I have never been impressd with the hot water generation from my Carrier GT-G 5 ton unit. There is usually a five degree or more delta on the in vs out but the 80 gallon storage tank never gets over about 80 degrees F. 

In reading here, I notice that the recommendation from engineer is "Cold water inlet out to desuper, return from desuper tees into boiler drain; hot outlet to other tank." for the proper hookup.  The GT-G manual suggests the opposite direction.

Does it make any difference which way it flows?

My system is hooked up as follows (using the alternate piping scheme):

The only thing that I believe matters is if the desuperheater output is directed to the bottom of the tank, in your case is the dip tube still in place? If yes, then you should be fine. If the dip tube has been removed then flow would matter.

Check out this link http://www.marathonheaters.com/cont_heatinstall.html  It shows the manufacture's suggestion for hookup to a desuperheater for a Marathon water heater. 

Regards,

Yes, I left the dip tube in place.

Do you think my expectations for the hot water generator are too high? From what I read I was expecting a much higher generation of hot water.

Thank you,

Jim

 

 

I have no problem with reversing my earlier advice per the drawing above - basic idea is to pull from and deliver to bottom of tank to allow it to naturally stratify, putting warmest water at top for use by main heater. Either scheme will have close to the same result. Oh yes - leave the dip tube in place.

Hot water generation is typically only about 10% of total system heat output. 6,000 Btu (10% of 5 ton nominal). 6,000 btuh delivered to an 80 gallon tank raises it only 9 deg F per hour, and it'll manage that only with continuous operation and no use of hot water.

Are all your water lines well insulated?

Please correct me if Im wrong ( only experience with priority ) pulling from the cold seems better , for the reason that when water is used you are pulling the coldest water from the line ( colder water better heat exchange ) does this thinking hold water chuckle chuckle

It may seem to be the better choice, but stratification will have the coldest at the bottom of the tank anyway.  Cold water entering the tank will fall to the bottom (directed that way by the dip tube) and the warmer will work its way to the top.  Personally, I don't think it matters.

The water lines are all well insulated.

The 9 deg F per hour is telling. The unit doesn't run long enough to heat much water.

Is there an industry standard for how long a properly sized system should run per some unit of time?

That is dependent on the load / loss of the home
in other words on a design temp day for your area the system ( without back up ) should run 100% of the time and just maintain temp
on warmer days the system should cycle how much and how long would depend on how far away from design temp you are.
I should side note many systems are sized above design and require aux heat at or close to these temps

Jim,
Don't forget that every degree you add to buffer tank saves you money by activating heating elements for less time in the downstream tank. Too many variables to predict what tank temp should be, but anything over ambient waves energy.
Good luck,
J

Thanks, Joe. While I do realize that I am always on the lookout for more! I just recently put thermometer sensors on various points and find it interesting observing how things are really working.

Thanks to you and everyone on this forum for sharing their experience!

I should also mention that most systems don't deliver nominal tonnage during winter heating season owing to lower EWT than rating conditions. You may only be seeing 4,000 Btuh actually making into the preheat tank, resulting in just 6 degree tank rise per hour.

Any heat at all into preheat is better than nothing, and that heat costs about 1/4 that of the resistance elements in the main tank.

I have a 1600sq.ft. cape in CT that I am installing a closed loop gshp in. The house has oil fired steam heat and had a 40gal. stainless tank with a heat exchanger that circulated boiler water through it to heat the water. I replaced this with a 50gal. electric water heater. My question is, can I use this tank with my hot water generator in a closed loop configuration using the heat exchanger to preheat my water feeding the electric water heater?

If the tank is well insolated I see know reason it couldn't be used as a buffer tank for your electric water heater.  I would expect that you would not use the exchanger though, just connect directly with the desuperheater.  Is this what you have in mind?

My water is hooked up the same as Jim's. While doing some work on the lines a couple of days ago, I noticed that the hot water coming from the geo seems to be radiating up into the cold water lines. Would it be best to install a check valve above this "T" or is the heat going up not enough to bother with? Has anyone else noticed this happening on their system?

Greg

yes , install a spring check right above the tee. keep as much water in the insulated tank as possible , also I suppose it is possible use of cold water could cause some backfeeding if you have an expansion tank on the hot side

Thanks, I do have an expansion tank right above the tank.

Greg

Greg,

Are you sure there isn't a check valve already installed?  Most (if not all) system with expansion tank have the tank due to the checkvalve being required in the system.  If you have a valve in place it might be leaking or maybe someone forgot to install it??

Regards,

Eric,
I do have a check valve, but it is where the water line enters the basement. Thats about 30' from the mech. closet.

Greg

Insulate the cold water lines up to and a foot or so past the first bend to horizontal