IF it had a lot of shade and depending on location, along with deep overhangs and a more thermal mass form somethign like real stucco (not that fake junk) or tile floors, it could probably get away with 2.5 ot 2 tons. But without knowing locations and total window area and solar gain, it's a guessing game. Interesting ot seperate heating and cooling system. Seems like it would have made sense to use a 5 ton water to water chiller with a heat pump mode instead. IF you already have a water to water heater, you have everything in place ot do both.
At some point, that's what i don't understand. These units have these desuperheaters but for some reason that industry is reluctant ot move towards chilled water. Yes, you'd need a storage tank and another pump, but equipment performance and effciency overall would improve and you gain so mcuh in what yo u can do for dehumidification and controlling systme capacity.
With chilled water zoning is a cinch. Just put a separate air handler for each zone, similar to a minisplit. Storage of excess capacity during times of low demand to cover times of high demand could be useful too.
First cost is what kills chilled water system selection for most residential. Also does not seem a practical choice for smaller homes. For multi-story, larger residences, I see it as more viable than traditional zoning with ducts.
Originally Posted by 54regcab
With a smaller house I would focus on the improving the enclosure and reducing the tonnage requirement of traditional DX equipment to notably below how an equivalent sized house with an inferior enclosure would require.
Building Physics Rule #1: Hot flows to cold.
Building Physics Rule #2: Higher air pressure moves toward lower air pressure
Building Physics Rule #3: Higher moisture concentration moves toward lower moisture concentration.
I was just reading through the whole thread and like I said before your explanations are good and make sense to me. Just to throw in a bit more info for those that are curious; we are located in Northern Saskatchewan, Canada. When we designed the system I wanted Hydronic heat but some areas of the main floor did not lend themselves to hydronic heat (hardwood floors) and besides we wanted some air conditioning. This is why we have a split system. This past winter was our first winter in the house. The water-to-water system was not yet in service and the 3 tons of heat we had worked fine up to about 0C after that it was a bit of a struggle but fortunately we have a big wood burning fireplace and it was a mild winter. Next winter will tell us how the heating portion works. The biggest disaointment has been the de-supraheater which only appears to work in heat mode and so we get no benefit from that for a good part of the year. Again, thanks to everyone.
The desuperheater only works when the system is running, and 7 tons for a 2200 sq. ft. super insulated house in your climate, probably in any climate, is massively over sized for cooling, but may be sized correctly for heating.
Originally Posted by SaskBob
Desuperheaters don't perform very well when the equipment only has short run cycles.
Only the 3 ton unit has a de-supraheater to provide domestic hotwater. It was my understanding when we purchased it that it would utilize any capacity that was not required for the house i.e. when the unit was not busy heating or cooling the house it would work on bringing the domestic hotwater up to temp. That's not what seems to be happening. You're right, the only time it seems to work is when the pump is running in heating mode. This would seem to indicate that I am splitting the heat output of the pump between heating the house air coils and heating the domestic water tank.
Originally Posted by mark beiser
the desuperheater should only be on the cooling system... there's no reason to desuperheat the heating side... it's needed to HEAT the loop...
Originally Posted by SaskBob
I fail to understand why you have two systems... I'd think a heatpump style design could be incorporated, but I suppose having 3 tons dedicated to cool air, and a separate 4 ton system just to heat the water for your hydronic loop (I'm guessing radiant floor?) makes some sense.
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I'm wondering if we are talking about the same thing. The de-supraheater I have is an option that was supposed to use surplus heat to provide domestic hotwater. At least that's what I understood. I also assumed that it would do this any time the pump was not busy heating or cooling the house
Originally Posted by vstech
Again, the reason we have two systems is because we wanted hydronic heating throughout. However hardwood flooring does not like radiant floor heat and radiant floor systems are not suited for providing cooling thus the second system. Some vendors might have a single heat pump that can be split between the two methods; Climatemaster requires two separate pumps.
Getting back to basics. Desuperheater is only a means to use the - waste heat - of a running compressor. A higher efficiency of the heat pump provides LESS waste heat. Google - desuperheater - to see other explanations and set-ups.
Originally Posted by SaskBob
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