Hot water to detached garage.

[Elbartolli]

What would you recommend? I have a single cold water line to my heated detached garage. I have a small bathroom and a laundry sink out there for clean up. There is natural gas as well as 100Amp service in the garage. I do a lot of painting as I am in the renovation business so I am cleaning brushes etc at least once a week.

I would like to install a water heater of some type but not sure which is the best way to go. Electric vs. gas. Tankless. vs tank...anything else I should consider. I am in Western Canada if that makes any difference.

Thanks in advance.

[SewerRatz]

If you go with a gas heater, I would recommend a direct vent or a concentric vent heater since you do your brush cleaning in the garage. These types of units draw their combustion air from the outside.

Rinnai makes a unit that would not break the bank and handle that single bathroom with no issues if you are interested in tankless that is. Its the R50LSi it is a concentric vent unit. One thing is you have to make sure the gas piping to the garage can handle a max load of 150K BTU's here is the link for this unit. http://www.rinnai.us/tankless-water-heaters/r50lsi/

Now if you rather have a tank heater, Bradford White DS1-40S6FBN. This unit is what they call a direct vent that uses the concentric vent piping. It draws the fresh air from the outside and has a sealed combustion chamber. Max BTUs is 42K so gas size piping is not a big issue here. These water heaters cost about double of a standard vent heater, but it is worth it for the safety of getting its combustion air from outside.

Now as for electric a 20 gallon tank probably would do the job perfectly for you, if you have a shower and like to take long showers maybe go with a standard 40 gallon unit. Its funny the 20 gallon units save lots of space but I noticed in many cases they cost as much as a 40 Gallon. You just have to have a 220 V line ran to it. The advantage is ease of install, and cost. disadvantage is your using electricity to heat the water which in most cases can cost more than a NG unit, and slower recovery time if you run the unit out of the hot water.

I do hope this helps a bit.

[jadnashua]

What things, other than maybe the cleanup sink, need hot water? How much volume at one time, and is good pressure a requirement? A tankless will have some pressure loss across the heat exchanger...some are fairly high, some are not. A small electric WH tank would be the easiest to install. In a heated environment, the standby losses would be small.

[Dana]

It sounds like you never need more than a 3-5 gallon draw at a time, in which case a well insulated low-standy tiny electric tank like a Bosch Ariston series would do. Recovery time on a laundry draw will be well under a wash cycle.

Gas tank heaters have high standby losses- you'll be getting less than 25% actual efficiency out of 'em. The US "EF" tests are based on ~60gallons/day use, which masks standby losses.

A full-on whole-house gas tankless would be ridiculous here- your flows and total volumes don't call for it. A crummy Bosch 1600H (magneto igniton, atmospheric draft for cheap venting) would be more than enough and have next to zero standby loss. It'll be only very slightly less efficient than a more sophisicated tankless, but it'll be 1/3 the installed cost, and more than 2x as efficient as a gas fired tank due to zero standby loss. It'll take about as much space as a 6-gallon Ariston electric tank.

The total installed cost a tiny electric tank will be half or a third of the bottom-of-the line tankless. (no venting- minimal plumbing- you just plug in to a 15A wall socket.)

Standby losses on the Ariston series (foam insulated) are about 30-35W, or 250-300kwh/year.

Gas fired tanks have standby losses of over 100 therms( 280m^3)/year, and will cost more up front.

A gas tankless that doesn't have a pilot light will have essentially no standby loss, but will cost 2-3x as much to install. (A cheap tankless with a standing pilot will burn at least 50 therms=140m^3/year.)

In B.C. I expect a tiny well insulated tank is your best bet for this application- you're not taking 20 minute showers here.

[SewerRatz]

The trouble with the little or small 110 V electric units usually 6 gallon is they cost nearly as much as a 40 gallon unit. Which is why I recommended a 40 gallon unit. Also I think he would be using more than 6 gallons of water to clean his paint brushes. Plus a possible shower if there is one in the garage. I would hate to see him go with a unit that is undersized and he doesn't find out till that one day where he has a lot of brush and equipment cleaning to do, and less than half way through it he starts to get ice cold water.


As for a tankless or a gas fired tank, since he is using items with fumes, I think it is best to go with a direct vent unit, so it can get its combustion air from outside. Also I think he is asking here not to cheap out on the job, he wants something that will perform for him, or at least I hope he does.

[Dana]

In low volume use situations like this the cost of operation is largely standby loss. Standby losses on a bigger electric tank is 3-5x that of tiny foam-insulated ones. (It's all about surface area & R-value with electric tanks.) Bigger tanks also take more space- the li'l 'uns can live under the sink.

It's not all about upfront cost. $30/year vs. $100-150/year of standby makes a difference. If you don't need the volume, the smaller tank will be cheaper to run.

It would take a large number of years to make up the installed-cost difference between a $2/year standby tankless (like the mini-Rinnai) vs. a $30/year standby mini-tank. While standby losses are extremely low, the efficiency of a tankless isn't all that great in sub-2 gallon draws- figure ~50% best-case, no matter what the EF or steady-state thermal efficiency numbers say. A 0.82EF unit like the mini-Rinnai only truly hits those numbers in the real world if all draws are more than 5 gallons, and I suspect NONE (or very few) of the draws for clothes washing & brush cleaning will pull that much water at a time. High efficiency front loading washers typically pull in less than a gallon at a time, even if the full wash volume is higher. Unless he's cleaning brushes under a steady blast, not a trickle, for several minutes/10s of minutes at a time, it' gonna suck there too. But it'll still beat a gas-fired tank by 2x in this app, because of the high standby losses of gas-fired tanks.

But there are both efficiency & safety aspects to going with the sealed combustion unit vs. a cheaper atmospheric tankless in a heated garage. The combustion-air requirements of the atmosheric unit represents a steady infiltration heat loss to the garage that needs to be made up by the heating system, so it's true standby loss as viewed from whole-house point of view won't appear on the spec sheet. In cool-winter parts of western Canada it will be significant. (In Kelowna or Calgary, hell yeah, in Vancouver or Victoria, not so much.)

[Dana]

I may be overestimating the standby losses for top-of-the line 40 gallon electric tanks- those with 2"+ of foam insulation are only 1.2-2x the standby of most foam-insulated mini-tanks. Beware the "bargain" 40 gallon tanks though.

Distribution losses are also a significant factor in small-volume draws. Whatever you set up, minimizing the plumbing distance between the heater and the load (washer or sink) could be a larger operational loss than the differences in standby loss in big vs. small tanks. But under-sink minis are hard to beat on that front too, assuming the washer is hooked up to separate faucets at the same sink. (You'd have to work at it to end up with as much as 3 feet of pipe between the tank and faucet when it's under the sink.)

I'm still thinkin' a point-of-use mini tank is the way to go. There are likely even lower-loss versions of that ilk than the Ariston- they just seem to be universally available, and cheap/easy to install. I'm not sure how the Eemax mini-tanks compare on standby, but they're also pretty cheap & easy for under-sink installation for minimal distribution loss.

[Elbartolli]

This is a great site btw and I appreciate all the advice. A point of use mini really does seem like the way to go. There is no shower just a laundry sink that requires hot water. Still weighing the options but I now have the info I need.

Thanks guys.