Under sink hot water heater recommendations?

[Matt Putnam]

I'm planning to put a utility sink in my shop during the upfit. I'll be running water from the house out to the shop but a cold line only. Having cold water only would be sufficient but I know I'll want some (at least) warm water in the winter time (even though I'm in South Carolina).

So I need to determine what to use for heating water - and largely do the planning now so I can wire accordingly. The shop will have plenty of spans of time not used at all (so many interests, so little time ). I imagine that makes an on-demand, under sink water heater a better option (compared to a small tank). Y'all agree? In a little research, I noticed some are 110v and some are 220v. I'm hoping someone has been down this path ahead of me and can make some recommendations -on the voltage and other aspects I should consider. Any clear winners? Or any clear ones to avoid?

Thanks for the input.

[Charles Lent]

You are asking about what they call a "Tankless Water Heater". They keep very little water hot and in reserve for when you open the valve. Then they require significant amounts of power to heat the water passing through them and the amount of power required is based on the flow rate needed.. They are available in gas or electric and can be obtained from plumbing suppliers as well as the big box stores. If gas is available, it would be a better choice economy wise, but you will need to vent it out through the wall to the outdoors.

I have a 120 volt 13 amp unit mounted under a re-purposed bathroom sink in my wood shop and I would NOT advise getting one like it if you want much more hot water than what you would need for hand washing. I can get 1-2 cups of really hot water from my heater at full flow before the temperature falls off rapidly to just warm. The flow will remain hot if all you want from it is enough hot water to wash your hands, but if you draw more than just a couple of cups of hot water at full flow, the guy behind you will not get really hot water to wash his hands. For my shop it is adequate, so it just might work for you too. I work alone and rarely want hot water for anything but washing my hands. I keep the hot water flow low by mixing in some cold water, so what I actually wash my hands with is about 110-120 degrees F and I use as little hot water as possible.

My heater was free, from someone who was not satisfied with how it worked, because he was expecting to be able to fill his sink with hot water from it. He replaced it with a much bigger 240 volt unit drawing much higher current. I also switch my unit off when not in the shop, to save some energy by keeping it from cycling when it will not be used. It recovers in just a few minutes when I return to my shop and turn it back on.

Charley

[Matt Putnam]

I also switch my unit off when not in the shop, to save some energy by keeping it from cycling when it will not be used. It recovers in just a few minutes when I return to my shop and turn it back on.

Charley

Thanks, Charley. That's good information. I don't have gas out at the shop (it's detached from my house) so I need to limit my scope to electricity. I think my hot (or warm) water needs will be very few. If I need to get something really hot or need a lot of it I can walk the 30' into the house. In fact, I don't have any particular needs for heated water in mind in the shop, but now's the time to get things in place. I do think I'll go ahead and get a wire (120v) in the wall before closing it up for potential future use. And I hadn't thought about switching it but that sure makes sense - especially given the recovery/heating time you describe. That will help towards my goal of not having water heated in the shop for weeks on end while not used.

[Charles Lent]

Your shop is the about the same distance from your home that mine is. Are you planning to heat and/or air condition your shop? My 14 X 26' shop is insulated, and I have a 2 ton window style heat pump mounted high and through the North facing wall. It's done a pretty fair job of heating and cooling my shop for the last 20+ years, except when the outside temps go below about zero or above about 100 deg F. Fortunately, this doesn't happen too often here. I think that, for those of us who iive in the Carolinas, it's probably the best, and safest, way to heat and cool our shops with just one unit. The 12 X 20 furnace air filters will just fit under the plastic cover and over the coils, so I buy the better quality pleated filters and also use the unit as my shop air filter. My shop has a 60 amp 240 electric sub panel running off the house 200 amp main panel. The big power users in there are the 5 hp air compressor, the heat pump, Since there's no room for any more power tools in my wood shop, I don't see that I'll ever need more power than this out there. I have 50 amp outlets in the garage for my welders (other end of the house) but since I can't run everything at once, I've never needed more. My mechanic and metal working tools are all in my garage, but slowly much of it is moving across town to my son's very large welding and metal shop.

Charley

[Matt Putnam]

Are you planning to heat and/or air condition your shop?

I plan to heat/cool it with a through-wall (motel style) heat pump/AC. I'd like to have a mini-split but can't justify the expense for the limited time I get in the shop. Great timing had a local motel close and do an auction and my dad and I got a half dozen (literally) of them. They're "as is" so we'll see how they do. My suspicion is that they'll keep the shop - 20'x30' (plus an 8'x10' room) - reasonably comfortable but not as nice as a real unit. I look at it as a fairly economical way to take the edge off. And we know the edge isn't so bad in the Carolinas. I am insulating the walls as I cover them and will spray in stuff on the ceiling once it's in place.

My shop has a 60 amp 240 electric sub panel running off the house 200 amp main panel.

I just installed a 100amp sub panel running off one of my house's 200amp main panels. I think it has 24 slots so I should be OK. I keep coming up with add'l needed dedicated circuits (air compressor, dust collector, water heater, etc.) but I think I'm still OK on the panel.

[Mike Cutler]

I'm planning to put a utility sink in my shop during the upfit. I'll be running water from the house out to the shop but a cold line only. Having cold water only would be sufficient but I know I'll want some (at least) warm water in the winter time (even though I'm in South Carolina).

So I need to determine what to use for heating water - and largely do the planning now so I can wire accordingly. The shop will have plenty of spans of time not used at all (so many interests, so little time ). I imagine that makes an on-demand, under sink water heater a better option (compared to a small tank). Y'all agree? In a little research, I noticed some are 110v and some are 220v. I'm hoping someone has been down this path ahead of me and can make some recommendations -on the voltage and other aspects I should consider. Any clear winners? Or any clear ones to avoid?

Thanks for the input.

Put in a small 15-20 gallon water heater, storage type. Keep it in an insulated cabinet, set it to ~ 105deg F. and use a programmable line voltage controller. Friends had one in an uninsulated barn for 20+ years. No problems
They have line voltage controllers that can connect to WiFi and are controlled with an App on your phone now.

That said, I think you'll find yourself using it a bit more than you anticipate.

[Tim Bueler]

At my old location I had 2 places that required periodic hot water. One was a shop sink like describe. I installed a small tank type water under the sink, it was either a 6 gal. or a 4 gal. model, can't remember. I had each set up on a mechanical, 24 hr, line voltage, 240v timer that would heat water for an hour or so in the morning. Plenty of time to get a full tank of hot water. If I was going to be in that work area all day I could flip the switch back on and I had second "off" tripper set to turn the water heater off at the end of the day so I wouldn't have to remember to do it manually.

One of those tanks was in a seasonal use area. For the off season I would remove the "on" tripper. If I knew I was going to be using the space I could turn the heater on an hour or so ahead of time and the "off" tripper would would turn the heater off later. You could even set trippers to run the heater a couple times per day depending on hot water usage but for my purposes I had plenty of hot, decreasing to warm, water throughout the day just using that one "on" period.

Used one set up for about 10 yrs and the other for 20 yrs or more (same heating unit) before we moved.