Carl Odle, Homeowner with common GEO problem?? We recently had a Carrier GT-PC Geothermal Heat Pump with Desuperheater installed. Since then we have noticed hot water coming from out of the faucets when the cold water is selected (single lever faucets). Our installer added a backflow valve between the buffer tank inlet and cold water inlet with no effect on problem. It seems to be only happening when Geo' is running. Is the added water pressure from the Geo' causing this? If so would a pressure reducer between the buffer tank and the hot water heater fix it?

By the way Bergey,
The DSH tanks are hooked up the same as you show on your site for a two tank setup. The installer added a backflow valve between the DSH return and the Cold water inlet where it "T's" also, but no help.

Posted By Carl Odle on 24 Feb 2014 09:41 PM
By the way Bergey,
The DSH tanks are hooked up the same as you show on your site for a two tank setup. The installer added a backflow valve between the DSH return and the Cold water inlet where it "T's" also, but no help.

Oh my!  Perhaps the first change coming to the Bergey Hall of Fame diagram?!

That makes no sense to me... We've never had a complaint like that with any install.

If piped like in this drawing I could see getting hot water at the taps when the DSH is running...

If the DSH is capturing all the incoming cold water, the only place the rest of the house can get cold water from is the reverse flow out of the buffer tank. Since the DSH is dumping its product (warmer water) at the bottom of the dip tube it stands to reason that the rest of the house is getting warm water on the cold side.

Carl. Can you upload a picture of your set up?

No, the DSH return is feeding one side of a "T'" the other side goes thru a backflow valve to the cold water source (not inline) and the remaining side of the "T" goes to the cold inlet of the Buffer tank, just like the example on Bergy's site.

Carl - when you experience hot on cold, is there only one tap set open?

Do you have any type of recir line on your plumbing system?

the DSH return is feeding one side of a "T'"

the DSH return should be feeding the buffer tank through the drain T.

it sounds like your installer reversed the direction that the water should be circulating

Posted By geodude on 26 Feb 2014 01:13 PM
the DSH return is feeding one side of a "T'"

the DSH return should be feeding the buffer tank through the drain T.

it sounds like your installer reversed the direction that the water should be circulating

Why should the DSH be feeding at the bottom?

Because we don't want to pull debris off the bottom of the tank and feed them into the DSH's circulator.
We draw water UP through the dip tube, through the DSH and re-inject in to the drain.

However, even if your contractor reversed the flow that still would not explain hot water at the cold tap.

Bergy

This is the recommended way to install. It avoids pushing dirt into the GEO from bottom of the buffer tank. No recirculating pump except the one used by the GEO for the DSH.

So we agree there is potential for debris at the bottom of the tank. We suck the water up the dip tube which is about 6" above the floor of the tanks. We then inject water along the floor of the tank stirring up all this debris. Previous threads agree that a portion of this debris filled water short cycles right back to the DSH.

Is this not a way to guarantee debris in the DSH rather then to protect it?

GEODUDE: Can't seem to get the pic' into the message. Where do I go to find instructions for this? GEODUDE: Picture of system now on page 2.

Posted By FBBP on 26 Feb 2014 11:57 AM Carl - when you experience hot on cold, is there only one tap set open? To FBBP: Yes, just opened one at a time. It happens on all taps including shower and tub.

The installer was here and removed heat trap nipples in the buffer tanks inlet.
This seems to almost eliminate the hot water in the cold facuet issue.
He says that any restriction in the DSH return path will tend to force hot water into the powered water heater and then into cold side of single lever facuets or shower/tub mixers.

When the DSH comes on it produces a negative (or reduced pressure on the cold water service in the house, depending on the main service pressure/volume and the strength of the DSH pump) and a positive or greater pressure on the hot water side of the house service.

If you are using single lever faucets and say you have a double vanity, she is washing her face with warm water and he is drawing cold water to brush his teeth, due to the difference in pressure the hot water from her faucet sends some out her tap and the rest back into the cold water line and hence he gets warm water at his cold tap.

Similair situation may occur if there is a recic line on say a two story house, though unlikely.

Unless there is a coaxial flow in the cold water line servicing the buffer tank (highly unlikely) I don't see any way that hot water can enter this line and back track through the cold service if plumbed per Bergy's original drawing.

Therefore you have to look for some place where there is a cross connection. This does happen in single control faucets. It could happen if there is a Y hose connection or something like that.

If you have higher end shower controls, that the balancing valve is open all the time but you shut off the shower with a volume control valve, these might allow the waters to mix due to the difference in pressure.

In any case, I doubt that it is the piping per se, but rather the imbalance of the pressure that is causing the problem.

Posted By Carl Odle on 26 Feb 2014 03:24 PM
GEODUDE: Can't seem to get the pic' into the message. Where do I go to find instructions for this?

Carl,

You have to use the "Quote" or "Reply" tab to access the attachment area. You will see the attachments tab at the bottom of the page .

Bergy

Posted By Carl Odle on 26 Feb 2014 03:43 PM
The installer was here and removed heat trap nipples in the buffer tanks inlet.
This seems to almost eliminate the hot water in the cold facuet issue.
He says that any restriction in the DSH return path will tend to force hot water into the powered water heater and then into cold side of single lever facuets or shower/tub mixers.

Heat trap nipples have balls in them to prevent water moving where it's not wanted. The cold side has a float, so trying to draw water UP through the dip tube is not possible(see pic). That's why my drawing requires the removal of backflow devices.

Carl - I believe the attached layout will serve you better.

The DSH circuit does not interfere with the domestic circuit. No pressure imbalance.

It is a simpler system to plumb.

It allows the buffer tank to hard stratify, no mixing of hot water with cold, so the finishing tank always gets the hottest water available, saving heating costs.

There is much less chance of debris getting to the DSH.

You can make more hot water in the buffer tank since the DSH only gets the coldest water from the bottom with no mixing or short cycling. The DSH will not shut down on high limit set point until the bottom of the tank reaches that set point.

You can save the heat elements from the buffer tank for your first set of replacements for the finishing tank. $$$