tankless WHs

Rod Kotiga

TK-3 all day. With kids Tm-1 or 2 TK-3s tied together. Depending how north they live they should be able to take two showers at the same time with 1 TK-3. Hot tip, see if you can install it on an outside wall to keep the venting real short. For one it eliminates any condensate build up in the flue and class 3 s.s. venting is stupid expensive. This goes for any flash w.h. Recirc. hot water works great on these units too. Also webstone mfg makes valves for flash w.h. that should be law on these units, there sweet !! Webstone exp with a pressure relief valve. I forgot to mention another BIG plus on flash water heaters over storage tanks and that is when a problem occurs with the heating system and they eventualy do you still have hot water.

Rod at Piping Hot

[Deleted User]

tankless water heaters for radiant

has anyone tried it? sounds reasonable. any reasons not to?

Chris S

tankless

I have a home running on a Takagi tankless.
We set it up as part of a primary loop with high, & low temp radiant running off of it. First full season, but it's working well. I wanted to install a mod-con, but the customer wanted this.
It's a less expensive install, but I think the mod-con would use less energy.

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ScottRW

I looked into using tankless when I first started installing radiant. My suppliers' rep steered me away with the explaination, that the tanless heaters aren't designed to keep up with the demand that a radiant system could ask for. Sooooo, I never tried it. I'd be interested to hear from anyone else who's had success or failures using tankless for radiant. Thanks.
Scott

[Deleted User]

i'm asking simply

because the manufacturers say that it's a good idea. of course they would. and they've gone on to suggest tandem installs for larger systems. depending on the cost of the modcon, you could tandem 4-5 tankless and stage them, or use individual units per zone

Jim Wy.

We've done 7 radiant jobs using Rinnais over the last 5 years with three problems that need to be adressed.Be careful of where you choose to hang them because during certain stages of operation they can be a little noisey. Flush the system w/ clean water, if the little fiter gets dirty the unit doesn't get enough flow to heat well or even fire.In cold climates you should order the extreme cold climate vent terminal or the vent intake will freze shut & code out @ about 10 below.

Rod Kotiga

We've put in a few as well and they seem to work great. A few for radiant and one baseboard job. Definatly cheaper in price than the Knights we normally use but then again, it's no Knight either. We used Takagis exclusively for hot water now. Storing hot water is a thing of the past, and few of these things tied together would satisfy even the largest of monster homes out there. Never liked my mod cons working at 180 for a storage tank, what's the point ?
I do know that you might want to check the warrenty if you use it in a radiant application. Takagi I think is 2 yrs if used in a radiant as opposed to 7 if it's used for domestic hot water. That's the part we didn't like.

Rod at Piping Hot

[Deleted User]

warranty

very good point!

so, for a two person household who wash cloths in cold water, and seldom use the bathtub because they're showerers, what'd be an appropriate lp takagi?

Alan(OnVacationInOregon)Forbes

Tankless

We've done quite a few jobs using the Noritz tankless heaters for combi DHW/radiant applications. I like the Noritz because of the low pressure drop through the HX (10' of head, 2 gpm). We install a Taco X-block to service the radiant and the 008 circulators can easily handle that pressure drop.

Jim Wy.

It depends on your incoming water temp. as well as needed g.p.m. If they advertise 8.5 gpm thats on a 45 degree temp. rise,which is not very realistic in wy.our water comes in around 45* in the winter so we need to figure a 65* temp. rise for showering.You'de probably want to figure another 20+* for your kitchen usage.Sence a tankless varies fuel consumption w/ demand it doesn't cost any more to operate a more powerful unit. I would be reluctant to put in anything less than 180 MBH. in this area.

[Deleted User]

flash wh?

under-sink/point-of-use?

valves for flash w.h.? explain?

[Deleted User]

w.v.

well water; near constant 55deg year round

bob eck

Anyone that is installing tankless gas water heaters for domestic hot water are any of you installing a fiberglass holding tank before going into the tankless water heater to take the cold water temp from 45* F in the winter up to room temp like 60* - 65* F so the tankless would give more GPM than if water entering the unit is at 45* F?

[Deleted User]

hmmm, another good idea,

provided that the installation environment allows for it. the basement in this install would be about 60-65degs; saving 5-10degs

Jim Wy.

I would get that well water tested & consult a factory rep w/ the results. I've had to learn that one the hard & expensive way. Well water for different reasons can plug up a tankless unit causing lots of inconvienent service calls w/ no hot water.These units are awesome but not in every situation.

Jack

Have you reviewed

your customers heat bills against degree days, heat loss calcs?

[Deleted User]

good point jim

they can be sensitive to mineral content?

[Deleted User]

no, not at all

it's my sister's place, and she and her husband were wondering how wasteful their 60gal tank is, considering that it sits there burning up lp for such little use. but a smaller tank may be a more cost effective, simple route

ScottRW

Tanklees for radiant

So, back to the original post..... why would you (an installer), install a tankless instead of simply buying an electric boiler? I've used the Argo boilers with great success. Cost is less than a tankless, and they are designed for the long haul that a radiant system demands on a heat source. They hang on the wall and take up less space then a tankless. Am I missing something????
Scott

Rod Kotiga

Iv'e used those boilers too and they are very reliable but they take big power and will definatly involve an electrician and all of his T&M. Flash water heaters you just plug in.

Rod-

Mike East

Works great but...

you need to consider a few things.
1. Rinnai suggests that their unit should not be installed on heating systems with over 160 deg water. Low water temps, they say, can be maintained all day long.
2. Do not be fooled by the imput BTU of these units. A small on-demand water heater might be a 190,000 btu unit, but due to the way the unit restricts flow rate you really only have about 60,000 btu's available in a heating application. Remember if you are looking at a 20 deg rise, these units, on average, can flow at about 6gpm = or 60,000 btu.
3.Finally, remember that these are not condensing appliences and that they are "efficient" in domestic hot water production, because they only run when needed. When space heating you need to look at their cumbustion efficency and be careful when marketing them as a high efficient option to a home owner.

All that to say, I believe there are some great applications for them as space heating units, it is just not every case. When applied properly I believe the homeowner will be quite happy with them.

noplumber

Takagi

To answer your question, I would recommend the Takagi TK-3 that will give you 4.1gpm at a 80 degree rise. This will be good for a couple of showers as you mix down the hot water and this will give you enough flow for two showers at a time.

noplumber

Hard Water

Anything over 7 parts per grain of hardness will create big problems with all tankless units.

noplumber

Tankless

The use of tankless heaters on radiant low temp loops is fine. We have a bunch of these set-up in New England and they are working great. The use of these units on high temp systems (180) is not the ideal set-up. You will shorten the life of the copper heat exchangers at the high temperatures. Also be careful to check the quality of water to make sure you do not have hard water. The Takagi Tk-3 unit is probably the best in the market for it's size.

Mike.C_2

Thanks!!!

Thanks for all the people standing up for this use.
Also thanks to the other people. You know who you are.
I have used many Rinnai for heating purposes.
Now Rinnai does not recomend them for heating only purposes for the mere problem of inspectors having problems with some ratings. I like them very much in certain applications. I have also used a Noritz in some snow-melt applications and that works really good also.