I have a Trane heat pump, installed when the house was built in 1995.
I also have a nice gas furnace. I am currently using the furnace for
heat and use the Heat Pump for A/C only.
I'm concerned about the pressure equalizing noise coming from my
reversing valve when the A/C shuts down. It seems to be getting
louder, too. I'd hate for it to fail in the deenergized state; I'd
lose A/C, and I don't even use it for heat! Besides the noise is
I'd like to simply put the valve in cool mode and not worry about it
any more. I could do this by putting 24v on the solenoid and taking it
off of control by the thermostat. Even if the solenoid fails from
running full time, I'd rather take that and buy a replacement solenoid
instead of suffering a valve failure...
Can the solenoid stand to be under power 24/7?
And its going to help it how?
THe OP states that the changeover is getting louder and louder...why?
Hes wanting to put a bandaide on what sounds like a simple issue thats not
going to get better, and wiring the solienoid 24-7s a great idea, since
there is a life expectancy built into all the parts, and 24-7 aint in the
Basically, I don't need the valve to operate anymore since I don't use
the unit in Heat Pump mode. And with the valve currently moving every
cycle, I'm concerned that wear may cause it to fail. This concern is
reinforced by the sounds the valve makes.
I want the valve to stay in Solenoid Hot position.
Since this sound is new with the new thermostat that runs the Heat Pump
in Cool only, I'm almost certain that the original Heat Pump thermostat
kept the valve solenoid Hot whenever it was in Cool mode, compressor
running or not.
They build them to last for 18 - 20 years.... so whats the problem??
As I understand it, you re-engineered the system by installing a different
kind of controls on the system, and now you are not happy with the way it
What was wrong with the original controls and setup??
A lot of heat pumps make some kind of noise with the system running and the
If it really bothers you that much, replace the heat pump with an A/C that
matches the controls you put in.
Why does this sound like there was another problem with the system and
instead of getting the actual problem corrected, he just changed the
I had a digital thermostat installed. The original was purely analog.
I didn't need the Heat Pump heat cycle because I have an efficient gas
furnace. So I bought just an AC thermostat. The way the A/C guys
hooked it up, the same power goes to the solenoid that goes to kick off
a cycle. So the valve switches to Cool when the stat calls for A/C and
switches to Heat when the cycle ends. By putting 24V constant on the
solenoild, I'll stop the cycling of the reversing valve, and eliminate
any risk that it could get stuck in the Heat position.
ok, so you wasted extra money on a heat pump you didn't need.
AHH HA!!!.......You reconfigured the controls like I said, now you are not
happy with the results, because you didn't understand how a heat pump works.
Did it do this when the original thermostat was in the system??
Thats actually what it was designed to do unless you use the correct
controls on it.
With the correct controls, when in cool mode, the stat will hold the RV in
the correct position for cooling, and will shift back when put in heat mode.
And void the warranty, among other things.
Now take the cheap POS stat you bought back to Wally World or Home Cheapo or
wherever you got it from and get a competent tech with the correct controls
out there to do it right.
Nope... Came with the house. Electric company was offering a kickback
to the builder back in '95. We bought the house in 2001. Didn't even
know it was a heat pump until I heard the unit running when we got our
first cold snap.
I understand how a heat pump works. My A/C guys redid the thermostat
when they replaced the upstairs heat pump (compressor hard faulted to
ground.) They did the stat wiring. I'm looking to make it more to my
liking by making the reversing valve not cycle.
I'm about 95% certain it did not. I had never noticed the exhale sound
of the valve reversing before.
That's all I'm looking to do. And the outside unit will always be in
It's 10 yrs old...
That's who did it. You can argue with them over their competence.
The stat is a Honeywell TSATCCNAC01-B. Not a POS.
Lookit, Steve, I'm not an HVAC guy, I'm a controls geek (among other
If your 'exhaling' description is accurate, you have a pressure equalization
problem that will RUIN your compressor if not addressed. It is only
referentially related to the valve itself.
Your guys screwed up... plain and simple. I don't know what's going on...
I'm not there. But it sounds like the RV is coming in after a compressor
start or weakly on compressor start. Some units have 'soft close' valves
while others snap shut and labor the compressor even more.
If you had a HP stat, then replace it with a HP stat that will bring on the
various equipment as designed.
Get somebody who knows what they are doing out there.
PS I do commercial work exclusively, and a resi system might be designed
differently. All I know is that 'exhaling wheeze' is pressure equalization
trouble... I'd guarantee that!!
The RV switches frequently, Jake, even under maximum load ( IE
defrost cycle in heat mode ). Every 30 - 90 minutes or so, in heat
mode, it all of a sudden SLAMS into cooling for a while, and then
SLAMS back into heating. This SLAMS the pressures from one extreme to
the other, as far as the coils are concerned. Of course, compressor
discharge is still compressor discharge, etc.
The difference the compressor sees is limited to the amount of
gas in the discharge pipe between it and the reversing valve - a
matter of a foot or so. Part of that very small 'shock' is dissipated
up the suction line, also.
It does not bother the compressor even a little bit. If it did, you
would have 'heat pump compressors' ( designed to handle it ) and
'cheaper regular AC only compressors' ( not designed to handle it ).
Ain't no such critter. Go to the store and try to by one sometime.
Can't do it.
Yes, the noise is pressures equalizing. No, it will not ruin
Don't bet actual cash money on it :-)
It's not 'trouble' at all, it's just pressures equalizing.
They are designed to do that, and that's what they do.
Thanks for the correction and the explanation... I kinda 'belched' out that
answer only because I didn't like to see monkeying with controls is all....
I stand corrected on the issue.
BTW, the 'belch' wasn't a bullshit one, though. We see pumpdown modes on big
equipment all the time before they do switchovers (like in duplexed
systems). I was just curious why you wouldn't have one on a resi system? I'd
think (oh no, here I go thinking again) that lessening the system shock
would be good for all the components and might even make them less
Or maybe I'm wrong, AGAIN (Damn, I hate that (-; ).
The 'shock' of the pressure change really mainly hits only the
coils, IE, some copper pipe, which doesn't really care. Not too much
of it hits the compressor, in volume ( and thus, 'work' ) terms.
The noise is just noise.
Call me an idiot if you like... do I still not get this?
The RV is switching the suction and discharge around? So you have high
pressure at the suction and low pressure at the discharge (for a little
Doesn't the compressor have to 'make up' the P in the switched discharge
line to be efficient? And I'd worry about the mechanicals of low pressure
carrying lubricant successfully (it would appear the compressor is operating
in a 'vacuum')? Why wouldn't a modern compressor, like a scroll, want to
turn backwards when this happens? That should mean more 'work' to keep her
Dumb questions, probably. I'm still just curious... I deal with GB systems
all the time that work harder than this stuff.
Yep. The outdoor coil ( used to be discharge condensor ) is
now the evap, and the indoor coil ( used to be evap ) is now the
condensor. But, the high pressure seen at the compressor suction line
is only momentary as the indoor coil is pulled down to suction
pressure ( while the outdoor coil goes to discharge pressure ), NOT
for the entire defrost cycle !
Who P'd in the discharge line ???? Damn, I hate when that
happens ..... not as much as the guy who tried P'ing in the discharge
Yes and no, in that order. Yes, carrying the oil is always an
issue in ANY suction side, as the oil is a liquid ( mist ) entrained
in a vapor at that point, and dependent on velocity to carry it around
No, the compressor does not go to a vacumn. A different
expansion device takes over from the first one, ( which is now out of
the circuit, either by check valves around it, or other means ). The
( other ) expansion device is now metering liquid into the outdoor
coil , which is now the evap ( I'm talking about heat mode here ). In
defrost, they change back to AC mode, and the discharge again goes to
the outdoor coil, this time to assure there's no ice on it.
The power of the compressor greatly overpowers the power of
the refrigerant pressures. If it didn't, you got problems :-)
The RV is working for Cooling mode just as it is supposed to. It is
energizing properly and moving properly. It's just that I don't need
it to cycle at all.
Here's how the system works with the original stat... There is a wire
from the stat that turns on the compressor (red on my unit) and a
separate lead that sets the position of the RV via its solenoid (orange
on my unit). When in Cool mode, there is 24V on the orange RV solenoid
wire at all times. The stat cycles the compressor per normal A/C
demand requirements via the red wire. When switched over the Heat
mode, the orange wire is switched off, the RV solenoid is deenergized
and the RV swaps to heat. The stat still cycles the compressor per
normal heat demand requirements via the red wire.
When the A/C guys installed the digital A/C thermostat and set it to
operate in A/C mode all the time, they disconnected everything but the
red wire. At the HP, they tied the red and orange wires on the unit
side together so they both get 24V when the stat asks for A/C. What
this means is that the RV cycles every time the A/C cycles.
The sound that the RV is making when it deenergizes is a normal sound
for an RV that is deenergizing at the end of a cooling cycle. Prior to
making any changes, using the original stat, the RV would have made
this noise if I had switched the stat from Cool to Heat during a Cool
cycle. But because the orange wire only changed with mode, not with
cycles, the valve didn't swap often... only maybe 20 times per year or
so. Now it is doing it on every A/C cycle.
My A/C guy says the valve is good for this duty cycle, but I'd rather
not take chances with it. I don't need the valve to operate any
longer, but I need it in the Cool position. This is the hot position
for the solenoid. (From what I've read, if this was a Ruud system,
Cool mode would be deenergized, and I could simply unplug the
My options are:
1. Leave it alone, let the RV cycle with the A/C, hope the A/C guy is
right about the duty cycle and puyt up with the noise.
2. Wire the solenoid to 24V and leave it energized so that the valve is
always in Cool mode.
3. Do #2 with a switch in the line so that I can manually deenergize
the solenoid and let it "rest" during the winter when I am not in
Cooling Season. (or simply unplug the wire from the 24V source...)
Hope this helps understand what I'm doing.
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