Radiant heated floor plumbing below slab

[cmalinowski]

Hi all. Thanks for previous help. I am getting ready to lay my loops and was planning to put my loops' start/end in a crawl space below the slab level. I'm wondering if this is okay. Seems like it would be hard to fill to some extent (was planning on glycol since I'm not here in northern NY a lot in deep winter), and maybe getting air out would be PITA, but are there other issues I should be concerned about in doing it this way? And, yes, the loops would be exiting the slab horizontally into the wall and then curving down to the plumbing in the crawl space. Crawl space is ~4.5ft high.

Thanks,
Chris

 

[Packard V8]

Life would be much easier, simpler, less expensive, easier to service (and it will require service) if the boiler were in a utility closet in the garage.

How many square feet will you be heating? Is this a closed system; heat only?

jack vines

 

[yeldogt]

There is no issue with that -- make sure to insulate the slab and if you do use glycol make sure the boiler is OK with it -- or used a heat exchanger.

Good loop layout makes for nice operation and smart pumps save on electric

 

[yeldogt]

Life would be much easier, simpler, less expensive, easier to service (and it will require service) if the boiler were in a utility closet in the garage.

How many square feet will you be heating? Is this a closed system; heat only?

jack vines

My guess it's in the basement of the house

 

[cmalinowski]

Life would be much easier, simpler, less expensive, easier to service (and it will require service) if the boiler were in a utility closet in the garage.

How many square feet will you be heating? Is this a closed system; heat only?

jack vines

Fair enough on the service. My HVAC system is in there already. As is current domestic water heater.

Closed system. Heat only. Although I'm still considering a boiler that pulls double duty and does DHW either for the whole house, including garage apartment, or just the garage apartment.

My guess it's in the basement of the house

It is under the current house. The crawl space is easily accessible, just a tad short for making into an actual finished basement.

 

[Kezorm]

Is crawl space conditioned? Or at least stay a reasonable temperature above freezing year round? Even with glycol, I wouldn't think you want the equipment too cold on regular basis. Don't know if that's a problem though. Only you can decide if want to live with 4.5' headroom. Seems sufficient, but I'm not the one that has to work in there . Otherwise no technical problem going down.

Here's my current project with garage loops down into basement. Slab was poured today

 

[fitter30]

1/2" oxygen barrier pex 300' max length for a loop. Spirotherm best device for air elimination. Do not mix heating hot water with domestic hot water without a heat exchanger for separation. Do not use automotive antifreeze use only boiler or chilled water antifreeze. The mix doesn't have to be 50% but not less than 30% for the inhibitors. Can find find info on the slush % on their web site. The floor coverings if using wood check with the manufacturer.

 

[cmalinowski]

Is crawl space conditioned? Or at least stay a reasonable temperature above freezing year round? Even with glycol, I wouldn't think you want the equipment too cold on regular basis. Don't know if that's a problem though. Only you can decide if want to live with 4.5' headroom. Seems sufficient, but I'm not the one that has to work in there . Otherwise no technical problem going down.

Here's my current project with garage loops down into basement. Slab was poured today

Crawl space is conditioned. HVAC heats/cools it like the rest of the house.
Thanks. That photo looks like about what I'm doing.

1/2" oxygen barrier pex 300' max length for a loop. Spirotherm best device for air elimination. Do not mix heating hot water with domestic hot water without a heat exchanger for separation. Do not use automotive antifreeze use only boiler or chilled water antifreeze. The mix doesn't have to be 50% but not less than 30% for the inhibitors. Can find find info on the slush % on their web site. The floor coverings if using wood check with the manufacturer.

Thanks. Was going to use cryo-tek. I doub't I'll need to use glycol, but if something goes bad and a storm causes issues for days in sub-freezing temps while I'm not here, I feel better with glycol in the system.

 

[Packard V8]

Do not mix heating hot water with domestic hot water without a heat exchanger for separation.

Interestingly, some companies/installers/codes mandate separation, while others say no problem running both through one water heater.

We have radiant hot water in only one cement floor/tile sunroom, for fifteen years have been using a dual outlet single chamber 80-gallon Bradford-White water heater with no issues.

jack vines

 

[yeldogt]

Interestingly, some companies/installers/codes mandate separation, while others say no problem running both through one water heater.

We have radiant hot water in only one cement floor/tile sunroom, for fifteen years have been using a dual outlet single chamber 80-gallon Bradford-White water heater with no issues.

jack vines

The issue with a tank and duel use is getting water stuck in the loop over the summer ...... since it is easy to cross over to the cold side and used for drinking etc.

 

[yeldogt]

Crawl space is conditioned. HVAC heats/cools it like the rest of the house.
Thanks. That photo looks like about what I'm doing.

Thanks. Was going to use cryo-tek. I doub't I'll need to use glycol, but if something goes bad and a storm causes issues for days in sub-freezing temps while I'm not here, I feel better with glycol in the system.

I don't know that PEX -- not that I know them all. Just make sure you use a proper O2 barrier product

 

[cmalinowski]

I don't know that PEX -- not that I know them all. Just make sure you use a proper O2 barrier product

Sorry, cryo-tek was the glycol I was going to use. Using 02 Barrier Pex-A. Thanks.

 

[fitter30]

Interestingly, some companies/installers/codes mandate separation, while others say no problem running both through one water heater.

We have radiant hot water in only one cement floor/tile sunroom, for fifteen years have been using a dual outlet single chamber 80-gallon Bradford-White water heater with no issues.

jack vines

Open systems dhw sitting in piping all summer that there is no flow bacteria can grow even leagionela disease.

Open hydronic system - Legionella Disease

How do I tell if a hydronic heating system is an open system? Is there a specific component I need to be looking for? The attached link are about Legionella disease. I am also including a blurb from the ReportHost software that I use about the potential concern. A hydronic/domestic hot water...

www.google.com

 

[Mr onetwo]

Your drawing shows pex in middle of slab which then runs into floor joists.Staple pex to styrofoam to gain a bit of clearance.Attach your manifolds to the floor joist and then bring your supply and return up to it with a spriovent.I would never do an open system...should be outlawed in my opinion.

 

[cmalinowski]

Your drawing shows pex in middle of slab which then runs into floor joists.Staple pex to styrofoam to gain a bit of clearance.Attach your manifolds to the floor joist and then bring your supply and return up to it with a spriovent.I would never do an open system...should be outlawed in my opinion.

Thanks. That would have been a good idea, but that drawing is not exact. The area between the basement concrete wall and the first joist is only about four inches or so (but at the top of the concrete wall). Updated drawing below. And there is spray foam insulation all in that cavity. The pex will be at the foamboard (heat sheet), I just rushed the drawing.

I am partial to making this a closed system, so that's most likely what it will be. I think that is more convenient for me anyway.

 

[yeldogt]

There is no problem having the manifolds on the wall and the pex going up to the floor. All my houses work that way. In some cases when you have many loops on an upper floor you have to extend the main supply and return so as to limit the PEX used ... but the water does not care.

My last project has a small loft on the third floor that was serviced with one loop of PEX .... no problem running it to the mechanical room. Using a spriovent is always a great idea and adding the proper fittings to be able to power flush the system. Often you only need to do it once -- but, w/o the proper fitting it's harder to get the air out

 

[Mr onetwo]

no worries...with a spirovent removing the air you should have no problems.I like bumping the pressure up to around 20 psi...helps with air removal.I still think I would mount a manifold station to the bottom of the floor joists and have the pex out of the wall as straight as possible.

 

[yeldogt]

Spirovent is one of the best ... it's not going to fix an air locked loop. Spirovent has a screen and it's designed to slow the water as it flows through the body ..... the screen catches the bubbles. Much better than just having an open area on top