Tankless Hot Water Heating

KenO · Dec 6, 2019

Opus said:
You mentioned electricity cost so thought that might have been a big factor. From your reply I guess you can't change electric companies. I can't because I'm on a Co-op but most can in Texas. I have coworkers that change companies every couple of months and go with whoever is offering the cheapest rates. I've thought about solar but it is such a huge $$$ investment and with all the hail storms around here not sure it is such a great idea. Have a good friend that her panels got shattered from a hail storm last year.

Yeah we can't change electric companies in AZ, at least where I live. So I do what I can to reduce my electricity usage and the solar helps a tremendous amount during the summer months.

Dr. Dendrostein · Dec 9, 2019

KenO said:
Yes the manual for the Rinnai says adding a loop will reduce the warranty. I find it interesting since the manual shows various configurations for infloor heating, hydronic hot water HVAC systems, etc. Honestly for the number of cycles per day, I don't think it will affect the unit. I have 3 Rinnai tankless units on the house. The kitchen unit gets the most cycles, with the amount of use our kitchen sink gets.

Of all tankless I've bought for home use, Rinnai my favorite, the other brands ask for bad parts sent back, Rinnai never did that to me.

KenO · Dec 9, 2019

Dr. Dendrostein said:
Of all tankless I've bought for home use, Rinnai my favorite, the other brands ask for bad parts sent back, Rinnai never did that to me.

That’s good to know.

KenO · Dec 26, 2019

I received my NG gas bill and I wanted to give an update.

First of all the NG heating system has been working great, I am now keeping the tank at 78 degrees vs 75 last winter.

In looking at my NG bills, here are the numbers:

Previous bill (Oct-Nov 2019) which was prior to installing the tankless hot water loop was $20.21.

Last year for what is my current billing cycle (Nov-Dec 2018) it was $27.18.

This bill that just came (Nov-Dec 2019) was for $28.59.

My last bill came on 11/22 (Oct-Nov 2019) and the system went live on 11/26. So it was close to a full month's cycle. So based on the slight increase in my NG bill, I am going to say it is costing me about $0.30 cents a day to maintain my 600 gallons at 78 degrees.

I think it was a success.

Blue Spot Octopus · Dec 26, 2019

Bravo, I did not think it was going to work as good as it did.

KenO · Dec 26, 2019

Blue Spot Octopus said:
Bravo, I did not think it was going to work as good as it did.

I too was blown away by the numbers. I'm assuming around and $8 increase. Thanksgiving was in this cycle and I have a gas range and oven. I did a lot of baking and cooking for Thanksgiving. In addition our weather has turned a lot chillier so the water coming into the house is colder so all 3 of my tankless heaters have to work harder to raise the water temp up for showers, laundry and kitchen.

Anyway I look at it I'm glad I did it.

Dr. Dendrostein · Dec 26, 2019

KenO said:
I received my NG gas bill and I wanted to give an update.

First of all the NG heating system has been working great, I am now keeping the tank at 78 degrees vs 75 last winter.

In looking at my NG bills, here are the numbers:

Previous bill (Oct-Nov 2019) which was prior to installing the tankless hot water loop was $20.21.

Last year for what is my current billing cycle (Nov-Dec 2018) it was $27.18.

This bill that just came (Nov-Dec 2019) was for $28.59.

My last bill came on 11/22 (Oct-Nov 2019) and the system went live on 11/26. So it was close to a full month's cycle. So based on the slight increase in my NG bill, I am going to say it is costing me about $0.30 cents a day to maintain my 600 gallons at 78 degrees.

I think it was a success.

Impossible! !!!.......Hahaha

Dr. Dendrostein · Dec 26, 2019

Awesome, comrade

Mical · Dec 26, 2019

Awesome endeavor! Hats off to you for taking your idea to functional.

Dr. Dendrostein · Dec 26, 2019

Thanks for sharing, I'm in planning stages for small camping tankless on LG. the run time should be short. I'm in always sunny Callyfornia, so 100 gallons total volume tanks are outside. Can't wait to start.

KenO · Dec 26, 2019

Dr. Dendrostein said:
Thanks for sharing, I'm in planning stages for small camping tankless on LG. the run time should be short. I'm in always sunny Callyfornia, so 100 gallons total volume tanks are outside. Can't wait to start.

Post your plan once you get it done.

KenO · Dec 26, 2019

Mical said:
Awesome endeavor! Hats off to you for taking your idea to functional.

Thanks! Now I'm wondering if I should try bumping my temp up to 80? Not sure if it's worth it.

The Aquatic Arsenal · Dec 26, 2019

Very nice write up! Thank you dor sharing!

KenO · Dec 26, 2019

The Aquatic Arsenal said:
Very nice write up! Thank you dor sharing!

You're Welcome!

Daniel@R2R · Dec 27, 2019

Very cool setup! Thanks for sharing!!

KenO · Dec 27, 2019

Daniel@R2R said:
Very cool setup! Thanks for sharing!!

Hopefully it will help someone else who might be thinking about this.

Todd Jacobs · Dec 27, 2019

I have a tankless sstem for my homes hot water and im happy with it takes a few min to get hot water to top floor but once its hot its great my question is because u have copper pipe on outside are u testing for copper levels in ur tank and why not use pex pipe outside so no copper pipe is being used at all ???? But that being said u look like u have one great set up

KenO · Dec 27, 2019

Todd Jacobs said:
I have a tankless sstem for my homes hot water and im happy with it takes a few min to get hot water to top floor but once its hot its great my question is because u have copper pipe on outside are u testing for copper levels in ur tank and why not use pex pipe outside so no copper pipe is being used at all ???? But that being said u look like u have one great set up

The copper is only on the domestic hot water side. The aquarium water never comes in contact with the copper pipes.

TheReefJunkie · Dec 27, 2019

Nice idea! I’ve worked in the mechanical (HVAC/R) for 20+ years. Just be sure to keep and eye on your calc and mag levels and watch the temp difference on the supply and return of the heat exchanger (reef side). Heating the water indirectly (via a second heat exchanger like you’re doing) “shouldn’t” cause any issues but it depends on the temp rise across the heat exchanger. Calc, mag and other properties in the water will precipitate out of the water column and eventually plug up the heat exchanger. That’s why the manufacturer demands water purity for the on demand heater itself - due to the crazy temp rise across the heat exchanger. Interested how this works out long term. Following!

afuel · Dec 27, 2019

TheReefJunkie said:
Nice idea! I’ve worked in the mechanical (HVAC/R) for 20+ years. Just be sure to keep and eye on your calc and mag levels and watch the temp difference on the supply and return of the heat exchanger (reef side). Heating the water indirectly (via a second heat exchanger like you’re doing) “shouldn’t” cause any issues but it depends on the temp rise across the heat exchanger. Calc, mag and other properties in the water will precipitate out of the water column and eventually plug up the heat exchanger. That’s why the manufacturer demands water purity for the on demand heater itself - due to the crazy temp rise across the heat exchanger. Interested how this works out long term. Following!

Ditto on this subject. I would worry about build up in the heat exchanger over time and if that time comes the only way to clean it out is with chemicals like a scale dissolver. Tankless water heaters need to be be back flushed annually with chemicals I would think that the heat exchanger would need to same attention