Which water heater to choose?

[furman90]

Hi,
This is my first post to The Garage Journal Board and would appreciate any advice you might pass along as related to water heaters.

We are in the process of building a workshop and need to have hot water in a couple of areas. We are not sure which water heater to choose.....tankless or the small capacity, 2.5 to 6 gallon, heater. The heater would be placed under/near the bathroom sink and one near the utility sink.

We have no experience with either type. Any suggestions; pro's or con's; personal experience? Any info. would be greatly appreciated.

Thanks,
Furman90

 

[Chaz]

A 2.5 gallon isn't enough to wash your hands well. A 6 gallon may be... I've never owned one of those . Tankless heaters are nice- but expensive on the front side.

 

[Ryf]

I would spend based on usage, tankless will save you big bucks on occasional use water long term. paying to heat water you dont intend to use for days or weeks is expensive. good luck with your build!

 

[porschedude996TT]

I have a small tankless that takes a while to warm up and it is under the sink. It also limits the total GPM flow rate with the aerator which is .5 GPM. An electric tank heater is a waste of energy since I don't spend everyday in the shop. I wired the heater with a 30 amp capability but I am reluctant to buy a larger one. I guess I have the best for the moment.

 

[plumbstupid]

You should give Bosch and Emax a look. I've installed both and they seem to hold up pretty well. Most of the small point of use W/H require a flow reducer at the areator. For a shop sink they are hard to beat. The big advantage is your not heating water when your not out there using it.

http://www.bosch-climate.us/product...r-heaters/bosch-tronic-3000-point-of-use.html

http://eemax.com/PointOfUseLowFlow

 

[justsam]

Sounds like you are considering individual Point of Use type units.

How are these to be powered? A tank less unit can be either and one that will do the job may take a lot of power, or if gas, requires venting and ample gas supply.

I would not recommend the small under sink tank less units. I have an Eemax SP3012 in my main home and at best it increases the water temp about 40 degrees. So if your source is about 40 degrees you get 80 degree water. Not really hot water. Of course I could use flow restrictors and increase water temp. but that is not what I would want in a garage.

What I have in my garage, and highly recommend, is a small tank type, in my case an Artisan (sp?) 6 Gallon. Been in place over 5 years, no problems, and works to wash hands, fill mop buckets, etc. It is 120V and no venting. I have not had an issue of running out of hot water for the things I do.

I do not know operating costs, but it is not killing me, even at PG&E rates.

 

[koditten]

Well water or city water? If you have a well, usually the water is "hard". This make using a tankless less atractive. They scale up from the hardness.

In our cottage, we have a conventional gas water heater. We leave just he pilot light going. The water is warm enough for a shower without lighting off the burner. The second shower will need to light off the main burner.

You can get timers for electic water heaters if you go that route.

 

[furman90]

Thanks 'Justsam'! Your reply makes alot of sense.

furman90

 

[jvitez]

Deciding on water heating is really about math, then opinion.

You need to answer a few questions: how much water will you be using all at once ("dump" load), and how long between uses? How fast do you need the water to come out of the faucet? How often will be using hot water, daily, weekly, irregularly? Hard or soft water? Does it ever go below 32F where you are? Is your shop heated?

A tank type water heat will be able to deliver about 70% of its volume once it's fully heated up to whatever thermostat setting you use, the the water cools off rapidly. Every heater has a Recovery Capacity, meaning how much water will it be able to heat in one hour by a certain amount of temperature rise. You can get this information from a sticker on the heater or on the manufacturer's website.

So, if all you need is to wash hands, rinse a few tools, fill a bucket once in a while, a 6 gal water heater will give you 4.2 gallons of hot water. Max comfortable water temp is about 100F, so if you set the heater for 130F you'll get about 5.5 gallons of 100F water before the tanks dilutes down. Is this enough? A 1500 watt element will take about 1 hour to heat 6 gallons back up to your set temp at average ground water temps. Can you wait 1 hour before needing another 5-6 gallons of water again?

Figure out the most you'll usually need and then you can calculate exactly the size and type of water heater that will meet your needs.

+1 on hard water: no tankless heaters unless you plan on a water softener.

BTW: if you don't freeze where you are, and you only will need to be in the shop irregularly, you can put a 120 volt water heater on a regular light switch, and simply switch it one when you go in the shop. The tank will be fully heated in about 1 hour, and you won't be wasting electricity heating water all the time.

 

[VHF]

I used an Eemax EX95T tankless unit in my kitchen for over a year to supply the kitchen sink and dishwasher. With 60F incoming water the temperature rise was adequate for this use.

9500W / 240V = 39.6A. Eemax recommend #8 wire. I put it on a 40A breaker. (I think NEC does not consider a tankless water heater to be a continuous load, so the 80% rule doesn't apply.)

Advantages of tankless include smaller physical size, no standby losses, unlimited hot water (subject to flow rate and temperature rise restrictions), reduced potential for bacteria growth, and no need for PTRV (unless required by local code.) (*All* tank type heaters (even little 2 gallon) must have a pressure-temperature relief valve.)

Disadvantages: Larger wiring required, higher instantaneous power consumption, cold water sandwich.

Elements of both tank and tankless water heaters will have a shorter life with hard water.

According the manufacturer:
NOTE: An EX95T (9.5 kW) unit at 240 V will deliver 1 gallon per minute at 65oF
temperature rise. For example, with incoming water temperature at 45F the
unit will produce 1 gallon per minute at 110F.

 

[Highbeam]

I used an Eemax EX95T tankless unit. Eemax recommend #8 wire. I put it on a 40A breaker. (I think NEC does not consider a tankless water heater to be a continuous load, so the 80% rule doesn't apply.)

.

I've wondered about this before. Even electric boilers specify a wire size that doesn't jive with the 80% rule. These are resistance heaters that are touted as supplying limitless hot water. Why weren't you required to feed it with a 50 amp breaker and 6 gauge wire?