Converting from solar hot water to a traditional hot water system

jack63ss · January 22

We have had solar hot water since 1978 and it has been great except for one thing. I have already replaced my tank twice and it appears I need to replace it again. First two tanks rusted out, so the current tank is stainless steel. However it appears the pipes in the tank rotted out so I need to replace it again. When we replaced it 13 years ago it cost us over $2500, and I can imagine what it will be now. So we decided to investigate going back to a traditional system.

The way our system works is that the solar tank system pre-heats the water before it goes thru the furnace. My first question is what is the probability my furnace can create enough hot water by itself ? My household is only 2 people, so usage is not that high. Second, what type of electric water heater would we need in this situation and should it be before or after the furnace ?

Thanks

Jack

hot_rod · January 22

I'm the #1 fan of ST, my first question is what the failure of the tank is.

By far the longest lasting solar tanks I have seen are the stone lined, Ford, Vaughn and private labeled to US boiler and others. The stone lining counteracts some of the water conditions that take out other tanks.

Bottom line, 2 people probably do not use a lot of HW unless you fill a large soaking tub daly? or 30 minute showers.

48 year old collectors probably don't owe you much?

What are your fuel options? Gas, LP, electric?

Electric HPWH may be the most efficient way to go. Incentives in most areas make them first cost very affordable, check here for what incentives are in your area.

www.dsireusa.org

The jury is still out on the expected life cycle of HPWHs. . Aggressive water that may have taken out the previous tanks would take out a HPWH also, possibly. Compressors and controllers would be an $$ repair down the road.

Gas or LP tanks seem to go about 7- 10 years, again depending on you water.

Yet another popular option is a tankless gas or LP.

I'm not sure what you mean by furnace? many solar hot water systems are two tanks, the solar preheats before the main water heater. Some of those 1970 vintage systems also supplied hot water to a fan coil, like a Myson. So you would get heat and hot water, from the solar is that what you have?

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ethicalpaul · January 22

I installed a solar hot water system in my last house with no hope of ever recouping the cost (a hobby).

Today, I would just install a heat pump water heater, with a 50 gallon tank that would more than suffice for any two people

The jury is still out on the expected life cycle of HPWHs.

But we know that traditional water heaters today are not expected to last more than 7 years so what exactly are we afraid of regarding heat pump water heaters?

hot_rod · January 22

https://forum.heatinghelp.com/discussion/comment/1883509#Comment_1883509

The concerns from installers on various plumbing discussion lists are a rash compressor failures within the first year or two.

7 years would be reasonable, especially if it was a "free" HPWH, covered by incentives :)

Larry Weingarten · January 22

Hi, I must be the number two fan of solar thermal, having started installing in in 1978. 😊 It isn't hard to get fifty years from a glass lined tank if you check the anodes periodically. I prefer to have two magnesium anodes in a tank, and then check them every six years or so, though this depends on the quality and conductivity of your water. Installing a powered anode eliminates that bit of maintenance. If you have copper waterways in your solar collectors and the water is not hard or aggressive, the collectors could still be in good shape. And, what do you mean by furnace as a backup heater? Is it a boiler that heats water? One more approach, if you decide to keep the solar is to use a Marathon tank, made by Rheem. It's plastic, with very good insulation and a lifetime warranty… no anodes to check. 😉

Yours, Larry

ethicalpaul · January 22

https://forum.heatinghelp.com/discussion/comment/1883518#Comment_1883518

You'll forgive my dismissal of a bunch of old dudes hating on new technology by endlessly repeating the same handful of failures they heard about from friends of friends, as opposed to actual evidence 😅 (see also, Pex, Sharkbite, ProPress, ad infinitum)

I love that Rheem Marathon @Larry Weingarten, if only they offered a heat pump version with that tank on it.

hot_rod · January 22

https://forum.heatinghelp.com/discussion/comment/1883527#Comment_1883527

How many plumbing chatrooms do you follow?

Experience from actual everyday installers is a good place to start. Or ask the counter personal at plumbing wholesalers. A drive around the back of any plumbing wholesaler give you some idea of what works and what fails.

Or call Rheem, A.O. Smith, etc and ask how many HPWH compressors they have warrantied. I'm sure they will share that info with you :)

That being said, I suspect a good portion are mis-installed, put in a small closet where the previous electric of gas tank resided.

The fact that installation manuals have added a section about calculating the room volume seems to indicate more guidance was needed.

Also the outdoor air adapters are more commonly seen with the tank sales info. The vent adapters were not talked about when HPWH became mainstream. Now Home Depot sells them.

https://www.greenbuildingadvisor.com/article/attaching-ducts-heat-pump-water-heater

ethicalpaul · January 22

I hear you but still I would be hesitant to use conversation at a supply house counter for actual data.

Without jinxing myself, in a couple years when mine hits 7 years old with no hiccups I'm sure everyone will spread my story far and wide to restore Rheem's good name in the heat pump water heater space 😂

hot_rod · January 22

https://forum.heatinghelp.com/discussion/comment/1883537#Comment_1883537

You'd rather hear it from online armchair experts then than actual installers and service folks? :) I'll stick with the boots on the ground on this question.

If components were not failing, troubleshooters counter talk would revolve around what is failing I suspect. The fact that they are at the counter tells that they are repairing or installer plumbing components.

I do training for a few companies like this in my area , Any Hour has 150 trucks on the road in my area,100% service, no new construction. They have a wholesaler branch VMI vendor managed inventory within their building, just for their trucks, the counter manager can tell me exactly how may XX they sell or warranty per month.

I always ask the group of technicians, what is working and what isn't. See where maybe Caleffi can help with components, or new product potential. So I feel I have good eyes and ears on the going on's.

I suspect the same brand compressor shows up in many different brands, so maybe just a "bad batch" 😲

I like the concept of properly applied HPWH, I think they are still on an equipment, or quality control learning curve, however.

AI knows 😀 which runs in line with what the service techs in trainings are experiencing.

ethicalpaul · January 22

No, I’d rather hear it from actual data. But that doesn’t exist. But the lack of actual data doesn’t mean I swallow whatever opinions are out there. I’ve heard many incorrect opinions as I’m sure you have.

People have a tendency to spread negative stuff far and wide about stuff they are afraid or ignorant of, while keeping quiet about the stuff they are comfortable with. Confirmation bias. I even suffer from it myself so I try always to doubt my own opinions first!

hot_rod · January 22

https://forum.heatinghelp.com/discussion/comment/1883564#Comment_1883564

Actual data comes from actual people doing the actual warranty repairs. What lacks is an independent group compiling the data and making it available. YET! Bits and pieces of the failure numbers is out there when you ask around.

Larger, progressive companies track product failure rates in their software. That info often gets shared throughout users of the same software. The last thing they want to do is sell a product with a high % failure rate.

I rather doubt the big manufacturers that have compressor failure data will openly share that. Or the compressor manufacturers themselves?

No different than a steam boiler model with high failure rates, word gets around. Very quickly in this day and age.

Converting from solar hot water to a traditional hot water system

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