooling.
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"Awsome" wrote in message
In regard to my post, as I do not know how much knowledge you have on refrigeration system I should have mentioned what TX valves (Thermostatic Expansion Valves) are and what they do. They control the superheat that is they usually are set so that there is a round 10f degrees difference between the start of the coil and at the end of it. although this can vary.
They are a valve with a sensor on it that fills the coil with refrigerant, the sensor tells the valve to throttle when the coil is full The valve is at one end of the coil the sensor the other.
They control the superheat that is they usually are set so that there is around 10f degrees difference between the start of the coil and at the end of it. although this can vary on the design of the system.
These valves are usually fitted to larger systems. A capillary tube just meters the refrigerant into the coil and it has no idea if the coil is full or empty, but relies of the amount of refrigerant in the system to fill the coil, hence capillary systems have a balanced charge, a charge of gas that is exactly correct for that system to fill the coil, too much or not enough gas will interfere with the operation of the system.
Systems with TX valves usually have a receiver, a pressure vessel with an extra supply of refrigerant in it to ensure that the coil is full.
While capillary tube systems work fairly well they can have a few problems when the outside air temperature goes beyond their normal working range. One is running cooling when it is quite cool outside.
I had a client who wanted to run cooling at night when the temperature was about 60 f and she set the thermostat right down low. The system being a capillary system did not like it.
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Thanks for your detail input.
I have experienced with auto AC systems and knows TXV etc. I am doing this installation by myself. I have checked with few HVAC tech guys in my area and they haven't done this kind of job before so they ridicule my idea. I know theoretically it is possible but practically how successful I don't know yet.
OK here is my penny thought:
1. Run equal length of lines for both air handlers from single heat pump. 2. Both air handlers have TX Valves 3. Only one thermostat will be installed to control the heat pump and 2 air handlers, run either in heat or cool mode. 4. Two bi-directional dryers will be installed on the splitting lines at Heat pump along with TX valve. 5. My air handlers are 3.5 ton each, I guess 4Ton heat pump will be fine as long as handlers are greater in capacity ? 6. AC ducts are already in place so that shouldn't be a problem but to be safe side I will go over again with Manual J heat load/loss calculation. 7. Any thing else I am missing besides above raised points by other folks ???
Thanks in advance to every one for their valuable input.
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Your going to have some serious issues with your plan.... starved evaps and flooded condenser comes to mind..... along with having some serious sizing issues. You need to do some serious homework on humidity control, as well as airflow charicteristics... I suggest start with some of what Lew Harriman has written on humidity control. FWIW, even here in south Mississippi where humidity is a serious issue, and design is for 75F @ 50%RH inside when its 100F @ 80%RH outside (think 110+ heat index), 2100sqft only requires 3 tons. Bigger is *NOT* better.
I am assuming your going to attempt to do this with R22... not a good idea, the current price is up around $400 for a 30lb can and rising. I can't think of a single thing your doing right with this debacle.
Spend the money and get it done right the first time so you won't have problems/issues with the system itself, or problems/issues with the ductwork.
You can do what you want, its your money.....
BTW... you wouldn't happen to be an EE, would you??
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I wondered the same question.
Christopher A. Young Learn more about Jesus www.lds.org .
BTW... you wouldn't happen to be an EE, would you??
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Sorry my friend you are all wet!
In any refrigeration works you can not have larger evaporators then capacity of condensing Unit "Regardless if is AC or Refrigeration system" in some refrigeration system it can be done but then you need to utilize suction pressure Regulators you prevent overloading Compressor. but for AC it will not work. you can have just apposite larger Condensing unit but then again you will need Evaporator Pressure Regulator or and Hot gas bypass to prevent evaporator freeze up. Sorry
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"Awsome" wrote in message

I wonder how many compressors he will burn out...................
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replying to Awsome, Paul Krupa wrote: Old thread! This is exactly how multi-unit mini split systems are set up. It takes some work to make this work with a conventional system. Use solenoid valves for each loop and use TXV valves. This is mandatory. Use a two stage compressor.
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Wrong in your TXV description of how it works. The TXV doesnt respond to how full of refrigerant the cooling coil is...rather, it responds to the SUPERHEAT at the exit of the Cooling Coil independent of 'how full' the Cooling Coil is of refrigerant. Please dont write up a treatise unless you know what you are talking about.
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" snipped-for-privacy@gmail.com" wrote in message

Hey stupid, read what I wrote :-
// I should have mentioned what TX valves (Thermostatic Expansion Valves) are and what they do. They control the superheat that is they usually are set so that there is around 10f degrees difference between the start of the coil and at the end of it. although this can vary.\\
As for the rest of it, it was written to try and explain in layman's terms how it works.
It seems that you are so obsessed with showing how stupid you are, that you cannot read basics.
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ANd also... TXV's are not just for larger systems ; they appear on very small tonnage comfort cooling systems in addition to small reach in coolers, freezers, pie cases, beer coolers, etc... So please., stop giving misleading information on which you know little about.
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On 3/2/2012 12:41 PM, snipped-for-privacy@gmail.com wrote:

Goodman supplies a kit to convert their A coils to a TVX system. It includes the little wire with the hook on it to pull the piston out of the housing where the valve bolts in place. It includes a fitted insulating cover and everything needed for a conversion. I've used them to improve the operation of problem systems I come across.
TDD
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" snipped-for-privacy@gmail.com" wrote in message

Hey stupid, in case you did not understand, here we are talking about moderate size air conditioning sytems, not bloody pie cases, or freezers.
I am answering a persons who is not a refrigeration mechanic and so I talk in layman's and general terms.
There is always one dickhead like you who has to come in and try to show how bright they are, well you didn't, you just made yourself sound stupid, as usual.
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replying to Awsome, Tony944 wrote: I find you question little in question. Let say you have two man carrying each 100lb. bag cement, and now you eliminate one man and put those two bags on one man how far do you think he will get???
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