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Old 02-29-16, 06:13 AM   #1
flavin
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Question Efficiency of Tank less heaters and programmable Thermostats

I am planning on saving money I spend on my house in Montreal every year. As an initial step towards energy saving is that I have changed my windows to UPVC windows. I am planning on even changing my fixtures in kitchens and bathrooms by changing them to low flow type and to a programmable thermostat or WiFi thermostats. As I was going through the web in detail about this and I found an article related to how to go energy efficient with our windows and other appliances. And I found that Tank less water heaters can save a lot of water and can contribute on our water bills. But my question is, what about installing Tank less water heater, I guess installing the entire setup can cost a lot. I have never thought about it. Any suggestion regarding Tank less water heaters and programmable thermostats.

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Old 02-29-16, 08:09 AM   #2
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Flavin,

Bon jour and welcome to the site! I have put in tankless water heaters in all my homes and it really is not bad at all. They come in natural gas fired and also electric.

Each has advantages and disadvantages, but they are simple to put in and not difficult. They have advantages of both efficiency and long life. And most countries give tax rebates for putting them in.

Most gas units need an ac 120 V power line (I believe the Bosch types use "D" size 1.5 v batteries), a gas line sized appropriately for the BTU output and a vent. Garage install is a snap as you don't need input make up air.

Do not think that bigger is better. The large units require a larger volume flow of water to kick on the heater. For example, the Tagaki brand has a 90,000 BTU (90 kBTU) unit that takes less than half a liter (quart) per minute to turn on the gas valve. But the larger kBTU units require more volume flow to kick on. For this reason, you can't trickle water out and have it warm.

You also need to size your unit in terms of water rise and water flow. For example, in Florida the cold water out of the ground is already about 70 F (20 C). A temp rise to 110 F (45 C) is easy to get and does not require a lot of gas (or electricity).

But your water is COLD - about 40 F ~ 5-6 C. It takes a LOT more fuel to get the temp up for home use.

There is a trade off: water flow vs water temp rise. You can use a small tankless water heater (say, 70 kBTU) on your cold water if you only need 4 liters (quarts) per minute of hot water. But most house hold use needs at least double to triple that in terms of volume flow per minute.

This larger amount prevents the infamous shower effect where one person is enjoying a nice warm shower and another unknowing person starts the dishwasher (or maybe knowing . . . ) . The reaction/words of the person in the shower are always interesting.

So let us know if it is gas or electric. A lot of us here have done one or the other - I have done both.

Steve
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Old 03-01-16, 02:34 AM   #3
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Programmable thermostats are super easy to install as well. A decent basic thermostat like the honeywell pro 4000 costs about $35 and installs in 15 minutes. 4-5 low voltage wires and you're done. Wifi thermostats are the rage now. There are a few honeywell wifi units in the $100-120 range, the nest are closer to $230.

Regarding the tankless, the bigger gas units require a larger gas supply pipe. My tanked water heater used 1/2" pipe, my tankless (190kbtu+) requires 1" pipe. Similarly with electric powered water heaters, typical tanked uses a 30 amp 240vac circuit vs. tankless might require 60 amp 240vac. Upgrading either gas piping or an electrical circuit might add a significant cost to the project. I love my tankless, family of 4 we often use less than $5 a month in gas usage.
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Old 03-01-16, 11:01 AM   #4
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I purchased an Eternal GU145S by Grand Hall. Very efficient in it's sweet spot, but I have had numerous problems I described in other posts. They now have a smaller one that can run on a 1/2" gas line. Might be ok if you swap out the plastic pressure switch for a metal one.

I got it because of the low head loss due to its combined tank/heat exchanger (which also eliminates "cold water sandwiches"), as I am using it in a combined DHW/hydronic heating system. Most tankless models have a tremendous amount of head loss due to the water path used to improve efficiency. A condensing storage heater such as Westinghouse's WGR050NG076 is also a good choice.
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Old 04-06-16, 02:43 PM   #5
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Some newer houses is "medium pressure" 2psi gas systems. You may be able to use the existing gas line and just add a $20 regulator.
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Old 05-29-16, 12:39 AM   #6
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Just noticed this thread, so am a little late but here goes.
We purchased a Bosch tankless at Home Depot in Mazatlan MX., price was about $250USD it uses propane.
We use it for an outdoor shower, and it works quite well. On occasion we have used it to heat our hot tub, 300+ gallons water in 50degF to pool temp 105deg F.
We sometimes use it to warm the hot tub up just a little prior to lighting the wood heater.
We only use hydrogen per oxide in the tub and change the water every 4 to 12 days depending on useage.
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Old 05-29-16, 06:30 PM   #7
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Since I am too cheap and lazy to replace perfectly good working equipment I would just put in a small hot water heater tank or tankless in the bath room or a hot water circulator on a timer.

Tankless heaters are cool but for $1,000 for a decent gas one to replace a working water heater, I don't know.

If you put a 2psi regulator on the main what happens to all the other 0.4psi stuff you have had all along?
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Old 05-30-16, 08:12 AM   #8
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Quote:
Originally Posted by oil pan 4 View Post
Since I am too cheap and lazy to replace perfectly good working equipment I would just put in a small hot water heater tank or tankless in the bath room or a hot water circulator on a timer.

Tankless heaters are cool but for $1,000 for a decent gas one to replace a working water heater, I don't know.

If you put a 2psi regulator on the main what happens to all the other 0.4psi stuff you have had all along?
Look at the Takagi, $500 buys a decent water heater.
2Psi systems are only in certain parts of the country.
https://www.socalgas.com/for-your-bu...vated-pressure
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Old 05-30-16, 11:39 PM   #9
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Just what I thought, everything still needs a 0.4psi regular.
Which I guess is better than running bigger pipes.
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Old 06-04-16, 07:23 AM   #10
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Regulators are only about $20 at supplyhouse.com

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