Greetings fellow R Wallies. I am designing (in my head for now) the ultimate water to water heat pump. It needs a capacity of around 48,000 btuH, so I am thinking four one ton compressors piped in parallel through FPHX's. I'd LOVE to dedicate one compressor as the lead, and if possible, connect it to a variable speed motor controller (0 - 10 VDC control signal). I'd always start on high speed, then roll compressor motors RPM's down to match the load. I will build my own water storage tank out of 3/4" plywood and 4X4 treated lumber posts with a polyethylene liner. This open tank will have two coils in it. One for input (multi source) and one for extraction. The extraction loop will be glycolized, as will the input coil. The storage medium will be water, and I do expect to freeze this tank solid. My math works out that at full output capacity, and only utilizing 80% of the open tanks capacity (leaving room for expansion when mass expands due to freezing) I'd have 19 hours of reasonable COP (roughly 3:1) before I start getting into trouble, and in reality, this heat source will only be used to maintain my home at standby conditions, that being 40 degrees F. When I want it warmer, I enable my LP Modcon boiler. Anyway, to my questions.
1. I realize the need for check valves on the discharge of the compressors.
2. Is there a need for separate oil separators, reservoirs, etc like are used with larger compressors?
3. Is it possible to vary the speed of these little compressors without compromising their life expectancy significantly?
4. How big does the FPHXers need to be in order to properly move the btu's around.
5. What kind of water temperatures can I expect on the load side of the system with an EWT to the HXer of 40 degrees F and a corresponding source side temperature of 32 degrees F.
I do not intend to vary the flow on the source or load size (hydronic), and plan on maintaining a narrow temperature differential. I also realize you will most probably ask me for additional information that I missed on the first pass...
Thanks in advance for your input.
It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.