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Amana ASH13 heat pump - 4-wire vs. 5-wire

I am troubleshooting my heat pump system as it is running constantly thus costing a LOT more (i.e. double!) compared to our neighbours' homes of similar sizes with the same heat pump equipment. Ours is a 1 yr old home, 2700 sq ft [not including (heated) crawl space basement], 2 levels, family of 3. Heat pump = Amana ASH130361; Air handler = Goodman ARUF364216 (with Goodman HKR-20CB 20KW heater kit); Thermostat = White-Rodgers 1F89-211. HVAC contractor is unsure of cause so he replaced t-stat (with same model) thinking that may solve problem.  It hasn't & with it being the Holidays they are closed.

There are 2 concerns I have since identified:

1. W2 wire (white) @ heat pump is not connected to anything, &

2. Comfort Alert diagnostics module is indicating yellow "alert" flash code 7 (= open run circuit).

Reviewing the equipment's installation manuals it appears that the heat pump connection should be 5-wire (for C, W2, O, Y, R).  Our system, however, is connected via 4-wire (no W2).

Could the heat pump's disconnected W2 be contributing to these &/or other system problems (i.e. frequent &/or long defrost cycles, high electricity usage, non-staged heat strips, undersized, etc.)?

Thank you. Dogstar.


  • Ironman
    Ironman Member Posts: 7,062
    edited December 2010
    W2 wire

    The "W" wire at the outdoor unit is for turning on the electric heat elements inside when the heat pump goes into defrost. The reason for this is to temper the cool air that is produced when the heat pump is defrosting. This is because the heat pump is actually in the cooling mode during defrost to put hot gas into the outdoor coil and melt the frost. So, if the wire is connected, you'll have a little bit better comfort, but you'll actually use more electricity.

    Your real problem is with the outdoor unit flashing a code for an open run circuit. This means the compressor is not starting (at least some times) and you're heating solely from the heat elements in the AHU. That's why your bill is so high. And unless you live in Maine or Minnesota, 20kw is too much for a 3 ton heat pump.

    Find a competent contractor an have him check it out. Your present one appears clueless. Check the"Find a Contractor" tab above.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Dogstar
    Dogstar Member Posts: 5
    Wiring, fault alert & heater elements

    Thank you, you've confirmed my suspicion regarding this contractor.  To clarify, is it a fair assumption then that the system's installation could/should have the:

    (a) outdoor unit's primary terminals (C, W2, O, Y, R) connected via 5-wire cabling (per manufacturer's wiring schematic), at a minimum, not 4-wire wherein the W2 terminal was left disconnected?

    (b) diagnostic module connected to the thermostat's “L” terminal to promptly display alert codes?

    In addition to the intermittent compressor start fault, during the heat pump's defrost cycles (without the engaged indoor heater elements) the system may be unnecessarily cooling the house thereby further challenging the system to maintain indoor setpoint temperature, particularly on colder days?  This may also explain why the system seems to have the auxiliary heater elements enabled a lot.  And at 20kW that's a lot of electricity.  Ugh!

    Would an outdoor thermostat installation &/or indoor thermostat upgrade allow the system to further stage the auxiliary heater elements to minimise how much/often they come on?

    I figure I'm better prepared to ask another contractor the right questions if I have a better understanding of how the system should really work.  Your help is sincerely appreciated.

    Thank you.  Dogstar.
  • Techman
    Techman Member Posts: 2,144
    edited January 2011
    Heat Pump

    an "open " run winding does not heal or repair itself.So I doubt the compressor was running,and you are running on electric heat only. There would be none or short defrost cycles,depending on the circuit board.1st stage of heat is the compressor,2nd stage of heat should be 1st stage of auxillary electric heaters,then outdoor temp sensors control when 2nd stage of electric {3rd stage of heat} comes on ,  and so on.But ,knowing the  "balance point" temps  of these stages comes in handy . Or being there during cold temps.,in order to set the controls.
  • Dogstar
    Dogstar Member Posts: 5
    Emerson Comfort Alert diagnostics module

    Thank you.  I took a closer look at the heat pump's Emerson Comfort Alert diagnostics module (543-0012-00) ... the compressor’s run (R), common (C) & start (S) wires are NOT routed through the Comfort Alert's marked “R,” “C” and “S” holes.  I'm going to guess this may be causing the (erroneous) "open run circuit" alert?

    [  If so, why then would the HVAC installer/service vendor not catch this during their troubleshooting visit last week?   Yup, per Ironman's suggestion ... "Find a competent contractor and have him check it out. Your present one appears clueless".  ]
  • Techman is correct as usual

    As Techman mentioned, if the compressor is not operating, the heat pump system cannot possibly defrost. When the system goes into defrost, the outdoor coil becomes the condenser coil, which allows the heat from the hot compressor discharge to melt the ice that has formed on the outdoor coil.

    Many people do not fully understand heat pump systems and often assume that they are not working properly because of the lower supply air temperatures as compared to fossil fuel furnaces. For this reason, and some others, it is not uncommon to see installers wire both the first and second stage heat to come on with first stage. This can be disasterous, especially when the electric bill comes. The reason for this is to simply eliminate the "the heat pump is blowing cold air" call but, on the flip side, it increases the number of "why is my electric bill so high?" call. 

    Search under the SYSTEMS tab above and click on the HEAT PUMP link for lots of cool (and hot) information on these often misunderstood but completely awesome systems.
This discussion has been closed.