Replacing old nat. gas Apollo Hydroheat 50gal in improved 1,500sq ft. ducted basement. EnergyGuide reads: "First hour Rating 98 - Model(s) A5 50 65.ONQRT8 5FJ - Only models with first hour rating of 87 to 99 gallons are used in the scale." Got a good plumber but he's never even seen an old hydroheating system before viewing mine. He recommends an AO Smith with first hour rating 93 - Recovery rate 90degree = 67 - energy factor .058 at 65,000btu input. This GCVX50 is replaced by GCRX50L which has first hour rating 98 - Recovery rate 90degree=61 and energy factor .060 at 60,000btu input. Which one would work better or is there a water heater model better suited for replacement? Advice appreciated.

either sounds good

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"Measure Twice & Cut Once" - Retired U.A. Local 1 & 638

From what I read, that is a combi-boiler of sorts. In other words, there is a coil inside a water heater that supplies the hot water for an air handler. I think those first hour ratings are on the DHW. Are you currently, or do you plan on using it for DHW also?
[www.htproducts.com] Scroll down and watch the presentations by Dave Davis. It's a great product, but like any other it has it's limitations. You need someone that specializes in HVAC, that understands what you need, and the limitations of any product selected. If not, you will most likely be left holding the dirty end of the stick. A traditional hot water heater is not designed for that application. Typically hot water heaters used for space heating fail rapidly (limitations)



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Thanks for the reply. Developer ran through the neighborhood in the mid 80's installing these hydro-heating systems as a cheap alternative to full gas furnaces. The heat exchanger/blower/Grundfos pump box sits below duct work entry no more than 15ft from 50gal Apollo water heater. The water heater has two additional side connectors to cycle hot water to and from heat exchanger via the insulated copper tubes. The water heater ALSO has the conventional connectors to provide domestic hot water for the shower and faucets. I actually had two of these units, one for the 3 bedroom upstairs (which I switched out to a gas furnace) and this second Apollo unit in the 2 bedroom, living rm, kitchen, bath, downstairs in the improved basement. Can't change out downstairs dug out basement because I don't have the space required for a water heater and gas furnish in the area currently housing just the Apollo water heater.
Oddly enough, this system is from 1988 and it has run extremely well and has provided adequate hot water for both domestic water use and heating. I've always thought of the Apollo as a super heavy duty glass lined heater that was designed to heat and provide DHW. The Apollo company went under years ago and my worry now that putting in a "regular" heater might run me out of hot water frequently. Did watch the Dave Davis videos, incredible system but might be overkill for 1,500 sq ft. I'm heating. Lowest it gets downstairs without heat in winter maybe 45-50 degees.
No one in plumbing or heating/cooling is familar with these systems. Had a noise reverberating through the upstairs unit years ago and plumber said to get a HVAC guy to check the system. They HVAC guy came out and said it was a thermo coupling problem on water heater - get a plumber. Realized years later it was actually the bearing in the Grundfos plump going out that created the noise traveled from heat exchanger to water heater.

Thanks for the reply, the plumber has been really upfront about letting me know he's never worked on and knows nothing about this system (see reply below) which is why I'm looking for additional confirmation before going through changing out a water heater that has to provide DHW AND heat the downstairs improved basement.

At best, you had 55000 btus available for space heating, if you have their largest unit. You probably would be best going with a wall hung combi boiler. Your biggest challenge will be finding one that is small enough for the space heating. I'm not a big fan of Navien but some of theirs are limited to about 50k, regardless of the fact they claim differently. They have a 5 gpm circ inside that limits them to 50k max.

I'd suggest you get as much information as possible off the hydroheat unit, and the air handler, and go to heatinghelp.com. They will steer you at units that will work for you.

Once again, thanks for the help Paul. Thanks to you, I noticed for the first time that it states on the heat exchanger box: "water coil: hot water only max temp 190 max psi 100. Don't know what that means but I included it in my question over at heatinghelp.com.



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