> The 28kW limit is from the Boilermakers Union, not ours [IBEW] =P

Ahh gotcha, they must’ve pushed for some good ol trade protectionism after electric boilers came out and high-power tankless water heaters are within their wheelhouse or something like that. I wouldn’t consider it a pressure vessel but I don’t blame them for scooping up the work, lol. I’m not in the union myself, but I do manage IBEW electricians and know enough to be dangerous ;)

> As much as I hate AFCI breakers, I do love a well-designed "stupid" heat-response timeout that's in compliance with the NEC. You're correct that residential waterheaters are not "continuous loads" – had slipped my mind.

I believe electric tank style water heaters under a certain size are considered continuous loads, but tankless are not.

> I used a tankless/instahot heater (and helped install a few hundred in the early 2010s) and am so much happier with my hybrid/heatpump tank-type (it is so much cheaper to operate, requiring a relatively minimal upkeep of: an annual drainage). Plus: there are no "miminum flow" requirements/bullshit, which results in some tempermental dishwashing among the water-conscientious (sp?).

Heat pump water heaters seem amazing, 25% of the power usage of a resistive heater, and especially for $250!

I wasn’t aware of minimum flow requirements for tankless heaters, I suppose it’s necessary to prevent overheating/steam or something? I mostly see tankless water heaters as part of emergency eyewash station installations, most commercial buildings around here either use boiler water for domestic hot water heating or have point-of-use tank water heaters near sinks/bathrooms.

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ProllyInfamous 2 hours ago | parent [-]

>IBEW electricians and know enough to be dangerous

You definitely sound just like us =P

>minimum flow [for tankless]

Yes, my brother has a kitchen pretty far from his tankless and if you don't have a disrespectful (i.e. anti-environmentalist) flow going, it's going to get cold and then stay that way for quite a while. It is aggravating, even as an occassional guest in his house – the whole damn line has to heat back up, again!.

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phil21 an hour ago | parent [-]

> . It is aggravating, even as an occassional guest in his house – the whole damn line has to heat back up, again!.

For point sources located far away from the heater, you are supposed to install a return loop. Modern tankless have a tiny (1-3 gallon) superheated tank and recirculation pump designed specifically for this use-case.

You can pry my continuous water heaters from my cold dead hands. What is much more annoying is running out of hot water when you have a peak guest load in your house right before an evening event and everyone is taking showers at the same time after a day out.

Since I use very little hot water otherwise, it pencils out for the environment too! The few times a guest is in a far guestroom and needs to use a small point of use hot water source, the few extra gallons of use to wait for it to kick in is a rounding error.

The two tankless heaters I have installed in my place are by far the single best upgrade I did since buying the house. I often comment on how much better my quality of life is with them vs. before they were installed.

I would never use a water heater with a tank ever again unless forced to. Other than air conditioning it is basically one of the top luxuries I work to provide for myself. My wife can take a bath, 3 other guests can shower all at the same time along with two loads of laundry and a dishwasher cycle going. No worries and no waiting around for an hour for hot water to regenerate. Since it's designed for peak loads and only spins up the second unit on-demand, it's much better in terms of energy use than a boiler designed to support those types of loads it sees 2 or 3 times a year at most.

If I were re-designing my system today I might do a heat pump water heater in-line with a continuous water heater, and the continuous only fires up once the tank runs empty.

	▲	ProllyInfamous 10 minutes ago \| parent [-]
		In your personal usage preferance (tankless), the only reason you would consider using a tank again is if you wanted a reasonably-efficient backup generator/offgrid/standby (or the free dehumidification/energy savings). I've used both and from an environmentalist living in a humid subtrop. rainforest, the hybrid tank (heatpump) makes most sense. Thankfully, they also have heating elements (and can run both heat sources, simultaneously).