Ducted Chilled Water Fan Coils with ASHP Hydronic Systems

BB2024

Hi There,

I'm in Australia and find this form very useful (except for constantly having to convert from imperial to metric )

I have a question regarding ducted chilled water fan coils. I've noticed a number of discussions surrounding hydronic vs reverse cycle A/C and the uptake of the latter being much greater in the US than the former. It's very similar here in Australia, even for the "cooler" southern regions (Melbourne/Hobart etc) where ducted reverse cycle A/C is very common and reverse cycle split-systems even more so.

As previously discussed here, the main problem is that why would you install a large kW inverter A/C system that can cool and heat and then have the additional cost of hydronic just for heating? Although hydronic heating is a much nicer type of heating, it doesn't make much financial sense.

The uptake of ASHP for underfloor heating is becoming more common as it can cool as well as heat but really only applies for new builds or large extensions.

My question is why can't I seem to find much discussion around existing build configurations with an ASHP for heating and cooling by using a 2-zone system, one for the radiator panels and the other for a ducted fan coil. When the system is in cooling mode, the radiator zone can be turned off so the water can be chilled below dew point and pumped through the ducted fan coil (something like a Carrier Idrofan 42EP)?

Is there something I'm missing with such a configuration? The cost of those fan coil units don;t seem very expensive, especially when compared to regular panel fan coil prices.

Is the main issue not being able to run both heating and cooling at the same time? I've seen diagrams where 2 buffer tanks are used, one for heating and one for cooling that might alleviate this. But I'm my case, I can't see a case for needing to run both at the same time.


The cost of this type of Hydronic heating/cooling system doesn't appear to be too much more than what it'd cost for an equivalent ducted Reverse Cycle A/C system, in Australia at least.

Any thoughts or comments would be very much welcome

HVACNUT

I believe what you're referring to is a Chiller system. With the use of electric valves for isolation, the loop would distribute heated or chilled water through the fan coil(s). More used in commercial applications in the States, but I've seen a few residential systems. 

WMno57

Is this what you are looking for?
https://www.spacepak.com/solstice-air-to-water-heat-pumps

BB2024

WMno57 said:

Is this what you are looking for?
https://www.spacepak.com/solstice-air-to-water-heat-pumps

Yep that's pretty much exactly what I was thinking! Are these types of configurations common or being discussed as a future option..?

BB2024

HVACNUT said:

I believe what you're referring to is a Chiller system. With the use of electric valves for isolation, the loop would distribute heated or chilled water through the fan coil(s). More used in commercial applications in the States, but I've seen a few residential systems. 

I don't know what the difference between a chiller system and an air-to-water heat pump is but in my head the heat pump would perform as chiller system would, they can heat water to 65c (149f) and cool it to as low as 5c (41f) in some systems.

Hot_water_fan

In the US, these systems are extremely rare. Not saying they don’t exist, they do! But the US is predominantly ducted systems and many of the hydronic systems out there are in older houses that don’t have centrally ducted AC and are also…not going to be around forever. The Caleffi Idronics journals are an amazing resource if you want to learn more about air to water.