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Water heater for shop sink

I am looking at water heater options for a utility sink in my shop. I have a small boiler (Triangle Tube CC50s) that heats the slab, but it runs at very low supply temps (seldom gets above 85 F) so that isn’t likely an option. The sink has only 120 V nearby so that rules out an electric tankless heater, without making a sizable investment in a 240V circuit, and I have not been able to find a small natural gas fired heater, only propane units. I am now leaning towards a small tank unit like the Bosch ES2.5 that will run off 120V, yet still provide plenty of water for my occasional use of the sink. I am normally just hand washing so volume need is low.

Any thoughts on good small tank style heaters? Brands to favor or avoid? Other water heating alternatives I may have overlooked? I’d love to have a natural gas fired tankless, but they just don’t seem to exist for a one sink application. And the extra cost of energy for an electric unit is probably offset by the need to not drill another vent hole through my wall for a gas-fired heater.

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 17,760
    I have had outstanding success with small tank type heaters running on 120 VAC 15 amp circuits for just that purpose. Like this one: https://www.homedepot.com/p/EcoSmart-6-Gallon-Electric-Mini-Tank-Water-Heater-ECO-MINI-6/205610804
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Voyager
  • hot_rod
    hot_rod Member Posts: 15,390
    the tank Jamie the mentioned, you can upsize the element wattage to whatever circuit you have. About 1600W on a 20 A, 120v

    or a 12 gallon tank if it fits
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Voyager
  • mattmia2
    mattmia2 Member Posts: 4,321
    It will likely last a vey long time with the small amount of water used for hand washing. Like a heating system, the life is largely a function of how much fresh, oxygenated water you bring in to the system.
  • Zman
    Zman Member Posts: 7,117
    I think the 120 volt electric is by far the cheapest option if you have spare capacity.

    Your triangle tube boiler could be set up to heat your hot water via indirect as well. You would pipe it and set up the controls for DHW priority. The boiler will stop heating the building for a short period of time and increase the temp to make hot water. The feature is already built into the boiler controls. I would only go down this path if you either don't have any electrical capacity or if you want extra hot water to wash vehicles.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
    Voyager
  • Voyager
    Voyager Member Posts: 290
    edited December 2021
    I bought a Bosch ES2.5 since it was readily available locally and at a decent price. It was an easy install and seems to work pretty well thus far. Not sure how long it will last, but for $150, if I get past the 6 year warranty I can’t complain much as an indirect tank would be much more expensive to buy and install and I suspect would probably be about as much money to operate as the additional standby losses would likely offset the efficiency gained using the gas boiler as the heat source. Time will tell.

    The biggest pain is having to pull the heating element annually to clean it and check the anode rod, but it looks to be a fairly easy procedure.
  • mattmia2
    mattmia2 Member Posts: 4,321
    Voyager said:


    The biggest pain is having to pull the heating element annually to clean it and check the anode rod, but it looks to be a fairly easy procedure.

    You could just ignore it and replace it for another $150 when it leaks in a couple decades too. With as little water as moves through it for an occasionally used hand washing sink the anode should last a very long time.
  • Voyager
    Voyager Member Posts: 290
    That probably is the most economical solution if you figure the value of your time. However, I tend to be pretty rigorous on maintaining my vehicles and equipment so I likely will pull the element once a year as Bosch recommends.
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,363
    Hi, You might be able to save a little time by determining how fast the anode is being consumed and then checking/replacing it only as needed, which in my experience is every three to five years.

    Yours, Larry
  • Voyager
    Voyager Member Posts: 290
    Yes, I generally modify my maintenance intervals as I get to know a piece of equipment and how fast it wears/degrades. I assume the Bosch recommended interval is conservative and to account for the wide range of water quality their equipment will encounter. I live in an area with fairly hard water so I may need more frequent cleaning of the heating element.
  • Voyager
    Voyager Member Posts: 290
    Thought I’d provide an update for anyone considering a small under sink water heater. I have had the Bosch ES2.5 in service for a couple of weeks now. Overall, I would say I am marginally satisfied. My 75 gallon gas water heater will provide about 50 gallons of hot water before it starts cooling down when I am filling my Jacuzzi tub. I had hoped that the 2.5 gallon Bosch would similarly provide about 2/3 its capacity before the temp dropped noticeably. Unfortunately, not even close. I filled a 0.5 gallon ice cream pail the other day and the water temp was dropping by that time. After about 1 gallon is drawn, the temp is down to lukewarm. This is with the heater set about 1/2” on the dial above the “ideal setting” midpoint. I can barely wash my hands before the water temp is dropping rapidly.

    It appears that the tank has no internally baffling so the incoming cold water (probably 55 F from my deep well) quickly mixes with the hot water in the tank and dilutes it. I was hoping there would be baffles to keep the water stratified and allow the incoming cold water to push the hot water out of the top and not mix with it too much, but that clearly isn’t the case when the temp starts dropping rapidly after only 20% of the tank volume has been extracted.

    So, an OK solution for a workshop sink, but I would never install one of these in someone’s home as they would be quite unhappy with any normal sink use. You certainly could not draw enough hot water to even wash dishes in a kitchen sink. And even in a bathroom sink, this would be good for only one hand washing every 10 minutes at best. A frequently used bathroom would never have hot water.
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,363
    Hi @Voyager , A thought is to put a Neoperl aerator on the spout, but use one with a lower flow rate. That MIGHT help prevent mixing in the tank, keeping stratification intact, giving you more undiluted hot water. Here's a link: https://www.neoperl.net/oem/products/aerators/introduction.html

    Yours, Larry
  • Voyager
    Voyager Member Posts: 290
    I will probably try to experiment with cracking the faucet to lower flow rates, but I really don’t run it that far open for hand washing anyway and still the hot water fades pretty quickly. I was surprised that I could only get half a gallon before the temp dropped to luke warm. I guess I should have gotten a 4 gallon unit, but I was figuring closer to 1.5 gallons before the temp dropped off. Looks like at least a 4 gallon tank would be needed to get a gallon or so of hot water.