2nd Zone on Monoflow heats whole house

TimK2088

My 1968-built ranch is heated by a monoflow system with a Navien (gas) tankless boiler.

I created a 450 sq ft office/gym in my basement (I work from home) and my plumber installed a second zone on the monoflow system to heat it.

No surprise, when Zone 2 calls for heat, it prompts the whole house to heat up. In the attempt to keep the basement room at 68 degrees, the upstairs would be pushing 10 degrees above that.

He came back and installed a tee in an effort to prevent the return from heating the whole house, and it has improved, but the upstair's cast iron baseboards still get warm when zone 2 calls for heat and the upstair's thermostat is off.

He is good plumber, but admits to not being well-versed in monoflow systems. He is looking into the problem, so I thought I should as well. I just cannot speak to his level on exactly what he has done.

I can provide photos of the setup and consult with him on anyone's question, but I would like the get this settled prior to the New England winter.

Thanks in advance.

Big Ed_4

Either he tapped into the wrong section of piping or the mono flow does not have a flow control valve, because it was a single zone before

EdTheHeaterMan

MonoFlo® systems are a special breed of well designed systems that use pressure differential to make the heat go where it is supposed to.

1. Are your original radiators Convectors or Baseboard or cast iron?
2. did the additional basement radiators connect to the same one pipe main?
3. Did he put a thermostat in the basement
4. Does the basement thermostat operate a separate zone valve or a separate circulator pump?

A diagram of YOUR pipe design (original) and the added pipes would be helpful

This is a typical MonoFlo® design

The special Tee Fitting is usually found on the return side of each radiator.  That tee fitting causes the water flow in the one pipe main to be restricted a little, making the path going to the radiator an alternate route for the heated water to flow into the radiator.  Most of the water will continue thru the main with a percentage heating the radiator.  If the balance of that pressure drop is interfered with, then you can have heat going where it is not supposed to and no heat where you want heat.

If your plumber added a separate zone with a separate circulator and did not include Flo-check valves, then the pressure from one zone circulator can force reverse flow thru the other zone if that pump is off. That can add heat where you don't want it from time to time

The green zone represents the basement loop with a second circulator pump operated by a separate thermostat. Is your system at all like this diagram?

delcrossv

Did he put in two of these?

TimK2088

Ed

To answer your questions:

1. Are your original radiators Convectors or Baseboard or cast iron?

original radiators are cast iron baseboards, basement is new slantfin-styeled baseboard element.

1. did the additional basement radiators connect to the same one pipe main?

I would say yes, it looks that way (see photos)

1. Did he put a thermostat in the basement

Yes

1. Does the basement thermostat operate a separate zone valve or a separate circulator pump?

Yes

This photo shows his first connection (dark gray) to the baseboard below (from the main pipe). The lighter gray pipe is to alter the return (my understanding).

This photo shows the two zones.

This photo shows his original connection (dark gray) to the boiler.

This photo shows shows the new connection (lighter gray). My understanding is there is some trap or something that is supposed to alter the return. Again, my understanding is very limited.

Hopefully, this sheds some light. I can take photos of anything you folks need to help me out.

TimK2088

Delcross

It doesn't like he installed any of those.

delcrossv

You're ghosting your other zone. Note @EdTheHeaterMan 's diagram above where it says "flow check"

EdTheHeaterMan

Here is some information from this book https://s3.amazonaws.com/s3.supplyhouse.com/product_files/108119-Reference%20Guide.pdf that will help your plumber understand about Zoning With Circulators

Let your plumber have the link to this book, it is an easy to read informational coverage of your situation, that I read several times until I had a full grasp on the topic. I used it as the textbook for the one day seminar I used to teach.

This is old school ways to do stuff, it was written in the 1960s. There are newer ideas that may have improved the way we do things today, but your system is from 1968 with a new boiler connected to it. That worked well until the additional zone was added. I believe the Flow Check valves (or lack there of) are the reason you are having the issue.

You have 2 potions here. The valves need to be added OR you may be able to add the Flo-Check vlave like this to your existing pump.

https://www.supplyhouse.com/Taco-0010-025RP-IFC-Replacement-Kit-for-Select-Taco-00-Series-Cartridge-Circulators

EdTheHeaterMan

I also have not seen any MonoFlo® tee fittings in any of your pictures. Can you show me a photo of at least one of those tee fittings?

EdTheHeaterMan

Based on the limited photos. and assuming that you actually have a MonoFlo® one pipe system, I believe that this is your piping system before the added zone.

The above illustration is the design that Navien manual would suggest for your system. That includes 2 circulator pumps. One for the boiler and one for the system. If you do not have that near boiler piping design, then you may have this design (before the basement zone)

Notice in the Red oval, the boiler pump is missing and the Navian manifold is missing. This may work on a one zone system, however it will not work on a multi zone system.

Assuming you have the upper illustration properly designed near boiler piping, this next diagram is how you should add an additional zone.

Take note that the new zone circulator pump is TEEd off of the main AFTER the expansion tank. It can also be AFTER the existing system circulator pump TEE (But not after the actual pump).

I hope this helps your plumber.

Big Ed_4

The new zone is piped in to the system wrong , repipe the manifold on the secondary to add the new zone . The mono flow also needs a flowcheck …

TimK2088

These are the three T's that were added to create the second zone. Are these are not monoflow T's? I assume the one attached to the circulator is not, but the other two?

Thank you all for your expetise. Much appreciated.

EdTheHeaterMan

You definitely have Diverter tees.  (not MonoFlo® brand)  in the photos you just sent.  

It is difficult to tell what you have other than the Tees and some circulators. I would like to see some of the original tees (before the additional zone)  to verify that the original system is also a Monoflo® or diverter tee system.  Also can you step back about 8 feet from the system and take some pics so we can see all the near boiler piping.  That way I don't have to guess at what piping you might have.   

It is like guessing what kind of car you have based on these photos.

They don't show the whole car, so I can't tell you how to fix it. I can only guess and hope that you understand my illustrations.

delcrossv

https://forum.heatinghelp.com/discussion/comment/1815934#Comment_1815934

Umm. you don't use diverter tees to make a new zone. You use flow checks. Remember, flow will go to where there's less resistance.

TimK2088

Hopefully these are clear enough to tell a better story. I zoomed in on the piping below on one of them. Let me what else I can snap. Thanks.

Big Ed_4

Wrong …..

EdTheHeaterMan

Every new photo gives more information. Thanks

Well I can see from your new photos that you have an older design NCB model Combination Heating boiler and Tankless Water Heater. I can also see that the installer used the primary / secondary optional Navian manifold.  That is a good thing.  I still don't know if you really have a MonoFlo® system. That would be determined by the next 6 fittings that are on the pipe leaving the boiler indicated by the Red Line 

I can see that the new zone was connected incorrectly to the main system piping as indicated in one of my previous diagrams and shown here.  

When possible Can you show a picture of the next 6 fittings on the pipe leaving the near boiler area, (on the red pipe) and a picture of the old original radiators

This is a representation of what I can guess is your system as it is installed now

TimK2088

Thanks Ed, I agree, that is pretty much it.

I just took photos of those fittings you asked for, but I need to organize them before posting. It is a maze down here.

TimK2088

The first Tee off the main pipe from furnace breaks away from this crazy loop setup that was part of an old oil system and heads to first radiator tee.

This 2nd tee was added for the basement zone, which was soon capped off so another loop cold be added (mentioned earlier). There was another (capped) tee (not shown) that went to that now removed oil-fueled boiler.

This is the first tee off the main that heads upstairs to first radiator, a 90-degree, two-walled baseboard for living room.

This tee on the left goes up then heads left to the wall and up to connect to opposite end of 90 degree living room radiator.

The two tees on the right are the opposites ends of the 2nd radiator in living room. The one far left is the one shown above.

I could go on and on and send photos of the tees for every radiator in the house, but I think you get the picture.