Condensing boiler + baseboard system not holding up heat on cold days

jj2406

We recently installed Noritz tankless combi boilers for our apartment. The system runs in one big loop single zone for the apartment. When outside temperature drops below 32 degrees (we live in NY), the heat becomes weak. Usually the last room feels chilly, and the return temperature drops quite a bit. The apartment is about 900 sf, total length of the baseboard in the apartment is about 46 feet. Our contractor build the rest bare copper pipes in the walls (behind the baseboard moulding). It's a very old house with brick walls. What might be the problem? Our guess is insulation problems. Could the single zone be the reason?

Gordy

Could be several things.

Air in the lines.
To small of a circulator.
Supply temp to low for baseboard.

What model noritz?
What is the heating side temp set to?
What is the return temp from the baseboard?
Do you hear gurgling in the piping?
Does the domestic hot water work fine?

Gordy

Some pics of the noritz, Andy associated piping would also be helpful.

jj2406

Thank Gordy. To answer your questions: It's Noritz CB199, the total run of copper pipes are about 100 feet, heating temp is set to 180F. We didn't hear any gurgling sound, DHW works fine. We use fin tubes, should that be the problem?

Gordy

Pics of boiler, and associated piping?

Gordy

We need to know if the combi was piped primary / secondary. Do to the high headloss HX. The onboard circ may be to small to pump direct to the convectors.

Paul48

Is the unit short cycling and bouncing off hi-limit?

jj2406

Thank you Gordy & Paul48!

Photos are attached.

@Gordy, Each apartment has its own condensing boiler. The boiler has only one zone, does that mean only primary? There is an external pump, but is not activate. How does primary/secondary work?

@Paul48, I'm not sure, how do we check whether it's short cycling or bouncing off hi-limit?

Gordy

from the manual

Paul48

I think his are unopened.

Gordy

?

Paul48

Joking about the contractor never opening the manual packet.

Gordy

Gotcha Paul.

To the OP of this thread. Primary secondary piping hydraulically decouples the boiler flow from the system flow via closely spaced ts.

The boiler has an on board circ which may not be able to give the proper flow to the system if the head loss is to high.

By adding a circulator to the secondary (system side) the boiler loop (primary side) can have the flow it needs from the built in boiler circ, and the system side can have the flow it needs with out interfering with the flow rate of the boiler.

If the factory boiler pump is in speed 3' and the delta from the beginning of the loop for covectors is more than 20 degrees you need to pipe it primary secondary.

Now you say the circulator in the pic does not operate on a heat call?

jj2406

Thank you all! Somehow I tried to post response many times but couldn't publish...sorry for the delays (and I hope you see this one)

Gordy

So what did you figure out?

jj2406

It keeps saying 'Your comment will appear after it is approved'....when I posted my longer response which includes several more questions Over the weekend we had a home performance audit. The auditor pointed out the primary secondary piping was incorrectly installed. The Ts are not close enough. That might be the reason? Also to answer your earlier question - no the green circulator in the picture is not running. The contractor installed the circulator but didn't actually connect the wires...he said we don't need that yet...

Gordy

Well that's a start. The home energy auditor knows more than the installer.....

Gordy

So the circulator on the left services a future zone?

Gordy

I see other issues. Relief valves need to be piped to with in 6" of floor. Gas piping has no drip legs.

So these boilers are separate serving individual apartments?

Or are they suppose to be staged?

jj2406

@Gordy, that's our plumber's intention to use the external pump(Green Taco) for future zone purpose. We also noticed the relief valves issue, thank you for pointing it out. And you are right, we installed two boilers, one for each apartment.

We have be distracted with other renovation headaches, sorry for the late reply. Our boiler is currently piped as Primary / Secondary, the Closed Tees are about 8 inches apart; based on Noritz Manual, it said to be less than 4 inches apart, I'm wondering is this something we have to change, or we can live with it? Our secondary pump is not activated right now, my guess is that's the main cause of not getting enough heat, do you think I can just connect it and turn on the pump? Will our problem be solved? Thank you!

Zman

jj2406 said:

@Gordy, that's our plumber's intention to use the external pump(Green Taco) for future zone purpose. We also noticed the relief valves issue, thank you for pointing it out. And you are right, we installed two boilers, one for each apartment.

We have be distracted with other renovation headaches, sorry for the late reply. Our boiler is currently piped as Primary / Secondary, the Closed Tees are about 8 inches apart; based on Noritz Manual, it said to be less than 4 inches apart, I'm wondering is this something we have to change, or we can live with it? Our secondary pump is not activated right now, my guess is that's the main cause of not getting enough heat, do you think I can just connect it and turn on the pump? Will our problem be solved? Thank you!

Are you saying it is piped primary/secondary and the secondary pump is not running? That would be the entire problem....

Gordy

Yeah, and looking at the piping it appears "both" boilers are also somehow piped together. Unless my eyes deceive me. Looking at the space ts.

Can you make heads, or tails from the photos Carl?

JohnNY

Where are you located, jj2406? You need a pair of qualified eyes in that boiler room. We're not liking what we're seeing in those pics.

Zman

Gordy said:

Yeah, and looking at the piping it appears "both" boilers are also somehow piped together. Unless my eyes deceive me. Looking at the space ts.

Can you make heads, or tails from the photos Carl?

I can't tell what is going on. One of the stranger approaches to DHW and heat...
Some folks should not deviate from the I&O.

@jj2406
Any chance you could draw out what goes where?

j a_2

Sounds like a classic....Hold the installer accountable, don't be shy about it.....Gather only the facts, present it to him and see what he does....@johnnyny is 100 percent correct you need someone to look at the whole package...Get a written report and keep his invoice to present it to the original phony installer

jj2406

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Zman

Just sketch how it is piped. No one can tell what is wrong from the pictures and description post.
Putting a spare pump in series is not a normal installation.

jj2406

@Gordy @Zman Please see attached pipe diagram.



@JohnNY @j%20a, we locates in Ridgewood, Queens. Last weekend, we hired a Noritz Certified Plumber to inspect on site, he suggested the most easy way is to cut the common pipes. We would like to keep our piping as Primary/Secondary as Nortiz Manual suggested. Do you think we need to reduce our common pipe length from 8 inches to 3 inches? Can we just simply turn on the secondary circulator?

Thanks.

Gordy

The two ts should be 4 pipe diameters apart.

Now the other circulator that the "installer" said is for future use? Yet It's wired to the boiler? Yet you say this circulator is in the secondary loop that goes to your heating elements?

If so then the onboard pump is trying to pump through that circulator. Which is off....always.

You are positive it is not on, and running on a heat call?

jj2406

@Gordy Yes, he said for the future use. Yes, it's goes to the heating elements, the piping there is like (based on the image: Heat Supply - Expansion Tank - Secondary Circulator Pump - Heating Element (Fin Tubes) - Heat Return).

That circulator is not wired to the electronic circuit of boiler and it not activated in the boiler's control panel. I'm positive, the wire is just hanging in the air.

For two ts, do you think we can use this Webstone product? http://www.supplyhouse.com/Webstone-58644-1-x-1-Pro-Pal-Full-Port-Brass-Ball-Valve-w-Reversible-Handle-Primary-Secondary-Loop-Purge-Tee-600-WOG

If we don't change two ts, can we just wire the secondary circulator and activate that, as a temporary solution? I would like to know how necessary of changing those?

Thank you for the speedy reply!

Zman

You have a primary/secondary with no circ on the secondary. Sure the spacing is wider than it should be, it will never work without the other circ running. Energize the other circ and let us know what happens.

jj2406

We had our installer plumber bring the Ts closer and activated the circ on the secondary loop. He was not 100% sure we should use both internal and the external pumps. We tested and the returning pipe was hot with no time. It's gonna be cold this Friday and we will see how it goes this time.

Gordy

Thanks for getting back to us. And yes use both pumps. The boiler pump circulates water through the boiler while the system pump circulates water through the system, or emitters. The activation of the system pump was probably more the fix than the ts. However doing both takes that possibility out of the equation if there is future issues.

As you say a noticeable improvement right away is good.

Paul48

Here's some good reading. Maybe you could print it out, and find a tactful way to give it to your plumber. http://www.caleffi.com/sites/default/files/file/hydraulicseparation-tr07.pdf