There's no need to push the floor water directly through the solar collectors. The need is just to move the heat into the cold return water.

I'd buy a cheap 50 gallon hot water heater for a storage tank for the solar collectors and not use pex tubing as a heat exchanger. Coiled pex would require a non pressurized tank. Pressurized systems are easier. Use two small circulators- one circulator for solar collectors to solar storage and one another circulator for injecting the solar heated water into the floor return water. No heat exchanger is required. You would (probubly) need another expansion tank and two differential controllers.

I am planning a drain back non-pressurized system, no worries with summer boiling of glycol, will use system for DHW all year.

Got a bit side tracked: How to get the Delta T down? More flow. I could get high flow manifolds change the piping to 1" between the tank and manifolds. If I do that why not add a ECM pump an 2 zone valves. Will that work?

What about the other option of changing the heat pump piping, have the heat pump draw the water from the near top T & P port, send the heated water in to the drain opening. While the radiant return is sending 65*F water down the dip tube it will mix with the 90*F water coming into the bottom of the tank. 

ChrisJ
 

Zoning with 2 pumps vs. ECM circulator and valves- either way works. Where the ECM and valves really shines is when there are multiple zones (several...3 or more) In this case with only two zones I don't think it is worth the cost in terms of time and materials.
When both zones are calling for heat your heatpump is running for several hours. The 2 1/2 tons (30,000 btu's) going in are coming out of the floor.
If you invest in larger flow rate by changing the circulators and manifolds etc. you will still have 30k in and out. Adding solar to floor return will raise your systems capacity and efficiency. Your heatpump will run less or your floors can be warmer or they can heat up faster.

If you go with an unpressurized storage tank- a submerged flat plate heat exchanger with a small submersible pump can be a more effective heat exchanger compared to the pex tubing exchanger. Check out the dudadiesel websight. Dudadiesel has a computer program for heat exchanger sizing. Small submersible pumps can operate up to 120 degrees.

I meant brazed plate heat exchanger- not flat plate exchanger. Oops

you also have to be careful with PEX exchangers. if they have external EVOH barriers, those are sometimes water soluble. so you need something with an internal o2 barrier, or you'll have a non- barrier system... i.e. no cast iron or ferrous materials allowed.

Thanks for the reply Rob,

I was thinking to use pex-al-pex for the exchanger, Does that have an internal O2 barrier? or are there both types?

In regards to my 30*F Delta T, any advice? Is that a product of only heating the basement to 65*F?

ChrisJ RI

PAP tubing's barrier is the aluminum layer, and it's not water soluble and it's also internal to the pipe so you should be fine.

what's the question about the delta T? If you're heating you don't have a problem with delta-T. Low flow is good. concrete is very good at extracting lots of heat from the pipe in long loops until the 'crete itself is heated up. So this is a combination of your room/slab temperature, and conductivity.

If you have a 55 gallon hot water heater though, and it takes 10 minutes to drop, say, 20 degrees to trigger your heat pump, that's about 9200 BTUs you are dropping in 10 minutes. That's linear if I got the firing differential wrong... half for 10, double for 40, etc.

at a 30 degree loop DT, and about 55kBTU/hr of transfer (920BTU/min for 1 hour), you've got about 3.7 GPM of flow in this scenario. I don't see any red flag with that.

Thanks Rob,
I think for next winter I will have the plumber switch the piping for supply and return on the heat pump to tank. Also see how much $$ to add 2 temp gauges.

Having the warmer water from the top of the tank going to the heat pump for re-heating is good for another reason. My heat pump can heat air and water at the same time, but the supply air temp is affected by the temp of the water being re-heated.

ChrisJ RI

Adding temp gauges is a good idea. Sending the hottest water to the heatpump isn't such a good idea. Efficiency is higher when the water to be heated temperature is lower.

Surviver,

I actually have twin 55 gal tanks, the other one is for the DHW from the heat pump. The water is re-heated to 120*F using the full 4-tons of capacity, so having the radiants 95*F water being re-heated is more efficient then DHW.

Cold well water enters the tanks cold inlet at the top of the tank, re-heated water enters via a tee in the cold water pipe, just above the top of the tank. That set up seems to work fine for the DHW, but didn't work for the radiant, maybe because of the well tanks 40lbs of pressure.

That brings me back to one of my original questions, if the radiant return went straight through a tee into the top of the tank and the re-heated water entered the tee at 90 degree angle would the radiant return stop flowing, which it did when they were plumbed in reverse.

Thanks, Chris

Hi Chris:
Any comment by point by any viewers is welcomed-

YES ! Alpha-Grundfos ecm and Wilo and others pumps are available.  www.FlowCenterProducts.com for info and curves, as many on-line are.

Rep'd for Ohio Hydro-Temp distributing in 2003-2006-to about June-2011,
I can only appologise for not having a company-knowledge of your purchase, and you would probably have no need of a buffer- as the 15-minute (12 minm. time of the compressor could be affixed with a first-staging). By-Pass flows have had head preassure switches open and close - slow zone valves like 'BELIMO' reducing cold flows to compressor section- until warmed enough.

Since for others' views are relative and well-enough are accurate, they would see a little more, about the controller you have at  www.Hydro-Temp.com and the contractors can call me for a "Dealer's download site"  www.GEOPros.com or text, etc.
...
GEOPros TM: "4Synergy Series" in 2005, but installed the same style, 2003: an 8-ton, with only a 35 gal buffer-  but a PARALLEL-SERIES configuration for both low and high-mass radiant, true 96,000 btuh.
 
IBCboiler.com , USA rep jpa, would agree with me to increase high mass (IN SLAB) flow rates to 3.1/4 ft per second if glycol, and I'll say at least 2.1/2 ft per sec for common air removal (no glycol).
Same numbers for GT Loops air purging, most cases. -At least until all air is out-. And JPA likes even 4ft/sec in low-temp highly efficient low-mass apps in wood flooring, etc. Plus 'cling-on' air bubbles just don't move until closer to 3ft per sec, gassing from new fluids.  (Do you have a fast-fill, connected.?.. not that necessary, just a Q)

In Harrisburg PA
there is NO BUFFER TANK
on a 5-ton dual compressor, basement, and low mass uppers, with a great header by another who saw the zoning and staging and made the FIRST ZONE larger-15-minute-loading than the 18Mbh compressor 1st stage...
at 93/month budget all radiant HW and HVAC, seems decent for 2700 sq ft and walk-out basement.
In a 13000 sqft mansion of sorts with 2) 7-size 4Synergy Systems, H-T GT is also for all radiant and HVAC and HW, the buffer tank serves little more use than to avoid a COLD-DAMAGING-SLUGGING of compressors getting in to a common roof-top A/C-condition of TOO COOL OF CONDENSER temp/pressures, after starting "on a cold day". We added a 310-off-410-on pressure switch to keep circ pump off like an A/C condenser fan , to keep compressor-life, but not a slow BELIMO zone valve yet- in a By-Pass on-off-flow alongside adj a valve by hand for balancing a cold start condition.

1) Cold starts can slug the compressors in those, and any w:w design, charged close to optimum range of refrigerant.

2) a)Factory bottom-out, cold dip-tube in is fine,  but the HW supply to zones -secondarily-directly is usually out of the HOT top  or even T'd with the mid-port <<2)3/4" up to one 1" off. -- where some P/T valves are then moved higher a-top a T-in connecting those 2 ports.
---High mass slab apps have been used the higher of side inlet to work, -not the best.

b) 3/4" port is a part, but not all the TDH drag as correctly noted above.
1" within 25 ft circuits to 1.1/4" piping over 25 ft circuits if you really need a HIGHEST temperature from a heat pump, because the faster moving of the fluid can allow lower compressor-head-pressures/higher efficiency (the life of your system) at higher temps in smaller dT ranges. A meer wrong configuration can be more costly in efficiency and be cause to heat with natural gas, if available, with temps that allow head pressures over about 360- psig r410a. (that may be a sensor "off" at just 104-deg, going to H-T, or any unit, discharging 112 deg fluids at the outlet.

c) Pulling from tank bottom in this closed app has less concern as sediment stirs quickly by at the FLOWS OF 12-14 Gpm, 1/6 circ: dT will be well under 8-deg on TRUE 4-Ton as H-T does not state sizes having smaller compressors-
IE)
on a below 38-deg GT loop, at over 2.7 gpm/Compressor-ton,  even at that heat: 45MBtuh/500(water) leaves the number 90;
9gpm @ 10 degree diff,  or 15 gpm at a 6 dT---  

CHRIS: >> so when on, what is the delta to the BT ?

3) H-T "on": Stratification in 55 gal in 11 GPM flows is gone in 5 minutes.

4) Getting a zone to dump cool fluid nearer sensor you have noted, gets it recovering faster, and you can even remount this smart-sensor (be sure coated with water-repelling epoxy or I use "rain-all-weather- blue" relatively flexible PVC cement and I wipe it of a bit)... carefully make way for it if backing into hard foam. Or I have even mounted on a pipe, for cycling control, and fiddling/. Coat the Domestic HW Sensor as well, if not.

5) a) Garage and very cold slabs and basements rarely need over 80-degree fliuds, flowing dT under say 12 deg, again if possible , get over at least 2.2 fpsec...  I usually limit P-Al-P 1/2" OD to 260 ft runs.
KITEC, and others, can give you all P-Al-P design TDH / pump conversation, or direct you.
If you need it:
see www.FlowCenterProducts.com  for curves

b) If other masses require more than 90-deg, then a tempering valve (1" Honeywell, or better, etc.) is great for all slab runs, flow picks up nicely in the mix. I am noot understanding all your loads as described.

6) Mike P in Cinti simply added an HVAC stat in a central location when wanting H-T Forced-Air staging first.
A call to Forced Air at all... or fan circ "on" usually breaks AUX circ pump relay in H-T, as it is not a Priority as Domestic HW is, and this affects many dealer's minds in un-mentionable ways. So Bruce in Harrisburg and i allowed continutous low air speed in heating, going around the usual G-Relay to blower and in heating the fan is called with other relay added. Nicely radiant-like very warm air slowly distributes through ducting and RADIATES Heat Energy to flooring of coldes zone as well.
<< One customer has uninsulated flex throughout first flooring and it leaves a nice "blanket' of warmth under flooring at a 98-deg (IRD Programmer you can set) fan control.

7) SOLAR on the zone return as others advise,  just keep cool fluid in range ~ 90-98, with H-T if higher to max sensor of 106, is not needed.
I watch the head pressures at balanced-max loading sustained in bouncing between stages. Can all your zones be heated under 106 deg?
if not, consider fast recovery with a 2-staging stat having for air--- the w2 on regular set up (not needing a heat pump stat with H-T reg- setting going to Yellow wire at board. O-white at board- is the cooling only wiring) that the board takes over when called: Ht or Cl, as you may know. From any one or multiple zones, this needs planning, as it will by pass AUX circ relay, BUT: That relay can be energized directly through w1 or other means and like a HUGE DeSuperheater, while in Forced Air -most efficiently over 106 or 104 deg returning to "IN-Floor" at H-T , tha AUX temp will / can climb over 118 all the while.
And your head pressures are LOWER, and the amps can be 12% less than trying to heat HW in  a direct radiant 106-deg. returning.

8) typically not less than 3/4 gpm per 1/2" OD is do-able, but 1.1/4 gpm is much nicer to work with, check you fps, please.

9)  If to help further as you choose-  then I will review loads layout and Tank config requested, pdf:  [email protected]

10) ACES ! What are you doing in Ohio possibly ?  Nice website of info!  ALL here seem quite helpful ![script removed]JP

Chris:

Just found an origional Hydro-Temp plumbing in-Floor Radiant, !
They have the lower element removed from the Buffer-Tank
1" threads,(if not a bolt-on assembly)
and a pipe INTO that from "IN-Floor Radiant"-out of H-T to tank.
So the top cold dip-tube is alone for the return from zoning loop .
Then less chance of overly cold fluid getting into the condenser side of the Heat Pump System.
This will eliminate pump conflict, as would use of a side inlet at the LOWER side of your tank.

The Solar could use the UPPER side for returning to tank loop HX
and share pick up at return line T'd into cold dip tube from zoning loop.

I can eMail the pic but it shows also using same house water in parallel with radiant, as if uncontaminated.

I checked chart: 1/2" ID may be best over 1.2GPM each, but the slab as Rob said accurately, can have large dT, if H-T returns low in buffer tank.

I have a plate HX for 70,000 BtuH , all 3/4 threads SS, in solar to HW rated 120 deg exchange (a little less at 100 deg) I will check rating at HX comparrison with mfr.  ( $ 155. + shipping) .

Then heat would have to stratify.

But in the future with Dual Compressor anything:

3 staging allows designs to not ever need a buffer,
as 1.1/2" main feed header from an H-T can be the ' buffer ' to 3 to several zones, effectually.
That is how it works with one extra aquastat in a PA system.

The plumbing can be sketched for those wanting.

JP

Thanks for the responses JP,

 "(Do you have a fast-fill, connected.?.. not that necessary, just a Q)"
Yes I believe so, a pressure reducing valve(12lbs), if I flip the top it will send water in at well pressure.
I think I still have a little air in the floor, one loop was hit by cement finishing machine, had to put in a coupler. The inexpensive manifolds have no shut offs for each loop. Going to look into adding shut offs or changing manifolds.

"CHRIS: >> so when on, what is the delta to the BT ?"
Don't know, adding guages before next heating season. Maybe the Topfin aquarium thermometers will work.

"Garage and very cold slabs and basements rarely need over 80-degree fliuds"
So in my case it doesn't make any sense to heat the tank up to 95*F.

"A call to Forced Air at all... or fan circ "on" usually breaks AUX circ pump relay in H-T, as it is not a Priority as Domestic HW is"
A thermostat call for forced air does not stop AUX water heating, only a call for DHW will shut AUX(radiant) and begin heating DHW, all while continuing to heat forced air.

"Can all your zones be heated under 106 deg?"
Yes, both zones are in-slab high mass.

"A meer wrong configuration can be more costly in efficiency and be cause to heat with natural gas, if available, with temps that allow head pressures over about 360- psig r410a. (that may be a sensor "off" at just 104-deg, going to H-T, or any unit, discharging 112 deg fluids at the outlet."
I don't have NG available to me.

"It is recommended that you do not let the DHW run over 410 psig Head Pressure of the refrigerant, for any length of time for a 30-year system. Keeping sensor down to 110 or 112 has a usual  outlet temp over 118-122, respectively, (and higher out-T's plumbed on 3/4" restricting, and may have some Cu elbow-fitting erosion then)"
The DHW tank sensor is set to 118*F, "on" at 112*F. So your saying the actual temp in the tank is a bit higher, so I could lower max tank temp.
I have no idea what the refrigerent pressures are within my system.
Your saying I my get some copper pipe errosion using 3/4" instead of 1"?

 
"typically not less than 3/4 gpm per 1/2" OD is do-able, but 1.1/4 gpm is much nicer to work with, check you fps, please"
I don't know how to determine FPS or GPM.

I can tell you know a lot about the Hydro-Temp heat pumps, thanks again for your responses.

ChrisJ RI

Howdy Chris:

(RUSHED)
Just off the phone with H-T (note, all major brand tech's will usually chat with non-mfr specific tech's, so I have to say they are not all my answers, since 1980 GT Mfr mentoring to me:

Please filter if bad well water (all varies-; home depot here has $6-$9 kit testing)

Air will leave loops (taught~2.2) better for micro bubles and 'cling-ons' to be disrupted -at-  to 2.7 feet per sec -water,  more speed w/A.Frz's

 So too, does pressurized GT ground loops gain air over time from entrapped gasses in ANY fluids instilled... (JD Commented well, on another blog).
All we ever used since 1983 was pressureless designs , -evn radiant and icemelt , and Solar, all...AVOIDING that "sometimes reflushed every spring" by folks, which is why EVEN in radiant to 18 feet above the reservoir, T'd to go to higher reservoir, in mech room, but lower than system (to 18ft) if not moving fluids well enough for air-separation to ...etc. , and an air bleed or off reservoir, in joists in mech room well pressure
GFos tech sid get 5ft TDH over any pump in described GT or Radiant, if not presurized, they wanted higher NetPosSuctHd NPSH into pump, etc.


GOOD:
Going to look into adding shut offs or changing manifolds.
"CHRIS: >> so when on, what is the dT?
If you stretch vinyl elect tape - same color on pipes, read from any cheap IRed device, the DIFFERENCE to 1/10th degree can be picked off, even radio shack $29.
Or Walmart toKitchen stores have many choices of digitals that can be permanently strapped to pipe and read ambient, or if handy with tiny tools additional lead of a sensor can go elsewheres (electrnics soldering changes).

 "Garage and very cold slabs... is "HIGH MASS" and the "LOW MASS/ wood floors requiring higher temps (possibly underdistributed ) use the warmer loop temps.
 -as you may have meant or said.

 IF FLOW IS SUFFICIENT and DISTRIBUTION IS SIFFICIENT
then do a simple graph of "on" - "off" cycle on paper, determine how long it should run as is... and see if you can estimate (or just rial and error) to get use of lower Leaving Fluid: LW temps to circuits.

("A call to Forced Air >>> you are right:)
What I did was (as told) "G" Fan-on-call (not auto) WONT turn fan on recirc
IN AUX nor DHW,
 and AUX-IN-Floor is an IRD Prog (PALM Zire31, or equal) can be SELECTED in HW, AUX, to desuperheat, or PRIORITY on the 'RED' Control board...

Yours is PRIORITY then, BUT
PA, Bruce, --- relayed---  to green control wire 'hot' to fan ECM controller (NOT GROUND WIRE TO HIGH VOLTAGE) and has continuous warm recirc at lowest G-select "IDLE" on IRD Palm...
His ducts RADIATE heat to the floors too.

"~ in-slab high mass.
 
<< HIGH MASS = Slab, concrete, for that lower 80-90-deg use if distributable heat energy gets to desired reception.>>

"It is recommended that you do not let the DHW run over 410 psig, nor use ANY HIGHER pressure/temp
but usually always desired above ~ 290-310 if avoidable ever, in air, fluids, ever as possible getting a Heating distribution wanted, at the lowest AMPS...
again
Forced Air Hydro-Temp, can be 12% less costly than 4gpm/ton, hw produced at 104 degrees (!):
grab a cfc tech and read though cumbersome and ~ 1/2 hour fiddling... each mode, cycling "OFF"
While/WHEN SET UP:
I 'drove dealers crazy' to get me the Q- or Data aquisition of start-up, and made a specific-enough START SHEET for those not so doing...
...next at website coming changes.

Head Pressure of the refrigerant, for any length of time, for a 30-year system, requires attention.

Low DHW set: YES, IF-  IF works for you, and
IF- IF a 2nd  tank is set 125-130 for reducing bacteria build up seen in the pst 15 years
Some single ELECTRIC ONLY tanks just are set at the top element for 125+ ,  and even the low element can be completely unwired, to keep off, ever...

Hydronic errosion will be open for a rangeof FPSEC , average alloys today; Cu..
I believe 12 gpm long term is too fast per 33/4" ( and way too high head over the recommended max of 6GPM, circulation )
even 1" is generally maxed at 11 GPM and 1.1/4 at 14... for efficiencies that some IBR  guys pick on  GT about... ( as they see many outside recommended pumping watts) unles  a "slime-laminate' or something coats Inside Pipe...
an open-loop galvanized test line runs  , 2000+ GPM on 3" for going on 20-years, but no errosion at any elbows in a warehouse 'lab' at Structural Fiber/PentAire..

~
Go to TEST mode or with tech- Elect/HVAC/ Pump tech..
on Palm go to test mode,
or manually staying above HIGH voltage shelf... (!)
put in first stage...
isolate zone,
and read dT to a 1/10th degree...
and with gauges on rfg side ( yes I know we are to avoid any common use, cap tightly after done--- VERY TIGHTLY)
you can really be accurate by press/temp readings...
But estimate MFR compressor lable BtuH at being what the lable reads if loop is a good flow ! 2-deg difference on a little first staging, ( or less dT there) and at noe ? 43-44 deg entering ECL gle loop...
let's say 18MBTUh compressor is yielding 20,000 BtuH at 90-deg AUX zone loaded a half hour, running in test mode...
Entering less Leaving dt divided INTO 20,000, and that number, leaving the Hydro-Temp
divided by 500 for water, or the likes of 485 for with some 20% antifreeze ( can be off now,  without a table from the net)
so a 20-dT leaves 1000
 and then /500
leaves a 2 GPM flow...

Be better than a tired tech:
Read to a 1/10th of a degree dTemp.

People discuss those "great" P/T ports on loops, but Pressure drops can be subject to variations in OEM coils , etc... by stem-pressure gauge readings; and across pumps is more acurate/ IF NEW... and clear of impellar debris,...
so I check by estimated compressor BtuH which has Net views at things like BristolCompressors websites and copeland ,,, having ARI Heat pump conditions I see on gauges, or MATCH in field to get GPM without flow presure drops.

If you have PS or GPM  of a PUMP on the net , you can find pressure-drop across  your pump if you also have a low range (0-30 gauge and some adapter to hose threads and a hose-bib drain at entering and leaving. I would not go by installed pex off charts, with all the installation deviations creating variou pressure drops...

CHRIS:
Get a Palm Device (h-t loads softaware, ! $100.
and
record sensor readings AS BENCHMARKS to calibrated thermometer checks...
Those sensors are strapped on lines, once benchmarked, can be very useful in the future for determining changes for better or worse. Differences in Temps can be very accurate on these SMART-Sensors, with that System.

All are welcomr to correct me for Chris, anyways.

JP