Minimum Flow - Utica MGB CI Boiler?

Jason_37

Hi all-

Would anyone have access to the minimum and maximum flow rates for a Utica MGB 175 cast iron boiler? It is not listed in any of the installation manuals or specs sheets and the company will not assist a homeowner. The boiler is about 10 years old with the following specs:

MGB 175
175,000 BTU/HR
143,000 DOE
124,000 I=B=R

I want to confirm my bypass setting (via a 3-way mising valve)is allowing enough flow through the system. Thanks for any assistance.

Mitch_4

depends on delta t

flow rate = btu's / (500 x delata T)

Leah Frances

Correct

Correct, with my current Delta T of 50 degrees between the return and supply of boiler, I calculated a 5.75 GPM flow using the 143,000 DOE rating. I'm looking for input as to whether that falls in the acceptable range as well as effecient use of the boiler. The rest of the system (large gravity conversion)is piped pumping away with a B&G Series 100.

Mitch_4

personally

I like a large delta tee..so long as it has above 140 return H2O to prevent condensation I would think there would be no issues.

TK03

I read an article printed quite a while by I believe Gil Carlson, where he said cool water at a high flow rate is a problem but cool water at a low flow rate was not. The idea was to keep flow rate low and get the average water temperature above 140. This would mean bypass water around the boiler. Slower flow in boiler gets water hotter faster.Adjust flow as required.

Boilerpro_5

Yep,

that is how I see it too. If you run 1/2 gpm of 80F water into a cast iron boiler with an output of 80,000 btu/hr that contains 4 gallons of water, or more, you will generally see a good deal of internal mixing. I believe the Utica holds a decent amount of water so it shouldn't be a problem. The Weil CG series, however holds a very small amount of water, to you could have problems, I suspect. It tends to fall into the category of copper tube boilers in performance requirement.... got to keep decent flow moving through the unit. Factory techs have said maximum of 40F delta tee or so no matter what the water temp.

Boilerpro
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