Geothermal

Jimmy Gillies

We are looking at Geothermal units, heat pump, slikies etc.
I'm sure loads of you guys will have fitted these units.
So here is my question: One unit supplier recommend a buffer tank and another doesn't, what do you guys think?

I like the the unit with no buffer tank and a direct supply to my under floor heating(radiant) at 45*C(113*F), so that will give me a floor output of 50 watts/M2 in concrete. This unit supplier said this is the optimum running condition for cheap running costs.

But the other unit supplier(the guy with the buffer tank), says he can supply water at a higher temp, even to do the HW indirect tank! This has an appeal, as I can reduce my pipe centres etc. But is this type of unit costing more to run?

So what's the scoop?

I would be very pleased to have your thoughts.
Regards.
Jimmy Gillies (Scotland)

Einsiedler_2

max temp

Check what the max temp you will get from your Geo-therm sys.

In my area, we will not get more than 110F. whereas this is fine for infloor. It would hardly do the trick on an Indirect Tank.

How does the inclusion of a buffer tank raise the temperature anyway??

EIN

Colin

Geo-Buffer-Indirect

Jimmie,
We use Millbrook Hydron Module and the recomended install is with a buffer tank.

A rough rule of thumb is 10 gallons per ton of capacity. It's kind of like primary/secondary piping, each side of the system can perform at it's optimum level.Especially if the system is micro zoned.

Otherwise your radiant flow better match or exceed the flow requirments of the geothermal heatpump or it will be tripping off on high head preasure or temprature controls.

As far as the indirect is involved it usually is an additional smaller desuperheater coil installed in the discharge line of the compessor that domestic water from the waterheater tank is pumped past and robs about 10,000 BTUH from the heating side of the system.

Happy Hunting
Colin

hr

Great looking work, Colin

nice detail on the pex out of the slab and PAP work on the manifold feeds. What are all the lines in the P trap?

I've only done one geo thermal/ radiant, Jimmie same info as Colin the manufacture, HydroTemp, highly recommended a buffer be used to prevent the compressor from short cycling or tripping out.

I used a plain electric water heater and left the element in a back up should the geo go down.

hot rod

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Colin

drain pipes

Thanks HotRod
Drain lines are for HRV, A/C condensate, and water softner.

I had the opportunity to do a service call on his water softner last week and last years total comfort conditioning utility bill was $400.00 for aprox.3,600 Sq, Ft. radiantly heated (2 levels and a lower garage) and 2,700 Sq. Ft. cooled using chilled water off the Geothermal heatpump run thru a high velocity distribution system at a $.048 /KW electric rate.

Colin

Tom_35

geothermal hp's and buffer tanks

We are installing a job now that has multiple heat pumps on it and we are using buffer tanks. According to Siggy's instructions, we are in good shape with 2--50 gallon tanks, and we are doing the same as HR by using electric tanks.

Our heat pumps are providing domestic hot water via de-superheaters only and not on-demand. We have 6 heat pumps providing the radiant heating, with 4 of them equipped with de-superheaters.

We have always provided the buffer tanks on our geothermal systems.

Tom A

Jimmy Gillies

Thanks Colin and others.

Colin,
Very nice work. Sorry, Colin but can you please 'dumb down' a bit? Is the 10gal/ton for sizing the buffer? The 'NO BUFFER' guy says the output from the heat pump to radiant goes directly, at around 45*C (like yours EIL). Also he's saying that a 'buffer' makes the unit cycle, the electricity supplier don't like that and may ask you to disconnect it!!!??? Also, and I quote 'THE USE OF A BUFFER TANK IS STRONGLY DISCOURAGED'

So is 45*C(110-113*F) the output temp of most heat pumps? or can it vary depending on the unit. Is 45*C the optimum temp?

I would not use an indirect HW tank if we could not get 82*C to heat it, I'll use an electric one.

Thanks again Colin, perhaps it's a subject for Dan's new book 'Heatpumps for dummies'?
Best regards.
Jimmy Gillies (Scotland)

Mad Dog

Gorgeous Work Colin

Mad Dog

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Wayne_12

buffer tanks

The geothermal systems I have installed, the supplier always recommended the buffer tank. The tank will allow the heat system to operate with the heat stored in the tank, expecially when 1 or 2 small zones are operating. The heat pump is designed for the lowest expected outdoor temperature, concequenty the heat pump will cycle on/off on a light load, damaging the compressor and shortening the life of the start components.

Also use a storage tank designed with large threaded ports. The water flow into the storage tank should not be impeded from the heat pump unit.

The last system installed, I used brass nipples of the same size as the tank fitting to connect to the heat pump.