SpacePAK -- when does one need a SSIC?

JasonAtLogic

Hi Friends,

I'm researching use of a SpacePak CC32-40 air-to-water heat pump to warm a single-zone <900 ft2 home in New England (no domestic hot water). I'm asking "How does such a heat pump get a remote heat signal?"

Machines

• SpacePak CC32-40 air-to-water heat pump.
• Mestek 40-gallon buffer tank with (2) AUX electric resistance heating elements.
• SpacePak System Interface Control (SSCI) … maybe?

Simple System Design: two independent pumps running two independent loops…

• (External Loop) The heat pump will simply add BTUs to a 40-gal buffer tank for radiant.
• (Internal Loop) The thermostat will activate the circulating pump to move that warm water through the floors.
• The two loops will not know about each other. The BT acts as a bank; the thermostat makes withdrawls. When the BT gets cold enough, the Heat Pump should kick on.

The core question of "Where does the 'Remote Heat / Cool" signal originate?" may be better stated as "Does one need a SpacePAK SSIC to run heat?"

I've got a technical background, and have been studying the wiring diagrams of the machines.

Specifically,

• A CC32-40's Port 11 & 12 accept Buffer Tank temp.
• And a CC32-40 also records ambient temps…

so… a CC32-40 has all the inputs it needs to decide to heat, and [i] power an external loop circulator (Port 20&21), [ii] power a heater contactor to call for AUX heating with electric resistance in the BT, etc. (Port 23&23)

What am I missing about Ports 3&4 on the SSIC32-40? What additional logic would an SSIC add (at the cost of >$1000)?

Thanks in advance for any thought or experience you might share.

J

Ironman

The control simply has a set of dry contacts that can call the heat pump on from various inputs such as fan coils, AHUs, etc.

From the kind of system that you’re describing, a simple aquastat on the buffer tank should be sufficient.

hot_rod

It does have some features that may be useful, shown below.Outdoor reset, buffer control, able to switch a backup source on, etc.

Look at what comes on the HP control, it may have enough features without adding the SSIC

Floheating

From a controls standpoint, you’re right that the CC32-40 has enough inputs to manage buffer tank temperature and stage the heat pump and AUX based on tank sensors alone.

Where the SSIC usually comes into play is in coordination and protection logic rather than basic “call for heat.” It helps manage enable/disable conditions, lockouts, priority handling, and interaction between pumps, tank temps, and system states so the heat pump isn’t just reacting to one sensor in isolation.

In simple buffer-tank-driven systems, it can feel redundant, but it’s often there to prevent edge cases rather than to add core functionality

hot_rod

Outdoor reset is nice to have to maximize the HP efficiency. Does that come with the basic HP, or is the SSIC needed to run ODR? If a sensor in the buffer and outdoor sensor comes with the basic HP, that should cover your needs.

You mentioned radiant. Hopefully your loads require 125F or less, the comfort range of A2WHP. And if you could run down to 100 or less on mild days the ODR would do that for you.

You sell sheet or manual may show efficiency graphs at different operating temperatures. May as well maximize you $$ outlay.