reversing valves Window ac Heat pumps

[thepunk]

Actually I was on another forum and was asked to ask this question on this forum.  I am just learning about Air Conditioners, and have a few questions, anyhow here it is in a nut shell. On a reversing valve selonoid, window unit AC heatpump, if there is voltage, 120 at the reversing valve, does that normally mean that the selonoid is bad if the unit is blowing cold air in heating mode.  Or can the switch, reversing valve or thermostat be stuck.  Thanks. Enquiring minds want to know.

[Repair-man]

The mind is a terrible thing....

A heat pump reversing valve, when no power is supplied to the coil, is in the Cooling mode. For you to show voltage at the coil means it is being told to Heat. No voltage at the coil is for cooling.

[Icehouse]

Let's state the correct operation of a "Four Way Valve" commonly called a reversing valve.
On a call for heat, the solenoid is energized causing the valve to allow the change of direction of refrigerant flow from the compressor to the indoor coil which will bow reject heat into the conditioned space.
On a call for cooling, the solenoid valve is de-energized allowing the flow of refrigerant from the compressor to flow to the outdoor coil rejecting heat to the surrounding or ambient air.
If you need further explanation please read "Heat Pumps" by "Professor Eugene Silberstein" from Delmar division of Cengage publishing of which I am a "Technical Reviewer" for.

[Repair-man]

I think this particular user would benefit more from a simpler explanation  as provided here:

Heat Pump Ops

[Icehouse]

I have this article also. But did not post it as it relates to a split system rather than a "Window Unit".
You and I with our background would associate this, however he is Green 

[thepunk]

That is a beautiful looking reversing valve, simply beautimus.  I know how a reversing valve works.  But, I am stuck in a delema. This pertains to window heat pump ac units.  I have a question.  If a reversing valve has 0 volts across it.  And the defrost control has 120 volts across it, and the unit is blowing cold air with the thermostat  in heating mode, and from what I understand from earlier posts, when measuring voltage across a switch, and I presume the defrost control is a switch, then wouldn't the defrost control be the culprit here, since a voltmeter across a switch will measure 120 when the switch is open and 0 volts when the switch is closed, wouldn't the defrost control do the same.  Info. appreciated, when you say Green, you don't mean I am a tree hugger do you! ;

[Icehouse]

Patience "Grasshopper" will win out all the time, and Reading Is Fundamental. Why not buy the Heat Pump book (no I do not make money) and learn all the right information.
You will be rewarded two ways. 1. Educated rather than Guesstimated 2. Profitable, you can enter this business with a solid background.
I say Green as someone inexperienced, but looking to learn. 

[Repair-man]

That is a beautiful looking reversing valve, simply beautimus.  I know how a reversing valve works

If you don't need know how the valves work, just say so. The way you presented the post is far different from what you say now.

From your first post

On a reversing valve selonoid, window unit AC heatpump, if there is voltage, 120 at the reversing valve, does that normally mean that the selonoid is bad if the unit is blowing cold air in heating mode.  Or can the switch, reversing valve or thermostat be stuck.

I think I covered it. Solenoids have continuity if they are good. You're still stuck in electricity 101 

[thepunk]

I don't mind reading a book, that is what I am doing now  I checked out some of the stuff in the links you provided.  Where is the book.  I am concerned with 120 volts not 240.  I am asking a question pertaining to ac window units.  The stuff I checked out in your link pertains to 240.  Now I know 240 has 2 hot wires and one ground.  As 120 has a neutral a hot and a ground.  Now in 120 from what others have told me on this site, a switch on the same line whan volts are measured across it will give one of two readings, either 120 if the switch is open, 0 if it is closed.  Other techs on this site have told me this.  I checker out a couple links you provided on HVAC voltage measurements and that information tells me on a 240 line, same line, if a volt meter is across the switch, no matter what, if the switch is open or closed the meter will measure o volts unless the meter on one side goes to ground.  So, there is something missing here, what is the difference, between 240 on the same line with a switch or 120 with a switch.  Of course I know that 240 is 120 times 2, and one line is 120 and so is the other with one ground, now 120 is two hots with one hot and one neutral and a ground.  Can you please explain this to me, all I need is a simple explanation of the truth, and the truth will set me free.  If you know of a link that explains voltage measurements and 120 service please let me know, so I can get on with my life, ThankYou!

[Repair-man]

"It's life, Jim, but not as we know it"-  Dr. McCoy

Firstly, you have not grasped the concept of how 240  voltage is made. Once you do, all this will be painfully clear. Here is a good link to read:

Alternating Current-101

I want to hurt your brain one neuron at a time

[Icehouse]

This should also help: http://www.servicematters.com/tech_ref/4322537a.pdf

[thepunk]

I havew revaluated some of my material.  It looks like it is 240.  Though not explained very well.  I have a fair concept of the problem, just need to iron out some things.  I'll restate my question.  On a heat pump, window or outside, doesn't matter, both are 240.  One has 24 volt drop down one doesn't.  O.K. My particular unit has 240 with no drop down.  If my heat pump ac unit is in the heating mode, thermostat set for heating, but is blowing cold air.  I measure o volts across the reversing valve and I measure 120 volts across the defrost control contacts, what do you think is the problem.  If when measuring across switches and I assume the contacts of the defrost control are basically a switch and I get 120 volts with my volt meter then isn't the contacts open and they should be in the closed position when the unit is in heating mode and the selonoid not bad.

[Repair-man]

We help consumers with repair issues. You are not in that category.

Heat pump units are all different. They are wired differently, they use different control voltages and there are no PAT answers for the questions you are asking....

A defrost control does not have SQUAT to do with the heating and cooling, so forget what you read on this defrost control. It is there in case the outer coils get frozen up during operation in winter months and turns off the condenser fan motor so  the coils will defrost.


You are only concerned with one thing...is the reversing valve being energized when the unit calls for heat? It must be activated for the unit to heat. The easy way to tell if the coil is working is to hold a pocket screwdriver across the top of the coil. The magnetism of the energized coil will have an effect on the screwdriver blade.

1. Reversing coil is only energized for heat


Anything else is likely a thermostat or valve problem. Any further questions requires a specific model number on this forum, thanks.

[thepunk]

O.K. Apparently no one on this forum can answer a simple question.  Well, I'll find the answer, but I guess it won't be here.  So sorry!  Apparently you don't understand the question anymore than I do!  And I am new at it.  I am starting to find out there is no true answer to any of it, and one tech or another it doesn't matter,  and there is no real answer, because there are no real technicians, anyhow the term for technician is "Someone who is skilled in the field they work in" But there are no experts on any subject."  Oh well, you gave it half a shot!

[Repair-man]

That's gratitude for ya.

We've been making a successful living at this for 35 years, so even our halfshot is better than anything you'll find elsewhere, sparky. At least you can spell technician...that's the closest you'll ever come to being one.