Water Heater for Small Radiant Floor. Open or Closed?

StephenC

Hi All,

I want to connect a separate electric water heater to a single zone serving a bathroom floor and shower walls.



The expert at the wholesaler was adamant that I not use an unrated appliance for this application. Buuuut, if I do such a thing, it should be an open or combination system, on a circulator with a timer, to prevent stagnation in the non heating seasons. I want a closed isolated system with a backflow preventer to isolate the heating water from the potable.



We had a pleasant discussion but disageeing with him made him less than helpful.



I want to set this up as a  gravity circulated loop using a zone valve on a thermostat. Is there zone valve that will work for this?

Opinions and suggestions please?



Thanks

Stephen

Mark Eatherton

You're on the right track...

Stay away from open loop DHW/space heating systems unless you like Legionairres disease.



Having a timer and a pump on a combination system GUARANTEES that it will fill your tank with plenty of bacteria, AND it will be wasting energy in the middle of the summer.



Not sure of your reasoning behind going with gravity. Can you expound upon that before I comment as to the feasibility?



If you lose power, you lose your heat source as well, so it won't work during a power outage.



ME

StephenC

Gravity equals minimal parasitic costs

Hi ME,



I have done this sort of thing before with just a loop and constant gravity circulation. Nice toasty constant heat for bathroom.



I thought this time adding a little control would be sensible in light of rising electricity costs.



Definitely do not like recirculating bugs and was astonshed that the supply house radiant expert would advocate it and be insulted when I rejected it

The house has forced air oil with two woodstoves so I am not concerned about outages just warm floors when the lights are on.



Thanks

Stephen

Mark Eatherton

Fair enough then...

So long as you are aware of the issues associated with gravity operation (BIIG floor temperature differentials and potential flow issues with the wall if done vertically as opposed to horizontally and air elimination issues) then go for it.



Any zone valves should work. In keeping with your minimalistic approach to parasitic power, I'd go with a 120 volt zone valve and a line voltage thermostat to avoid ghost power consumption associated with a transformer in stand by mode. I've done that on boiler space heating system that were off grid and it worked like a champ. The end switches actually sent 120 volts to the boiler/pump combo so when all stats were satisfied, there was ZERO parasitic standby power consumption.



I've done DHW gravity circulation returns that work like a champ. But you (obviously) need height above the source to make it work.



Send your appalled wholesaler here, and will will enlighten him to the dangers of open systems. ;-)



ME

(Legionella Survivor)

StephenC

Past experience has been surprisingly successfull

Understood on the floor temp differentials.



The last time I did this in a basement bathroom I looped the supply up across the ceiling down the wall behind the mirror and across the floor and  then re-entering at the bottom of the tank. Surprising how well it has worked once properly purged of air. This has worked for years now with no added water or purging. The tank is turned off and on as the seasons dictate.



This time the tank is in the basement and the bathroom is two floors above. I ran the tubing up to the top of the shower wall first and then horizontal loops down the wall then across shower floor and rest of very small bathroom. 50 square feet max.



Is there any manufacturer you would recommend for valves that have the least restrictive flow characteristics?



Was that appalled or appalling? I would send him here but I am not sure he is the type that likes to be educated, especially if it was I who sent him. I do not think he likes the non plumbing and heating tradesmen.



Glad you survived Any lasting effects?



Thanks

Stephen

Mark Eatherton

Lasting effects...

Severely reduced lung capacity. The fillia of the lungs were severely damaged.



I suspect I will end up on oxygen full time before I leave the face of this Earth. Just glad to be alive. Could be worse. Thanks for asking.



If you want to educate your wholesaler without having him come here, have him go to contractormag.com and have him do an internal search of legionella + Yates, or legionella + Eatherton. Lots of gun powder for your bullet there.



ME

StephenC

No scuba diving for you then

Worth avoiding at any price!



Is the damage much like a smokers that somewhat repairs over time?



I would be happy to help educate this particular guy but suspect he does not like me now and any direction I may give him will make him more prickly than he already is. Bullets might backfire on me.



The reasoning he had for the open/combined system was that someone in the future could re-purpose the tank for its intended use as potable water heater and it would now be contaminated after use in a closed system. What do you think?



Thanks

Stephen

Mark Eatherton

I use to smoke...

But haven't for a long time, but this stuff doesn't seem to want to repair itself. The only good thing about contracting the disease is that there are no documented cases of re-contraction after the first round...



As for the use of a water heater, I consider them a poor choice of heat due to their continual heat loss, in fact I use to heat my own home with one, so am speaking first hand. I replaced it with a real mod/con boiler and reduced my fuel use by 30%.



But for an inexpensive heat source, they are considered a throw away appliance. When you are done, you throw it away.



Not all water heaters are approved for use as a space heating appliance, so make certain that the one you use is, or you may be throwing away more than one heater...



ME