possible 4 ton install questions

[homebuilt burner]

I have been given free of charge a Lennox 10ACB48-5P condensing unit and A-coil. Yes, I know this is an older unit and yes I know it is not very efficient. It is however the correct size for my home according to the heating and cooling calculations I have researched on the internet. Did I mention free and worked when remove from a building that was torn down??

I am a diesel mechanic and have the AC and refrigeration certifications and have worked on vehicle AC and refrigeration units, but not residential AC. I have refrigerant scales and vacuum pumps. I also work part time for a small company that does refrigeration but not residential AC. One of the refrigeration techs is more than willing to help me and also has reclaimers and manifold gauges, but has not done any residential AC work.

So my questions, on the electrical it calls out a recommended max. circuit breaker of 50 amp. and a minimum circuit ampacity of 31.2 What size wire should I run and what size and type of out side disconnect should I use?? ( the length from the breaker box to the condensing unit will only be about 10')

Next, I have access to R22 and other refrigerants, as this unit was designed for R22 should I stay with that or are their better options now?? (On automotive systems we often do changeovers to R134)

I am planning to pressure test with nitrogen as I do with mobile systems, or is this not needed?? Also, do you add dye and or oil to the charge??

My intention is to run a new line set and filter, solder and pressure check then weigh in an appropriate charge. Any other advice??

Our home is well shaded and we get very good breezes most of the summer so we really only use the AC for about 2-3 weeks a year or I would be looking for a better more efficient unit.

 

[brewchief]

Yes pressure test, no dye or oil, pull a good vacuum, # 10 thhn copper, #8 copper if romex, #6 aluminum, 60 amp fused disconnect with 50 amp fues. Stick with r-22.

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[homebuilt burner]

Is it code or good practice to put an outlet next to the outdoor disconnect?

And what size breaker double 60 or double 50??

 

[zmaxmotorsports]

Yes an outlet next to the condensing unit is always a good thing,Id use a non fused disconnect myself anyway.
On an old unit like that Id get my hands on a newer r22 drop in replacement.
You might have trouble buying freon with your automotive refrigiration license,You might need to pay an hvac guy to charge it for you.
A 50a 2p will be plenty,Id run a 20a for the outside outlet.

 

[zmaxmotorsports]

I have been given free of charge a Lennox 10ACB48-5P condensing unit and A-coil. Yes, I know this is an older unit and yes I know it is not very efficient. It is however the correct size for my home according to the heating and cooling calculations I have researched on the internet. Did I mention free and worked when remove from a building that was torn down??

I am a diesel mechanic and have the AC and refrigeration certifications and have worked on vehicle AC and refrigeration units, but not residential AC. I have refrigerant scales and vacuum pumps. I also work part time for a small company that does refrigeration but not residential AC. One of the refrigeration techs is more than willing to help me and also has reclaimers and manifold gauges, but has not done any residential AC work.

So my questions, on the electrical it calls out a recommended max. circuit breaker of 50 amp. and a minimum circuit ampacity of 31.2 What size wire should I run and what size and type of out side disconnect should I use?? ( the length from the breaker box to the condensing unit will only be about 10')

Next, I have access to R22 and other refrigerants, as this unit was designed for R22 should I stay with that or are their better options now?? (On automotive systems we often do changeovers to R134)

I am planning to pressure test with nitrogen as I do with mobile systems, or is this not needed?? Also, do you add dye and or oil to the charge??

My intention is to run a new line set and filter, solder and pressure check then weigh in an appropriate charge. Any other advice??

Our home is well shaded and we get very good breezes most of the summer so we really only use the AC for about 2-3 weeks a year or I would be looking for a better more efficient unit.

Id charge it by the gauges/pressure,not by weight.

 

[homebuilt burner]

I can get R22 through my other job. I actually have both licenses (I took both test at the time).

I should have clarified my intention was to weigh in a charge and adjust from there, according to pressure, there is a very good table in the installation manual, as I am unsure of what it would take to fill the line set.

 

[zmaxmotorsports]

I can get R22 through my other job. I actually have both licenses (I took both test at the time).

I should have clarified my intention was to weigh in a charge and adjust from there, according to pressure, there is a very good table in the installation manual, as I am unsure of what it would take to fill the line set.

 

[homebuilt burner]

Thanks guys. I'm sure as I start working on this more questions will arise. If you think of any other tips let me know.

 

[dave*99]

Inspect the equipment carefully. Try and figure out how long that equipment lasts in your area. My neighborhood was built in 1986. Maybe 10 years ago my A-coil sprung a leak. I replaced the system. Following year my next door neighbors unit died. So I replaced his. Then I did 3 more in the next 2 years. It was like they all had an expiration timer. It's a lot of work to do the installation so you hope to get some time out of it.

All of those systems in the neighborhood have since been replaced.

Oh, and don't use soft solder on the connections.

 

[Dagny]

Stay brite no. 8 will work fine.

 

[zmaxmotorsports]

Stay brite no. 8 will work fine.

 

[homebuilt burner]

Today, we brazed on some test fittings and vacuum tested both the A-coil and the condenser. Looks good to go ahead. When I cut the ends off of the condenser I could hear the vacuum leaking( it held vacuum while it was in storage for the last year) a good sign I thought. The A-coil that came with the system is a model # C23-51-1 Lennox. Can anyone suggest a filter for this system? I do not have that or any suggestion of such in the installation manual I downloaded. FYI this is an expansion valve system if that matters.

 

[justinjoyal]

Id charge it by the gauges/pressure,not by weight.

Charging by weight as per manufacturer recommendations works great most of the time.

Charging strictly by pressure? I sure hope you mean using superheat/subcool measurements.

 

[magicrat]

Today, we brazed on some test fittings and vacuum tested both the A-coil and the condenser. Looks good to go ahead. When I cut the ends off of the condenser I could hear the vacuum leaking( it held vacuum while it was in storage for the last year) a good sign I thought. The A-coil that came with the system is a model # C23-51-1 Lennox. Can anyone suggest a filter for this system? I do not have that or any suggestion of such in the installation manual I downloaded. FYI this is an expansion valve system if that matters.

I always test with pressure not vacuum unless using a micron gauge.....Ive been burnt by vacuum testing more than once on a very slow leak.....using a micron gauge though vacuum is accurate.....but what do i know...ur mileage may vary.

 

[brewchief]

Today, we brazed on some test fittings and vacuum tested both the A-coil and the condenser. Looks good to go ahead. When I cut the ends off of the condenser I could hear the vacuum leaking( it held vacuum while it was in storage for the last year) a good sign I thought. The A-coil that came with the system is a model # C23-51-1 Lennox. Can anyone suggest a filter for this system? I do not have that or any suggestion of such in the installation manual I downloaded. FYI this is an expansion valve system if that matters.

Air filter or filter/ dryer for the refrigerant? If filter/ dryer i would use a 16 cubic inch version of whatever brand is available, i like sporlan if given a choice.

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[zmaxmotorsports]

Charging by weight as per manufacturer recommendations works great most of the time.

Charging strictly by pressure? I sure hope you mean using superheat/subcool measurements.

Yep,Ive seen plenty of new installs over the years that were off by using the factory charge in the condensing unit.
You check equipment using temp/pressure,why wouldnt you charge an empty unit the same way?

 

[justinjoyal]

I thought you meant strictly by pressures!

 

[Stuff]

Just curious. How do you know what the oil level is in the old compressor? And how much does it matter?

 

[zmaxmotorsports]

I thought you meant strictly by pressures!

 

[homebuilt burner]

Next question in the series. What size wire do I need to run from the furnace to the condenser for thermostat hook up? The diagram shows the cool (signal) wiring running from the furnace to the contactor and a common. I am thinking that is probably 24 volt thermostat type wiring.

 

[zmaxmotorsports]

18g 2cond.

 

[homebuilt burner]

Thanks zmax.

 

[zmaxmotorsports]

Da nada

 

[Brian_WK]

I would also recommend running at least a 5 wire. Never know when you might want to add a thermostat with a outdoor temp sensor or have a wire break or get nicked in the wall. The extra cost is negligible. Or just run 3 sets of 2 wire labeling both ends.

Brian

 

[homebuilt burner]

I am finally getting some time to hook things up. I am having questions about the wiring of the signal lines for the condenser contractor. See attached photos of thermostat wiring where I attached the blue wire. Is this correct? And which terminals do I hook onto for the contractor signal wires?

 

[homebuilt burner]

Another picture

 

[Stuff]

I am finally getting some time to hook things up. I am having questions about the wiring of the signal lines for the condenser contractor. See attached photos of thermostat wiring where I attached the blue wire. Is this correct? And which terminals do I hook onto for the contractor signal wires?

Y and C normally go to the outside condenser contactor/relay.

 

[homebuilt burner]

But the blue wire I put on c only comes from the thermostat. It doesn't seem right to me. I must be missing something. Please explain.

 

[Stuff]

In your first picture you have the blue wire on C of the furnace control board. The board connects C to one side (usually grounded) of the 24vac transformer. The other side of the transformer is connected to the R terminal of the board (does go through fuse and other protection). The R goes to the thermostat and when a call for cooling the 'stat will connect R to Y. That way the compressor contacts get 24 volts. One feed from both sides of the transformer.

In general, the old thermostats don't need a C. The new ones rely on batteries. WiFi models use a C.

 

[homebuilt burner]

With it wired as shown it will not put 24 v to the contractor when the thermostat is switched to cool. I can manually depress the contractor and the compressor runs.

Do I have the thermostat hooked up correctly? I hooked the blue wire up there as well as taking the resistor out.

 

[brewchief]

Is the blue wire on C or is there an RC terminal?

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[homebuilt burner]

I put the blue wire on the RC terminal on the thermostat and the C terminal in the furnace. And hooked to the C wire in the condenser. Also there was a resistor that I took out of the thermostat. It was between the RC and the Ph which has the red wire on it as well.

 

[homebuilt burner]

I tried it to see if the condenser would come on with thermostat set below room temp and set to cool. It did not work and I did not get power on the Y terminal wire and C terminal wire. When it did not work I shut all power off to wait for assistance.

 

[brewchief]

Unhook the blue wire at the stat if there is no C only terminal and unhook it at the furnace as well. The RH and RC should be jumpered together unless you have a dual transformer system so either reinstall the little resister or simply use a piece of wire to connect them again, should be good to go at that point.

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[homebuilt burner]

Okay I'll try that tomorrow.

Thanks

 

[LS6 Tommy]

I always test with pressure not vacuum unless using a micron gauge.....Ive been burnt by vacuum testing more than once on a very slow leak.....using a micron gauge though vacuum is accurate.....but what do i know...ur mileage may vary.

You cannot leak check with vacuum, PERIOD. Micron guage or not.

Tommy

 

[homebuilt burner]

Unhooked the blue wire. Set to cool waited about 1 min blower fan kicked on 30 sec later condenser came on.

Thanks guys. Now to make refrig connections and leak check.

 

[homebuilt burner]

Finally had time to get the freon lines hooked up and charge the system. Pressures match the install manual.

Works great. Wife is happy.

Thanks for everything gentlemen.

 

[homebuilt burner]

bump for reference