Heat pump reversing valve with position sensor

[theoldwizard1]

The reversing valve is a key component of a heat pump system. Like any mechanical item that moves, it is subject to failure. I have no idea what is the most common failure (internal leaks ? coil failures ?). If you are designing your own heat pump system with your own controller, a reversing valve with a position sensor could be valuable in resolving problems.

Does this exit ?

[NiHaoMike]

Measure the temperatures on each of the 4 lines. That's how they're diagnosed in the field.

[jeff5may]

They don't really need a position sensor. 99.9 percent of them are spring loaded. They return to the inactive position when you deenergize the coil. Most heat pumps are rigged so they are in heating mode when not activated.

In addition to temperature and pressure checks, about the only other thing you can check is the coil. When they do fail it is not easy to diagnose.

[theoldwizard1]

Originally Posted by jeff5may

In addition to temperature and pressure checks, about the only other thing you can check is the coil. When they do fail it is not easy to diagnose.

Which is why I asked if any had a position sensor ! If the valve is directly operated by the coil, then it probably would not be hard to put some kind of linear position sensor on it.

How common are "pilot operated" valves ?



The sensor could go on the pilot valve, but that really won't tell you if the main reversing valve is stuck/in the wrong position.

[jeff5may]

Originally Posted by theoldwizard1

How common are "pilot operated" valves ?

The sensor could go on the pilot valve, but that really won't tell you if the main reversing valve is stuck/in the wrong position.

They are 99.999% all pilot operated in heat pumps. In fact, the only real difference is the size and resulting flow capacity. They are a little more compact than your picture, but functionally they are identical. Default operation is heating mode in most units.

Service techs usually have two sizes in their trucks: small and large. Small ones go in units rated less than 3 tons, large go in units 3 tons or higher. For really large (commercial) units, they are special order items. The coils are all the same size, so the techs leave the old coils on the new valve after it is changed. (if the coil was not the problem; if it was, the valve is left alone and the coil is changed.)

In reality, the valves don't usually have mechanical problems during the life of the unit compared to other components. This is why they are hard for techs to diagnose. In residential units, most techs try to condemn the unit and have it replaced before they troubleshoot things like clogged TXV's or frozen reversing valves. It goes like this: "If I fix this unit, I can only guarantee it for 90 days. For 200 dollars more, I can sell you a whole new outdoor unit that will pay for itself in energy savings. And it has a five year warranty."

[theoldwizard1]

Originally Posted by jeff5may

It goes like this: "If I fix this unit, I can only guarantee it for 90 days. For 200 dollars more, I can sell you a whole new outdoor unit that will pay for itself in energy savings. And it has a five year warranty."

WOW !! I heard almost those exact words about 3 months ago ! In my case the compressor was smoked !!

[F357]

Originally Posted by jeff5may

It goes like this: "If I fix this unit, I can only guarantee it for 90 days. For 200 dollars more, I can sell you a whole new outdoor unit that will pay for itself in energy savings. And it has a five year warranty."

The cheap/free units we get on craigslist gotta come from somewhere.