Open system safety?

AlwysCld

Hello,

I'm considering buying a house with radiant heat (wall panels), which is currently powered

by a gas water heater (needs to be replaced).  The space is roughly 1300 square feet on two levels.  The water heater is used for both domestic hot

water and for heating.  I'm wondering about the safety of mixing

water from heating with water for drinking and cooking.  There is not

space in the closet for a second water heater.  My questions:



<ol><li>Is it safe to use the same water heater for both drinking and

heating system if we run the system at least a few minutes every day

(even in summer) to prevent stagnant water building up?</li><li>If not, are there creative alternatives, given the space limitation?  Or would we need to make space somewhere for a 2nd heater? 

</li><li>Is there a particular type or brand of heater you would recommend using for this job?   How many BTUs do I need? </li><li>There is no temperature-pressure gauge and the system has been running at 120 degrees.  Can long-term low temp use cause problems with the system?  Or is it a sign that the system was not installed properly and may have other problems?

</li></ol>I appreciate any tips you have.  I have no experience with plumbing and would need to hire out all work for this repair.  Should I drop my offer and run?

Mark Eatherton

The hazards of open systems...

can not be dealt with thru timers or flushings. The bacteria responsible for Legionaires Disease is omni present in water. Under ideal conditions, the bacteria thrives and multiplies, and your system running at 120 degrees F is within the ideal growth range. It's not a matter of IF you are being exposed to this potentially deadly bacteria, but more of a matter of the quantity you and your family members are being exposed to, and their overall health condition at the time of exposure.



I was exposed, and contracted LD, and at the time, I had a measly head/chest cold. It danged near killed me.



I could go on for hours and hours about the potential threat this system exposes you to, but I think it would be better if you educated yourself. Go to www.contractormag.com and use their on site search engine and put Legionella Pneumophila into the search engine. Dave Yates and myself have numerous articles there for your perusal and education. Thats the HEALTH side of things.



If in fact your wall panel heating system is constructed of ferrous materials (steel, cast iron) then they are being exposed to continual supplies of oxygen which will eventually cause component failure and an early system death due to corrosion.



I would suggest that you have the heating system inspected by a qualified Hydronic Heating specialist (no offense to my bretheren and sisteren) not just a plumber. If there is only one tank there, and no flat plate heat exchangers, then it is probably a combination open loop system.



As an alternative, you could set a new high efficiency modulating/condensing boiler, and a small reverse indirect to provide DHW. I know not what your utility bills have historically been, but what ever they are, converting to this high efficiency system will reduce your energy consumption by 30% at a minimum.



I wouldn't necessarily walk away from the project yet. If your inspector finds issues, then you can make a counter offer, reducing the sales price by the cost of recommended reparations, and if they balk at your offer, then walk away.



You've started down the right path of education. Now stick with it and hold to your guns. It was most probably done by a weekend warrior homeowner, and on paper, it sounds good, but in reality, done wrong it will cost you a lot of money to operate in the long run.



Let us know how it goes.



ME

AlwysCld

Converting from an open system

Hi Mark,



Thank you for your help and for pointing me in the direction of those articles.  You mentioned installing a "new high efficiency modulating/condensing boiler, and a small reverse indirect to provide DHW."  I googled this sentence (I have zero plumbing background) and came up with the Challenger Combination Boiler.  My question:



If we install a unit such as the Challenger Combination Boiler, will this convert our system to a closed system which uses a single heating unit?  How does such a boiler compare in size to a regular hot water heater? 



My preference, just to get peace of mind, would be to convert to a closed system if it's as easy as replacing the WH with a boiler.  With a closed system, is bacterial build-up a concern?  I've seen recommendations to put propylene glycol in closed systems, but I'm not clear why this would be necessary if the water doesn't mix with the domestic supply.



Thanks again for your help!

Mark Eatherton

It depends upon what your final wishes, wants, needs and goals are...

If you have a large fixed volume to fill, i.e. a 1 man, 5 woman soaking tub, then you will need some stored volume to quickly and easily fill that fixed volume tub. If your family doesn't use a bath, but only showers, then it depends upon how many parallel showers you want to take at the same time. If you can schedule them back to back, then the Challenger will work for you. It also depends upon the heat loss calculations. Which ever load is greatest (DHW versus Space Heat) is what you'd size the appliance to. This requires a heat loss to be done.



As for foot print, it may be slightly bigger, but still worth the effort. Your biggest challenge will be figuring out how to get the products of combustion out of the house. You can't re-use the old flue pipe systems unless they happen to be the right kind, size and pitch of plastic.



Doing this will definitely convert your system to a closed system. The potential of legionaires disease is still present, but can be handled by holding the DHW at a higher temperature for scald sanitization, and mixing the water temperature down to avoid scalding issues. The closed loop space heating side of the system may contain bacteria, but it is rarely opened up, and should (hasn't) been an issue.



There are three conditions that warrant the use of glycol.



Snow melting systems (DUHHhh)



Structural preclusion (exposed piping in overhangs)



Unsupervised buildings with the possible loss of fuel (LP or oil) or electrical power. If none of these are an issue, I wouldn't use glycol. It's more trouble than what its worth.



HTH



ME



PS, O00pps, I posted this out of sequence...:-)



ME

NRT_Rob

it may also be

that the current water heater has plenty of OOmph and all you need to do is install a heat exchanger on the side. that would definitely be the cheapest/path of least resistance and your house is not very big.



but it depends on your heat loss and climate whether that would make more economic sense than a replacement with a boiler.



the challenger is brand new. be aware of that. generally I don't like combi boilers as they must be of minimum output to provide DHW on demand that typically is 3x a conservative guess at the heat load average of a home your size... in order words, the boiler side is oversized even just for one shower's worth of on demand water heating.



If you must go replacement, high efficiency water heaters like the Phoenix Evolution which have heat exchange built in will retain your footprint and system topology, provide a LOT more DHW output, and will not suffer from short cycling/oversizing issues. Downside is that compared to a well design mod/con system they may be slightly less efficient in heating mode. but for a drop in replacement that's not a very likely comparison...

AlwysCld

Heat Exchanger

@font-face {

font-family: "Cambria";

}p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; }











Hi Rob-Thanks for your response.  You’re right-we don’t really know that the current water

heater isn’t effective, but it’s past warranty, so we're going to replace it before

moving in.  We live in Seattle, so

not terribly cold, but we sometimes turn on the heat during the

summers.  Again, I’ve no  plumbing background…what does a heat exchanger

do?  Is that part of converting to

a closed system?  And what is a mod/con

system? 





 





Does the Phoenix have two separate tanks?  I still don’t quite understand the mechanics

of how a to convert this to a closed system.  

AlwysCld

Tankless Option?

@font-face {

font-family: "Cambria";

}p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; }











Mark-thanks for the tip on glycol, sounds like we wouldn’t

need it.  We’re a 3 person

family.  We usually stagger

showers, but often run dishwasher or washing machine during showers.  We’re hoping for an economical fix that

wouldn’t involve installing a lot of piping, such as piping in to the utility

room to allow for a larger water heater. 

Our current water heater is in an outside closet, so venting should be relatively

easy.  There’s just not a lot of

extra space in there.  We’ve also

tossed around the idea of installing a second, tankless  WH just for DHW, because it may fit in

the closet.  Thoughts?

NRT_Rob

heat exchanger

separates two fluid streams, such as domestic and heating.



Modcon is a "modulating/condensing boiler". Such as the challenger.



the Phoenix and its ilk would NOT require a second tank. they are a tank, with a heat exchanger on the side.



If your house is well insulated I would question the economics of this, but if economics are not making the decision, so be it. a lot would depend on a heat load calc, which should always be the first step in any major heating system overhaul.

Mark Eatherton

Call my friend Paul Pollets...

It's going to cost to get him there, but I can assure you that once he's been through your system, you will know what your options and needs are.



http://www.heatinghelp.com/professional/95/Advanced-Radiant-Technology-LLc



ME