Changing out my 1931 boiler

JohnHenry_2

Hello,



I’m changing out my old converted coal boiler to a Navien CH-210 Mod/Con.



I’m changing out the gravity flow iron piping with home runs off of 3 separate manifolds (one for the basement, one for the first floor and one for the second floor).



I’m keeping the cast iron radiators.



The heat load on the house is approximately 50,000 Btu/hr.



Attached is a rough schematic of the system I’m going to build.



The primary loop piping is 1 in copper. The secondary loop piping is 1 inch copper. The inlet and outlet piping to the manifolds is ¾ in copper. The circulator on the primary system is built into the Navien unit. The circulator on the secondary loop will is a constant pressure variable speed pump (yet to be sized). The manifolds I’m using have flow control and a flow meter for each home run. I’m not sure if I’m going to use zones but am leaning towards using them so I put zone valves on the schematic.



A couple of questions:



1. Do you guys see any inherent deficiencies in the basic design of this system?

2. Navien states that the expansion tank must be installed in the pressure side of the primary loop before the hydro tees. Doesn’t this conflict with seemingly accepted practice of pumping away from the expansion tank?





Thanks in advance for any help you can give me,



John Henry

lchmb

curious

Check page 22 of the manual. It show's the tank prior to the zones..

http://www.navienamerica.com/PDS/ftp/CombiGasWaterHeaters/Installation_Manual/CombiBoiler(CH)_Installation.pdf

CMadatMe

CH-210

Is not a mod/con because it is not a boiler, it's a water heater. A water heater is meant to do one job, deliver hot water. While the marketers do a great job of promoting these as a heat source you should at least know what you are buying. 

Only a ten year warranty on that heat exchanger where as a good condensing boiler has a much better warranty and is made for the job.

JohnHenry_2

It seems you REALLY dislike these units...

The CH-210 modulates it's firing rate to meet the heat demand. It also condenses the exhaust gases to recover the latent heat of vaporization. How is that not MOD/CON?



While we're on the subject of definitions, doesn't a boiler make steam? The Navien unit doesn't make steam, it makes hot water for a hot water radiant heating system. So i guess my original post was incorrectly titled. It should have read "Changing out my 1931 converted coal fired water heater for my radiator heat system". My apologies.



If you can point to any specific design deficiency this unit has, I'd very much like to hear about it. Thanks for taking the time to respond to my post. It's very much appreciated.

JohnHenry_2

It does but...

Doesn't "pumping away" mean basically pumping away from the expansion tank rather than towards it? Thanks, I appreciate the reply.

CMadatMe

Boiler

Mod/con is the terminology used in our industry for a boiler. A boiler is rated and stamped as a primary heat source. In some municipalities you cannot use an on demand water heater (CH-210) as a primary heat source.



You can do whatever you wish. Just understand what you are purchasing.

JohnHenry_2

How is

The CH-210 not a primary heat source? Can you point me to any documentation or point out any lack of documentation that says it's not a primary heat source?



Do you know of any specific design deficiencies that make this unit unfit to heat a house? I has a water heating circuit dedicated to heating the water in the heating system.



I chose this unit primarily because it modulates down to 20K Btu/hr so it won't short cycle too much on my 2400 sq ft poorly insulated house while it will also deliver enough hot water for two simultaneous showers. The fact that the cost was 1/3 of any other unit that came close to my output specifications sealed the deal. Plus, a VERY reputable heating contractor in my area proposed one of these units in his bid to do my system.



It seems you continue to say this is an unsuitable unit for the marketed application without giving any specific reason as to why. You only say that it's unsuitable, even when asked why you think that. That's like saying "because", which isn't an answer.



Because of your lack of any actual reasoning or corroborating documentation, I can only surmise that because you work for a heating distributor and Navien is allowing internet retailers to sell these units at a low markup (I paid 30+% less than a jobber installer I got a bid from would have paid to his distributor), the bone you're picking is financial rather than technical.



Again, if you know any design or manufacturing shortfall in these units, I would very much like to learn about them.



Thank you very much for your interest,



John Henry

JohnHenry_2

BTW,

I like your tag line at the end of your posts. I've been using mine since I owned an auto repair shop in '92...

lchmb

generally

If you think about it, all of your zones are "pumping away" from your expansion tank the way they recommend piping it. The system circulator just keep's proper flow through the unit..

lchmb

Chris

Although not a mod/con it is listed as a duel function (combi) system and is rated to be installed  as a heat source. What area's would not allow this to be installed where the manufacturer list's it as a heat source? It's even listed for Mass which has a history of being a tough area...

I've never even looked at one prior to this so just trying to learn..;)

CMadatMe

Primay Heat Source

The CH-210 is rated as a water heater. It does not have the stamp or approval to be described as a boiler. That's why the installation manual states water heater/space heating. Now Navien does make a ASME rated unit, which has a cost pretty much the same as a condensing boiler. Many local codes do not allow a water heater as the primary source for the heating system. If yours does and your happy with your choice then install it.



Your in the auto biz. If I put re-treads on my car will the car move? While they work they are still inferior to new tires, subject to early failure and require me to pay attention to the wear and tear. Same for the on demand heater used in a heating application. There are plenty of post here on tankless issues as well as other sites. I'm also sure there are plenty here that will tell you the same.

As for the showers. If you live in a climate that has 50 degree incoming water temp and you want to make 120 your living on the edge with 2.5gpm heads. Max that unit will put out in these conditions is 5gpm. Pressure balance and thermostatic valves also tend to force you to bump up that set point temp so your temp rise increases.



I'm not aruging with you or telling you what to or not to install just presenting the facts.

meplumber

The problem comes with the "H" stamp.

I am not aware if this unit has the H stamp or not Ichmb.



However the problem lies in whether a unit is approved by the ASME as a central heating appliance. If they have done so then it has an "H" Stamp. The biggest problem that I run into here is with property insurers. Particularly commercial property insurers. No H stamp. No install on a commercial property. Period. As for residential, it depends on how up to date an inspector is. Not all municipalities inspect up here.



But for my license, I install boilers with H stamp for central heating and water heaters for domestic. IMHO, this is a glorified water heater.



There are other areas that are cracking down on them due to the prevalence of poorly installed mixed systems where the heating water and domestic water are allowed to mingle. Legionnaires breeding ground.



This unit is their first step to separating the waters. However, without the H stamp, it is still a domestic water heater as far as the ASME and thusly the insurers are concerned.



Maybe Al Leitter could enlighten us further. From an insurance perspective.

lchmb

very nice

nice explanation..thank you..;)

bill_105

Insurance?

I saw this thing from the get-go. I think the tank should go right after the boiler.

This insurance thing though. Years of it. Don't do this or don't do that! You won't have coverage!. Tell that to the Bank of America or Countrywide.

I'd like to read a thing about coverage of the east coast vs. west coast. Out west , show up with the checkbook.

HDE

ASME

To help everyone understand ASME, the boiler section dictates material types, wall thicknesses, and pressure testing and rating, besides the most important part and also the most expensive, a ASME engineer reviewing the heat exchanger and unit.

After this special blessing, it receives the ASME H stamp on the heat exchanger, or S,A,M,V,E,HV, U and many others for whatever it's testing approval it's for.



So I ask you do you think a manufacturer operates two different manufacturer lines for ASME and non-ASME heat exchangers? Not



In fact when you review the ASME CH240, they are required to go backwards in technology to meet ASME, such as use copper waterways versus the stainless steel they use in the non-ASME CH combi units.

JohnHenry_2

I was wondering about that...

Thanks for the insight HDE. I was thinking that the heat exchangers on those units had top be nearly identical as I just couldn't see Navien operating two different heat exchangers for essentially the same unit. It just didn't make sense to me. I had spoken to Navien about the differences between the different CH units and as near as I could tell it was in the burners which is why I felt comfortable going with the CH-210.