Replacing water storage tank - does new one need to match current specs?

[solarvt]

Hi,

We have a two-panel residential solar hot water system with a Rheem 80-gallon storage tank which recently gave up the ghost after many years of service. (this system came with the house we bought 20 years ago, and we have been maintaining it ever since.)

1. Does a new tank need to match the old specs? In particular; the coil exchanger size and capacity? An identical-replacement Rheem is super-expensive (model Rheem 81V – 80HE – 1), with most available replacement options coming in at at least half the price. Looking for advice in finding a new tank. Current spec: 80-gallon tank with a exchange coil capacity of just over 2 gallons. Three-person household in the northeast, for which this 80-gallon tank has been more than adequate.

2. If we replace the tank with one which has an electric backup, can we use this tank with a future PV system for PV-powered hot water once our aging solar panels inevitably fail? ie. Would a tank with electric backup be suitable for regular electric use?

Thanks!

 

[OzSolar]

1. Does a new tank need to match the old specs? In particular; the coil exchanger size and capacity? An identical-replacement Rheem is super-expensive (model Rheem 81V – 80HE – 1), with most available replacement options coming in at at least half the price. Looking for advice in finding a new tank. Current spec: 80-gallon tank with a exchange coil capacity of just over 2 gallons. Three-person household in the northeast, for which this 80-gallon tank has been more than adequate.

In a perfect world you would replace it with an identical tank, but pretty much any solar tank you find is likely going to work. Also, I wouldn't fixate on the coil capacity, rather I'd try to search the specs of the tank. Look for something like "for up to two 4 x10 panels".

Due to the very limited selection of solar hot water ready water heaters, they are all going to be pricey. This may be a good time to look into using regular tank and an external exchanger. It would be a bit of a project and you may not have the room for it.

2. If we replace the tank with one which has an electric backup, can we use this tank with a future PV system for PV-powered hot water once our aging solar panels inevitably fail? ie. Would a tank with electric backup be suitable for regular electric use?

Yes, assuming I'm understanding your question.

 

[solarvt]

Thanks for the reply.

Also, I wouldn't fixate on the coil capacity, rather I'd try to search the specs of the tank. Look for something like "for up to two 4 x10 panels".

Unfortunately, I haven't seen anything regarding panels in the specifications that I've seen. e.g. Vaughan, Bradford White, Rheem. It looks more like "first hour rating" and "continuous rating" (gallons per hour) Vaughn spec sheet here, for ex.: https://www.vaughncorp.com/residential/special-purpose/solar-65-119-gallon/