electric hot water heater with added heat exchange loop?

[h2ofun]

Thinking of adding an electric hot water heater in my system, since have so much free electricity. I would add it before my existing
propane hot water heater. But, I want to find a product that also has a heat exchange loop in it so I can tie it into my spa heating loop.
Any leads? I have this heat exchange loop in my solar hot water tank, but since in the winter the tank does not get over 75 degrees, does not
work trying to heat my spa to 100.

 

[shs1]

As part of our geothermal pond loop system, one of my water storage tanks is a Superstor SE 80 gal tank that has a heat exchange coil built in. That heat exchanger coil is used for radiant heating in our home. While the water in this tank, as well as my other tank without the heat exchanger coil, is normally heated by the geothermal system, it does also have a resistance heating coil which comes in handy if the geo system is down.

 

[h2ofun]

Great lead. I found this also

HTP - SuperStor Ultra Max Multi Source Indirect Water Heater

The SuperStor Ultra Max Indirect Water Heater generates over 50% more hot water than many water heaters of similar size and offers extreme cost savings.

www.htproducts.com

I just wrote my installer and asked what he thought. Seems could be plumbed in to do exactly what I needed.

Thanks

 

[zƬesla]

As part of our geothermal pond loop system, one of my water storage tanks is a Superstor SE 80 gal tank that has a heat exchange coil built in. That heat exchanger coil is used for radiant heating in our home. While the water in this tank, as well as my other tank without the heat exchanger coil, is normally heated by the geothermal system, it does also have a resistance heating coil which comes in handy if the geo system is down.

Interesting, I have a Superstor (60g?), however did not realize there was a radiant option. Ours is just potable. Still trying to figure out how best to replace our 30+ year old oil boiler with a HPWH and something non-gas for really cold days when we need the baseboards working.

 

[shs1]

In California, at least, one is not allowed to use domestic water for radiant heating, and who would want to? We have 2 80 gal Superstor tanks for domestic water and, as described above, one of them has a heat exchanger coil and the water flowing through that coil is then used for radiant heating. That is also good as the water used for radiant heat is not as hot as the domestic hot water, which is good for our hardwood floors installed directly on top of our Warmboard subfloor. The water in the tanks is heated by our geothermal heat pump that extracts heat from our pond loop in the winter. In the summer, if AC is needed, then heat from the air in the house can be transferred to the domestic hot water rather than the pond.

 

[wwu123]

Great lead. I found this also

HTP - SuperStor Ultra Max Multi Source Indirect Water Heater

The SuperStor Ultra Max Indirect Water Heater generates over 50% more hot water than many water heaters of similar size and offers extreme cost savings.

www.htproducts.com

I just wrote my installer and asked what he thought. Seems could be plumbed in to do exactly what I needed.

Thanks

There was a bit of discussion in the other thread from someone who posted a photo of their SuperStor Ultra (not Ultra MAX) with a boiler for heat exchange, if it helps any. I couldn't figure out from the discussion what was running where though, esp not all the input and output ports nor piping were fully visible in the photo...

Do you have enough solar to go off grid in winter?

 

[BGbreeder]

In California, at least, one is not allowed to use domestic water for radiant heating, and who would want to? We have 2 80 gal Superstor tanks for domestic water and, as described above, one of them has a heat exchanger coil and the water flowing through that coil is then used for radiant heating. That is also good as the water used for radiant heat is not as hot as the domestic hot water, which is good for our hardwood floors installed directly on top of our Warmboard subfloor. The water in the tanks is heated by our geothermal heat pump that extracts heat from our pond loop in the winter. In the summer, if AC is needed, then heat from the air in the house can be transferred to the domestic hot water rather than the pond.

Just to clarify, the rule is that the radiant heating system fluid must not be domestic potable water, I.e. a recirculated fluid, right?

 

[zƬesla]

There was a bit of discussion in the other thread from someone who posted a photo of their SuperStor Ultra (not Ultra MAX) with a boiler for heat exchange, if it helps any. I couldn't figure out from the discussion what was running where though, esp not all the input and output ports nor piping were fully visible in the photo...

Do you have enough solar to go off grid in winter?

That was my photo The baseboard FHW goes through boiler (not SS). The SuperStor is potable only and holds water heated by the boiler at temp.

 

[wwhitney]

In California, at least, one is not allowed to use domestic water for radiant heating

Code reference?

Cheers, Wayne

 

[CrazyRabbit]

can’t you install a spa heat pump heater?
also, a heat pump hot water heater is cheaper to run then propane (pro pain)…. A conventional propane heater is on par to operate then resistance hot water. Now a condensing flu hot water heater or on demand propane heater is cheaper to operate then resistance heater. But heat pump is cheaper then all!

 

[shs1]

Code reference?

Cheers, Wayne

This is what I was told by the company that installed our system and if you google on domestic water for radiant heat, it says that it is prohibited in most states and adds, that since the water used for radiant heat may sit uncirculated for many months when heat is not needed, who would want that mixed with their domestic water. Legionnaires’ disease is a real issue in such a situation. I cases where mixing domestic water and radiant water is allowed it seem that some system that assures daily circulation of water in the radiant system is required. I am not a code expert, but not having domestic water sitting in radiant tubing just makes sense to me.

 

[shs1]

Just to clarify, the rule is that the radiant heating system fluid must not be domestic potable water, I.e. a recirculated fluid, right?

Yes, that is my understanding. The radiant water should be in a closed loop and not mixed with domestic water. It seems that there are lot of practical reasons for this.

 

[Unclepaul]

It may be that radiant underfloor heating systems are not rated for domestic water. Plastic tubing may leach, copper connectors sweated on with lead based solder, heat exchangers not stainless steel etc. Would not want to drink water that has sat for any time in those coils.
May be safe, but not tested, so not approved.

Old fashioned rooftop black plastic solar water heaters may be solution. Pre warms water prior to entering spa heater or hot water heater.

 

[wwu123]

So I can envision in the coming zombie apocalypse, a few desperate survivors will ransack abandoned homes and cut open the radiant subfloor piping for a bit of drinking water - but other than that, who really wants to drink water from their radiant subfloor tubing?

 

[mspohr]

In California, at least, one is not allowed to use domestic water for radiant heating, and who would want to? We have 2 80 gal Superstor tanks for domestic water and, as described above, one of them has a heat exchanger coil and the water flowing through that coil is then used for radiant heating. That is also good as the water used for radiant heat is not as hot as the domestic hot water, which is good for our hardwood floors installed directly on top of our Warmboard subfloor. The water in the tanks is heated by our geothermal heat pump that extracts heat from our pond loop in the winter. In the summer, if AC is needed, then heat from the air in the house can be transferred to the domestic hot water rather than the pond.

I don't think OP is looking to use DHW for radiant heating. I think he is looking for something like the Superstor tank with a heat exchange coil inside. That's how most of these systems work.

 

[h2ofun]

can’t you install a spa heat pump heater?
also, a heat pump hot water heater is cheaper to run then propane (pro pain)…. A conventional propane heater is on par to operate then resistance hot water. Now a condensing flu hot water heater or on demand propane heater is cheaper to operate then resistance heater. But heat pump is cheaper then all!

Lets see if I understand the question.

Today, I have a 400KBTU propane heater for my spa. I love this since I can heat the water about 1 degree a minute, which works great when I change the water. It means I do not have to leave it on since it heats so fast.

From what I understand, electric stuff heats much slower. So if I had on spa, it would have to be on all the time, which I do not want.

 

[h2ofun]

I don't think OP is looking to use DHW for radiant heating. I think he is looking for something like the Superstor tank with a heat exchange coil inside. That's how most of these systems work.

yep

 

[shs1]

I don't think OP is looking to use DHW for radiant heating. I think he is looking for something like the Superstor tank with a heat exchange coil inside. That's how most of these systems work.

And that is why a recommended the Superstor tank with the heat exchange coil. Not sure why we were then discussing using a tank without a heat exchange coil for radiant heating.

 

[wwu123]

Lets see if I understand the question.

Today, I have a 400KBTU propane heater for my spa. I love this since I can heat the water about 1 degree a minute, which works great when I change the water. It means I do not have to leave it on since it heats so fast.

From what I understand, electric stuff heats much slower. So if I had on spa, it would have to be on all the time, which I do not want.

Makes sense you want to heat up your spa quickly, but 400K BTU/hr = 117kw. Seems like even if you dumped all 7 powerwalls at max output plus theoretical max of your solar panels simultaneously, you're only getting about 80kw. So your original post said (implied resistance?) "electric hot water heater", if you want fast heating, just pipe several on-demand tankless electric hot water heaters directly into your spa loop to dump up to 80kw....

But when you reference "heat exchange loop", sounds like want to use a large tank of hot water like a thermal capacitor or thermal battery, building up that solar/Powerwall energy into a buffer tank of heated water over a somewhat longer amount of time. and then be able to rapidly heat exchange the energy to your spa water at the time you need it. Never mind that a heat exchanger won't be able to transfer the energy that quickly, unless it's unreasonably hot (otherwise a massive tank); I think the heat pump suggestions are merely pointing out that you'll extract 2-4X the amount of heat for the given electricity, than if you use resistance heating, in any buffered scenario. You do have a lot of free electricity, more than anyone else here, but it doesn't strictly translate to a lot of instantaneous heat; if you're buffering why not get more heat for your electricity? Why would it be different from what you love about your indoor mini-splits?

 

[h2ofun]

Makes sense you want to heat up your spa quickly, but 400K BTU/hr = 117kw. Seems like even if you dumped all 7 powerwalls at max output plus theoretical max of your solar panels simultaneously, you're only getting about 80kw. So your original post said (implied resistance?) "electric hot water heater", if you want fast heating, just pipe several on-demand tankless electric hot water heaters directly into your spa loop to dump up to 80kw....

But when you reference "heat exchange loop", sounds like want to use a large tank of hot water like a thermal capacitor or thermal battery, building up that solar/Powerwall energy into a buffer tank of heated water over a somewhat longer amount of time. and then be able to rapidly heat exchange the energy to your spa water at the time you need it. Never mind that a heat exchanger won't be able to transfer the energy that quickly, unless it's unreasonably hot (otherwise a massive tank); I think the heat pump suggestions are merely pointing out that you'll extract 2-4X the amount of heat for the given electricity, than if you use resistance heating, in any buffered scenario. You do have a lot of free electricity, more than anyone else here, but it doesn't strictly translate to a lot of instantaneous heat; if you're buffering why not get more heat for your electricity? Why would it be different from what you love about your indoor mini-splits?

I currently have a solar hot water setup. (Should never have done it since the in winter, at best, it only gets to 75 degrees)
I have one exchange loop in the tank solar that goes to the spa. Does nothing worth while in the winter. And it does take way too long
unless the tank is at like 150 degrees like it is in the summer.

So, I only think about fast heat when I change the water and want to use that night.
Otherwise, a slow, constant heat with an exchange loop is fine. It is a nice small pump running.
So, if I added another tank, with loop, and it can be heater like a water heater, it just gives me another option
to heat the spa in the winter I would be hoping via the two exchange loops in series. If the solar is colder, I guess the
water going it might even back heat that tank.