Preheater for tank or tankless systems

I remember seeing an article about a preheater that hooks to the hot side of a bathroom faucet, shower, or line to provide both. This preheater was powered by 125 vols, had 5 stages, and was thermostatically controlled. Here is how it works.

On the initial faucet (hot) turn on - all 5 stages of heater turn on to deliver on demand hot water. As the water standing in the pipe is delivered to the preheater (on hot side), the 5 stages turn off one at a time as the temperature of the water increases, until the hot water from the tank or tankless heater delivers the fully hot water. This seems to be the best idea I had heard of, but I cannot find anyone who sells this system. If anyone knows where I can find that unit, I would be ever so grateful!! I have an 1886 Farmhouse and one room is VERY FAR away from the main unit.

A number of the show folks, This Old House, James Dully article, etc. have stated that this doesn't exist, but I have the article , but cannot find it. Please help.

fcompagnari said:

This preheater was powered by 125 vols, had 5 stages, and was thermostatically controlled. Here is how it works.

Click to expand...

At 120v, the max amp draw should be ~12A.
This gives you 80 BTU/min, enough to raise 1 GPM by 10F. Not much of a boost.

I suppose it's possible that it could connect to a dedicated 20A circuit and draw 2+Kw. I imagine that would provide a little more "oomph".

You can just picture guys feeding off old ungrounded 14AWG circuits that also run the bathroom and 2 bedrooms. And a hallway. Etc.

Have not seen it. Seems that a device with a 5 heating statges would be a little complicated and pricey. Maybe it just was never practical.

heater

That would be a much too complicated device for a 120 volt system. Larger tankless heaters have multiple elements which may be wired that way. At 120 volts you would need ALL the power, ALL the time, just to make the water warm, it would NEVER make the water hot if the water is flowing through the heater at the same time. Even point of use heaters, which DO heat the water as it flows through, require up to 6,000 watts of 240 volt power to generate the little stream of hot water that their flow regulator delivers. And you would NEVER be satisfied with the amount of water you got from them, because it is JUST BARELY ENOUGH to wash your hands and that is all they are designed for. There is really no reason for a "staged" heating system, if you have a thermostat which turns the heaters off when the design temperature is reached. It would just reach that point faster, instead of trying to "sneak up" on it. The reason you probably cannot find it is that they spent hundreds of thousands of dollars developing and manufacturing the device, and then only sold three of them, or gave them to friends to try out.

Your best choice would be a recirculating system. That would give you instant HOT water.

Depending on the sensors and the layout of the recirc system, you may not end up with tepid cool water, at least a lot of it. In the system I have, the pump is under the vanity. it has a thermostat on it that determines when it runs (and it can be put on a timer). I've got it set so it just gets the water warm, but hot isn't far away. If I flush the toilet, it uses up almost all of the tepid water, and cold is there. It's only if I use the sink first is the cold not fully cold. If you can get power under the sink, the whole install is plug it in, remove the hoses from the supply, put them on the unit, and install new hoses back to the supply. It takes all of 10-minutes if you're slow (if you can get power there - I just ran a new outlet from the one above into the bottom of the vanity). Most others will end up with more hot circulated into the cold line. since it is furthest from the supply, the other sinks in the house get hot, rather than warm instantly. Normally, all I want to do is wash my hands with at least warm, and it's always there. The shower gets hot in less than 10-seconds where it took over a minute before. All in all, I'm satisfied. If you can put in dedicated return line(s), it will work better and you have more options.

circulation

FEW bathroom sinks have an electrical outlet under them. That is why Grundfos developed their "Comfort" system. The pump mounts on the water heater where there is either a plug, or access to one with an extension cord. The "regulator manifold" mounts under the sink and performs the "thermostat" function.

True, but adding an outlet in the vanity is often pretty simple - fishing a new wire down is usually pretty easy. And, there's no cutting of pipes or soldering involved since the thing is essentially plug and play. I did mine during a remodel, and had easier access, but still, it's not a big deal. Maybe more if you need to call both a plumber and an electrician. But, in the places I've lived, there wasn't an outlet available, so would have needed that work done in either location, and it was easier and faster with the unit I have. Your results may differ...