Floor heating not working

GeneBA

Contractor installed brand new Navien NCB-190/080H with manafucter suggested manifold, stainless loop in the picture. DHW works ok. Radiant floor heat is not working. Contractor figured out 2nd loop was wrong, somehow preventing SP water from going into the floor supply so he added a valve, always closed.

I set space heating temp at 125F. Boiler shows supply 123 F and return 116 F. supply 3/4'' pipe is hot and temp gauge shows about 110 F. The external pump is on return line and return pipe is barely warm, not even 100.

External pump was working with with old SlintFin for many years, no problems at all. Zone valves are old but also fine. Lever is opened.

Floors are cold. I can't explain it. is the water going anywhere?
Btw, I did the pump and zones cause plumber wasn's sure.

Is something off in my plumbing? Is the delta T too small?

been using electrial heaters for a month now,
many thanks

EzzyT

So the bad news is that your boiler needs to repiped it’s all done wrong. Start with trying to find another contractor. 

GeneBA

Can you point out what is wrong? This is the 2nd contractor who is a professional plumber. I don't know much about plumbing so I can't figure out what's right

psb75

Does this boiler have an onboard circulator?

GGross

Pump installed incorrectly, it can't have the motor shaft vertical like that, also it would likely be much better if it were piped on the supply pumping away from the expansion tank, I would double check the flow arrow on the pump body and make sure it is pumping the correct way , no dirt leg on the gas line which won't affect your flow but needs fixing, relief valve piped horizontally instead of vertical, this setup won't let you shut down or bypass the fill valve due to being piped right next to the expansion tank, that tank should really be piped different

Looks like what the plumber did originally was pipe the boiler as a secondary loop, and the heating as another secondary loop off of the "primary loop" which would be where the expansion tank is in this case, the issue you had originally is that there could be no flow in that loop as there was no circulator there, which would mean no heat making its way to the floor thats why the valve was added. I may be missing something very obvious as there is quite a bit to unpack here. Considering the initial piping strategy the plumber chose to employ could never work, let's not assume everything else is piped or installed correctly either

What controls the radiant floor heat? (thermostat etc) and how is it connected to the boiler?

How many radiant floor loops?

what size tubing was used in the floor?

how long is each loop?

Can you share a picture of how the piping connects to the radiant floor manifold, if possible show where the pump is in relation to the manifold supply/return.

GroundUp

It's not piped very well, but after adding the valve it's correct enough to work. There is no flow in your heating loop so either it's airbound or the pump is bad. Since the pump is mounted wrong, that could very well have been the case, but 99% of the time when a radiant system is commissioned and doesn't flow, it is airlocked. Having run the pump for a month with no flow now, it is most likely bad as well. When replacing it, it's better practice to have it on the supply side.

Ironman

GeneBA said:

Can you point out what is wrong? This is the 2nd contractor who is a professional plumber. I don't know much about plumbing so I can't figure out what's right

Being a “professional plumber” doesn’t mean that they know hydronics. Most don’t and are generally the most difficult to correct because they think that do.

Plumbing and hydronics are two distinct trades. Some are competent in both, but that’s the exception, not the rule.

Find a good hydronic contractor.

Try the contractor locator above.

Grallert

How far is the boiler from the floor manifold location? The set up as it is looks like it would be trouble to purge. When you swap the pump location I would install a purge station in it's present location. I would also use plastic fitting on all the neutralizer connections.
I would bet there is air in the floor loops. How long are they? Feet of tubing in each look?

GeneBA

GGross - I can't tell you how thankful I am for your analysis

It seems the contractor is unfamiliar with Navien manifold loop. So he built another loop.

Long story short, after 2 hours, floors did get tiny bit warmer, boiler displayed "AIR", burner stopped and the unit started losing water pressure. At 6.8 psi, boiler went into "lock-out" and flashed red. Plumber suggested to add water using make-up valve but boiler would lose the water in ~15 minutes. I hear dripping in the drain but can't tell which valve is doing it. He piped all output valves into one drain pipe.

What controls the radiant floor heat? (thermostat etc) and how is it connected to the boiler?
A: yes, three room thermostats talking to R-W connections on the boiler.

How many radiant floor loops?
A: 3 zone, one per room

what size tubing was used in the floor?
A: looks like 1/2'' red PVC.

how long is each loop?
A: no idea. small 900 sq ft apartment in New York city

GeneBA

GroundUp said:

It's not piped very well, but after adding the valve it's correct enough to work. There is no flow in your heating loop so either it's airbound or the pump is bad. Since the pump is mounted wrong, that could very well have been the case, but 99% of the time when a radiant system is commissioned and doesn't flow, it is airlocked. Having run the pump for a month with no flow now, it is most likely bad as well. When replacing it, it's better practice to have it on the supply side.

Yes, it even says so on the pump label. Plumber did purge air from the zone but you are right, boiler sounded like a washing machine for half hour, gurgling water and eventually shut itself down with "AIR". Navien has a built-in air purge for SH (space heating) program so I used that.

anyway, I turned floor heating off, closed 1'' ball valves on supply/return to zone manifold and just trying to restore DHW for bathrooms. It's working but losing water pressure. Never had these problems with old SlantFin, 85A

This is nuts. Wife told me to let it go. I had two different contractors in my apartment
on/off for two weeks

GGross

Most likely scenario is that the system wasn't properly purged of air to begin with. Since we know the boiler is losing pressure I would start with that. I have seen many otherwise excellent installs where circuits were not properly purged and left airbound, I would almost put money on it in this case. It is possible there is a leak somewhere as well, and where there is a leak, there will be air also.

I would still look into fixing the other things listed through this discussion, and it would be worth checking to make sure the boiler wasn't losing water through the relief valve if you heard water in the drain, the drain water could have just been condensate from normal operation though.

GeneBA

Grallert said:

How far is the boiler from the floor manifold location? The set up as it is looks like it would be trouble to purge. When you swap the pump location I would install a purge station in it's present location. I would also use plastic fitting on all the neutralizer connections.
I would bet there is air in the floor loops. How long are they? Feet of tubing in each look?

It is ~7 feet from boiler to zone valves, added a picture. I got a small NYC apartment. Everything is within arm distance. My neutralizer already has plastic tubing in/out. Is that what you meant?

How long are floor loops? I have no idea, rooms are not big at all. Plumber did purge zones for few minutes but maybe missed one zone. Everything does point out to air problems. I am confused as to how losing water pressure in SP loop is related to air problems.

psb75

Boiler displayed "AIR" and locks out at 6.8 psi? You'd best believe there is air in the system. Especially if it is a new boiler. And you if you don't seem to get flow through your floor loops. It is best if there is NO LEAKING. That promotes air induction.
Bleed the loops individually at the hose bib (red rotary handle) on your return manifold. Or have someone knowledgeable about "bleeding" a system do it.

GGross

"I am confused as to how losing water pressure in SP loop is related to air problems."

As the air works its way through the system, and eventually out a vent of some kind, the pressure in the system will drop. Generally once the initial purge is done correctly the drop is negligible as you work the remaining small amount of entrained air out of the system. You have a drop of between 4 and 6 psi depending on the cold operating pressure of your system, so I would say that you either had a significant leak, the relief valve blew off, or the initial purge was unsuccessful and this is the air that was trapped in your loops finally making its way to your boiler.

I would say a few minutes is likely not the correct amount of time it would take to properly purge and then pressurize the system.

psb75

Air leaving the system will make the pressure drop, BUT the autofill valve should bring it back up to pressure (~15psi.) Check the screens in the back-flow preventer/autofill assembly.

GeneBA

psb75 said:

Air leaving the system will make the pressure drop, BUT the autofill valve should bring it back up to pressure (~15psi.) Check the screens in the back-flow preventer/autofill assembly.

Yep, contractor said the exact the same. He wants me to get a new autofill valve from local supply. He also asked to fully open/close relief valve (on top of the boiler) once. Maybe the valve was stuck. It seems there is less dripping now.

psb75, if the auto fill valve is frequently adding water, isn't that bad? I understand it opens up occasioanly but it seems I have a leak. radiant loops are a closed system so it is a valve issue or the pipes in concrete cracked, very unlikely...

I am also going to follow up GGross advice and purge the zones thoroughly.

GGross

I call open auto fills boiler killers, not a fan.

Personally I like to have fill valves valved off so that if a leak occurs we know about it, we can open the valve to allow for filling if needed, if a leak develops that we can't find we can leave the valve open temporarily until the leak is found.

Currently the valve on your heating system side of the fill valve would also close off your expansion tank, so if you ever need to close that valve for any reason you must make sure the boiler is OFF and the gas valve is turned OFF. Your boiler must always be able to "see" the expansion tank in the piping or you will build pressure and the relief valve will blow off, and it may make it so you have to change pants, or much much worse.

Ironman

I think we’re all overlooking the elephant in the room: a199k btu boiler connected to a floor that has an output of less than 20k btus? And that’s with all zones calling.

GGross

@Ironman

according to the manual it has a low fire Input rating of 11,000 BTU on space heating, still possibly oversized for light load days but they don't go much lower

GeneBA

GGross said:

I call open auto fills boiler killers, not a fan.

Personally I like to have fill valves valved off so that if a leak occurs we know about it, we can open the valve to allow for filling if needed, if a leak develops that we can't find we can leave the valve open temporarily until the leak is found.

Currently the valve on your heating system side of the fill valve would also close off your expansion tank, so if you ever need to close that valve for any reason you must make sure the boiler is OFF and the gas valve is turned OFF. Your boiler must always be able to "see" the expansion tank in the piping or you will build pressure and the relief valve will blow off, and it may make it so you have to change pants, or much much worse.

You scared me sufficiently that I am looking for another contractor. Wife is joking that Navien with parts and labor is more expensive than her engagement ring. In retrospect, I should've paid few hundred to fix the old LX 85A Slantfin. It was reliable. If you know good plumber in NYC, please message me.

GGross

I didn't mean to scare you! I just wanted to make sure that if you were about to dig into that fill valve you understood that closing that valve would also block off the expansion tank.

But I agree you should get a more competent contractor in, bite the bullet, get it fixed correctly, I know it sucks and is going to cost a good amount of money

GeneBA

Ironman said:

I think we’re all overlooking the elephant in the room: a199k btu boiler connected to a floor that has an output of less than 20k btus? And that’s with all zones calling.

Are you suggesting the unit is oversized? I did not pick the boiler. Contractor suggested the model NCB- 190/080H by looking at how many bathrooms I have. Two other apartments in the building went with NCB-240/130H. As a dumb user, I can say the boiler is NOT producing enough hot water for two showers. The old setup with combi + 40 gallon storage tank was better.

GGross

there is some confusion with Navien model numbers. They actually have two input ratings, one for DHW and one for space heating. Yours is acutally a 160,000 BTU/hr input rating for DHW and 80,000 BTU/hr space heating, with a low fire of 11,000 BTU/hr.

You can only get 3.7 GPM of DHW out of your current boiler, thats at a 77 degree rise.

So while your boiler is undersized for DHW production, it is probably as close as navien gets to correct size for space heating. If you went with the larger size you would have gained 1.5-2 GPM of DHW delivery, and been left with a boiler that ws oversized for space heating.

In my opinion this job would have been a perfect fit for a little Viessmann 85,000 BTU boiler with 40 gal boiler mate, slightly better low fire rating, and way more hot water. If any other units in your building are changing equipment tell them to seriously consider a small size boiler with boiler mate. Combi's can be nice sometimes, but they are generally not correctly sized for either application they serve.

psb75

You're in luck. There are a few good NYC heating guys on this site.
I "second" the Viessmann recommendation with indirect DHW tank.
Or the Viessmann 222F B2TB.

GeneBA

GGross said:

there is some confusion with Navien model numbers. They actually have two input ratings, one for DHW and one for space heating. Yours is acutally a 160,000 BTU/hr input rating for DHW and 80,000 BTU/hr space heating, with a low fire of 11,000 BTU/hr.

You can only get 3.7 GPM of DHW out of your current boiler, thats at a 77 degree rise.

So while your boiler is undersized for DHW production, it is probably as close as navien gets to correct size for space heating. If you went with the larger size you would have gained 1.5-2 GPM of DHW delivery, and been left with a boiler that ws oversized for space heating.

In my opinion this job would have been a perfect fit for a little Viessmann 85,000 BTU boiler with 40 gal boiler mate, slightly better low fire rating, and way more hot water. If any other units in your building are changing equipment tell them to seriously consider a small size boiler with boiler mate. Combi's can be nice sometimes, but they are generally not correctly sized for either application they serve.

You are correct, one tiny edit. During winter, nyc water is about 42F. To get to my 125F, need 83F rise. in my opinion too, NCB-190/080H is undersized for DHW for multiple bathrooms and familes of three+.

DWH Temp Rise NCB-190/080H

77 °F (42.8 °C) rate 3.7 GPM (14 l/m)
85 °F (47.2 °C) rate 3.4 GPM (12.9 l/m)

https://www.navieninc.com/products/ncb-190-080h

hot_rod

Fixing the primary loop would be fairly easy. Cut and cap or put in a valve.
Derate the heating output closer to the load.

GeneBA

hot_rod said:

Fixing the primary loop would be fairly easy. Cut and cap or put in a valve.
Derate the heating output closer to the load.

gm. just want to clarify for my understanding. by primary loop, did you mean space heating loop? Contractor installed Navien manifold kit. I believe it creates proper loop. then he built yet another loop and finally realized and put in a valve like you said, in always closed position. system started working but very poorly for radiant heat. I think the setup is trapping air near the closed valve cause the boiler is losing psi in space heating.

https://www.afsupply.com/navien-30026576a-manifold-kit-for-ncb-h-and-nfc-h.html

hot_rod

You need to determine if the boiler is not providing the necessary supply temperature, or the piping and distribution is not able to move the heat into the system.
Generally if the boiler reaches temperature and shuts off during a heat call, then the issue is in the piping side. Air, undersized piping or control valves, plugged strainer in the piping, etc.