Weil-Mclain Series 4 EG/PEG-75 Boiler under sized header installation question

gardenman

Hi, I don't know if this is the right category but my question is that, I bought a house that has hydronic heat using a Weil-Mclain Series 4 EG/PEG-75 Boiler, Input - 300,000 BTU/hr Output - 240,000 BTU/hr. The house is three stories plus a basement. Total is about 6300 sq ft.

The manufacturers specification says that the header pipe for the boiler should be 2" however for whatever reason the installation happened with an 1-1/2" pipe. I live in NYC and have been advised to replace the header with what the manufacturer has specified as this configuration may be inefficient meaning I am using too much fuel.

Any experience with this type of situation and any views on the need to replace the header?

bburd

How well does it work? Does the system heat evenly and quietly? No water hammer? No spitting from the air vents?

Can you post some photos of the boiler and nearby piping, taken from 6-8 feet away to show from floor to ceiling?

EdTheHeaterMan

Is this boiler connected to steam radiators or hot water radiators? That makes a difference because your NET output is only 217,000 BTUh on a water system. 1-1/2" pipe can move 220,000 BTUh out of the boiler and the 1-1/2" return will bring back colder return water to be reheated. So if you have a water system then you are good to go.

On a steam system the steam needs a larger area to move through the system so Weil McLain specifies minimum pipe sizes and minimum number of boiler risers to the header. That is so the steam does not move too fast and drag extra water into the steam main. That will be a problem called Wet Steam.

So do you have steam or water?

gardenman

https://forum.heatinghelp.com/discussion/comment/1818518#Comment_1818518

It works ok, however, I am in the middle of a renovation and have added some more radiators and broke up the series connections by separating the heat loops for the second and third floor into independent loops. Even before this renovation it did take a bit of time for heat to get to the third floor however it would eventually get there. Here are some pictures. The three pumps are shown below and the B&G 100 on the 1-1/4" pipe is the one that heats the first, second and third floors.

gardenman

Thank you for taking a look and sharing the info. This is a forced flow hot water system. What I saw on the manual was this chart:

Note the EG 75 recommends 2", however I spoke to Weil Mclain tech support and they said this model 75 is on the edge of their 2" vs 1-1/2" recommendation. Net net, if it works, don't mess with it.

The net BTUh output is 249,000 from their tech support guys. Were your figures for 1-1/2" pipe carrying 210,000 BTUh for black pipe or copper? I have black pipe headers and returns.

Theoretically, I may be able to get a little more efficient by increasing the header? I am assuming the return probably needs expanded as well?

bburd

Ah, it's hot water, not steam. The term "boiler header" is usually used for steam boilers.

As @EdTheHeaterMan said above, your 1.5" header is slightly undersized, but within reasonable limits from an engineering standpoint. That by itself will not affect your fuel consumption compared to the 2" header specified by the manufacturer. I see no reason to change it.

Of course, the header is a small part of a large system. The overall balance will be affected by the sizing of the rest of the piping and the circulators.

gardenman

https://forum.heatinghelp.com/discussion/comment/1818586#Comment_1818586

Thank you. This is helpful.

EdTheHeaterMan

Your boiler, using water, has a NET output of 217,000. That is the number of BTUh your system should be sized for.

You also have more than one pump pushing water into the boiler That may actually cause more water to flow than recommended. The recommendation is based on a noise free operation. Think of it like this, you can fill up a 3 gallon toilet tank in about a minute or less after a flush. But it is noisy, But it does not bother you because you are expecting it, you were the one who flushed. Now the 3 gallons a minute is going through a 3/8" supply tube.

Now thing about that same water running noise happening while you are sleeping about 3 to 4 times an hour for about 10 minutes at a time. That would get annoying. In order to keep those water pipes from making that running water noise, you design the pipes to be bigger with less GPM flow.

Here is a handy chart we use to select the proper size pipe for a given portion of the system

Now look at the 1/2" pipe size in the chart called "MAXIMUM FLOW RATE" (center left).  That states 1.5 GPM.  That is about half of the water to fill the toilet tank that was through a 3/8" supply tube.  Can you see how a pipe may actually be able to move more than the maximum?  you just get a little noisier water flow.  And with all the noise of the circulator pumps and gas burners operating, you probably don't even notice the noise in that boiler room.   

Now look at the lower right “SHARED PIPING SIZE” chart.  1-½ copper can move 22 GPM quietly and maybe even more with a little noise.  The iron pipe size can move 25 GPM quietly and maybe even a little more with some noise.  If you analyze that chart of rules you may have noticed that 1 GPM is equal to 10,000 BTUh of heat moved by that water when the temperature is 20° different from the supply to the return.  

I want to assure you that these calculations are not Rocket Surgery.  There is a lot of “Close Enough” going on here.  If Katherine Johnson used this method of calculating the orbit trajectory of those mercury rockets back in the 1960s, Kevin Costner might still be floating in outer space today!  

8.33 pounds of water to a gallon, times 60 minutes in each hour, times 20 degrees between the in water temperature and the out water temperature does not equal 10,000

8.33 x 60 x 20 = 9996 

So if you believe in your heart that making the 1-½” pipe a 2" pipe is going to save you any money on lower operating cost, I have this bridge in Brooklyn for sale.  I will PM you the details

gardenman

Thanks for thinking through this and sharing the data! Sounds like the recommendation to change the header may have been a little self serving. I don't have any problems with noise in the system so will leave it as is.