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Discussion Starter #1
Just finished my first hydronic heating system. I did it in my own house before I venture out to other projects. The problem I am having is the Tagaki water heater I used keeps going to standbye. In order to get it to fire I need to close and then rapidly open any valve in the system. It seems like its not getting enough pressure differential from hot to cold. It is a closed loop system. I am using two Grundfos pumps on one zone. One pump moves water through the pex pipes the other is a recirculator.

Any ideas?


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Discussion Starter #3
According to tagaki the unit activates at a flow of .5gpm and deactivates when it drops to .4gpm. When it does operate it delivers consistent 120 degree water and the flow rate with pumps on is 2.2 GPM. Gas is 1” reduced to 3/4” 5 ft from inlet and it is the first appliance after the meter. No obstructions in 3” venting.


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What temperature is your high limit set to.
Do you have zone valves that are reducing the flow.
Are you getting error codes.
With a system like you speak about, you may need a three way valve to maintain the flow if you heating modulates temperature.
 

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Discussion Starter #7
What temperature is your high limit set to.
Do you have zone valves that are reducing the flow.
Are you getting error codes.
With a system like you speak about, you may need a three way valve to maintain the flow if you heating modulates temperature.


The water heater is set at 120. Im not sure what the high limit setting is. It is cycling on and off now. Seems to be running more consistently but not constantly.

My return temp is 105.

I have 3 loops each 300 ft. And I used aluminum plates throught.

The system is floor joist retrofit. I do not have reflective foil in place. I apparently just realized that is necessary this AM.

Grundfos circulators set on high speed.

Thank You for your help. I am going to post a picture of the setup.


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Discussion Starter #8
Update:

Got ahold of Tagaki. Depending upon flow and temp setting the unit auto shuts off. In my case it is when income temp is in excess of 112 degrees. I adjusted the temperature control on the unit to over ride the factory 120 up to 140. This is turn will not shut the unit off until water reaches 132 on the return side.

Also adding double foil bubble insulation.

Much warmer!


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Update:

Got ahold of Tagaki. Depending upon flow and temp setting the unit auto shuts off. In my case it is when income temp is in excess of 112 degrees. I adjusted the temperature control on the unit to over ride the factory 120 up to 140. This is turn will not shut the unit off until water reaches 132 on the return side.

Also adding double foil bubble insulation.

Much warmer!


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Remember the floor finishes like carpet insulate the floor so it takes more heat in your radiant.:wink:
 

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There would definitely be dip switches inside unit to change from 120-130 domestic to a 180 limit on a hydronic system.. awesome thanks for the post and keeping us informed
 

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I have hardwood throughout


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hard wood temp should be under 90 degrees or you risk warping the wood...





Q. Are there any design limitations you need to be aware of?A. Radiant heat is very efficient but does have some limitations. When ceilings exceed 10’ high, the amount of cubic air that needs to be heated can create problems for a hardwood floor. Rooms with high ceilings can create a situation where the floors can become too warm due to the high volume of space to be heated. Rooms with high ceilings may require radiant heat to be installed in the ceilings and ceiling fans mounted to circulate the air.NOTE: All systems should have a fail-safe to ensure that the surface of the floor never exceeds the recommended surface temperature of 85º

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=12&cad=rja&uact=8&ved=2ahUKEwin6I_XoOvlAhVRJKwKHSIYB7IQFjALegQIABAC&url=https%3A%2F%2Fhallmarkfloors.com%2Fpdfs%2FRadiant-Heat-Guide.pdf&usg=AOvVaw13mBnb4sCEHJVJ9Lh4zju0


 

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Discussion Starter #13
The system is operating as it should. It is set at 72 and that seems to be the limit to how high it will go which is more than fine. Next phase is adding more lines and duffuser plates since I only installed one run of 1/2” with plates between each bay. I think it would heat up faster if i doubled the amount of pex and plates. Does that make sense?


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The system is operating as it should. It is set at 72 and that seems to be the limit to how high it will go which is more than fine. Next phase is adding more lines and duffuser plates since I only installed one run of 1/2” with plates between each bay. I think it would heat up faster if i doubled the amount of pex and plates. Does that make sense?


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Yes and increase efficiency... mod con boilers work best with low return temps and best way to do that is large emitters think infloor poured the entire floor is the heat emitter
 

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The system is operating as it should. It is set at 72 and that seems to be the limit to how high it will go which is more than fine. Next phase is adding more lines and duffuser plates since I only installed one run of 1/2” with plates between each bay. I think it would heat up faster if i doubled the amount of pex and plates. Does that make sense?


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But if the tagaki is a plain Jane tankless it may not give you the flow needed to double the amount tubing. Do your homework before you go to the trouble of adding a bunch of tubing.


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Discussion Starter #16
are you referring to the max flow rating of the machine?

I figured flow was based on speed of grundfos pumps


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The system is operating as it should. It is set at 72 and that seems to be the limit to how high it will go which is more than fine. Next phase is adding more lines and duffuser plates since I only installed one run of 1/2” with plates between each bay. I think it would heat up faster if i doubled the amount of pex and plates. Does that make sense?


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how hot is the water going through the pex?
 
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