Combined radiant and forced air Geothermal Retrofit - need advice and opinions

[JCT]

That is a good question typo or maybe they are saying it has to be hot or cold not both at the same time? They are for both though. I have put about 100 of these in and they work great along with their ground loop pump pack

[frumper15]

I've used the QT non-pressurized flow center for all my installs and love it - I'm going to be trying out their prefabbed pvc manifold with the mechanical fittings for my next one - should save a bit of time making it on the jobsite. Definitely going to consider using that HSS Buffer tank for one of the options on this job. Thanks guys.

[frumper15]

Question for you guys. I would like to offer the HO the option of generating all their Domestic hot water via Geothermal (with some kind of electric or propane backup). They currently have a 75 gallon natural draft propane water heater. It's rated for 75,000BTUhr and 130 gallons first hour rating. I somewhat doubt they require that amount of hot water at any given time, but I also don't want to be the guy that undersizes it and they hate their system in the future.

I have two trains of thought here - provide a reasonable amount of preheated hot water in a storage tank - at least 50 gallons. Use the geo desuperheater with a buffer tank so I'm not trying to heat 50 degree well water, but hopefully 90+ degree buffer water.

Beyond that, how much capacity should I be adding or what size dedicated W2W should I be looking at to meet this need? The smaller WF w2w units are only 1.5 or 2 tons that seem to be for just domestic production.

Should I just use a larger storage tank (75-100 gallons?) and let the Geo do its thing over time? The other thought is to have my auxilliary be something like a boiler/domestic combo unit made by navien or Triangle tube that could make up for any need instantly - but that's an awefully expensive backup solution. Looking for some guidance.

Thanks guys.

[SkyHeating]

I would put in at least an 80 gallon storage tank with an NSW040 dedicated water unit and then run a desuperheater off the other unit to a 50 gallon preheat tank. That should give you enough heat for most applications unless they are filling up 100+ gallon jacuzzi tubs. I have noticed a lot of houses on wells have 80 gallon tanks. This could be because the well can't keep up with a 50 gallon so they use the 80 so there is no buffer tank from the well. So the current 75K btu unit may not be needed at all. I would just ask about their water usage and take look at their tubs/showers

[frumper15]

Here's a question I should probably already know the answer to - if you use a dedicated water-to-water unit for the domestic hot water, do you need some kind of heat exchanger between the domestic water and the unit, or can you run the domestic directly throught the unit (like the desuperheater)? I know the desuperheaters on the units I've used have double wall vented heat exchangers so they're safe for potable water, but what about the primary on a W2W unit?

[JCT]

most units you can run right through i think. I know the northern heat pumps i put in you can they are rated for domestic.

[frumper15]

I'm in the home stretch of designing this project (yes, I'm a little slow on it). I have 4 distinct designs that I've settled on (that will find use beyond just this project).

My "best" design is the waterfurnace Synergy3D (actually branded as american standard) unit to provide both the forced air and hydronic side of the equation. The place I'm getting hung up is the domestic hot water production (still). When I'm supplying the hydronic side of things I'm also including the garage floor heat (currently supplied by a separate water heater). That bring my heat pump size up to 4 ton from 3 tons. Air conditioning is still OK, my first stage cooling doesn't exceed the calculated load, but I can't go any higher than 4 tons.

That being said, I would still really like to offer Geo-heated domestic as an option, but it's looking like I would either be on electric backup heat (if setting the hydronic side to priority) or won't be able to keep up with the domestic load (if leaving the air side as priority).

The plan is to use a Triangle Tube SME Multi Energy tank that has 100 gallons of primary boiler/hydronic water surrounding a 60 gallon inner tank of domestic hot water. The Geo unit would be tasked with keeping the water in the inner tank at 120 degrees so the outside water should be also at 120 degrees when everything is said and done. Radiant floors would draw from the 100 gallons of primary water and the desuperheater would also temper a preheat buffer tank (mostly for summer benefit as the Geo will be supplying the heat in cold months anyways.).

Am I making this too difficult? Am I chasing that last dollar of savings but adding a lot of cost and potential disappointment? Should I just KISS and put in an instantaneous Hot water heater behind a buffer tank and call it a day? I'm looking for a sanity check here and hoping you guys can set me straight.

[frumper15]

This has me looking at things again and I thought I would add this wrinkle: if I use the existing water heater as the buffer tank and leave it powered (propane) it could effectively serve as an auxiliary heat source for both the domestic hot water and the hydronic floor application. I will also have the electric strip heat for the air side backup as well, so then it would be a decision of putting the unit in hydronic or air-to-air priority mode.

I would effectively have 160 gallons of 120 degree water when the tank has satisfied and having the Geo in air priority would mean the house would never be without heat and that would leave all the gaps between cycles to work on heating the water back up to temperature (and a large portion of the house heating would be covered by radiant floors as well). I haven't found an effective way to measure how much of my demand would be taken up by domestic hot water production and it really varies depending on usage. I think it's more important for me to use a reasonable assumption and make sure I have a viable backup source of both air and hydronic heat.

[frumper15]

I think I may have stumbled my way into a viable idea on this topic: Rather than use the Geo as the final domestic water heater, I should use it on the preheat tank. Sort of.

Tell me what you think about this: I leave the Geo in Air priority so that I'm certain the house is always kept warm (priority #1). Keep the existing Hot water heater in place and set to a comfortable temperature (120 degrees). Set the SME tank at a temperature slightly higher than the powered water heater (125 degrees) for the Geo to shoot for. No need for a desuperheater as all the heat would be coming from Geo anyways.

The way I picture things going is this: Geo will not have trouble 90% of the time keeping the SME tank at 125 degrees so the powered water heater will do nothing but serve as another holding tank, and hopefully standby losses are low enough that it won't even need to fire as the entering water will be hotter than its setpoint. If it does get to point the Geo can't keep the SME tank at 125, the hot water heater will kick in (only after it has used up its heated water) and even then it will only need to heat water that should still be above 100 degrees. The lower water temperature water for the radiant shouldn't be a problem as it is for comfort not heating (with the garage being the exception, but that is kept at 50 degrees anyways.)

[arc8]

My "best" design is the waterfurnace Synergy3D (actually branded as american standard) unit to provide both the forced air and hydronic side of the equation. The place I'm getting hung up is the domestic hot water production (still). When I'm supplying the hydronic side of things I'm also including the garage floor heat (currently supplied by a separate water heater). That bring my heat pump size up to 4 ton from 3 tons. Air conditioning is still OK, my first stage cooling doesn't exceed the calculated load, but I can't go any higher than 4 tons.

With a 4 ton Synergy3d unit, is there enough capacity from the hydronic side to take care of the load? Can this Radiant heat meet the need for the whole project? If not, the "AIR" side is the priority!

You can use any means of supplementing the Radiant heat as you wish.

The plan is to use a Triangle Tube SME Multi Energy tank that has 100 gallons of primary boiler/hydronic water surrounding a 60 gallon inner tank of domestic hot water. The Geo unit would be tasked with keeping the water in the inner tank at 120 degrees so the outside water should be also at 120 degrees when everything is said and done. Radiant floors would draw from the 100 gallons of primary water and the desuperheater would also temper a preheat buffer tank (mostly for summer benefit as the Geo will be supplying the heat in cold months anyways.).

I would use the desuperheater (water assist) to heat a pre-tank before any DHW device/equipment.

Am I making this too difficult? Am I chasing that last dollar of savings but adding a lot of cost and potential disappointment? Should I just KISS and put in an instantaneous Hot water heater behind a buffer tank and call it a day? I'm looking for a sanity check here and hoping you guys can set me straight.

You can. You do want it simple and less costly and maintenance free, don't you. What would your warranty be after everything is installed??

[CraziFuzzy]

I don't think multi-stage chillers are out there in small loads because it really doesn't matter that much. The fact that you are using a chilled water system already gains you a lot of the advantages of multistage (being able to scale the system to the load). With a properly sized buffer tank, it doesn't matter that the compressor itself cycles - the cooling can continue just as much as needed.

[SolarMike]

If you are chasing that last dollar of savings, I would suggest to remember that your biggest annual load is heating and your best efficiency is when you can drop that down as much as possible in temp.

I don't know what percentage of the house is floor heated but if possible Treat your floor as the primary heating system. Put all your heat into a 120 gal tank and heat it to 40C (104F). Use a 3 way mixing valve with an outdoor reset (Taco has a stand alone unit) on the floor heat which i assume is in a gypsum cement (please). (you can increase the tank temp to 50C (120F) setpoint when the outdoor temp is below freezing. Depending on the tubing layout, your return water temp to the tank can determine when the fan coil comes on.

As propane is the current energy source and, in most places, there is not much difference between propane and straight electricity, for DHW just use electric elements to boost the incoming to 50C (120F). This, of course, assumes the DHW load is not huge, as mentioned earlier.

Use a second tank (50gal) for a chilled water buffer and take it down to (4C) 38F. The system would use 2 pumps, one for the heating tank and one for the cooling tank. of course the HP has to have a reversing valve. A normal fancoil will distribute the cooling.

This is probably the simplest way to really do it.

[Oldsolarguy]

I use to do retro fits with my old company. With radiant and geo, the w2w dedicated is the easiest way control wise to go. Install a buffer tank(size according to load) and then distribute with either a central pumping method and zone valves or use a primary loop with injection pumping to the zones. As far as keeping the gas as backup and installing a water coil, I think that would be a good idea to promote for the customer having a 5k propane bill. As for another idea, water furnace makes a dedicated w2w with a tank for domestic hot water use. You can do multi units on one loop, just size the loop for the total tonnage load, and then pipe to each unit as normal with flow centers. Overlapping controls could be done with a dedicated radiant stat, either wireless or hard wired as allowed.

[GT1980]

...multi-stage chillers... the cooling can continue just as much as needed.

CF
and Sky

etc:

sk, in re: WF 3D, W:W etc---

What are 3 or 4 ways to heat the Domestic HW?
How long has that been successfully accomplished?
How long has your installation been trouble free?
Were there others in the 1980-90's?
in HEAT-RECOVERY HW, that has been patented since 1981, how did others do that similarly during the patent years?

From in 1993 we installed a Hydro-Temp of AR,(OEM was then building to 75 tons, as all through the 1980's-) --- and this '93 install was simple small HW gen DeSuperheating which made ~ 9000 btuh HW on a cold tank ( off a 36,000 btuh compressor, some call a 3.1/2ton by AIR-ratings, but a 3-Ton by w:w ratings).

I did not know to ask:

How do you heat HW any other way?
by then
they had over 15 years experience with another way.
We had not heard of it from FHP, WF, Trane, ComfortAire, Addison, Aquacal, Carrier/Climate-Master, etc...
we were always told until WF 3D
and a WtrHP:WtrHP with and HVAC STILL can be seen rather simplifying the whole idea(s) of-
1) Heat and Cool AIR
2) DeSuperheater on GTHVAC
3) More HW from a separate wtrHP:wtrHP and zoning Radiant or Pool or Ice-Melt or DHW

in 1979 Jeff Abbe and Jim Schafer became GRACE GEOTHERMAL of NE OHIO (the late GraceGeoThermal- 2013, sold off in 2003).
They serviced a really simple Wtr:Wtr... (as I joined in 1982 from starting in Dayton OH 1980)
I changed the GFos SSBronze circ at 26 years later, also, now my customer...

TETCO (then COP 4.1, 5 gpm 52f water 43k compressor (4-ton AIR ratings/ 3.1/2ton Water:WaterHP ratings))
had a 3-way valve to a 7+ ton Air coil in the Return-Air of an oil furnace [ saved 750-900 gallons for this customer ] as it also had DomHW production from the very same water looping,
PRIORITY
and
HEAT-RECOVERY as first staged cooling was ONLY 6GPM through the chiller barrel of the GT to the AIRCOIL in the oil furnace, and 2nd stage was either diverted to the then condenser-well side and out of the building, or 3-wayed changed to heating DHW on Demand -Prioritized.

STILL RUNNING. TETCO had heating-only PriorityHW NO REVERSING VALVE with Warm-Air GT that dropped into returns of any furnace. Just interesting how 90%+ customers got used to the compressor noise out of the ducts, quiet enough- as they saved 80% over oil, 63% over electricity- net, 45+% over propane and 25% over nGas 10-year averages, little maintenance for the 'chiller' GT-HVAC.

Hydro-Temp DOUBLE Priority IS
Priority DHW full condensing (and 3-Staging in Dual Compressor, or NOW RATED VFD)
while
well and loop pumps are off line in Cooling Mode- "series flow refrigeration" allows this since 1981.
with
as we installed since 2003, 2nd Priority to radiant, (or can be added+ or only Pool heating, etc)

All we did was keep the discharge refrigerant under OEM and reasonable "redlines" in various zoning, etc.

NOTE:
dual compressors 3-to 12 tons, common, as both GT-HVAC and W:WHP Priority, and CHILLERS for process, comm, etc.

VFD 2.1/2, 4 (49k output rated) and 63k ~ 5+ Ton, then Dual compressor 7.1/2 -to 12 ton, and multiple compressors to 75, for up-to-date

ratings for any chiller or W:W or GT-HVAC with oversized heat exchangers as ordered and meeting Energy-Star(tm) can be upwards of 50% oversized for many ranges of SIMPLIFIED proven HW uses.

Staging and VFD GREATLY eliminates and does completely eliminate any need for a storage-buffer tank if first loaded calls of a zone are about over 2/3rds the lowest output of the compressor, and the cyclic use is over 8 minutes off, and 12 -15 minutes on ~ under 3 cycles per hour. Been done well, easily and all:
DHW
Heat Recovery in Cooling
Radiant
and great affect of HVAC Air Quicker-Temp recoveries in intermittent ambient conditions of seasonal changeovers, some keep the floors at 70-72 year round, forced air adds heat or cooling AT HIGHEST COOLING CFM getting more dehumidification, (warmed flooring) as a situation may be wanted.

[ZoneRider]

We offer a GEO specific zoning product and often do custom panel builds that combine forced air and radiant zoning , you can always look us up at www.arzelzoning.com or contact us at 1-800-611-8312 if you would like to know more

[GT1980]

...to know more

I will contact you!

Arzel in Cleveland has those cool pneumatic add on's and 5 or so furnace-brains for HP and GT too

have you seen then "pop" in a collapsible zone damper that you reach right inside 6 to 12 " rounds from the small trunk opening and POPS OPEN to fill and set the damper in 2 seconds? !

They interface many ways too

The Hydro-Temp GCRed Zone board is wireless to IRD Palm point from 30" away, though,; and has 4zn; has 3 relays double throw , pwr on/off and each programmable to over a dozen utilities.
4ht 3c
from a regular HC stat or can add a HP stat 2h2c if you want the stat to do the first stage.
Blowers
Compressors
all with radiant and DHW Priorities , both on the board.

on their website, and the manual is available, too.

More so other OEMS are also just building in zoning with the units.