Help selecting a hot water heater

[killahog]

Hello , This is not related to a Garage or shop but I would really appreciate any input or suggestions. I recently installed a Direct Ground source vertical loop Geothermal system for my house. I am contemplatiing replacing my 120 gallon electric hot water heater with a smaller 50 gallon electric heater. The installer reccomended replacing this old water heater with a 50 gallon storage tank that would receive the pre heated water from the Geo system and then transfer it to the new electric hot water heater. I was thinking i would be able to find a storage tank that would be insulated and cost less than simply buying 2 complete hot water heaters but I am not having any luck so far. So if anyone has experience in doing this could you please explain what route you took .

 

[rburke65]

Could you use the 120 gallon tank that you have mow for the holding tank?

 

[Firebrick43]

Does the geothermal have a heat exchanger or does it need one in the "preheat" tank which would make the storage tank actually a indirect water heater and because of low volumes sold and cost of the heat exchanger a little pricey.

Have you thought about a heat pump water heater? Yes no preheat from the geothermal but it would be getting its heat indirectly from the geothermal and would assist in cooling/dehumidification in the summer

 

[killahog]

I considered using the existing 120 gallon tank but I am unsure if the GEO could effectively preheat that quaintly of water. I have not considered a heat pump hot water heater because I don't want to pull any heat from the basement that is mainly uninsulated block and difficult to heat now.

 

[Firebrick43]

Understand on the basement being cold. As far as preheat goes actually that is ok if it doesn't bring it up as much as a smaller tank. Any preheat btu is a btu the electric hwh doesn't have to do. The lower the temp the larger the delta t and the more efficient at heat transfer. If you raise the water from 55 to 70 that a lot your hwh doesn't have to do and boost recovery rates way up.

The real problem with your tank is if it's a glass lined tank it's life my be over anyway. 8-10 years. Going with a marathon hwh with composite tank may be worth the extra money. Does the 120 gallon tank have a heat exchanger built in???

 

[Jackfre]

Heat-flo make some nice SS storage tanks in all kinds of configurations. Be careful storing moderate temp water. It is the ideal Petri dish for growing Legionella. If you do this I would run the final tank at 140* and mount a tempering valve on the outlet.

 

[killahog]

My current HWH does not have a heat exchanger, it was a heater that was installed by the electric company and in exchange the consumer allledgedy received a discount on the rate . When I purchased the owner was paying a monthly rental fee for the tank .When I contacted the utility company they signed ownership over to me at no cost. I guess they dident want the liability of owning such an old unit. I don't know if it is lined with glass or not .

 

[Rockhead261]

My OCD demands I point out that there's no reason to heat hot water. Thank you for your kind consideration in this matter.

Sent from my SM-G930V using Tapatalk

 

[Radix2]

Can you describe your system better? Your geothermal takes heat from the ground loops and produces hot water for radiant heat? You want to use this in an indirect tank to make potable hot water? You currently have a simple 120 g electric HWH?

I am confused by the use of preheated water to an electric HWH...how is this going to keep the drinking hot water separate from the radiant loop water? Don't understand the configuration..

 

[toyotadriver]

My OCD demands I point out that there's no reason to heat hot water. Thank you for your kind consideration in this matter.

Sent from my SM-G930V using Tapatalk

Actually...there is a reason. It's a mysterious device called a thermostat. Your tank is full of hot water. You open a hot water faucet. Hot water leaves the tank and is replaced with some cold water. The cold water absorbs heat and thus the tank temp begins to drop.....but the water is still hot. Thermostat (that mysterious device in action) reaches a set point and the activates the heat source and.......wait for it................heats the already hot water even hotter.

So, calling it a hot water heater is not incorrect because yes, it does indeed heat hot water.

Pretty crazy stuff eh?

 

[JimRB]

I have a geothermal in Georgia. My HVAC runs about 10 months of the year. The 240V to the hot water heater is turned off about 9 months of the year. 50 gallon hot water heater with the desuperheater plumbed into the drain valve. Low flow shower heads. Water pipes insulated. Just 2 people in the house.

I have never seen a hot water heater bigger that around 50 gallons in houses but I suppose in different markets people do different things. If it were me I would start with just a 50 gallon hot water heater and a disconnect for the 240 volts right next to the hot water heater. See if the geothermal can keep up with your demands. Or turn on the 240 and see if a 50 gallon can keep up.

 

[Reflex]

It is not likely you will find a 50 gallon storage tank. Most manufacturers consider storage tanks to be a commercial item. That is, they are normally seen in a commercial application. For this reason, there is very little demand for small storage tanks (under 80 gallons) when compared to tank type residential water heater demand. An 80 gallon storage tank is considerably more expensive than a basic heater because of it's construction and low demand compared to a residential water heater.

Even when an 80 or 120 gallon tank type residential water heater was available (they be made after April 15, 2015), two 40's or 50's were much less expensive. One thing to consider before installing two 50's is your electrical service. The 50's will/can use the same electric element(s) size as your 120. This means that you'll need an additional breaker (unless your 120 is a two element wired for simultaneous operation). As a general rule, a 40 or 50 gallon electric will use (2) 4.5 kW/h elements of which only one can/will fire at a time (called interlocking - google A-6 circuit).

Regarding the usage, your new ground source system should provide a significant amount of hot water when in use. The heaters should fire very little if the system is set up properly and space heating or cooling demand is on the high side.

Best of luck,

Reflex

 

[coldh2o]

Actually...there is a reason. It's a mysterious device called a thermostat. Your tank is full of hot water. You open a hot water faucet. Hot water leaves the tank and is replaced with some cold water. The cold water absorbs heat and thus the tank temp begins to drop.....but the water is still hot. Thermostat (that mysterious device in action) reaches a set point and the activates the heat source and.......wait for it................heats the already hot water even hotter.

So, calling it a hot water heater is not incorrect because yes, it does indeed heat hot water.

Pretty crazy stuff eh?

Hahaha!

 

[killahog]

Can you describe your system better? Your geothermal takes heat from the ground loops and produces hot water for radiant heat? You want to use this in an indirect tank to make potable hot water? You currently have a simple 120 g electric HWH?

I am confused by the use of preheated water to an electric HWH...how is this going to keep the drinking hot water separate from the radiant loop water? Don't understand the configuration..

Radix What I have installed is a ground source loop Geothermal system that operates using a heat pump. i have a propane forced air furnace as a back up unit for when the geothermal cannot provide all the heat necessary. What I am trying to accomplish is to use the residual heat from the heat pump to compressor to preheat my hot water. in the schematic provided with the heat pump it illistrates the use of a non active tank as a holding tank, i am trying to find a less expensive way to get a insulated tank other than buying a complete electric hot water tank.

 

[killahog]

My OCD demands I point out that there's no reason to heat hot water. Thank you for your kind consideration in this matter.

Sent from my SM-G930V using Tapatalk

I considered using the term low temperature water increaser but it just didn't sound right .

 

[Firebrick43]

If you have that option installed you are good to go! Just plumb as noted. That is basically a heat exchanger and circulation pump. I was figuring it would have to be mounted externally

 

[Firebrick43]

I would use a rheem marathon WH as the electric backup or main tank. They won't corrode due to thier composite tank. Set it at 130 and many of your HP works as advertised you are going to use a lot less electricity .

 

[killahog]

i will look into rheem as a main tank , Thank you

 

[Radix2]

Thanks for posting that. Your HP has quit a bit of hardware to make this work and keep the potable water safe.

Unfortunately I really doubt that you will find anything less expensive than a std electric HWH.

On my build I was looking at using an indirect tank off the boiler for hot water...one would think that a tank with no moving parts or heating system would be reasonable compared to a full heater, but they are $1000 plus the zone pump etc...

The marathon heaters are really nice and efficient and last forever...but again it is a $1000 solution.

Two basic electric tanks will be by far the least expensive solution. And it gives you two back up elements for free!

 

[hippie2cams]

you sir, need to quit worrying about that cool water temperature maximizing system and get back out in the woods wherever it is that you live and start hunting for this years great trophy. Since you did not put a location down in your profile. Now I am forced to try and find this location so I can move in next door and participate in what looks like excellent hunting

 

[AndyCBR]

I had the same system in a previous house I built. I just used a 40 gallon electric as a storage tank for the preheated water that went to the heat exchanger. This tank was fed to the inlet of the gas powered 40 gallon water heater that raised the temp of the preheated water the rest of the way.

It worked quite well as the gas water heater was being fed 100 degree or so water (even hotter in the summertime).

Again, I don't think you're going to find a much cheaper or better solution than a cheap electric water heater to be used as a storage tank.

 

[killahog]

I had the same system in a previous house I built. I just used a 40 gallon electric as a storage tank for the preheated water that went to the heat exchanger. This tank was fed to the inlet of the gas powered 40 gallon water heater that raised the temp of the preheated water the rest of the way.

It worked quite well as the gas water heater was being fed 100 degree or so water (even hotter in the summertime).

Again, I don't think you're going to find a much cheaper or better solution than a cheap electric water heater to be used as a storage tank.

Thanks Andy I am going to have the contractor install 2 new Electric storage type heaters, they said they would add the cost into the installation of the GEO system and that would qualify for the 30% tax incentive. I gave serious consideration to a GEO electric hot water heater but I dont like the idea of heating the house and then having a hot water heater pull the heat from the room and exchange it with cool air, not to mention i don't have a drain accesable for the condensate generated by the hybrid hot water heater.

 

[laser3kw]

My OCD demands I point out that there's no reason to heat hot water. Thank you for your kind consideration in this matter.

when I read the title, I was drawn to read this entire post to see who would point this out.
When this is said at work, the same "argument" ensues. And then the "circular argument" - when you heat "hot water", what do you call it? "Hotter water"?

 

[AndyCBR]

Thanks Andy I am going to have the contractor install 2 new Electric storage type heaters, they said they would add the cost into the installation of the GEO system and that would qualify for the 30% tax incentive. I gave serious consideration to a GEO electric hot water heater but I dont like the idea of heating the house and then having a hot water heater pull the heat from the room and exchange it with cool air, not to mention i don't have a drain accesable for the condensate generated by the hybrid hot water heater.

I think that is a good idea. The GEO HWH is an overly complex solution IMHO.

The beauty of the heat exchanger to a dummy heater is that the potable water and working fluid of the geothermal system never mix.

This system is much more efficient in cooling than heating but any amount you can preheat the incoming water to the energized water heater, the better.

 

[killahog]

I was unable to find a hot water storage tank for less than buying a complete tank so here is what I ended up doing. I bought 2 complete 50 Gallon units and had the connected together. The one on the right is just for storage.

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