How to properly use / configure Navien hydronic system

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Joe B

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Hi,
Should a Navien hydronic heating system turn on and off four to five times an hour?

I am living in a place with a Navien CH-240 that drives domestic hot water and an in-floor, six-zone hydronic heating system. The hydronic system uses PEX tubes under a concrete floor. I have only ever had forced air and typical water tank heaters before.

Now, I am used to having one thermostat in the home, and programming it to have different behaviors at night, morning, away at work, and evening. You know, typical stuff. But it seems that this system I am living with now is... different.

Each zone has an Uponor thermostat wired to the main control panel near the Navien. If I set one zone to, say 70, then when the temperature drops to 69 I hear the thermostat "click," the Navien kick on, loud at first, then low hum for a while, the floor gets warmer, the temperature rises in the room, the thermostat "clicks" off, and I hear the Navien do it's last loud thing and then go quiet / off.

Ok, the problem is, some nights I hear the thermostat "click" on and Navien spin up, and then "click" off, and then on and then off. Is that normal? Especially at night, this happens for many hours and is a little annoying. But more importantly, it's like the Navien is burning gas and electricity all night.... shouldn't it be, I don't know, "smarter"? My gas and electric bills certainly don't seem any less than normal (but I don't really know).
Because of this annoyance, I usually only warm one or two zones and leave the rest at around 65 so they too don't click on and off all night.

Is it better for me to set all of these thermostats at a higher temperature than what I normally would with a forced air system?

Is it better to keep them at a constant temperature, like 70, rather than trying to turn things down at night or before I leave home for the day, like I would with a schedulable forced-air thermostat?

Should I raise the temperature of the hydronic water so that it releases more heat in the floor, longer?

Thanks for any insights and tips... I am not sure I am explaining why this system confuses me as it does.
 

fitter30

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Brand and model of thermostats? What are your heat emitters? Furnaces heat air, boilers heat objects that radiate.
 
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Bannerman

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What is the water temp setting? It is likely the water is too hot which is resulting in the temperature to rise too rapidly in each zone to quickly satisfy each zone thermostat, which is then resulting in the boiler short cycling.

The CH-240 utilizes a modulating burner with a gas input of anywhere between 20,000 BTU - 199,000 BTU. When the water temperature setting is appropriate to match the building's heat loss, the burner should run almost non-stop with the smallest flame needed to supply sufficient BTUs.

Of course, during the Nightime and Away setback temperatures, fewer BTUs than usual will be needed, so each zone thermostat will be satisfied more quickly, but circulating cooler water should result in longer circulation time than currently needed to cause each zone thermostat to be satisfied which will in turn result in longer boiler run time without cycling while using a smaller flame.

One method to match the water temperature to the heating requirement is to utilize an outdoor sensor to tell the boiler the exterior air temperature. This method will cause the boiler to vary the water temperature in relation to exterior temperature so as the exterior temperature becomes colder, the boiler will increase the water temperature accordingly, and vice versa.

The video below is intended to explain the concept even as the Navien model mentioned is not the specific model you own.


See page 38 of the CH Operation Manual regarding using an outdoor sensor with your Navien Combi Boiler model.
https://www.navieninc.com/downloads/ch-asme-operation-manual-en
 
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Joe B

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Brand and model of thermostats? What are your heat emitters? Furnaces heat air, boilers heat objects that radiate.
Thanks for asking. These are Uponor thermostats connected to a Wirsbo thingamagic that is then connected to the Navien controller itself.

The heat emitters are in-floor (concrete floor) pex hydronic system.
 

Joe B

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What is the water temp setting? It is likely the water is too hot which is resulting in the temperature to rise too rapidly in each zone to quickly satisfy each zone thermostat, which is then resulting in the boiler short cycling.

The CH-240 utilizes a modulating burner with a gas input of anywhere between 20,000 BTU - 199,000 BTU. When the water temperature setting is appropriate to match the building's heat loss, the burner should run almost non-stop with the smallest flame needed to supply sufficient BTUs.

Of course, during the Nightime and Away setback temperatures, fewer BTUs than usual will be needed, so each zone thermostat will be satisfied more quickly, but circulating cooler water should result in longer circulation time than currently needed to cause each zone thermostat to be satisfied which will in turn result in longer boiler run time without cycling while using a smaller flame.

One method to match the water temperature to the heating requirement is to utilize an outdoor sensor to tell the boiler the exterior air temperature. This method will cause the boiler to vary the water temperature in relation to exterior temperature so as the exterior temperature becomes colder, the boiler will increase the water temperature accordingly, and vice versa.

The video below is intended to explain the concept even as the Navien model mentioned is not the specific model you own.


See page 38 of the CH Operation Manual regarding using an outdoor sensor with your Navien Combi Boiler model.
https://www.navieninc.com/downloads/ch-asme-operation-manual-en
@Bannerman Thanks for this input, it's the first I had heard about it, despite reading about it in the manual.

I'll have to study what you wrote to figure that out for my situation.
 

fitter30

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Looking at the thermostat to see if there was a way to adjust the type of floor ( concrete slab or wood) but there isn't. Normally water temp runs 5-10*f over thermostat setpoint. Types of floor coverings have a max temp like hardwood 85* check with the manufacturer. Like Bannerman wrote turn the boiler setpoint down try 85* boilers are more efficient running than cycling. Since this combi water heater/ boiler is new to u they take yearly service look on utube how their cleaned on dhw side and where the filters. Heres a user's manual and can download others at this safe site.
 

John Gayewski

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Part of the issue seems to me would be so many thermostats. Your tubing should be sized for each room. One room loses 15k BTU you should have tubing to replace 15k btuh. That doesn't need a thermostat if the next room has the right amount of heat for its respective size and a thermostat. One thermostat should effectively control both of those rooms and really all of them. If you have every room set differently then your controller will tell your boiler to turn on and off a lot.

Don't use set backs. Hydronic heat uses radiation to heat every object in the house that's why it's so comfortable. Why would you cool everything in the house down and then spend the energy to heat it back up?

Hot air furnaces don't heat objects (they do but not efficiently or effectively). The reason you feel comfortable in a house with warm air is because your bathing in warm air. You turn the heat on, yay it's warm in here (no it's not). They can be ok with set backs because comfort isn't achieved in the same way.

I don't think I've heard of so many thermostats. Generally if you want a room cooler you turn the flow to that room down. Not the boiler.
 
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