My next project natural gas tankless hot water heater.

[pinballlooking]

It power vents so the blower motor has the biggest power use.

Yes it uses 89 watts in operation and 4.2 watts in standby. 175 watts in freeze protection mode but it is in a insulated garage so it should not have to use the freeze protection mode.

[Daox]

Wow, that is a lot more than I would have expected.

[pinballlooking]

I would have liked it to use less power in standby. It can vent up to 100 feet so a blower motor is a must.
The Navien NR-240A-NG I was looking at uses 200 watts.

[stevehull]

Originally Posted by pinballlooking

I have a Bosh AquaStar 170V. My family has grown since we put in that tank. It does ok but we could use more GPM now. My old unit has a pilot and was about 80% efficient not too bad. It also does not keep the water at as a steady temp as the new electronic controlled tanks.

Pinball,

Interesting. I also have an Aquastar 170VP (P for propane), purchased in 1987.. In that time, I have had to do a few fixes (thermocouples, rebuild kit for modulator value), but am thinking of another unit. My main gripe is that the water modulator valve does not keep water temp as well regulated (just the same as you) as I would like. It owes me nothing and has long since paid for itself (perhaps several times over).

How did you choose the replacement and how much $?

Oh, I forgot, with large winds, the pilot light of the 170VP would blow out, but this was easily relit. It would be nice to have electronic reignition . . .


Steve

[pinballlooking]

Steve

I had all the same issues you have had 170V except for the thermocouples.
I finally increased the holes in the screen for the pilot light. So the pilot would no longer go out.

The 170V is 80% efficient so like me you won’t see a big savings switching to this tank. With no pilot you will see some.

I really liked the Navien NR-240A-NG my neighbor installs them. If you buy them over the internet they will not warranty them. They will not talk to a home owner for any repair so that ended me buying that one.

My neighbor the Plummer said stick to Navien, Rinnai, Takagi.
I almost bought a Rinnai but you have to use their special vent pipe and that stuff is so expensive.

The Takagi has a 15 year warranty on the heat exchanger even with a circulation pump control as long as you use a aquastat and/or timer
http://www.takagi.com/download/2013-Warranty-info.pdf
You vent it with 3” PVC this is cheap and I can easily do this myself. I love the Energy Factor of 0.95.

You can get a smaller unit but the bigger unit does not use more gas than the smaller one unless you are using lots of water at the same time. So it really does not make since to go with the smaller unit. The cost difference is not that much either. My Plummer friend told me don’t even consider on less than 199000 BTU’s

The electronic controlled water temp is so much better than on the 170v I did a long shower today and I did not need to adjust the temp at all.

The Takagi has free isolation valve and pressure safety valve kit deal. (this really saves money)

I bought it from build.com and found a coupon code. I paid $1,096.16 shipped with isolation valve kit.
Takagi TH3DV - Build.com
Mark

[stevehull]

Ok, need some help here on what to do re water heater (fits right in with this discussion).

Old home, now for sale, has the 25+ year old tankless Aquastar 170. Next year, we are tearing down old farmhouse where we live now and rebuilding on foundation. Lots of reasons, but cast iron pipe plumbing is clogging up, old electricity/wires in house are bad, roof needs repairs, etc, etc, etc. We knew it was temporary housing when we moved here.

Anyway. I do heat/cool former and present farm house with open loop GT heat pump. In the summer (May - September), I have a loop from desuperheater that essentially fills a 55 gal electric water heater to capacity (120 F) each day (old farmhouse). I turned off one element as I super insulated this "preheat" tank. At least that is what I called it before I found out GT heat pump/desuperheater would fully heat it up in the summer.

I will move these (heat pump/water heater tank) out of old farmhouse and will reinstall in home when rebuilt. In meantime, while rebuilding, we will live in mobile home on property (also heated/cooled with GT heat pump and use an electric water heater storage tank for stored summer desuperheater water).

For the other six months, I have used electric resistance heat for this water, but I kick myself as this is one of the poorest uses of 1 phase 240 VAC. Clearly, in the mid winter, like now, I get almost no hot water from the desuperheater and use resistance heating for hot water.

I do have (and will have) propane so I could easily plumb in a tankless water unit in the rebuilt farm house, after the pre heat tank, to fire up if there is not enough hot water (turn off tank resistance elements).

My thinking is that my ROI is probably best just using the existing tank. However, we have LOVED the efficiency and use of the Aquastar as it supplied gobs of endless hot water. When we had three young children, this tankless water heater was a wonder to behold.

But it is hard to complain about essentially free hot water from the desuperheater for 1/2 of the year . . .

Thoughts?

Steve

[pinballlooking]

In your situation a 40 gal gas energy efficient hot water heater with an active pilot would be good.
When you provide it hot water just the pilot would be almost enough to keep it warm. Then in the winter the tank could provide hot water at a reasonable price. The price to get one will be less than a good tankless heater.

[stevehull]

Pinball,

Had not thought of that solution! You are correct that a high efficiency propane fired tank unit is far cheaper than a tankless. I can plumb the GT heat pump desuperheater heated tank in before the propane fired tank and turn off the electric resistance elements.

We have propane as we both dislike electric resistance element stoves and also use propane for the dryer (in winter). In summer, the clothes line works . . .

In thinking about this, I can actually use BOTH tanks to store water (clearly water not as hot) and have a larger reservoir of preheated water. First, fill the propane fired unit with desuperheater water and when that is full, fill the storage tank behind it.

Easy to do; just plumb the supply line with hot water from GT heat pump desuperheater and have the return line come from storage tank cold side.

Great suggestion.

Steve

[pinballlooking]

I have added a small expansion tank , a check valve and a recirculation pump.
I did a loop back return with Insulated ½ pex on my hot water line.

I added insteon home automation switches in the bathrooms and at the kitchen sink.
When you turn on the bathroom light I kick off the recirculation pump for a set amount of time. It depends how far the bath is from the tank as how long I run the pump. It either times out say for 2 min or when you shut off the switch it will also turn off the recirculation pump. I will also set it to run before the boys go to school because that is a set time each day.

I really like this setup I am not wasting natural gas by running recirculation pump all the time but I don’t have to waste water and wait a long time for hot water.


The only thing I have left to do is add in the aquastat and experiment with my inverter for when power goes out.

[pinballlooking]

Here is a picture of the small expansion tank, a check valve and a recirculation pump.
It looks like an erector set now.

I also put in condensation drain the top part of the condensation drain I put in clear tube so I will always know if it is draining.

In another blog I saw where someone else put in a flow switch so whenever someone turned on the hot water they would kick off the recirculation pump. So if they went into the bathroom the would turn on the hot water for a couple seconds then when they came back the water would be hot. They also used a aquastat to save energy. (I like my setup better but his setup if cheaper to install)

I changed the ½ bath to run the pump 30 seconds because it is close to the tank. This new tank is really working well it keeps the water a very constant temp unlike my old tankless water heater.

We keep our water pressure pretty high so that is why I added the small expansion tank.