Help Needed: Troubleshooting radiant heating issues

[jake28]

Hi Garage Journal Users, and a happy new year to you.
I'm at my wit's end troubleshooting why I don't have radiant heat and welcome your input.

Location: 1600 square foot residence, radiant heating throughout, split into two zones.
Hardware:
- Navian tankless condensing water heater
- 3 Nest thermostats
- All of the hardware, plumbing, and tubing is 14 months old, installed as part of a thorough remodel.

Scenario: Two weeks ago, I lose all radiant heating. I'm heading on vacation, so I don't worry too much about it. I come home and try to get the radiant working. No dice. I turn all of the nest thermostats to 85, and they don't go up a degree. Floors are all cold to the touch.

Kicker: I have piping hot water at every faucet, tap, and shower head throughout the residence, same as always.
The radiant hot water out pipes coming straight out of the heater are cool to the tough, and indicate ~62 degrees.

Troubleshooting to-date:
- I've reset all of the Nest thermostats.
- I've power-cycled and reset the Navian tankless heater. No error codes indicated.
- I've power cycled the Thermostat controller.
- I've power-cycled the recirculating pumps.
- I've cut power to the heater system at the breaker, and power cycled that.

Any tips or tricks highly appreciated.

 

[jlv03]

Where is the pump? Is it working?

 

[Jackfre]

Navien make good units. They make a good water heater, as you have found out and they make good COMBI BOILERS, which you need. Takagi are the only manuf I am aware of, and I represented Rinnai for 29years so know the market, who authorizes their tankless to be used as a heating device. The problem with tankless as heaters is that you get cross wise with the flow/delta T side of things. Tankless think that they are going to be providing shower temp water for you so they anticipate, in the Bay Area, say a 60* inlet temp running up to 120* for the hot to mix at the shower valve for say a 108* shower. I think the Navien have a minimum of 15k btu and a minimum flow rate of about .6-.8pm . If you look at GPMxDelta Tx500=BTU you will begin to see your flow and delta T issues. As a source for radiant which is looking at a low flow rate and a low, say 10-20* delta T, you can begin to see the problem. Also, you need a hell of a big circ, like say a TAco 009 or such. When I introduced the Rinnai tankless in the New England States in ‘01 I told all of my customers taht it was not a boiler, but a water heater. I also told them that if they chose to ignore my advise to loose my number. They called and I went. You can throw a lot of dough at pumps, storage tanks aquastats, etc and still not have what you need, which is the Navien Combi Boiler. Call Navien tech. I believe that you will find the same answer.

 

[jake28]

Navien make good units. They make a good water heater, as you have found out and they make good COMBI BOILERS, which you need. Takagi are the only manuf I am aware of, and I represented Rinnai for 29years so know the market, who authorizes their tankless to be used as a heating device. The problem with tankless as heaters is that you get cross wise with the flow/delta T side of things. Tankless think that they are going to be providing shower temp water for you so they anticipate, in the Bay Area, say a 60* inlet temp running up to 120* for the hot to mix at the shower valve for say a 108* shower. I think the Navien have a minimum of 15k btu and a minimum flow rate of about .6-.8pm . If you look at GPMxDelta Tx500=BTU you will begin to see your flow and delta T issues. As a source for radiant which is looking at a low flow rate and a low, say 10-20* delta T, you can begin to see the problem. Also, you need a hell of a big circ, like say a TAco 009 or such. When I introduced the Rinnai tankless in the New England States in ‘01 I told all of my customers taht it was not a boiler, but a water heater. I also told them that if they chose to ignore my advise to loose my number. They called and I went. You can throw a lot of dough at pumps, storage tanks aquastats, etc and still not have what you need, which is the Navien Combi Boiler. Call Navien tech. I believe that you will find the same answer.

@Jackfre greatly appreciated insight, thank you. So, long story short, should I be looking to add a dedicated boiler for the radiant system?

 

[kj_mustang]

What does the Nest thermostat connect to? Don't see a pump to circulate the radiant floor heat. If the floor loops are not separated from the domestic hot water, ie the same water flows through both, then strongly suggest you read up on "Open radiant systems" and figure out how to not let that water sit stagnant in those radiant loops for so long.

 

[Jackfre]

You are satisfied with the hot water from the tankless. You can either add a small boiler or go to a combi boiler. With the combi you cold sell the tankless you have and just go with the combi. My preference is for individual appliances, but your have to be able to vent them out. I do not know how much radiant load you have on your system, but in the Bay Area it probably is not a great deal…yes? The advantage of the stand alone boiler is you can get a boiler sized to the load. There are quite a few boilers today that fire 10k-60k btu. Navien makes them as does Rinnai and others. From a troubleshooting standpoint individual appliances are preferred in my book.

 

[Jackfre]

The thing about having a boiler is that you get all, or most of the bells and whistles. You can pipe it Primary/secondary (“Primary Secondary Piping” by Dan Holohan. Dan writes so a layman can understand it. Not an easy thing and the boiler will likely have the primary circ built into the boiler. As well and one of the greatest advantages of the boiler is that it will have Outdoor Reset Programming built in. You can run a radiant system with just a fixed temp water, but the ODR system just makes them sing and imho, improves comfort. If youy have the resources the heat only boiler is the way I would go.

 

[yeldogt]

maybe some more pictures ...

Who did the install .... did it ever work.

It must have some pumps and heat exchanger

 

[PoorUB]

Hi Garage Journal Users, and a happy new year to you.
I'm at my wit's end troubleshooting why I don't have radiant heat and welcome your input.

Location: 1600 square foot residence, radiant heating throughout, split into two zones.
Hardware:
- Navian tankless condensing water heater
- 3 Nest thermostats
- All of the hardware, plumbing, and tubing is 14 months old, installed as part of a thorough remodel.

Scenario: Two weeks ago, I lose all radiant heating. I'm heading on vacation, so I don't worry too much about it. I come home and try to get the radiant working. No dice. I turn all of the nest thermostats to 85, and they don't go up a degree. Floors are all cold to the touch.

Kicker: I have piping hot water at every faucet, tap, and shower head throughout the residence, same as always.
The radiant hot water out pipes coming straight out of the heater are cool to the tough, and indicate ~62 degrees.

Troubleshooting to-date:
- I've reset all of the Nest thermostats.
- I've power-cycled and reset the Navian tankless heater. No error codes indicated.
- I've power cycled the Thermostat controller.
- I've power-cycled the recirculating pumps.
- I've cut power to the heater system at the breaker, and power cycled that.

Any tips or tricks highly appreciated.

We need more info!
Does the Navien provide domestic hot water too, or only for the radiant?

We also need more information as to the controls. What gives the boiler and pumps a call to heat the radiant?

Are the pump(s) for the radiant running?

 

[fitter30]

Have the install manual page 87 look at the info, check heating setpoint. This is a safe site.

NAVIEN NPE-180A INSTALLATION MANUAL Pdf Download

View and Download Navien NPE-180A installation manual online. NPE Condensing Water Heaters. NPE-180A water heater pdf manual download. Also for: Npe-210a, Npe-240a, Npe-210s, Npe-240s, Npe-150s, Npe-180s.

www.manualslib.com

 

[jake28]

Hiya team, thank you for the suggestions and questions.
- Yes both the domestic hot water and radiant systems worked when new.
- The navian provides hot water for both DHW and the radiant.
- The DHW and radiant are on separate loops.
- A professional plumber did the install (for whatever that is worth).
- I have two pumps for the radiant. One of the pumps indicates only 1-2 GPM (which, based on nothing, seems really low)

Update:
- I had a plumber friend come by yesterday, with experience with this specific system. He is not the original installer.
- He cleared and cleaned every filter screen.
- He bled there system for air (none found)
- He confirmed the thermostat controller for the nests is working and receiving inputs.
- He confirmed that the radiant pumps are working, but flow rate is low.
- He suspects a faulty thermostat sensor on the radiant supply side, that is reading the supply side temp as far higher than it actually is, and as such not calling on the naviant system to supply hot water to the radiant loop (hence no hot water at radiant outflow)

Will run downstairs for a better photo of the whole system. Thanks for being faithful detectives in this.

 

[jake28]

 

[fitter30]

Heating side is total piped wrong. Should be piped with a primary secondary loop. What is that wiring and valves in that access under the combi? Look at page 4

https://www.google.com/url?q=https://www.caleffi.com/sites/default/files/file/hydraulicseparation-tr07.pdf&sa=U&ved=2ahUKEwjZ57u_i571AhWEkYkEHb7KD28QFnoECAgQAg&usg=AOvVaw2Mr1-t4ldKcgh9qPHuLAS1

Your zone pumps have to create flow for heater to turn on and don't see any check valves in discharge of pumps.

 

[yeldogt]

Just trying to figure out what is going on there is impossible.

I'm assuming the pump in the heater is for the heat loop out of the boiler --I'm seeing lots of pathways. And --- is that a return line in through the bottom of the spirovent .............trying to be a blend (cold) for a loop through a temp valve?


confusing

 

[fitter30]

Just trying to figure out what is going on there is impossible.

I'm assuming the pump in the heat is for the heat --I'm seeing lots of pathways. And is that a return line in through the bottom of the spirovent trying to be a blend (cold) for a loop through a temp valve?

Just trying to figure out what is going on there is impossible.

I'm assuming the pump in the heat is for the heat --I'm seeing lots of pathways. And is that a return line in through the bottom of the spirovent trying to be a blend (cold) for a loop through a temp valve?


confusing

What are your heat emitters? Just have two zones? Combi heaters to get 95% efficiency have to have 130*f return water for condensing. Above 130* efficiency drops to 85% doesn't matter what brand.

 

[PoorUB]

I have issues with no primary/boiler loop.

Is the water flow through the boiler so low it will not trigger a flow switch??

 

[fitter30]

Run both pumps and back the adjustment off the temp valve have on idea why its there. If u get flow through the heater shut one pump off at a time and valve the other pump off check the flow. Then the other way. Pumps need discharge spring check valves installed if this works. Without knowing how many feet pipe ,number of fitting, pipe size and brand, model of pumps and heat emitters pump might have to much head then pumps wouldn't move water.

 

[jake28]

@PoorUB @fitter30 @yeldogt Thank you for the input.
Update and remedy: After a week of waiting for plumber to come by, and then ordering a whole rebuild kit from Navien, and waiting another 2 weeks for parts to arrive, we ended up solving the symptoms, and I have heat. ('We' is generous: I asked questions based on things I'd read here, got slow head shakes in return, and then played the guy with beer after he fixed things.)

I didn't have the depth of knowledge, or patience - frankly, to interrogate the other underlying issues.
- The plumber (not the original installer) said the routing and install looked ok to him. Messy in some spots, but functional. Seeing as he could have sold me on needing to rip and replace, I'm inclined to believe him.
- Ended up replacing a thermostat on the radiant side and water pressure impeller/sensor on the DHW side of the system.

This may be anti-climatic, or just deeply unsatisfying, but I have heat. For now.

 

[PoorUB]

Glad you have it figured out!

Never the less, I still have issues with the plumbing!

As for what you plumber said that he didn't have any major issues with it. Not meaning to pick on him, but my bet is 3/4ths the guys in the field don't understand how or why the proper plumbing on a high efficiency boiler. Many are stuck back in the cast iron boiler days and they could get away with more sins. I have been to many boiler schools for various brands of high efficiency boilers and they all say one thing, primary, secondary loop. Now there is an occasional boiler with a primary loop built in, but yours isn't one.

Sure yours works, but it is not correct.

Where I worked last and sold HVAC equipment we were recommending primary/secondary loops for all boilers, even cast iron! Many of the manufactures were too. It protects the boiler from sins in the rest of the system, poor water floor for the main problem.
Your Navien can handle up to roughly 15 GPM. You floor can handle 1 maybe 1-1/2 GPM. At 1 GPM you are at the very bottom of water flow for that Navien.

 

[jake28]

Thanks @PoorUB, I suspected the result wouldn’t be satisfying. Part of the excellence of this board is that latent expertise readily available, your’s included.

Should the system stop working, I’ll fly you out to San Francisco to address it!

 

[PoorUB]

Should the system stop working, I’ll fly you out to San Francisco to address it!

Make that two tickets, my wife will insist on coming too!