Radiant floor heat provided by Tankless. Need explanation...

[2002sheds]

Hi All,
Our house is heated by a 2 zone open-loop radiant system with PEX. We occasionally need to clean out the sprayer diverter in the kitchen sink faucet and the supply line itself (when it is really badly clogged with grit).

I installed a fine mesh filter on the cold water supply pipe before it reaches the water heater (or anything, really), but it has done nothing for the grit that is already in the nearly 2,000 feet of PEX. I'd like to install another filter ahead of the domestic hot water line, but I can't quite wrap my head around the plumbing, so I am unclear of where to place it.

Below are pics of the system, from outside and inside the structure. My question is this: How does the water heater "take in" water from the pex loops in this system (when domestic water is not being used and heat is called for, activating the re-circulation pump)? It seems to me that the pressure from the source line would be greater than the pressure from a -re-circulation pump, but I really don't understand, so that is just a guess.

I am asking because I would like to determine where to place the filter, and trap that grit.


Thanks!
David

 

[Fitter30]

Sharing the same heater heat and domestic hot water isn't the best idea. Dhw just sits in the heating piping all non heating time stagnating. Heres a 200 mesh filter rated for 200*f for outlet of the heater dhw side and put a cartridge filter on the cold water then you will know where the grit is coming from. Ever get rust color water from dhw?
https://www.freshwatersystems.com/products/rusco-hot-water-spin-down-filter-system-3-4-fpt

 

[Sponsor]

 

[2002sheds]

Hi Fit,
Thanks for the response! No rust color, and the risk of Legionnaires is hopefully low because there is quite a bit of movement every day. The system was installed by an experienced radiant floor plumber, but if I should consider a change, I am open to hearing how to modify…

Thanks for the recommendation/link. The filter looks a lot like the one I now have out in front of the incoming water.

I’d still like to learn how the water goes back through the heater to warm the water in the radiant tubing. As I said earlier, it seems like to me that any water that is routed back to the heater would be competing with the pressure of the incoming water. Obviously, it works… I just don’t understand how…

Thanks,
David

Sharing the same heater heat and domestic hot water isn't the best idea. Dhw just sits in the heating piping all non heating time stagnating. Heres a 200 mesh filter rated for 200*f for outlet of the heater dhw side and put a cartridge filter on the cold water then you will know where the grit is coming from. Ever get rust color water from dhw?
https://www.freshwatersystems.com/products/rusco-hot-water-spin-down-filter-system-3-4-fpt

 

[Bannerman]

seems like to me that any water that is routed back to the heater would be competing with the pressure of the incoming water.

Water pressure in the system will be equal throughout the entire system including at the inlet and outlet of the pump while the pump is not operating.

The pump will be activated by a thermostat to create a pressure difference between the inlet and outlet to cause water to circulate through the heating loop since the heating loop and WH will provide a path between the pump inlet and outlet.

 

[2002sheds]

Hi BanMan,
That is exactly what I was trying to learn — thank you!!!
I am pretty certain that whatever grit is present arrived before I installed a fine mesh filter ahead of the water heater.
Hot water that has its own line from the heater to a bathroom provides no grit. The only issues there are hard water deposits that form on the shower head.
I am leaning towards installing a fine mesh filter as recommended previously) under the kitchen sink. It “should” catch grit before the hot water faucet and dishwasher… or at least I hope so

Thanks,
David

Water pressure in the system will be equal throughout the entire system including at the inlet and outlet of the pump while the pump is not operating.

The pump will be activated by a thermostat to create a pressure difference between the inlet and outlet to cause water to circulate through the heating loop since the heating loop and WH will provide a path between the pump inlet and outlet.

 

[Fitter30]

To separate the system it would probably take a repipe on the heating side to add a plate heat exchanger another pump, expansion tank , air eleminator , fill valve and regulator. Also the Taco pump is installed wrong the motor should be in the horizontal or motor up if vertical. You can google the install manual for reference. It has lasted
because it has had city water pressure and a open system.

 

[Bannerman]

Fitter, the pump appears to be Grundfos.

When a water heater is utilized for both DHW and an open loop hydronic heating system, the pump will be typically required to operate for a specific amount of time every 24-hours to ensure the water in the hydronic loop wil not stagnate, but will be circulated every day during the non-heating seasons.

 

[2002sheds]

Fitter, the pump appears to be Grundfos.

Hi BannerMan,
You are correct — the recirc pumps are Grundfos. The control boxes are Taco, as are (I think) the valves.


Thanks,
David


When a water heater is utilized for both DHW and an open loop hydronic heating system, the pump will be typically required to operate for a specific amount of time every 24-hours to ensure the water in the hydronic loop wil not stagnate, but will be circulated every day during the non-heating seasons.

 

[Fitter30]

That brown pump ( brown color represents bronze) sure looks a taco but its still piped wrong google a install manual.

 

[2002sheds]

Hi Fitter,
Great catch... and will do!

Thanks,
David

That brown pump ( brown color represents bronze) sure looks a taco but its still piped wrong google a install manual.