water heater and recirculating system

[Jud McCranie]

This question is about building instead of repair, but I don't see a better place to ask.

We are building a house with a garage and three small living floors above it. The plans originally called for one of the instant on water heaters (running on natural gas) on the second living floor. The way the house is laid out, it would have to vent towards the street. In order to keep from venting towards the street, the builder wants to put the water heater in the garage and use a recirculating pump system. The way I understand it, the heater comes on when there is water flow. The recirculating pump would keep water circulating all of the time, so the heater would be on all of the time, right? Does this sound like a good plan?

[RBM]

The recirculating pump would be controlled by an aquastat and would only run when the pipe cooled down. The pump is bronze, and expensive. Overall you'd be better off if you can find a warm location to install the heater

[Jud McCranie]

I asked the builder if it was temperature or water flow that made the heater come on, and he said water flow (i.e. demand). A factor I was concerned about is that with the heater on the middle floor, it is only one floor away from the others. In the garage it would be three floors from the top.

[hallerb]

Go with a REGULAR tank! Go large like 75 gallons high BTUs.

Tankless have lots of downsides, and a tandard tanks stanby loss helps heat your home in the winter

[Jud McCranie]

We don't have room for a tank unless the tank is down in the garage.

[charlie]

yes. no.

with a recirculating pump why would you need the instant-on, since there'd already be hot water there due to the pump?

the pump runs all the time, keeping hot water near all the taps all the time. you really only need one or the other.

regards, charlie

[trader4]

In any of the systems I'm familiar with, the pump does not run all the time, which would be very wasteful. There are 2 types of systems that I know of, both of which are designed to run with a conventional water heating syste, ie water heater tank, or furnace fired hot water"

1 - System uses a temp sensor at the point of use and runs the pump whenever temp drops. May also have a timer, so it only does this during times when use can be expected, shuts off during 1am-6am, etc 2 - System has a button you push, which turns on the pump and gets hot water to you in 10 secs or so. I'm sure you could also easily hook up a motion sensor to this as well.

[charlie]

well, obviously, since you don't know of it, it doesn't exist.

of course, the system that's on my house, and lots of other buildings in my area, must not exist either? so when i go look at that pump in my utility closet, it isn't really there?

[trader4]

I didn't say you couldn't have a system with a pump that is constantly running. Only that I haven't seen one and if you look at the ones that are available online, they are either temp or push button activated, because for most applications, it's wasteful to just keep a pump running 24/7. Are you suggesting that the OP install one that runs 24/7? BTW, the fact that you have a pump in your closet doesn't indicate how it's controlled. All of these systems have a pump.

[Goedjn]

Why is having the vent on the street side a problem? Is this a zoning/HOA issue, (in which case you should build somewhere else, where the color of your underwear isn't dictated by totalitarians) or just an esthetic preference?

[Jud McCranie]

Thanks, that's what I thought, but I wanted to get some other opinions. They wanted to put in a switch so you could cut off the pump if you wanted to, but then what's the point?

[Jud McCranie]

The shortest distance is to the street side, and he didn't want the vent to look bad. But they are only about 4x4 inches, and we looked and them and decided it isn't that bad.

I was just over there about an hour ago, and we are NOT going that route.

Thanks for the input, everyone.

The builder wanted to do it for esthetic reasons, but we decided that having a small vent on the street side was a lot better than the alternative. We are building there because that is where our land is.