# Using a indiract with with Radiant



## czplumbing (Nov 24, 2014)

so I have a question about a radiant set up I am working on. I am going to be using a NCB 240 Navien Combo unit. One side doing the domestic hot water and the other doing a 3 zone radiant heat system. the way I was going to set it up was coming right off the manifold and treating it the same as a boiler feed and return. with a circulator going to each radiant manifold. The Hvac company told the contractor I should put a indirect hot water heater in the mix having the boiler heat the indirect and run the radiant manifold off the domestic loop on the indirect. I see how that would work but is that not over kill? Though behind doing that is to stop the boiler from short cycling, but once the boiler gets each zone up to temp wouldn't it just maintain heat ! Being this is the first radiant job using a tankless unit I want to make sure it is set up right. I spoke with a rep from Blackman and he said my set up with out using the indirect was fine as I have also seen other system set up exactly the same and up and running, but I was seeing how you guys set them up and if you had any thought on this would be much appreciated


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## ShtRnsdownhill (Jan 13, 2016)

Ive done a bunch of radiant, but always used a cast iron boiler , those wall hungs are having issues...I just looked at a 3 year old navien unit and the domestic water heat exchanger is split and leaking ..a freaking nightmare...luckilly I didnt install and sent her to call navien as it still under warranty..


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## camper (Jan 17, 2016)

have not had any problems piping these boilers with radiant heat using the primary secondary loop with outdoor reset have piped using boiler water temp set for 1 floor covering and also piped with thermostatic mixing valves for different water temps for different floor coverings have also piped with tekmar controls #150 &152 with floor sensors to maintain certain floor temp and have outdoor shut down on them


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## czplumbing (Nov 24, 2014)

I will be using 3 tekmar stats with slab sensors and 2 uponor radiant manifolds. one manifold will be doing basement witch is a 3 loop and the 2nd manifold is a 8 loop split up to two zones using actuators , pushing them will be 2 bumble bee 007 circulators with IFC .


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## Jessedog11 (Feb 6, 2016)

I think Blackman is wrong, their is a flow sensor on the domestic side that is a priority switch that shuts down the Heating zones in favor of Domestic HW. Unless your wiring the relay with a priority option, you may have a problem.


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## ZL700 (Dec 8, 2009)

czplumbing said:


> so I have a question about a radiant set up I am working on. I am going to be using a NCB 240 Navien Combo unit. One side doing the domestic hot water and the other doing a 3 zone radiant heat system. the way I was going to set it up was coming right off the manifold and treating it the same as a boiler feed and return. with a circulator going to each radiant manifold. The Hvac company told the contractor I should put a indirect hot water heater in the mix having the boiler heat the indirect and run the radiant manifold off the domestic loop on the indirect. I see how that would work but is that not over kill? Though behind doing that is to stop the boiler from short cycling, but once the boiler gets each zone up to temp wouldn't it just maintain heat ! Being this is the first radiant job using a tankless unit I want to make sure it is set up right. I spoke with a rep from Blackman and he said my set up with out using the indirect was fine as I have also seen other system set up exactly the same and up and running, but I was seeing how you guys set them up and if you had any thought on this would be much appreciated


If you use a combi boiler, why would you use a indirect? if you want a indirect, use a dedicated boiler

You cant pump through the domestic side as its meant for intermittent max 5 GPM flows because its designed to heat water up to 5 GPM at a high temp rise. 

Boiler side is for closed system heating with a must do primary/secondary piping set up and the domestic side is intended to function like a tankless water heater. Anything else will be a failure soon.

Installing it any other way than how their manuals and drawings show will become a major headache & financial mistake for you.


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## Jessedog11 (Feb 6, 2016)

ZL700 said:


> If you use a combi boiler, why would you use a indirect? if you want a indirect, use a dedicated boiler
> 
> You cant pump through the domestic side as its meant for intermittent max 5 GPM flows because its designed to heat water up to 5 GPM at a high temp rise.
> 
> ...


why would you use a primary secondary set up on a condensing boiler?


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## ZL700 (Dec 8, 2009)

Jessedog11 said:


> why would you use a primary secondary set up on a condensing boiler?


 Because many condensing boilers like the Navien combi unit requires it.
The pump inside is a boiler pump only, not capable of operating system flows.


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