Air to water heating: flat plate with water storage or long copper pipe in water storage?
in an effort to make our house more comfortable, and to eliminate the drift of air we currently are in the opportune to raise the living room floor with a sub-floor and by doing so, include in-floor radiant heat.
plan is to:
raise living room floor (440 SF) by about 14 inches, with standard plywood and 2×12 timber.
on top, install R10 EPS insulation with 5/8 PEX/O2 barrier 6 inches on center, encased in 2.5 inches of sand/cement and 15 mm laminate flooring
the spec’s form the 5/8 tubing tells me thy radiate 12,146 BTU when indoor temp is 20C and water running through them is 35C, I’m happy with those numbers.
heating the water I’m planning a 12.000 or 18.000 BTU ductless heatpump (R410A)
this is the easy part for me, I’m struggling with the water heating.
i’m capable to install a 500 gal thermal battery (water tank)
the main question for me is
Do i run copper pipe in the water tank, through what the R410A runs, or do i put a brazed plate heat exchange in.
I have trouble finding heat exchanges (affordable, and capable to handle the design pressure of the ductless, what has a tag of 610 PSIG).
beside that, the heat exchange would require a pump to circulate the water through, where a straight pipe in the tank would not require a pump to heat the water, only a pump for running the water through the pex.
the indoor unit of the ductless has 95 linear feet of piping in it (be it that it is finned piping)
in terms of efficiency, would it be good to install 95, or for that matter 150 feet of copper pipe in the water tank, acting as a radiator ?
I cant find any info on this, where my neighbor has just some pipe in a tank, and i wonder if it would even be efficient or not (he douse not know)
how would I need how long my copper pipe needs to be, is it a matter of the longer the better ? or follow the amount of fined pipe of the indoor unit ?
once I know what route i go, the question is, how to control the heat pump.,
we are at the point to buy a heatpump for a other project, so i can maybe switch them over, as whit the radiant heat, i dont need a indoor unit, so why buy a set, when i can also only buy a outdoor unit.
the thing is, outdoor units comunicate with indoor units, so if I eliminate the indoor unit, how do I run the on/off, would thy take a certain voltage to control ?
on my large marine aquarium I have a controller that I can set at a temperature to start, and a temp to stop, and I had in mind to use similar feature, where the heatpump would start heating the water at 30C and bring it up to 38C and then off.
the in-floor heating would run on its own thermostat and control
any input/ direction would be appropriated,
thanks
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Replies
Kevin. Where are you located? How do you heat now? Is the living room on a slab? On first blush, your plan sound kind of complicated. But we need more information.
Kevin,
We also need some translation.
You wrote, "heating the water I'm planning a 12.000 or 18.000 BTU ductless heat pump."
I'm confused by the word "ductless." A "ductless heat pump" is an air-to-air heat pump used for space heating, not water heating.
Perhaps you are talking about an air-to-water heat pump? If so, what type? Is it a split-system model like the Sanden? I assume it is, because if it is an ordinary heat-pump-water heater with an integral compressor, you can't use that type of water heater for space heating.
in deed, I want to use a heat pump, if I where to go with a air to water type, then there was no question, as it would have the exchange build in.
there are houndreds of heatpumps availeble, ye only a few $$$$ air to water once.
beside that I curently run ductless once in the house.
I have seen on Google many video's of people playing around with plate heat exchanges.
so it comes down to, me wanting to remove the indoor unit, and either replace it with a brazed plate heat exchanger, with pump and such to run water through it, or connect a long copper pipe and hang it in my water tank.
the units running now are Daikin FTXN15KVJU / RXN15KEVJU
as my plan, leave the indoor out, and replace it with either of the 2 options I had in mind, the indoor unit has around 95 feet of fined tubing
Translation: You want to build your own homemade air-to-water heat pump.
It sounds like you intend to run copper tubing filled with refrigerant through a flat-plate heat exchanger, or through a water tank. I don't recommend that approach -- it probably violates plumbing codes.
Re, the initial question: Do i run copper pipe in the water tank, through what the R410A runs, or do i put a brazed plate heat exchange in.
translated:
A) do I run a copper pipe, as any line kit for refrigeration, in a designated water tank (thermal battery)
or
B) is it best to run a brazed plate heat exchange in line with a heatpmp, with counter flow water from the tank, through the exchange and back to the tank.
this very same principle is used in pool heat pumps, and air to water heat pumps
so on the end, yes I want to build my own air to water, as I have the heat pumps, and even if I had to buy new, air to water heat pumps from the factory are not that common in the 12.000 to 24.000 BTU range, and when thy are, thy are often $$$$$$$
Europe is far more ahead on this subject, was it not for the Hrz difference (50 vs 60) I can find as much models, as I can find screws at the HD
Using a reversible chiller with or without the buffer tank can work just fine. The modulating Chilltrix reversible chillers are very well suited to radiant floor applications where peak water temperature requirement is only 35C.
With an air source chiller the refrigerant loop and heat exchanger to the water is fully contained in the outdoor unit. The hydronic heating/cooling loop plumbs directly to the outdoor unit, so in colder climate an anti-freeze solution needs to be used in the hyrdronic loop.
http://www.chiltrix.com/documents/CX30-Install-Operation-Manual.pdf
http://www.chiltrix.com/
There are others, both modulating & single speed.
See also:
http://www1.eere.energy.gov/buildings/publications/pdfs/building_america/airtowater_heat_pumps.pdf
A Sanden air source heat pump hot water heater can also be used for low-temp radiant floor applications.
http://www.sandenwaterheater.com/
http://www.sandenwaterheater.com/sanden/assets/File/Advanced_HPWH_Research_Fall2015_NAPHN2015.pdf
page 4, component 19 of http://www.chiltrix.com/documents/CX30-Install-Operation-Manual.pdf
exactly what I mean, also R410A, around $3,500
the sanders unit also same principle, yet at a cost of $4,000 +
all the same more or less to what I have, except I'm missing the heat exchange, woe what I'm looking at options (the A or B) but you got the picture exactly.
I could do a calculation on heat los/resistance and such of a copper pipe with a initial temp, and the temp of the fluid it is in, to find the length of pipe needed to reach equal temp of the gas in the pipe vs the water it sits in.
then just get a line kit of that length I need, the water tank is not connected to any potable water of any kind and is isolated from it.
lets call it it is not in the house, but i want to use it to heat my green house, way back in the yard, I just want to heat water, preferably with as much of the things I already have, yet I'm looking to do this as efficient as I can
By the time you've gone up the engineering testing & learning curve scrapping multiple prototypes and ruining the climate with the released R410A you will have spent many times the cost of a pre-engineered solution that works efficiently & comes with a warranty, such as a Chilltrix or Sanden.
The plate heat exchanger (component #19) in the Chilltrix is what they use to isolate the refrigerant from the water, and it's not a particularly expensive component. But a decent performing system is more than a collection of components. It has to be purpose designed to work together, then refined to be able to work EFFICIENTLY together. The variable refrigerant valves, sensors and software/control algorithms to ensure that it works efficiently and doesn't self-destruct take time & testing to develop. Using a set of components & control algorithms designed for air-to-air systems would hardly be optimal, even if you are somehow able to make it to work AT ALL.
With most mini-splits (not sure about the Daiken) there are intelligent controllers in both the indoor & outdoor units that communicate via a digital protocol. If you want to make it work with a hack on indoor head for a refrigerant to water heat exchanger you'll have to figure out how the smarts in the indoor unit work, as well as how to tweak it to make it work efficiently with the hardware hack.
There are many thousands of engineering hours and testing in a Chilltrix or Sanden air-water heat pump system. If you can somehow get a hacked up Daikin to work AT ALL just by tinkering it will be a significant achievement. But to get it work at mini-split efficiency would be a miracle.
I think i have the wrong forum: ruining the climate with the released R410A
if you have a problem with R410A, don't get it on me, talk to your state representative
when it comes to ruining the climate, I know another 1,2,3 and way, way more, yet this is not what it is about, you could have also mentioned, sorry, this is the wrong place to ask these questions.
I try to be positive here,, a bit forward thinking, see where I can improve something, be it improving my comfort only, and only where i reasonably can, improve the efficiency of a system.
i thought there might have been people that might know some ways here and there, to do something, like you often read suggestions on other forums, yet i get a rattle of what not about trying to re-engineer and what not,
sorry, I have miss understood this forum, i learned a lot from it in the passed but this I don't find positive at all,
all the best, thanks for the input
Kevin,
In my experience, this is a very helpful forum, filled with smart, experienced people who are willing to go out of their way to provide good advice and to lend a helping hand.
We strive to help people find affordable solutions to problems connected with green building. We favor solutions that are cost-effective, energy-efficient, and good for the planet.
In that vein, I think that Dana Dorsett gave you good advice. The Chiltrix can be easily purchased in the U.S. and is an affordable solution to your problem. GBA has an article on the Chiltrix that you may be interested in reading. Here is the link: Air-to-Water Heat Pumps.
Like Dana, I think that you are underestimating the difficulties, and overestimating the advantages, of building your own air-to-water heat pump.