Radiant Floor Water Heater...what to do next??
Last Post 26 Apr 2014 02:26 PM by jojojo. 29 Replies.
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jojojoUser is Offline
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19 Apr 2014 01:46 PM
Hello everyone!  I have done some reading on this forum...but never posted until now, as I usually can find my answer by reading older posts.  However...I currently have an issue that I haven't found by reading.

Question 1....We have radiant floor heating in our basement...run by an electric water heater that services only the floor heat.  We just had to replace the water heater after 5 years.  The plumber said the water heater went bad because we turned it off during the spring/ summer. What should we do with the water heater at the end of the heating season????

Question 2....Is is necessary to put antifreeze into the closed loop system...and what percentage of antifreeze does everyone use?  And what kind do you use? We live in the Midwest (Iowa) which can get very cold in the winter. I want to be sure that my mix is sufficient after they refilled my system from the water heater replacement.


Thank you kindly in advance, any and all suggestions would be appreciated.
Jolene 
sailawayrbUser is Offline
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20 Apr 2014 10:22 AM
Did the plumber explain why he believes turning off the water heat caused it to fail?

Antifreeze is only typically used when a HR system is at risk of freezing . If the HR system was properly designed and installed, and will always be operated during freezing weather, it should not be at risk of freezing. Only propylene glycol should be used to protect a HR system from freezing…never use ethylene glycol. It is often recommended to use at least a 30% propylene glycol concentration to inhibit the growth of bacteria in the system. Apparently some bacteria actually like lower concentration levels of propylene glycol. Also be aware that use of antifreeze will significantly reduce the HR system heat transfer efficiency and will also work the circulator pump(s) harder. We have free DIY HR floor heating software on our website that allows you to enter the actual antifreeze concentration and determine exactly how it will affect the HR system performance.
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jonrUser is Offline
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20 Apr 2014 10:51 AM
With any fresh water heater, you should check the anode rod every few years. If it's gone, the tank will soon follow.
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20 Apr 2014 09:07 PM
True enough. However, if an anode doesn’t last for many years, I would also start thinking about higher levels of galvanic corrosion. Galvanic corrosion is an electrochemical process in which some metals corrodes preferentially when other metals are in electrical contact. Normally, the anode (usually made out of magnesium, aluminum, or aluminum/zinc alloy) will sacrificially corrode to protect the steel water tank. However, if you have brass or stainless steel components in the HR heating system, both the anode and the steel tank will be at high risk of galvanic corrosion. Here is the galvanic series which will give you indication of what metals will experience galvanic corrosion:

http://en.wikipedia.org/wiki/Galvanic_series
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jojojoUser is Offline
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20 Apr 2014 10:09 PM
Thank you for the information.

No, the plumber did not give a specific reason as to why turning off the water heater caused it to fail.....he could not find a specific reason....and just said by letting it sit all spring/summer/fall then turning it back on for only 3-4 months MIGHT have caused it to fail. That is why I am interested to see what others do to their water heater when not in use during the off heating season.

If I do not turn the water heater completely off and let is sit....then my only other option would be to turn the thermostat completely down(which we do anyway) on the floor heat...and turn the water heater to lowest setting (90degrees) and let it heat all spring/summer/fall until we start up the floor heat again. I am not sure, but would that be better on the water heater??

Interesting about the antifreeze....I will go on the website and check out the performance calculations. Wish we did not have to worry about freezing....but not sure it would be a good idea to not use some antifreeze....as we can lose power for long periods of time. That would be the only time we really need to worry about freezing.

thanks again
jolene

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21 Apr 2014 09:47 AM
You can also use corrosion inhibitors which should make it last longer if the problem is internal corrosion. I wouldn't leave it on all summer.

Question: are typical water heater heat exchangers durable with the greatly increased number of "heat on" hours that use as a boiler entails?
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21 Apr 2014 09:55 AM
Jolene, I would have asked the plumber what actually failed…the tank, the temp controller, the heating element, etc. Folks turn off water heaters all the time when they are not living in their building (i.e, on vacation or part-time home) or turn off the heat for the season. This is something that you should do. For gas water heaters, you typically turn the dial to vacation mode which basically just keeps the pilot light on and does not heat the water tank. For electric water heaters, you just open the circuit breaker. You should also turn off the water supply to the water tank, but you must make sure that you accomplished the aforementioned steps before doing so. Gayle
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21 Apr 2014 10:01 AM
Jonr, real boilers are designed for high duty cycle heating applications and should be more reliable and last longer than water heaters. However, water heaters are much cheaper than boilers and folks often use them for HR heating applications with success. You can replace a water heater a couple times and still be ahead economically, especially if you DIY.  If you use a corrosion inhibitor, just make sure it is compatible with PEX and the other components used in the HR heating system.
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
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21 Apr 2014 10:18 AM
You have to love the master's dissertation...

To answer your question.

Assuming your water heater is serving a "closed" system.

Your plumber is making things up.

There is no reason to put antifreeze in any hydronic radiant floor (HRF) heating a basement slab, anywhere.

We use many water heaters in our design/build business but never electric water heaters, as they are not rated for space heating, are limited in output and take up more space than the equivalent electric boiler purpose-made for space heating.

Have a proper heat load performed and an electric boiler installed, size to the load with the proper inhibitor dosed and tested at commissioning.
MA<br>www.badgerboilerservice.com
jojojoUser is Offline
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21 Apr 2014 08:05 PM
Thank you all very much for the information/replies/suggestions.

Gayle---the plumber was unable to pin point specific cause of failure...at the start of the season we were unable to turn on/ start the water heater back up for the season as it kept tripping the breaker....they tried replacing different elements and other parts...but it kept tripping. Checked the electrical connections...breakers...etc. Corrosion did not seem to be an issue. Plumber was also very surprised because it was a good commercial water heater and 5 years was short life span for the brand/reputation in our area.

Badger Boiler--- I have a geothermal heat pump.....and in my area we get a special electrical rate...however everything must be electric...so no gas water heater for us.

As a couple of you have suggested.... I think I will continue to shut down my closed loop system water heater during the off months and hope my last water heater failure so soon was a fluke! That seems to be the best bet and makes the most sense.

There are obvious differences of opinions on the use of antifreeze...or not to use...so I will have to look at that issue closer.

Thank you all for the information!
jolene




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21 Apr 2014 09:43 PM
I did not suggest a gas boiler, rather an electric. I did not detect a difference of opinion "obvious" or otherwise, on anti-freeze either. If you are paying attention: the amp draw is an issue for a real electrician. Most plumbers are not qualified to specify or install an electric water heater, let alone diagnose a problem with one. If you have an electric boiler there is no "shutting down", since the boiler only "runs" when called by a thermostat. Why I bother...
MA<br>www.badgerboilerservice.com
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21 Apr 2014 11:11 PM
Borst and Badger - I beg to differ. If you have a walkout basement, that is not ICF, you should use antifreeze. No system circulates all the time, therefore freezing will happen. Didn't we have this discussion over a garage door ;-)
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22 Apr 2014 08:20 AM
FBBP....could you please explain what (ICF) stands for that you mentioned in your post...as I am heating a basement slab in the midwest. Sorry..new to all the terminology...and just trying to learn a few things out about our system.

Thank you kindly
jolene
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22 Apr 2014 09:00 AM
FBBP, you beg to differ with what? Borst suggested that “Antifreeze is only typically used when a HR system is at risk of freezing...” We don’t see how ICF, garage doors, or walk out basements pertain to this discussion.

Jolene, ICF stands for Insulated Concrete Form. ICF is sometimes used in lieu of 2x4/6 stick built construction for walls. You typically end up with 2.5” of EPS foam insulation on the outside, 6” of reinforced concrete in the middle, and 2.5” of EPS foam insulation on the inside. So ICF is not relevant to this discussion. It sounds like you experienced a premature water heater electrical component failure.
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22 Apr 2014 11:41 AM
Posted By sailawayrb on 22 Apr 2014 09:00 AM
FBBP, you beg to differ with what? Borst suggested that “Antifreeze is only typically used when a HR system is at risk of freezing...” We don’t see how ICF, garage doors, or walk out basements pertain to this discussion.

Jolene, ICF stands for Insulated Concrete Form. ICF is sometimes used in lieu of 2x4/6 stick built construction for walls. You typically end up with 2.5” of EPS foam insulation on the outside, 6” of reinforced concrete in the middle, and 2.5” of EPS foam insulation on the inside. So ICF is not relevant to this discussion. It sounds like you experienced a premature water heater electrical component failure.


***If the HR system was properly designed and installed, and will always be operated during freezing weather, it should not be at risk of freezing.***
No system always circulates unless it is under designed. When the room doesn't call for heat for a short period of time, the water next to walkout can solidify enough that the flow will take the path of least resistance through other loops. This allows the subject loop to freeze completely. This was the discussion we had about a leaky insuldeck crawlspace. Because this is pertinent on another current thread, I felt it was important enough to correct it here as that OP will probably also read this thread.
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22 Apr 2014 01:21 PM
Thank you for the terminology explanation......easier to follow along with all of you knowledgeable individuals!

Thanks again for the information....it helps homeowners like me learn a little more about the systems and how they run.
jolene
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22 Apr 2014 04:33 PM

***If the HR system was properly designed and installed, and will always be operated during freezing weather, it should not be at risk of freezing.***
No system always circulates unless it is under designed. When the room doesn't call for heat for a short period of time, the water next to walkout can solidify enough that the flow will take the path of least resistance through other loops. This allows the subject loop to freeze completely. This was the discussion we had about a leaky insuldeck crawlspace. Because this is pertinent on another current thread, I felt it was important enough to correct it here as that OP will probably also read this thread.

I stand corrected. After 25 years doing it the wrong way, I feel much relieved to get the truth about solidifying water, etc. Designed, installed or serviced a lot of radiant floor heating systems in cold climes, like, say Minnesota, have you? If so, have you also specified antifreeze for the potable water pipes, inches from the exterior and not protected in any way by thermal mass or year round ground temperatures?
MA<br>www.badgerboilerservice.com
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22 Apr 2014 07:05 PM
Hey Badger - I feel so much better now knowing you will be more careful in the future ;-)

Seriously - you have never had a client call about a cold area next to a walkout or a garage door during a cold snap? Even when there was a little bit of glycol in the system? When one loop shuts down?

'course maybe you don't see really cold weather like , say, Calgary? ;-)

No, I don't put glycol in potables, but then I don't put them in, on or near outside walls. There is no need to with decent planning. And I certainly never cut them into my ICF walls even though there is good thermal mass. I really dislike trouble calls when its -40 out.
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22 Apr 2014 08:16 PM
Precisely Badger/FBBP, “if the HR system was properly designed and installed, and will always be operated during freezing weather, it should not be at risk of freezing.” Only a fool would design a HR system with only room temp control feedback. Any competent HR designer would always use outdoor temp and slab temp control feedback so as to never allow the slab to get anywhere near freezing temp. Furthermore, for us installers that actually place the PEX in the middle of slab, we are unlikely to ever experience PEX damage even if the slab were to freeze. So sorry if you also just foolishly stapled your PEX to the insulation and you let the slab freeze without using antifreeze...hope you have good insurance and like replacing slabs. Don't give up...if you guys keep at it long enough, you will eventually learn to do it right.
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
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22 Apr 2014 10:43 PM
Okay....so am I safe in thinking that since we can/have lost power for long periods of time (24-72hrs) during winter storms...then my system is at risk for freezing and I should be using antifreeze in my system...

Thanks again
jolene

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