Some Knight questions

Larry (from OSHA)

This really applies to any mod-con boiler.

At some point soon I'll be replacing the old Weil McLain with the small Knight. For existing venting there is a 7" SS chimney about 18 feet in length. I was planning to use it as a convienient chase and the thought for intake air was using the existing makeup air hole in the wall of the boiler room as the spot for the fresh air pipe to be. My thought was if the equivilent length was the same there would be no problem. I was told that there could be pressure differences due to the location of exhaust verses intake due to wind and problems could occur such as too lean burning or something similar. Using the existing stack would be easy and I'm all for that. I don't think that there is enough room to put two 3 inch pvc pipes in there with 90's and other connections. (again, I'm trying to do it as easy as possible, but still do it right. If that's possible)

The thought of using the chimney chase as the intake and doing a saddle y off of it to the boiler would be easy but currently not approved by the mfr. So the question is if the exhaust is on the roof and the intake is on the sidewall, am I looking for problems?

Also, my indirect which has a double wall hx only has about a 10 to 15 degree delta t no matter how I pump it. Currently using a 15-58 super brute on speed 1. Does the Knight need to see more difference across its hx? I'm thinking there may be some flow issues here.

Any perspective is greatly appreciated.

Larry

Guy_6

Maybe

The Knight, like many others of it's genre, is essentially driven by blower speed. That is why the MFGs require that the intake and exhaust are about the same length and terminate in the same enviornment.
If the wind were to blow into the intake (and not the exhaust), the blowwer would be running in a slightly runaway manner, and therefore slightly out of control.
Likewise, if the wind was inbound on only the exhaust, it would slow things down.
I would contact Lochinvar and see if they will sign off on the concentric method that you had suggested. I have had people use it in the past and had no trouble whatsoever, as long as the exhaust was 10 inches or so above the top of the existing chimney (which became the intake).

Paul Rohrs_4

Email Ike

Email Lochinvar's Boiler Product Manager - Ike Gatlin

igatlin@lochinvar.com

He will give you the best advice on venting the Knight.

Regards,

PR


To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Ike Gatlin

Math is fun

Larry,
I have seen this done on other manufacturer’s boilers as well as Knight Boilers. Mod/cons using neg/reg truly do rely on equal conditions on both sides of the fan for proper performance. When I say proper performance I mean 100% rate.

Look at it this way, if you reduce the inside area of the 7" vent with the addition of the 3" vent, how much area remains? Is it equal to or greater than a 3" pipe?

Changing the area reduces the condition at the inlet of the fan vs. the outlet of the vent. The result is a slightly reduced rate. You can confirm this with an analyzer, and should do so.

As a manufacturer I can not tell you this is ok.

Ike Gatlin