Hot water heater as a boiler?

shashalou said:

I've heard that too, when the water is not moving. My heater operates as a basic air conditioner when it's not heating by piping new street water thru it.

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When you go on vacation, do you get someone to come by & flush the system every now & then? I've only ever heard bad things about this setup, so I'm curious.

Oh, wait - You & I didn't have a related discussion on BT last year, did we?

frenchie said:

When you go on vacation, do you get someone to come by & flush the system every now & then?

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I could be wrong, but I cannot imagine why that would be any more necessary than having someone come "flush the [plumbing] system" in a house without hydronic heat. In this kind of "open-direct" system, the heating components are never stagnant unless hot water *never* gets used anywhere in the house.
http://www.radiantec.com/systems-sources/systems.php

If the water doesn't get used for awhile because nobody's home, and you have a regular water system, the tank keeps the stored water hot enough to prevent nasties growing in it. Even so, there's occasional reports of legionella contamination in systems where the storage tank isn't kept hot enough...

Nobody cares if a closed hydronic system gets nasties, it's a closed system. You aren't drinking it, or showering in it. Also, the oxigen gets forced out of it after a few cycles, there's nothing for the nasties to feed on, and there's usually/probably antifreeze & other additives in it.

If the water doesn't get used for a while because nobody's home, and you have an open radiant setup, you're storing a bunch of water at ideal growth temp.

You should check out what the guys at heatinghelp.com have to say about radiantec - might make you think twice before linking anything from there. (Search the forum for "open radiant", as they don't name radiantec by name, because radiantec trolls the forum & threatens to sue & so on.)

Or just note that their open direct system, as designed, is non-code-compliant. At least here in NY, it would be illegal.

frenchie said:

If the water doesn't get used for a while because nobody's home, and you have an open radiant setup, you're storing a bunch of water at ideal growth temp.

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Where, and/or how? Having a check valve and a pump in a cold-water supply line does not make any part of the system an incubator, and any hot water remaining in that line after a heat cycle will soon cool to the same overall ambient temperature being experienced by plumbing throughout the house.

frenchie said:

You should check out what the guys at heatinghelp.com have to say ...
(Search the forum for "open radiant" ...

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I could not find a forum there, but I did find this:

The temperature requirements for healthy domestic hot water and the low temperature needs of your radiant floor are very different ...

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That is not always the case.

... low water temperature (below 140 degrees) is conducive to bacteria growth ...

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I have no idea how many radiant systems are fed by water below 140*, but mine certainly is not. Nevertheless, this discussion has got me to thinking a bit ...

I am preparing to install a radiant kickspace heater under the kitchen sink, and how to keep from having that heater become a seasonally-dormant "dead spot" in the overall plumbing has been a concern. I have a 3-way valve so the circulator pump can either warm the pipes or serve the heater, and I have been debating whether to have the hot water to the faucet come through the heater when it is not being used in order to keep its core "fresh" at all times ... and I believe that is what I will do. When the heater is on, the faucet will get its supply from ahead of the heater but from after the heater the remainder of the time. I would rather not have the heater "leaking heat" during the summer, but its blower will not come on unless the thermostat is up and demanding heat.

leejosepho said:

I have a 3-way valve so the circulator pump can either warm the pipes or serve the heater ...

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Oops! I just realized I will not need that valve, and that neither will the hot water to the faucet have to come through the heater. Rather, the heater core can be "refreshed" and will only "leak a little heat" when the manually-controlled recirculator warms the line.

leejosepho said:

I could not find a forum there

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Click on "questions", from the main page. Best hydronic/radiant forum on the web.

Or try this:

http://forums.invision.net/index.cfm?CFApp=2

, but I did find this:

The temperature requirements for healthy domestic hot water and the low temperature needs of your radiant floor are very different ...

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That is not always the case.

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It usually is. Radiant systems tend to come in under 110.

I have no idea how many radiant systems are fed by water below 140*, but mine certainly is not. Nevertheless, this discussion has got me to thinking a bit ...

I am preparing to install a radiant kickspace heater under the kitchen sink, and how to keep from having that heater become a seasonally-dormant "dead spot" in the overall plumbing has been a concern. I have a 3-way valve so the circulator pump can either warm the pipes or serve the heater, and I have been debating whether to have the hot water to the faucet come through the heater when it is not being used in order to keep its core "fresh" at all times ... and I believe that is what I will do. When the heater is on, the faucet will get its supply from ahead of the heater but from after the heater the remainder of the time. I would rather not have the heater "leaking heat" during the summer, but its blower will not come on unless the thermostat is up and demanding heat.

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Radiant kickspace heater? You mean hydronic, right?

Not all hot water heat is radiant, radiant refers to in-floor or in-wall heating, usually pretty low temp to not mess up the finishes. Hydronic systems use rads, generally run around 200... kickspace heaters are usually a hydronic coil, I don't know that dhw would be hot enough. Can you clarify?

frenchie said:

Radiant kickspace heater? You mean hydronic, right?

Not all hot water heat is radiant, radiant refers to in-floor or in-wall heating, usually pretty low temp to not mess up the finishes. Hydronic systems use rads, generally run around 200... kickspace heaters are usually a hydronic coil, I don't know that dhw would be hot enough. Can you clarify?

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Yes, I should have said hydronic, and please pardon my confusion. I am far from being an expert on this stuff. I installed radiant electric wire in a bathroom floor last year and that works far better than just about anybody else seemed to believe it would -- it provides all the heat the bathroom needs -- and now I am doing my first hydronic trial.

The BTU output chart for this particular kickspace heater ranges from 2266 @ 160*F to 3391 @ 210*F with the blower running at its low speed, but the internal control for the blower will kick it in at 120*F and the literature for the heater indicates it will begin providing heat at 130*F. Overall, then, we have yet to see how much heat I will actually get from water going in at 140*F, and I do have the option of raising my DHW to 150*F.

I've only ever heard bad things about this setup, so I'm curious.

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My systems have been in place in my residence and my cottage for almost 20 years. My residence is basically unoccupied for 5 months. I have no known problems with bacteria. The pump in one is located in the cold water line that feeds the heater and the kitchen without even a monoflo T and there is no warming of the kitchen cold, 12 feet away.

You & I didn't have a related discussion on BT last year, did we?

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I talked over there briefly a few years ago without success.

Where, and/or how?

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That question remains unanswered.

I have no idea how many radiant systems are fed by water below 140*, but mine certainly is not.

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Mine seldom gets over 140 deg and my residence heater in the summer is lucky to get to 110.

how much heat I will actually get from water going in at 140*F

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Not much, I'd say. I tried it unsuccessfully, with a little fan (noisy and the quietest I could find) behind a 10x10 radiator from a baseboard convector (I forgot what its called).

Well, and in spite of some fitting issues I just found out about, my water heater drives this kickspace hydronic unit just fine! The water heater has no problem staying above 135*, and the air coming out under the cabinet stays right at 20* less than the water temperature.

I'm glad I didn't suggest that brooder lamp.

It's single digits outside, my heater is set at max, just before the burner fires the temp into the radiator is 123
the return is 98, after it runs awhile it levels at about 135 and 105. I need it to run hotter but the factory thermostat just wont let it do it. Anybody know of a finer control that can safely replace the standard water heater gas valve?

shashalou said:

It's single digits outside, my heater is set at max ...

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Same here, but I heard we might get a heat wave next week!

Would it be possible for you to add an electric warming belt around the tank at the top of your heater? The cost to do so would not be great, it might be just enough to make the difference and all heat produced would remain inside.

blankets

the problem apparently occurs because the pump causes the water in the tank to mix rather than stratify--thus the temp of the water around the sensor is warmer than it ought to be and the burner wont fire. I already have a 6" blanket around the top and none near the bottom to cool the bottom faster.

Drink your boiler water and be happy!

If the water heaters are used for both heat and hot water and are not isolated from each intended use, you are consuming your boiler water every time you open up the hot water faucet. Have you ever heard of Legionella?

therinnaiguy said:

If the water heaters are used for both heat and hot water and are not isolated from each intended use, you are consuming your boiler water every time you open up the hot water faucet. Have you ever heard of Legionella?

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Not to argue, but to try to understand: Please explain. Frenchie had said something similar:

frenchie said:

If the water doesn't get used for awhile because nobody's home, and you have a regular water system, the tank keeps the stored water hot enough to prevent nasties growing in it. Even so, there's occasional reports of legionella contamination in systems where the storage tank isn't kept hot enough...

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As I understand what he just said, the only specific issue there is the matter of temperature.

Frenchie then continued:

frenchie said:

If the water doesn't get used for a while because nobody's home, and you have an open radiant setup, you're storing a bunch of water at ideal growth temp.

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I have asked where in the system and how that would be as described, but an answer has yet to be offered ...

I have a typical plumbing system in my house: Water comes in from the well, some of it gets heated and all of it eventually comes out at a faucet or fixture somewhere. Along with that, I have a recirculation pump and line going back to the bottom of the water heater so you can push a button in the kitchen and warm the line to the faucet before drawing any water, and I am not aware of there being anything dangerous about that. And then, of course, I have the hydronic unit getting circulated water from the same line being used by the kitchen faucet, with that water then being pumped back to the water heater.

Where is the problem you believe you see? Just like in anybody's house, the hot water line going to the faucet gets hot and cools again several times a day, and the same can happen to the recirculation line.

The only possibility for stagnant or incubating water I can see would be if the recirculation line was hot, then cooled and was left dormant for an extended period of time.

Is that what you are talking about?

If so, and to avoid having any problem there, I plan to supply hot water to the washing machine from the water-heater end of that recirculation line to be sure it always stays fresh.