Heating my floor with my DHW recirculation line.

JohnNY

So…at 55 years old I bought my first house ever. Fixing it up and remodeling it is every bit as difficult and expensive as I've been led to believe it would be. But that's a different conversation.

A few weeks ago I decided to finally connect the DHW recirculation pump (at my Lochinvar Noble combi boiler) and the tee at the farthest fixture that I installed and valved off in anticipation of this day. On my way running copper back to the boiler, I came across the two ends of the radiant heat tubing I'd set in the floor and stubbed down into the (40" tall) crawl space below. So I stopped and thought about it and connected my recirc lines to my radiant floor heat. Now my domestic recirc heats my floor.

The only control is a plug in Christmas light timer that runs my stainless steel recirculation pump for three hours in the morning and three hours at night, which is when my wife and I are home and is plenty of time to heat the small bathroom slab.

I'm very happy with how well it all works. Convince me that this is the worst thing you've ever heard or I'm going to do it again on my other bathroom next month.
TIA

John Cataneo

Derheatmeister

https://forum.heatinghelp.com/discussion/197244/heating-my-floor-with-my-dhw-recirculation-line

Just make sure that the Heat is still working even when it is 100 something outside and your AC is working..😕

As you can maybe appreciate and understand the formation of legionnaires is a risk with these kinds of setups.

Again….Not a big fan but Tekmar made a control that will purge the lines in order to prevent the formation legionnaires with this piping arrangement.

JohnNY

@derheatmeister
How's it going my friend?

I'm only using the combi for DHW at the moment…until I get to install my Runtal panels in the fall this year or next…and I don't think I need to worry about Legionella since I'm running the pump for two periods every day 12 months per year.

PC7060

Seems like a clever idea to me.

Have you configured to runs when water temp drops below a set level?

WMno57

Could be a Legionella problem. Maybe not under normal operating conditions, but what about conditions outside of normal?

Shower in early afternoon

Power failure

Equipment failure

If the combi could heat DHW to 140, then mix down to 120 before supplying to the bathroom, I think that would increase the margin of safety. An indirect tank held at 140 would be even better yet.

Legionella can't hurt you if they have been cooked long enough AND at a high enough temperature. Less time needs more temp. More time needs less temp. Once they have been properly cooked they cant start growing again.

Jamie Hall

I like it. My kind of engineering!

JohnNY

https://forum.heatinghelp.com/discussion/comment/1803708#Comment_1803708

No. It just runs on a timer and the boiler takes it from there. The DHW runs at 130° and gets mixed down to 115°.

WMno57

Cooking time and temp for Legionella

https://en.wikipedia.org/wiki/Legionella#Heat

JohnNY

I'm no scientist but I think the fresh, chlorinated water scouring the ~12 feet of ⅜ " Uponor tubing twice a day minimizes the Legionella problem, an issue which I knew would come up many times in this thread and was my only concern when activating this system. I hate guessing at this stuff and am hoping someone will chime in who knows the actual risk potential. PEX is used all over the country for domestic water and no one is running 140° through it. I'm not convinced the bacteria grows easily.
I'm also taking into account the small countless hydronic systems which lay dormant 7 months out of the year and run off of standard gas-fired tank-type water heaters without issue.
I'm not defending any of this. I'm just wondering how crazy I want to get to heat my 4' x 4' (including the toilet bowl) floor space.

mattmia2

I'd feel better if you used a hx, probably could figure out a cleaver way to get the lower temp as a bonus.

JohnNY

Thanks for this. I'm raising my temperatures.

@WMno57

https://en.wikipedia.org/wiki/Legionella#Heat

JohnNY

https://forum.heatinghelp.com/discussion/comment/1803715#Comment_1803715

Well, it's a combi so the next thing I'd do is set up a manifold and actually tie it into the space heating side. Clearly, I'm being lazy. I think there's a saying about the shoes of the cobbler's children having holes?

Matt_67

But then wouldn’t you need a buffer tank? Most recirc systems don’t run 24/7 anyway, I can’t really see a difference in the way you are running it. Only issue I see is heating when it’s hot outside, probably not more than 1000 btus.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1803717#Comment_1803717

My day job is designing/maintaining/installing AV systems and there is just a mass of unlabeled undressed wire behind my receiver, TV, and components and a few components sitting on the floor next to the cabinetry.

JohnNY

Here's what I did. Don't be jealous of my computer drawing savvy.

ChrisJ

My recirculating system just uses a Taco 006 and an aquastat.

I had mentioned running it through a towel rack awhile back and quite a few people here seemed to think that was a terrible idea for some reason.

Jamie Hall

I think it's fine. As I said above. I can't see that the bacteria problem would be any worse with that setup than it would be with any other recirculation setup.

JohnNY

https://forum.heatinghelp.com/discussion/comment/1803731#Comment_1803731

Both Liv Tyler and Sarah Jessica Parker warm their very hot British-made stainless steel towel racks with their DHW recirc lines. Same engineering firm did both their homes. I was the plumber. You'd be in good company.

hot_rod

Why not? I've done copper and stainless heated towel bars with DHW recirc.

I suppose if you exercise it once a day bacteria would not be an issue.

No different than a DHW recirc that timers off, I suppose.

If you tied it into the heating side of the boiler you could use the modulation, and anti cycle function to lessen short cycling.

ethicalpaul

do you even actually catch it from DHW? It always seems to be from AC cooling towers or fountains spewing particles into the air

every day for 50 years my shower supply pipe gets up to 120 or so, then you know what? It cools off to about 70 degrees over the next x hours. Am I supposed to be scared?

Mad Dog_2

Yes..it's found in Domestic HW systems in NYC often. Large housing projects and facilities with long pipe runs, poor or no recirculation, dead ends, the biggest cause, Water heater NOT maintaining a high enough temperature to kill regionally (160ish). It will die at lower temps but it takes longer. 160 kills it fast. Mad Dog

WMno57

The risk is a combination of quantity of Legionella and how immunocompromised someone is.

A couple dozen Legionella from a short length of 1/2 pipe will be handled by most people's immune systems.

A tank full of Legionella would be more risk, but most younger people's immune systems will fight it off.

Then there is the perfect storm of elderly people in the old folks home with long lengths of DHW plumbing. Maybe some stagnant parts of that plumbing that occasionally get flow. Elderly people are also at greater risk for burns from overly hot water. They lose the ability to sense hot, and lose reaction time.

Our immune systems change as we age. It's still OK at fighting off things it has been exposed to, but gets worse at fighting new things. COVID and maybe Legionella.

Some people have over active immune systems. Maybe they weren't exposed to enough germs at an early age? This can be good and bad.

Our immune systems fight threats with inflammation. Too much inflammation is a undesired side effect of an overactive immune system. Some forms of arthritis, heart disease.

Much left for Science to discover about our immune systems. Amazingly complex.

@JohnNY had a good point about his municipal water being chlorinated. I'm on a private well. More of a risk with my country water than Big Apple water?

ethicalpaul

I'm sure it's found everywhere, and I'm sure that if you have lowered immunity you are more prone to catch it. Those weren't my question. From my reading it seems clear that you don't actually catch it at home.

Jamie Hall

Looking over @JohnNY 's design again, I don't see a reason for concern about Legionella from the floor return line. That recirculated water is going back to the hot water heater, which is kept at above 120. That will do any bacteria in there in in short order.

@WMno57 has some good comments about the elderly and immune history, though. The ability of our bodies to fight off various problems — or not — does decline with age, but is also influenced by our histories of exposure. I've read — and I'm sorry, I can't find the references — that farm kids tend to be healthier simply because they have been exposed to more "stuff" early in life. Then of course there is our individual genetic variation. I thank God, for instance, that I've been very healthy all my life — but I am a farm raised World War II brat. The only health problem I have was caused directly by the Covid 19 vaccine I more or less had to take (myocarditis leading to congestive heart failure)(it will make you healthy they said. It will prevent Covid they said. Wrong on both counts).

JohnNY

@Jamie Hall Yes, and the drawing doesn't allow the space to draw it accurately. The hottest water reaches the fixture branches first, the floor is next in the circuit, then into the pump and boiler with a little bit of return water being diverted through the mixing valve. I'm not worried about it but I did raise my temperatures last night.

Larry Weingarten

Hi, Looking into the future a bit, a concern about being self limiting comes up. Constant recirc may be needed in hospitals, but demand recirc is a better fit for residential application, and it is substantially more energy efficient. A wireless remote or motion sensor can activate the pump, getting you hot water by the time you need it. Floor heating isn't going to play nice with demand pumping, so the option of upgrading to the more efficient approach is no longer really an option. Aside from that, it looks like a nice two for one.

By the way, I recently did some testing for legionella in a 5+ year old solar tank fed with well water. The bottom of the tank, where I drew the test water from, rarely exceeds 110F. Test came back negative. I'm thinking a good immune system is the best defense, so nursing homes and hospitals absolutely need preventive measures, but homes with right-sized plumbing, maybe not so much. 🤔

Yours, Larry

BoilerJake

The only potential concern I would have is overheating of that bathroom since there is no temp control - but I am guessing that you have a low enough flow rate in the DHWR line that it won't be an issue for the three hour period you run it?

The only other thing to consider - from a warranty perspective - is the flow rate through your 3/8" Uponor. Uponor limits DHW-R velocity to 2fps, which is about 0.6 gpm in a 3/8" pex line. The timer gets you around this for the most part (the wording is 2fps continuous recirc velocity), but just something to consider!

Zman

We have been inadvertently doing this for years by not insulating DHW and recirc piping. You are just focusing it a bit more 😉. I think if this were mine, I would put some smart controls or a lighting timer on the pump so I could run it for a longer period when it is cold outside and reduce that amount of time you are heating and cooling at the same time in the summer.. I like the idea although I can't help thinking of Jeff Foxworthy 😂.

Sal Santamaura

https://forum.heatinghelp.com/discussion/comment/1803859#Comment_1803859

Yes, one does. See this Mark Eatherton post for a first-hand account of how:

https://forum.heatinghelp.com/discussion/comment/1449875#Comment_1449875

Alan (California Radiant) Forbes

https://forum.heatinghelp.com/discussion/comment/1803868#Comment_1803868

Good point! A friend of mine has a neighbor who just had Uponor pay for their DHW PEX (red and blue) replaced after it failed. I don't know the details, but they put a flow restrictor on the return line.

Zman

https://forum.heatinghelp.com/discussion/comment/1803880#Comment_1803880

Mark's was a summer cabin on an old well and septic where the heating water had been stagnant for months. I think that the risk is very low on a constantly circulated loop with chlorinated city water.

WMno57

Paul asked:

do you even actually catch it from DHW? It always seems to be from AC cooling towers or fountains spewing particles into the air

Don't forget Windshield Washer Reservoirs. ☣️

https://www.bbc.com/news/10293519

ChrisJ

The incubation period for Legionnaires' disease is usually 5–6 days, but can range from 2–10 days, or even up to 16 days.

Meaning you're not going to experience any symptoms at all before that time.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10311690/

mattmia2

https://forum.heatinghelp.com/discussion/comment/1803888#Comment_1803888

We have a good portion of methanol in it to keep it from freezing.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1803859#Comment_1803859

The only people that died directly from the Flint water scandal were people that got legionella from the hot water system in a hospital because the added turbidity from the more aggressive water dissolving scale from the piping consumed the residual disinfectant and allowed bacteria to breed in systems that were not kept hot enough or with enough flow to prevent bacterial growth.

WMno57

"We have a good portion of methanol in it to keep it from freezing."

I'm embarrassed to admit that I've been running 100 percent H20 in the summer due to my thriftiness. After reading that BBC article I just dumped some methanol in my reservoirs.

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1803901#Comment_1803901

So you're agreeing with me that it's not an issue in homes? I can't tell.

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1803903#Comment_1803903

I personally feel it can be an issue and should be treated as such.

But I think it's pretty low on the list of concerns.

WMno57

@ethicalpaul

"On February 5, 2018, a study published in the journals Proceedings of the National Academy of Sciences and mBio concluded that the 2014–2015 outbreak of Legionnaires' disease in Flint was caused by low levels of chlorine which, at higher levels, would have made it difficult for bacteria to replicate.[73] Because chlorine reacts with heavy metals like lead and iron, high levels of both in Flint's water may have been responsible for the decreased amount of chlorine available.[74] On December 4, 2019, research institute KWR from the Netherlands
published the results of their re-investigation of the outbreak in Environmental Health Perspectives.

They found evidence for three sources: strong evidence for exposure to a Flint hospital in 2014 and 2015 for 42 of 86 confirmed cases, and weaker evidence for exposure to city water at home or living in the
proximity of a specific cluster of cooling towers, both only in 2014. Each source could be associated with only a proportion of cases."

https://en.wikipedia.org/wiki/Flint_water_crisis#Possible_link_to_Legionnaires'_disease_spike

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6957290/

WMno57

My first post in this discussion I said:

"Maybe not under normal operating conditions, but what about conditions outside of normal?"

Flint, Fukushima, Chernobyl and Mark Eatherton's cabin were all fine, until they weren't.

Building codes attempt to protect us in ALL conditions, not just the USUAL conditions.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1803903#Comment_1803903

You asked if people actually get legionnaire's disease from hot water, i referred to a case where they did.