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For about 40 years, I have been working with energy management and other control systems where control wires and cables must be run underground for short and long distances. Lightning and transient suppression on such lines has always been a problem, and no low cost solution will protect such...

OK.. Here is the real answer on how to charge a TWO SPEED HVAC Residential sized unit. To charge in COOLING mode Proceed as follows. 1) Assuming a good TXV, the Superheat in cooling should be from about 5F to 10F and is taken care of you automatically. 2) So how do you make sure you have the...

Thanks imok2! I think waiting until I get a really hot day to check the charge is a good idea. The high side pressure on a 75F day is > 215psi while the low side is <170 so the 10psi minimum pressure across the expansion valve "should" be satisfied. However, I will recheck on a 90F+ day and...

Thanks ccjersey. Your explanation sounds quite logical. I would expect that the expansion valve would try to "flood" the evap coil at low speed and thus could run out of liquid since the pump is running slower. I was considering that PERHAPS, the suction line pressure would rise so that...

Someone please comment. Did I not include enough data? What am I missing here. Thanks. Joe

I thought I knew how to charge HVAC and HP equipment but I am slightly confused by measurements made on my own new system that I just put in. The system is a two speed 3ton/2ton carrier AC (only) with TXV and the 58mvc furnace. Nominally, it all works fine, but I am not understanding the sight...

Weighing the R410a works well. But all up it takes me about an hour to do the removal, compute the right charge and weigh it back in. I am hoping that there is a faster way. But maybe not.

PING! Surely one of you Mechanical Engineering folk have a better answer to this question!?? Thanks.

I know that the optimum method of charging a HVAC system is to evacuate and weigh in the refrigerant. Then check the superheat to be around 10F in cooling mode. (No.. I frequently do NOT have the manufacturer's chart for the equipment I have to service!) My second best way is to install a...

Thanks for the information. I was thinking that modern expansion valves DID provide a positive shutoff for refrigerant when the compressor was not running. I notice that in both my heat pump and air conditioner, I can see liquid in the sight glasses when the compressors are stopped. Since the...

Carrier Residential Heat Pumps specify that if lines are longer than 90ft that a bidirectional solenoid valve be placed in the liquid line near the outdoor unit to eliminate refrigerant being able to flow back into the Compressor unit during the OFF cycle. 1) I am thinking that this must be...

Thanks Sterl for your comments. I think an optical scheme such as you suggest would work, but my experience with such devices outside in the weather has not been good. Dirt, water, and films are constant environmental factors which cause optical devices in the "dirty outdoors" to be...

I have placed the latest article on my work at http://www.gpsinformation.org/joe/HeatPump2.html This system has now allowed my heat pump to operate normally and with FAR FEWER DEFROST CYCLES all the way down to 16F. I presently have it set to switch over to natural gas at 20F as this...

Gepman: My motto is: You spend 40 years of your life working for others so that in your retirement you can run all the experiments you want of your own selection - guilt free! And sometimes make a $ in the process.. :)

Hello EmeraldCostHVACR. If you are warning me not to "mess around" with refrigeration equipment, I am modestly qualified. I have a HVAC Contractor's License, and a Electrical Contractor's License. And I have installed and engineered a myriad of smaller Air Conditioning systems. BUT.. My...

Hi Gepman, I did look at the Copeland site as you suggested. I would like to see a operating map for a heat pump in cooling mode and a table for the heat pump in heating mode for the Copeland ULTRA model, nominal capacity in colling. My 25HNA9 unit claims a nominal cooling capacity of...

Hi Gepman, The charts you linked to are very interesting. The "Operating Map" in particular is useful. The operating map appears to be for a heat pump in heating mode whereas the table appears to be in air conditioning mode. Do you also have an operating map for a heat pump in cooling mode...

Thanks gepman.. You are just FULL of interesting data! I was fascinated by the description of how they achieve 2 "stages" of capacity in this scroll compressor. They have a valve that they can open part way up the scroll to "unload" the compressor. I gather this means they simply do not...

Hmmm.. I notice that for the 25HNA9 48Kbtu/h rated heat pump: In Cooling Mode, the cooling rating at 350cfm/ton, 72F inside ambient, 96F condenser ambient air, the rating is 51.16Kbtu/h. Then for the Heating mode, the heating rating at 350cfm/ton, 70F inside ambient, 47F evaporator...

Hello Gepman, I was not able to get a cross to a Copeland number. Instead, the Carrier Rep sent me a document with all the curves and tables I needed for the 25HNA9048 (48Kbtu/h) unit so I am all set. I do appreciate your help and offer of more help. I still have a lot to learn I am SURE...