Tankless water heater wiring very weird!

[hillbilly1]

I think the name of the system was "Apollo", technically, it probably would not be called a "radiant" heating system, because it uses an "A" coil in an air handler, with the water circulating thru a gas fired tank type water heater and the coil.

 

[kwired]

I think the name of the system was "Apollo", technically, it probably would not be called a "radiant" heating system, because it uses an "A" coil in an air handler, with the water circulating thru a gas fired tank type water heater and the coil.

That is not a radiant heating system. It only heats air passing through the heat exchanger. A radiant heating system heats objects in the room via radiant energy. There often is some convection heat that rises off the heater also but the fact that it heats objects in the space makes the space seem warmer than it is. Open a door on a cold day in a radiant heated space and the air will recover quickly after closing the door because everything in the room is already warm. Although objects in a forced air heated room will eventually gain some heat, they will not gain heat as fast and will be cooler than the same room with radiant heat in it. Open the door in that space and it will take longer to recover because all the objects in the space are cooler.

The best example of a natural radiant heat source is the sun.

 

[hillbilly1]

That is not a radiant heating system. It only heats air passing through the heat exchanger. A radiant heating system heats objects in the room via radiant energy. There often is some convection heat that rises off the heater also but the fact that it heats objects in the space makes the space seem warmer than it is. Open a door on a cold day in a radiant heated space and the air will recover quickly after closing the door because everything in the room is already warm. Although objects in a forced air heated room will eventually gain some heat, they will not gain heat as fast and will be cooler than the same room with radiant heat in it. Open the door in that space and it will take longer to recover because all the objects in the space are cooler.

The best example of a natural radiant heat source is the sun.

You don't see many radiant heat systems here in the south, a few in warehouses and auto shops, but thats about it, virtually none in residential.

 

[mivey]

That is not a radiant heating system. It only heats air passing through the heat exchanger. A radiant heating system heats objects in the room via radiant energy...

Pretty decent summary here:

http://www.oregon.gov/ENERGY/CONS/RES/tax/Radiant.shtml

 

[kwired]

You don't see many radiant heat systems here in the south, a few in warehouses and auto shops, but thats about it, virtually none in residential.

Probably because there is more need for cooling than heating, and it likely makes more economic sense to incorporate heating with the cooling system.

 

[Sierrasparky]

Probably because there is more need for cooling than heating, and it likely makes more economic sense to incorporate heating with the cooling system.

that would make sense.

Boy have we digressed from my OP.:happyyes:

 

[kwired]

that would make sense.

Boy have we digressed from my OP.:happyyes:

All in part because someone introduced the idea of using the tankless heater for radiant heating. There are tankless 'boilers' that are for this purpose. They are not really the same thing as tankless domestic water heaters. I don't think you will get very good results from a device only designed to heat the water to 110-125 degrees for the purpose of space heating.

 

[Finite10]

that would make sense.

Boy have we digressed from my OP.:happyyes:

I'd stop at 422.11(B) if it's listed for use. (Haven't read every post, sorry.)

 

[blargh]

I just caught up with this thread; back to the OP's original questions:

Did it have a "Warning, more than one means of disconnect" on it or in it?

I would have thunk the same but the installation instructions actually show connecting up to 3 breakers parallel onto the power distribution block in the device. There is a statement that says in Canada you must use a single double-pole breaker but you can use up to three breakers in the US.

Check out page 13 and 14 of
http://www.buytankless.com/pdf/Hubbell-Tankless-O&M.pdf

A picture of the power distribution block is on page 19.

That user manual has a bunch of revealing details, page 13 in particular:

? The unit must be wired in accordance with the current version of the National
Electrical Code (US) or Canadian Electric Code (Canada).
? The unit must have its own independent circuits.
? When the heater is not within sight of the electrical circuit breakers, an additional
local means of disconnection of all ungrounded conductors must be provided that is
within sight of the appliance or a circuit breaker lockout must be used. (Ref. NEC
422.31)
? Wire entry must be through the electrical KO provided in the bottom of the unit.
? For Canada, per Canadian Electric Code, C22.1-02, the unit must be wired by a single
feed installation with one (1) double-pole circuit breaker.
? For US, the unit may be wired by a single feed installation with one (1) double-pole
circuit breaker or by a multiple feed installation with multiple double-pole circuit
breakers as shown below

(Emphasis mine.)

I really don't see what advantage there is to be had from the multi-breaker installation, other than a little bit of wire-bending hassle. The bolded bit seems to work around the disconnect requirements, technically. Anyone familiar enough with the Canadian Electric Code to tell us what C22.1-02 requires that the NEC doesn't?

If you have a parallel-breaker supply, if one of the breakers trips the others should do so immediately as well, as the current will then be far above their trip level... as long as none of the breakers are faulty.

 

[wireguy8169]

I guess I should have stated that power consumption was not the only complaint. In colder parts of the country, the water in the ground is colder and takes longer to heat or doesn't heat well in the tankless. Also, there were complaints about the water getting cold or having cold "spurts" even after getting hot and running for a while. Also, as has been mentioned, the water flow and pressure is not as good with the tankless. I guess the #1 thing was the high initial cost vs 20+ years to recover the cost via the supposed energy savings. And, they are not maintenance free, they get clogged up with scale after a while and have to be cleaned out. Of course tanked models get scale in them also, but you can drain them occasionally and minimize this. On the tankless, you have to disconnect them (plumbing & electrical) to clean them.

I installed a few of them on a farm to heat the water to the barn so the horses would drink, they were off of three 40A two pole breakers, did not have to have a common trip but did have a tag that it was feed by more than one source. I will say for that application where they had no hotwater heater and it was only for use to heat the water that went to the livestock seem to be a good choice. But I did think the meter was going to go into orbit when we powered it up the first time and that thing about spun off into space....

 

[kwired]

If you have a parallel-breaker supply, if one of the breakers trips the others should do so immediately as well, as the current will then be far above their trip level... as long as none of the breakers are faulty.

The units with multiple breakers do not have parallel supplies they have multiple supplies.

If it has 3 - 40 amp breakers and one should trip you lose 1/3 of the capacity (as long as it is not the breaker with the control circuit that is)

 

[kwired]

I installed a few of them on a farm to heat the water to the barn so the horses would drink, they were off of three 40A two pole breakers, did not have to have a common trip but did have a tag that it was feed by more than one source. I will say for that application where they had no hotwater heater and it was only for use to heat the water that went to the livestock seem to be a good choice. But I did think the meter was going to go into orbit when we powered it up the first time and that thing about spun off into space....

Hot water for drinking? Horses? Do they want tea or coffee mixed into it also?

All the livestock water supplies I have ever encountered often have heaters in them but is only designed to keep the water from freezing. Turn thermostat all the way up and you get maybe 60?F water at the highest. Maybe race horses or big time show horses are spoiled, I have never been around any of them so I don't know.

 

[blargh]

The units with multiple breakers do not have parallel supplies they have multiple supplies.

If it has 3 - 40 amp breakers and one should trip you lose 1/3 of the capacity (as long as it is not the breaker with the control circuit that is)

They could have designed it that way, but apparently they didn't. As the picture in post #12 showed, the inputs all come into the same pair of terminals in the power distribution block. So if the unit starts pulling over 120 amps for whatever reason, the "weakest" of the three circuits would trip, leaving the remaining two breakers handling 60+ amps apiece. They likely wouldn't hold up long under that load.

 

[kwired]

They could have designed it that way, but apparently they didn't. As the picture in post #12 showed, the inputs all come into the same pair of terminals in the power distribution block. So if the unit starts pulling over 120 amps for whatever reason, the "weakest" of the three circuits would trip, leaving the remaining two breakers handling 60+ amps apiece. They likely wouldn't hold up long under that load.

This information was discussed in the posts following that nearly three months ago.

There is either a mistake in showing the wrong unit in the photo or something like that. The unit in the photo could only be supplied by a single branch circuit. A multiple circuit unit would have multiple terminals for supply conductors.