My Tankless Hot Water Heater

Oldman · August 12, 2006, 05:10:11 PM

I was reading about our tankless gas hotwater heater. It states it will put out a 90 degree rise @135 gallons per hour. Given that our ground water now is reading 85 F that comes to 175 F. However, the maximum temperature it will allow is 140 F. If I set it for 120 F then I guess what I was told that I should be able to get 200 gallons per hour @ 120 F. sounds about right.

What do you all thinK?

Habanero Smoker · August 13, 2006, 04:54:14 AM

I can't help you on this one. If the theory works on a straight math formula, that sounds about right. If you install one, I would be interested in your final opinion. I've been thinking of one every since I saw a similar system watching Bob Villa. I don't use hot water that often, and it pains me to be heating 30 gallons of water that will be only used a few times a day.

Oldman · August 13, 2006, 06:57:01 AM

Hab, back in the early - 80's I built my first "portable truck-mount" carpet cleaning machine. To heat the water I used a 120,000 BTU Paloma that looked much like this Paloma below. It was a twin burner unit. You could run one burner or both. There were not electronics in those days. How that unit worked was there was a diaphragm that had a bladder inside of it and a drive pin the would move up and down based on how much water flower through the bladder. The more water that flowed through the bladder the higher the drive pin would go up. The higher the pin went up the more it opened the gas value and that increased the amount of gas to the burners. In those days they did not use the type of heat exchanger technology we have today. It was a simple flame through a tall radiator.

Today these units price out from $1,100.00 - $1,300.00

I no longer remember the flow rate or heat rise, but something in the back of my mind says I was getting about 170F with full flow. The reason I say this is I remember removing the drive pin and replacing it with a longer one. Thus I was able to attain 200F - 205F degrees.

I used that unit for 3 years, sold it to another cleaner who used it for 5 years and he sold it to another cleaner. That unit got dropped a few times and it bounced in the back of a truck for years. It always created hot water. I think Joe the guy that got it from me had to replace the bladder one time. It was a used unit when I first got it.

I got the Rinnai unit as they are several out at the beach. Many of them for years with no problems. The one pictured below looks like my unit. The one I have is an Outside Unit.

It has a controller:

While you don't need these I strongly suggest getting a valve kit. This will allow a service person to work on the Rinnia unit without having to turn everything off.

Now I got my unit for $535.00 and change because I got it from the gas company. One of the pluming companies I had come out to bid on the pluming told me they get close to $1,400.00 for my unit.

Due to the fact I live in the city and I place this unit on the outside we had to get 3 permits, and had to use licensed contractors. (Big ouchie) as such I have $1,800.00 in this deal. If I had used an inside unit and placed it where my current tank is at I would have had to only use one contractor. The reason I placed it on the outside is I did not want my metal roof cut for venting. If I had placed it on the inside I would have had to get the vent kit. All in all with the vent kit I would have had about $1,100.00 into it.

I have no fears that this 120,000 BTU unit will do nicely for us because of our ground water temperature. Rinnai does make a 180,000 BTU unit - I believe that is the largest unit in a tankless today.

I checked around with people who have had this heater for years and basically they all said the same thing. It has never needed servicing. I further found out that if you place it in a looped system where it will run 7/24/365 it has a 3 year warranty. That is a strong call in my opinion give the continual heating of the unit.

Anyway I hope this information has help you understand a little about these types of heaters.
Olds

EDIT: In the 16 years that I have lived here with Susan we have had to install two tank heaters. Cost was about $350.00 each. If the Rinnai is as good as I'm told and as good as that old Paloma I doubt that I will have to replace it within my lifetime. When you factor in that the average tank heater cost of old unit which is around $500.00 per year and the Rinnai will cost us around $120.00 max per year that leaves a savings of $380.00 per year. Multiply that by the average lifespan of these type of units which is 20 years and the savings comes to $7,600.00!

If the house have been already "wired" up for this unit or if we lived out in the country then my only cost would have been the unit and materials as I could have done all of the work myself.

oguard · August 13, 2006, 12:51:16 PM

Those are great little units.The next time my hotwater tank goes I am gonna switch to an instant water heater like that one.Inexpensive to operate takes up less room I can't really see a draw back ;D.I will install it myself as I have the proper trades tickets.It is funny in B.C. canada a home owner can get a gas permit do all the work himself and have it inspected,for me to do it on someone elses house I have to have a gasfitters ticket(6 week course plus a 2hour exam) be insured and have business license.Oh how government works ???.

Mike

Habanero Smoker · August 13, 2006, 03:33:34 PM

It looks like I may have to do some searching. It would be a better situation for me if I can find one that works on electricity (if they exist). Well I got time. I wouldn't get to this until spring anyway.

Kummok · August 13, 2006, 06:41:28 PM

Quote from: oguard on August 13, 2006, 12:51:16 PM
....The next time my hotwater tank goes I am gonna switch to an instant water heater like that one.....
Mike

I was thinkin' the same thing Mike, but I got tired of waiting for the ol' girl to give up the ghost. Ordered a new propane Rinnai last Friday. Don't wait too long....right now the IRS (US) is giving a $300 tax CREDIT for installation before 07 (Dec 31). Here in Homer the smaller, non-commercial sized unit is running $1134 from the local propane vendor. Had a chance to buy a Bosch unit for $500, but they've built up a bad reputation up here.....not the appliances, just the demand water heater, due to complex venting demands.

car54 · August 14, 2006, 02:28:58 PM

For about 5 years I used a wood hot water heater. It was the same shape and size of a gas heater but it had a fire box. I would use kindling and it would take about 45 minutes to get the water up to almost boiling point. It worked great. All you had to do is plan ahead.

Brad

iceman · August 14, 2006, 03:16:12 PM

Quote from: Kummok on August 13, 2006, 06:41:28 PM
Quote from: oguard on August 13, 2006, 12:51:16 PM
....The next time my hotwater tank goes I am gonna switch to an instant water heater like that one.....
Mike

I was thinkin' the same thing Mike, but I got tired of waiting for the ol' girl to give up the ghost. Ordered a new propane Rinnai last Friday. Don't wait too long....right now the IRS (US) is giving a $300 tax CREDIT for installation before 07 (Dec 31). Here in Homer the smaller, non-commercial sized unit is running $1134 from the local propane vendor. Had a chance to buy a Bosch unit for $500, but they've built up a bad reputation up here.....not the appliances, just the demand water heater, due to complex venting demands.

Just curious Kummok on your incoming water temp. Mine is cranking out of the well at 48F. and 29 GPM. Do you think I could get enough temp rise to make that thing work? Seems like I'd have to have one heck of a heat rise to get hot water.

Oldman · August 14, 2006, 06:41:18 PM

Hab said:

Quoteif I can find one that works on electricity (if they exist).

Yes those are made. But make sure you do your homework on them. I looked at them and there is a big spread on power used and performance.

QuoteJust curious Kummok on your incoming water temp. Mine is cranking out of the well at 48F. and 29 GPM. Do you think I could get enough temp rise to make that thing work? Seems like I'd have to have one heck of a heat rise to get hot water.

Check into the 180,000 BTU unit. Check into the cap on the water flow. I sure you don't use 29 GPM of hot water now... or that is one heck of a hot tub you got. ;D For a family of 4 I would think the one 180,000 BTU unit would be all you need given your ground water temp.. Also in your case I would suggest an inside unit and then vent it into the attic at a 45 degree angle with one turn in it to lengthen the pipe so the heat from the unit would help warm up your attic. I would even look at adding a few heat sinks to that pipe. With enough sinks you might recover up to 80% of that heat for your attic. More than that and you will lose your exhaust movement. That would not be good... :o

iceman · August 15, 2006, 09:13:08 AM

Old's, do they make a unit that will vent out the side of the house? It's a thirty five foot plus reach to the roof from the basement and no attic. I don't have any penetrations through the metal roof and don't want any because of the snow build up. Your right about the water flow. The most at one time through the heater would only be about 6 GPM. The rest would just be cold water through irrigation piping.

Kummok · August 16, 2006, 01:11:17 PM

Iceman,
If you've got the room, plumb in an uninsulated water tank (plastic?) in an interior heated space to feed the water heater. That takes advantage of ambient heat to raise your water temp in the tank and then feed that "warmed" water to the water heater. In all honesty, I haven't taken our city water temp (yet!), but have "experienced faith" in my local propane dealer, Alaska Propane, and they're selling the Rinnais pretty fast down here. Our high HEA electrical rates are one of the factors.

After looking around, I've decided on the Rinnai 53i "indoor" propane model. try www.foreverhotwater.com . This model uses a flue arrangement similar to the Monitor and Toyo fuel oil stoves....vents directly through an exterior wall. Mine's going on the interior wall of the laundry room in the back side of the house, bottom floor ("daylight basement") and venting through the wall at about 4-5' AFG.

iceman · August 16, 2006, 02:14:46 PM

Kummok;
I just got back from Central Plumbing & Heating in Anchorage. They have the same one you're talking about. Anchorage Well and Pump has a 75 gallon plastic holding tank with top or bottom draw options that I can put in the basement. I went over to the owner of True Values house to see his installation. Nice set up. He has had his Rinnai for over 10 years and swears by it. The newer units are more efficient than his but he still saves a fortune each year with all the kids. I have to wait until I get the commercial kitchen done downstairs then I'm going for it. I still can't get over how much room you can save with those things. (Not to mention the money)! Thanks for the ideas.

Kummok · August 18, 2006, 11:06:30 PM

What is Central getting for there's??? I'm paying $1134 + 6.5% tax down here. Also....be sure that they sell you the right model for your fuel type, (propane or natural gas)...there's two different models and, as I understand it they aren't interchangable by changing "jets" like lots of gas appliances :o That's why they aren't approved for manufactured homes, since the home manufacturer never knows what fuel type the home is going to have where it ends up being located....

Oldman · August 20, 2006, 03:03:47 PM

QuoteOld's, do they make a unit that will vent out the side of the house?

I saw this image the other day. It is located in the master bedroom walk-in closet.

Kummok · August 21, 2006, 10:25:56 AM

Hmmmmm, a gas fired appliance in a closet where clothing can be piled up against it.......the 35 year + firefighter in me has thoughts of job security with this arrangement?!?!? :o Haven't seen the install instructions yet or UL listing, (still waiting for Alaska Propane to call me for pickup), but that install just doesn't seem right.......