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The Wall


Joined on December 29, 2008

Last Post on July 29, 2014

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Call Hydronic Alternatives

@ April 1, 2014 9:41 AM in Automag zone valve with intermittent run-away heat

Gary call Paul Ross up at Hydronic Alternatives, they rep Auto Mag 413-543-8733

Its Not that Hard to Understand

@ April 1, 2014 7:33 AM in Navien 100,000 btu heating

Boiler/Primary Flow Rate = 5gpm
System Flow Rate = 10gpm

See attached....It's not btu/hr you need to worry about it's the (T2) System Supply Temp. Yes you can get 100,000 btu/hr but not of 180 degree water its impossible unless you're boiler is making around 190...

The PDF is converted from an excel file that I made into a calculator. I use it all the time on retrofit jobs to make sure my design supply water temp is enough to get the load of out the emitters.

I've had this conversation with Navien plenty of times. Once you bring it up they look at you like a deer in the headlights..

Here's Your Science Widdershins

@ March 23, 2014 5:45 PM in Want to move from oil to gas boiler. Best way forward?

Yes they publish a 120,000 btu/hr output. But what they don't tell you is at what water temperature. The on board circulator can only move 5gpm across the heat exchanger so if your heat loss is let's say 100,000 btu/hr and you need 10gpm across your system do you know where the other 5gpm comes from and its effect on the heating systems water supply temp? Snowmelt who claims is a Navien installer can't answer it so I wouldn't expect a homeowner to know it but I know SWEI does..

Of Course

@ March 22, 2014 6:52 PM in Floor Sensing Thermostat

You can. Do it all the time. You can get them where they are programmable, sense floor temp, air temp or a combination of both. Very common when you have radiant with Hydro Air as backup or the consumer is looking for just floor warming..

Agree With Iron

@ March 21, 2014 11:04 AM in Burnham ESC vs. Combi Wall Hung

But may I add one thing....What's in those 2 full baths? Human car washes or just regular shower heads? I also never understood why one would add another energy user when one piece of equipment could do the job.

Could the Navien provided 120,000 btu/hr for heating? Yup sure can but at what what water temp? The on board circ can only move 5gpm across the HX. so that heat loss Iron was talking about is critical and so is measuring and calculating emitter capability..


@ March 20, 2014 9:03 AM in Emergency contact info for Viessmann?

Anytime that wiring harness see's wet you have to replace it. I had a few but never came across no fault codes, usually get a burner blocked fault. The only time I come across no fault codes is when you don't make the flow switch and its usually because the boiler itself is air bound..If you ever have an issue down the road and can't get a hold of someone be more then happy to help you out..

Wish I Saw Your Original Post

@ March 20, 2014 7:40 AM in Emergency contact info for Viessmann?

Would have had you call me.. What was the issue in the end?

The Blind

@ March 19, 2014 12:26 PM in Want to move from oil to gas boiler. Best way forward?

The btu/hr output ratings are for DHW not heating period! The on board boiler pump will move 5gpm across the HX that's it period...Now how many btu/hr can you get out of that unit Snowmelt? After that the question is at what supply temperature..

And as a FYI they are not a different animal and cannot change physics..

To the original poster I'd take Tim's and Kurt's advice. They both are correct.


@ March 17, 2014 1:36 PM in Mod/Con Heat Exchanger Designs

Controls are all smoke and mirrors to this point and that includes the new zone control being used with the K2.

From a total platform and I'm a Viessmann guy I'd look at Lochinvar for one reason and one reason only...I can control my boiler/primary pumps flow rate to match the boilers modulation rate.

Honestly, I could care less about the HX's at this point. If you're installing correctly and servicing correctly they will all last. This debate over HX's is like the debate of which Pex Tubing is better...They will all last if you do the right thing


@ March 17, 2014 1:25 PM in NG Combi Boiler versus indirect tank and boiler setup

Utility rebates are for the consumer not the trade contractor. The Rinnai is a domestic on demand water heater the Viessmann is a boiler. So you have two different products not the same type of product.

Heat Loss Heat Loss Heat Loss

@ March 14, 2014 9:57 AM in boiler

Your question is very broad. I'll take the path of do the heat loss, measure emitters and calculate water temp needed to provide btu/hr to overcome the heat loss on your design day. Make the decision from there. Most homes are 35% over radiated so in many cases yes it does make sense to go mod/con.

Every job is its own and should be treated as such.


@ March 13, 2014 7:44 AM in Should we choose this boiler? CC125 125,000 BTU In/put 96,000 BTU Output Challenger Combo Boiler - Space Heating & Domestic Hot Water

2100 Sqft of Snowmelt would require roughly 300,000 btu/hr

4 x (90 x 500) = 180,000 btu/hr

How is this 2100 sqft of snowmelt working properly and effectively? Snowmelt in order for you at 4gpm to deliver 300,000 btu/hr you'd be running a 150 degree system delta-t.


@ March 13, 2014 7:39 AM in Primary Pump Viessman KM bus ?

The variable speed pump options in Coding 2 are shut off for N. America even though the coding addresses are in the manual.

Burnham Recall

@ March 9, 2014 9:10 AM in Burnham recall?


Visit all the recall information is there to include filling out the info for Burnham to send you the modification kits. It's not just a pressure switch. That was the Crown recall..

I Think

@ February 25, 2014 9:10 AM in The best Delta T for a mod-con?

Everyone is missing one key point...BOILER PUMPS are FIXED Speed. Boiler delta-t is always changing based on the systems flow demand and return water temp..You're selecting a boiler pump based on the flow rate wanted at design temp to get the full btu/hr out of the boiler.

If you are sizing a boiler pump for a 20 degree delta-t you will only get a 20 degree boiler delta-t on design day when the system side can pull out the entire flow rate of the primary/boiler side into the secondary and the secondary's delta-t is in full match and harmony..

Not Necessarily

@ February 24, 2014 10:41 AM in The best Delta T for a mod-con?

It's all going to depend on type of condensing boiler and the application. What I mean is what is the heat loss of structure, type of condensing boiler and each zone's heat loss. Boiler pumps tend to be fixed speed as is any 3 speed pump.

That pump is moving a fixed gpm flow rate every time it turns on. If you have a small zone let's say that only needs 2gpm but your boiler pump is moving 6gpm all the time the 4gpm left over has no place else to go other then to b-line right into the boiler return. This is sending 4gpm of nice hot boiler water back into the return thus elevating the boiler return temp and in most cases it takes the boiler out of condensing mode.

There are a few post above with some wrong math.


@ February 22, 2014 7:55 AM in Help!! staple-up insulation foil myth

R-Value is a radiant floors best friend. Like others have said R-19 is R-19 no matter the type. Sound like you have Onix tubing. The simple thing to do is to pull the installation manual and provide them with the manufactures insulation requirement.. If its installed with the minimum insulation as described by the manual then let them pay for it..


@ February 22, 2014 7:34 AM in Solution for consistent E8 Fault code on Viessmann Vitodens 222-F LP Boiler?

Is caused because the ionization current is outside the range. Generally gas pressure issue. I have come across a bad wiring harness between the the gas valve and control. Also make sure the gaps are correct on the ionization and ignition electrodes.

Concentric Venting

@ February 18, 2014 8:52 AM in Poly Pro venting....

Being a Viessmann guy have been using M&G's Concentric for a long time. Number one reason why you get condensate in the fresh air intake is running the vent through an unconditioned space. If you didn't have a proper connection you'd have cross contamination which is a much bigger problem then the condensate..

A Steam System

@ February 8, 2014 8:01 AM in Crown boiler doesnt keep up with thermostat

A boiler is not sized by Btu/hr in a steam system. It is sized by the sqft of EDR (Radiation) and the boiler chosen for the job needs to be able to produce that sqft of EDR. My suggestion is to start measuring radiators before you do anything else.

Oak Ridge

@ February 5, 2014 9:01 AM in NORA is back!!!!

Is a tax payer funded institution, just about everything when it comes to energy is R&D'd and tested there. Where do you think the Heat Pump Water Heater came from? Yes, GE developed its first but it was fully developed at Oak Ridge with GE.. What came out of it, Amercian jobs not a Heat Pump Water Heater made in China and shipped here like the others.

Just Another Reason

@ February 4, 2014 9:54 PM in NORA is back!!!!

Why our political system is broken. This has to be buried in a bill that has nothing to do with NORA or the bills subject itself. So someone got another politician to vote for his bill as long as this was in it. Wonder who owes who the next favor? But NORA is back, that's what's important right? Glad for the renewal just not in favor of the process..
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