Hi All, I was looking at the Polaris heating tank and I see so many sizes available. I'm looking to understand how to select the right size for my application and I really appreciate your input here. My total heat loss for our 1800sqft ICF house is 30200BTU/h for the main floor and 13500BTU/h for the basement so in total around 44000BTU/h for the entire house. If I will go with Polaris tank I'll use it for radiant heating and also for DHW system. I see they have 2 sizes 34 and 50 gallons and for each size 100K, 130K, 150K, 175K and 199K BTU/h. How to choose what I need. They recommend the 34gal for max 4 people and 50gal for more than 5 people. We are 4 so I'll go with 34gal but how I'll determine what heat size I need? Also, any feedback about Polaris tank is appreciated. Thank you.

Have not used Polaris tanks. Are they rated for radiant space heating? If your numbers are correct, then 100K and make your HR DHW zone highest priority. Or maybe something else that is smaller in closer alignment with your heat loss numbers.

The Polaris is a bit prone to short cycling in radiant heating applications. It has a simple on/off burner, with a narrow temperature band of operation hardwired into the control board design. That band can be opened up to prevent the short cycling if you're comfortable with component-level modifications of the control board (and voiding the warranty).

The HTP Versa series is purpose-made for combination hot water & heating applications, but HTP's Phoenix water heaters (which are quite a bit cheaper than a Versa) can also work. The Phoenix water heater burners have about a 3:1 modulation range, and won't short cycle nearly as easily as a Polaris in DIY combi designs.

I would plumb your system as in the picture below. It forces the cold water that enters the circuit when you shower(or use water) through the floors first.

This cools the floors in the summer.

And in the winter it preheats the water going into the hot water heater. Preheating the water takes some heat from the floors but the big advantage is that you will get almost endless shower because the water heater only has to heat the water up a little. Then once you are done showering the circulation pump will heat the floors back up. You will not notice the floors loosing heat, it is so very slight.

This will also allow you to size your hot water tank to your house heat load and not to a sum of them both.

Good Luck. I have used it on two of my houses and wouldn't do it another way. Some people don't like potable water in the floors but this circuit also flushes the floors every time you use water. I also don't use O2 barrier pex anymore because one circuit i did caused a funny taste in the water for six months because they coat the pex with some chemical.

https://www.radiantec.com/wp-content/uploads/opendirect_heating.gif

Yes, the HTP Versa would be a much better choice and we have successfully used them. While I understand the intent of what you wanted to achieve Newbostoncost, we could never recommend that approach. There is always the potential of having some loop that traps stagnant water and poses a potential health risk. That approach would also not pass code/inspection here.

The so-called "open" systems promoted by Radiantec and others are expressly disallowed by building codes in many areas.

They are allowed in Massachusetts, but only if the controls guarantee a minimum code-specified duty-cycle on all heating loops to avoid stagnation. That means under MA regulations you would be required to run your heating system on a minimum duty cycle even when it's north of 90F outside.

Using an exterior plate-type potable certified heat exchanger between the water heater and heating system water with separate pumps avoids the issue, and allows you to run the heating at different temperatures & pressures than the domestic hot water side. This topology works just about everywhere:

https://www.houseneeds.com/upload/images/media/hydronic-hot-water-heat-exchanger-wm.jpg

It has been pulled back out of the Michigan code. It was not allowed for one revision before being allowed again. It is a simple and in my mind a far superior loop to do with many less components.

The code said you couldn't use potable water for heating. That verbiage was pulled out of the main code. Not sure what it says in the NSPC. But my local officials have a hard enough time understanding the Michigan Building Code let alone going deeper into NSPC.

Heating system components are not required to be lead free. There are heating system components which use materials known to be carcinogenic. Today’s shower valves allow domestic hot water to enter the domestic cold water. Michigan doesn't exactly have a stellar reputation for keeping drinking water safe.

Hahaha...yes that Democratic city Flint is out of control.

Using components safe for potable water is quite easy. The hardest might be the check valve.

No the cause and false blame was Republican racketeer governor Rich Snyder and Republican hit man Bill Schuette who both just got kicked to the curb where they belong by the people of Michigan:

https://www.wsgw.com/the-flint-water-crisis-how-politics-caused-it/

https://www.motherjones.com/politics/2018/02/the-man-behind-the-flint-water-prosecutions-wants-to-be-the-next-governor-of-michigan/

And they now finally have Democrat governor Gretchen Whitmer actually trying doing something about it but are still hindered by Republican corruption like the rest of the country:

https://www.freep.com/story/news/local/michigan/flint-water-crisis/2019/01/02/gretchen-whitmer-michigan-flint-water-crisis/2463552002/

But if you are a delusional sucker ignorance is bliss.

Ouch...politics here?

Posted By rogerius on 11 Jan 2019 06:08 PM
Ouch...politics here?

Try not to feed the trolls, eh?

Just received the quote today and find out that the Polaris tank is 3x more expensive that a regular direct power vent propane tank. Based on this I'm thinking to use the regular heat tank for DHW and use the side connections with a circulation pump with heat exchanger for radiant heating circuit. The model is AO Smith G650T62P-PDV-ES2 (58K BTU/h) I verified and the regular tank is rated for this kind of application. Any thoughts? Will be 58K BTU/h too small for my case? My calculated heat loss for entire house is 44K BTU/h (including 15% safety factor)

The 67 gallons per hour at 90F rise indicates about 50,000 BTU/hr of burner output, assuming the entering water at the tank is cool enough.

http://www.gsw-wh.com/assets/documents/current/spec-sheets/GSW%20Power%20Direct%20Vent%20English%20GPD435N_0316rev1.pdf

If the 44K number has 15% of margin over your design condition load your real load is 38K? If yes, then the G650T62P-PDV-ES2 should have you covered for space heating even if combustion efficiency drops to the 80% range when the radiant is running at a very high duty cycle (which it might), but with next to no capacity left over for domestic hot water.

The G675T72N-PDV-ES2 would have enough to cover both with a bit of margin even under design conditions, but I suspect it's substantially more money.

Have you priced out the Phoenix Light Duty with the 76K burner? The Westinghouse branded version is a bit of the 50 gallon Light Duty with the 76K condensing burner is over 2 grand at Home Depot.

For even less money the 20 gallon RGH20-100F (100K burner, 20 gallon stainless tank) would have you covered if you don't have large tubs to fill:

http://www.htproducts.com/RGH75100.html

The Westinghouse branded version ( WGRGH20NG100F ) is under $1500 at Home Depot.

A 100K condensing burner has enough output to support a single 2 gpm shower with margin, but not two simultaneous showers + space heat. For a normal tub fill it's fine as you maintain a sufficiently high storage temp, but big soaker tubs could be a deal-killer. Even with a heating system drawing 50,000 BTU/hr out of it the recovery time between showers or tub fills would be very quick- longer than it takes to dry off, but quicker than it takes to dry off and get dressed. It's more water heater than the G650T62P-PDV-ES2 for your purposes, and might even be cheaper.

Warning...some of them are very noisy.....our is like a washing machine running with shoes in it when it is on. We use it to run our whole house with heated floor so it runs a lot. It has worked fine for 3 years but is loud.