Tankless Boilers

Kevin_16

Hello All,
I was just wondering if anybody out there has successfully used a tankless water heater in a radiant heating application?

More specifically if anybody has used a tankless water heater in a snow melt radiant heating application where you are putting glycol through the "tankless" "on-demand" water heater?
All your input is greatly appreciated!

Mark_7

tankless

nothing in Rinnai's manuals about glicol, units can be used for radiant heat. would have to e-mail techline on the glycol question.

Paul Rohrs

Rinnai

We have a Rinnai Continuum heater as a "BTU generator" for a slab on grade radiant job. It is finishing its 2nd year of heat without a hiccup.

I designed it for a zingle temp, single zone (by circulator). The t-stat calls for heat, enables the pump relay, flow through the unit actuates the modulating burners. Rinnai has a separate controllert-stat that we can use as a setpoint control. Water out at 110°, returns at 90°, and the modulating burners fire to accomodate. Yes, I have heard the concerns about head-loss and potential cavitation, but I have not experienced it.

You would really have to monitor a snow-melt application. The glycol might provide more head loss and long-term ph issues than you would care to deal with.

I also had an idea to put a Tekmar 361 on in conjunction with a constant flow application. Let me know if you are interested in more info.

Regards,

PR

Weezbo

an old timer....

once said that idea that i had was more of a long tem nightmare than it would first appear. i totally respect his opinion. something about the design of flash water heaters being incompatable with the recirc system in the long haul.however...my thought was control of the burn times and say a small 20 gallon as a storage mixing tank and Pump away from it.i gave the idea up years ago because he was rather eloquent in his experiential elucidation.....i like to hear of sucess stories so lets keep touching on this subject over the next few years....It is just a belife i have that indeed there may be some improvements in designes....

Kevin_16

Tankless Improvments

Actually you are right "old timer" their have been many improvements on the tankless water heaters. In particular I have some experience with the Takagi tankless water heaters. These heaters have there own thermostat in them to sense the incoming water temp. Therefore you do not need to purchase an extra aqustat. I have actually found that by using a recalculating pump in conjunction with a tankless water heater actually helps improve the efficiency of the unit.

Weezbo

Kevin....

the recalculating pump allows flow adjustments (much like a variable speed drive)to prescribe constant flow to prevent short cyccling?

Kevin_16

Play On Words

I aid that a recalculating pump helps the efficiency of the tankless system however I should have said that it help against any kind of freezing in the heat exchanger. Also this truly provides the customer with instantaneous hot water.

Kevin_16

Glycol

The only tankless heater that mentions anything about glycol is Takagi however I have heard some horror story's and I am just trying to see if their is any trut to them.

Kevin_16

Tankless

Has anybody used a tankless heater in a snow melt applications????

jackchips_2

Not snowmelt

but I am heating (during the season :-)) my pool with an Aquastar 240. It is tied in series with my 50 gallon water heater.

I heat the pool through a heat exchanger.

Kevin_16

Takagi

Have used a Takagi water heater or have you only used a Rinnia?

Paul Rohrs

Only Rinnai

Since I am a wholesale distributor, I only have Rinnai. I think it is a very well engineered product. Some space heating applications are ideal for these units, as opposed to a tank-type heater at 52% efficiency. Our tankless is at 82% and is modulating 10ea 19,000btu burners.

It only has a 58 heat exchanger and I think coupling that natural head loss with a high percentage glycol would cause major long-term, and maybe some very short term issues.

Also,check your email, let me know what you think about this alternative tankless application.

Regards,

PR

Kevin_16

Rinnia??

Why do you chose to sell Rinnia as apposed to Takagi? Do you think their is something better about the Rinnia unit?

Paul Rohrs

Wholesale

It is a major $$$$$ expenditure to stock the line right now. Indoor units, exterior mount units, residential, commercial, Nat Gas & LP. You have alot to stock right there, let alone the OEM concenctric vent material specific only to Rinnai. We have quite a bit of inventory, it would be a huge conflict and an uncessary budget fiasco for us to try and stock a second tankless line. And......Rinnai is a good line that performs well at a good price. Having said that, I still design around injection mixing, outdoor reset or condensing boilers with reset.

Regards,

PR

Mark_7

Rinnai

Dosen't Rinnai also give more GPM for the money?

Jack_23

GPMXDelta TX500=BTU

With any on demand heating appliance this formula represents the whole game. 500 is a constant. With a 009 you will get 4-5gpm thru a Rinnai 2532FFU C (commercial, which is req'd for space ht). Therefore the only number you can push around is the temp. Remember, while approved for space heating this unit still will operate like a water heater. It reads the incoming flow and temp. It looks at its set point temp and fires the appropriate amount of gas to reach it's output tmep. At 5gpm and 20dt it yawns and does its thing...at a very low firing rate. realistically, you are rarely going to get more than 60kbtu out of it although I know one fellow, who was damned sharp, who cascaded the return water temps (hydro-air and radiant) and got 120kbtu. I like them on low temp systems. Less so on baseboard and if used on baseboard, give it a break and run it at 160 as opposed to its max 180 output temp. At 180 I had one baseboard system bring the limits into play. Dropped to 160 and the problem went away. Primary secondary is best unless a very short loop. Get the high pressure drop off your distribution system with P/S. Put some vol in the primary. Glycol just adds viscosity to the flow/head loss for the primary circ. A high glycol mix requires a bizarre circ,IMHO. Go to www.rinnai.us, register and ALL info is available to you.

As this product is viewed as a hi priced water heater, which it isn't, and a cheap boiler there are a lot of heat apps out there. I can tell you that as the Rinnai rep I spend more time on heat jobs than on HW by a wide margin. Do your home work. You swing for the fences on your early jobs and I'll be seeing you. Hit singles and move guys around the bases. I love the product. It works. No on-demand water heating product has been successful long term in this country due to a lack of flow and technology. Rinnai has the technology/flow rates and they work beautifully (when properly applied by a guy who cares)and they (and the others)will change the way we heat hot water in this country. After all, we are the last tank type water heating market in the world.

If you are going to install Rinnai's you must become factory certified. Rinnai has been doing business in the US for over 20 yrs. They are very well established. They expect oto build a plant in the US in about 5 yrs. There have been many Far Eastern/European companies who get into and out of the US market. Look at the Mini-split AC folks who were in and out. Valiant anyone? Rinnai has an excellent tech group. This is especially true concerning unit operation. They haven't seen it all on systems, but they have had a hell of an education.

Another Rinnai product you should be looking at is the Energysaver direct vent wall furnaces. I don't intend to replace your furnace or boiler sales but every contractor has 1,2,5,10 or more jobs /yr where they are the perfect product. The most expensive in their catagory, but they will heat more for less than those who try to compete with them. Good, dinners on the table. Good thing, eh?

Brad_3

Rinnai eff.

Jack,

I asked Rinnai about difference in efficiency in the Rinnai unit at different firing rates, got no answer except it's 87% period. Can you get a more accurate answer? I only need 12k BTUH and will have a buffer tank, so better to hit it hard or soft for effiency?

Brad