Hydronic Radiant System Critique Please

SENWiEco

Good day folks
First many thanks for everyone’s help last June when I was looking for advise on Domestic Hot Water productions (https://forum.heatinghelp.com/discussion/170503/dhw-production-equipment-recommendations). In the end, I did decide to proceed with a hybrid hot water heater and will put it in a room under the garage that is isolated thermally and soundproof from the rest of the dwelling.
Now that the decision has been made to go this route for the domestic, I was able to greatly simplify the space conditioning system. While I am not a professional and have never designed a system before, I do have a significant knowledge gained via a formal hydronic heating course, extensive review of Ziggy's Modern Hydronic Heating text, and through discussions on forums like this one.
I was hoping for some critique on the layout I have come up with. Be as brutal as you like as long as you explain your disproval - if there is any :-)
I would be interested in any recommendations for tweaks or additions to the diagram. For instance, do I have check valves in all of the recommended places.
I have tried to include ball and purging valves wherever there is equipment that may need to be serviced and also at the bottom of multi-storey runs.
This system will be providing heating in the winter months and switch over to cooling in the summer months. There will be a significant portion of the year (shoulder months) when the system will be dormant due to internal heat gains and the high performance building envelope it is being installed into.
Many thanks in advance for any guidance provided. I will be happy to answer any questions if more info is needed.
I have attached the circuit diagram

Cheers

hot_rod

Consider a 2 or 3 pipe for the buffer, it leverages the tank better.

Do you have this manual? I think you can download it at www.spacepak.com/water-works.asp
I think Siggy creates these for Spacepak and they are some of the most up to date piping and wiring logic.

The BTU meter along with one of these inexpensive KW electric meters would give you some great data.

SENWiEco

Thanks Rod - I will spend some time looking for the manual. It was not readily found on a quick visit to their site.

I thought that 4-pipe buffer setup was more appropriate for constant temp systems that did not require quick changes in fluid temps and provided better stratification in the tank for increased efficiencies?

I thought the benefit of 2-pipe was to allow for the panel to become a 'priority' circuit that would first take the heated water produced by the heat source before it went into the buffer providing for a faster responding system, but at the expense of some efficiency?

As the panel supply temps will always be mixed down from buffer in winter and up from buffer in summer, is the 'priority draw' of the two pipe really appropriate?

Re BTU meter - yes this will be some interesting data. To provide the kWh measurement, I am hopefully working with Leviton to supply many circuits in the house with current draw monitoring including the heat pump and circulators/control circuits.

https://www.leviton.com/en/docs/The-Leviton-Load-Center-Brochure.pdf

SENWiEco

Just in case it is not clear - the heat pump graphic was the only one available in the software used to draw this. It will be refrigerant and not water connected between the outdoor heat pump and DX2W

SENWiEco

Sorry Bob for calling you 'Rod'.
Found this article that supports your suggestion. May be relevant for me because although I will not have fast changes in water supply temp, during the shoulder months I probably will have periods where days have gone by without the need for heat meaning the buffer tank will have cooled down. The two pipe priority would provide heat to the panels faster.

https://www.hpacmag.com/features/one-side-or-the-other

hot_rod

Look at the Manning 3 pipe method. He designs GEO specific applications and the 3 pipe has some unique advantages.

I think the link is in this post


https://forum.heatinghelp.com/discussion/164126/plumbing-buffer-tank-setup-htp-vs-john-siegnthaler

SENWiEco

Thanks Bob - watched most of the video.

Was interesting to see audience members who clearly did not understand hydraulic separation. Also interesting to see Manning POV that the buffer does not store energy. Clearly he works in projects where the heat loss of the building is huge and as he states "consumes the energy in a buffer tank in minutes". In high performance buildings, I believe the panel loads can often be fed via a properly sized buffer, for a long period of time without heat pump operation.

I have also re-read the manual you mentioned (realized I had a copy). I now agree the three pipe method is preferable. Thanks for pointing me in that direction. I have attached a modified diagram. I modified to three pipe, changed location of expansion tank and feed water, and purge valve. I also added check valves at top of tank and float vent.

Now I have realized I need some motorized 3-way valves so that when in cooling mode, it will feed into bottom instead of top of tank. Will spend some time getting my head around that and then repost edited diagram.

hot_rod

The one benefit of 2 or 3 is direct to load ability. Once the load is satisfied, or even reduced, the buffer begins to come into play. If the source runs when the load is finished the tank will, should, charge to the set point temperature. So in my mind it is always a buffer. How long it buffers depends on the load(s)

The more zones, or micro zones the more the buffer adds value.

Any source with a compressor generally calls for a buffer tank, as compressor won't stand for that cycling. Hydronic pumps can cycle, but prefer not to Pumps in combis for the DHW call bounce on and off every time a faucet opens.

My wife, like many others pre-washes the dishes before putting them in the dishwasher. So I hear the combi fire, stop, fire, maybe 20 times a minute until she rinses every plate, fork, etc.
Gas valve, inducer motor, pump cycle like crazy.
A battle not worth fighting

SENWiEco

Agree, some battles are not worth fighting.

Bob - thanks so much for your assistance. Does the rest of the system look reasonable?

Do I have check valves where needed? Anything blatantly obvious that is wrong?

hot_rod

On C-3 a check in the circ and check the return side also, if it is above the piping like that.

I'd rather a Discal at the red top, hot port, DirtMag on the bottom.

Probably no need for the Discal next to C-2, no harm in having it there.

Expansion and fill is in a good spot, but don't hang the tank off the bottom, it gets all the crud on the tank diaphragm like that.

I'd sensor the top and bottom of the tank, just for observation. Even an Azel with sensors strapped and insulated on the piping would give you an idea of how the tank is performing.

Keep the piping simple as everything will need to be well insulated, and all seams sealed for the chilled operation. Any exposed metal will sweat if not sealed well.

The nipples into the tank are a tricky insulation detail. I've taken my die grinder to the metal jacket to enlarge the hole to allow insulation tight up against the tank metal, or it will sweat and fool you into thinking you have a leak in the tank.

SENWiEco

Many thanks Bob! Great advise. I will make the changes.

With the DirtMag, I will need to find a new connection point for the expansion tank and make up water. Should I just add a tee to this area or would it be better to Tee off the tank drain and attach there so I am not introducing additional pressure drop with another fitting?

To clarify re the exp tank. You do not mean to not hang it by it nipple, just do not install so the tank would drain into it - correct? It won't be, it was just placed at that location in the drawing. It will be installed so its entry is above the tanks bottom port.

hot_rod

If you use the brass Dirtmag, there is a 1/2 port up top that you could connect a tank too. Use pex or copper to remote mount the tank.

Here are some expansion tank tips avoid tanks directly under any seps as particles drop onto the diaphragm.

SENWiEco

Many thanks Bob