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problems with steam indirect (14 Posts)
problems with steam indirectGood morning. I recently installed a Burnham Alliance indirect coming off a crown kingston steam boiler and I am trouble with the recovery time. There are two possible mistakes that I may have made during the installation. First is that I reduced down to 3/4" before the circulator. The boiler manufacturer calls for 1" up to the circulator and the indirect manufacture calls for 3/4". The second possible mistake is that the boiler manufacture calls for lowering the circulator as close too the ground as possible,which I neglected to do. Normally I do drop the circulator but this time I plain forgot. What is the reason for dropping the circulator? I was taught that it is to ensure that there is maximum weight behind the circulator to keep as much pressure behind the circulator as possible. My problem with this theory is that no matter how low you drop the circulator, only the water above the tapping will generate pressure behind the circulator. Please correct me if I am wrong. This really brings me to my third point which is that the tapping provided by Crown for the indirect( as per the installation manual) is approx the same height as the bottom of the glass gauge. I would have thought that the tapping should be much lower. Any advice that can be shared would be greatly appreciated. Thank you.
PipingThe instructions must be followed if you want it to work. The pump is placed low (typically 6" above floor) to avoid cavitation. The impeller can be damaged and premature pump failure will happen when the pump is in the wrong position for this application.
Here's the link to Dan's article:
ThanksI looked over the article.Excellent!The one thing that I am not getting is the benefit of dropping the circulator. The water that is above the supply tapping will put pressure/weight on back of the circulator. If you drop the circulator the only added weight/pressure comes from the water in the supply piping which is minimal at best. The weight of the water in the boiler that is below the supply tapping will not add any weight/pressure no matter how low the circulator is dropped. Wouldn't it make more sense to supply the circulator from the bottom of the boiler to utilise the full weight of the boiler water to generate pressure at the back of the circulator. I have a feeling that I am missing something and I am waiting for a "lightbulb" moment. Thanks.
Inlet pressureIt's the pump's inlet pressure that matters most. If the incoming water feed to the circ is too high, the impeller may be starved for water and cavitates. Mounting the pump higher than 6" greatly contributes to the ability of the circulator's inlet to keep at least 1psi.
Maybe Dan will jump in to help you see this more clearly.
I have at least 6 of the steam boiler with indirects in operation. All have been working for more than 10 years without any issues.This post was edited by an admin on July 3, 2013 12:39 PM.
head pressureWhat you're missing is that it's not the volume of water above the circulator that matters - only the height difference. So whether you have a 3 foot high section of 3/4" pipe filled with water or a 2 foot diameter tank filled three feet high, the pressure at the bottom is the same. So dropping your circulator in the piping will be just the same as connecting to a lower tapping on the boiler, and it is important to do to prevent cavitation in this application.
(In theory using a lower tapping is very slightly better since there will be a tiny amount of pressure loss in the piping, but that's a small effect).
Light bulbsI think that the light bulbs are going off in my head. I am finally getting it. Next question. I am working with a eight foot ceiling. Wouldn't it make the most sense to come out of the boiler, go up to the ceiling and then drop down to the circulator? This way I would have aprox 4 psi on the suction side of the circulator. All thoughts are greatly appreciated
Bulbs may be flickeringLooping up to the ceiling will not help, and in fact will cause problems.
NPSH (Net Positive Suction Head) at the circulator inlet will still be determined by the boiler waterline (think siphon.)
In addition, you will create a new problem: getting air out of (and keeping water in) that loop (again, think siphon.)
Circulator PlacementHas nothing to do with the lack of recovery. Its more about beating up the circulator. If you have an AL35SL or AL50SL they both want 6gpm with a pressure drop of 9' for the 35 and 9.5' for the 53. You have 3/4" piping. Needs to be 1". If that's a Taco 007 circ the pump curve at 9' intersects about 7.5gpm and at 9.5 just about the same."The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
If he has a 007he is going to have even more issues. I have not seen many wet rotors that did well with steam boiler. If you need 1" you need 1" The 3/4" is sized assuming a higher static pressure on the system. The secret to making system perform is to do it by the numbers every time.Cost is what you spend , value is what you get.
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indirectNext question. Manufacture only calls for 1" until the circulator. What is the collective wisdom about using 1" or 3/4" after the circulator? The tappings on the Alliance(50 gal) are 3/4". Thank you.
redoneWent back to customer. Admitted my mistake to customer. Dropped circ down. Piped 1" to the circ. Water gets hot. Recovery time is great. Lesson learned! Thanks
Congratulations!Good on you for being open and forthright with the customer!
Everyone can make a mistake, but the difference between a true professional, and a hack is in how the mistake is rectified. Keep your light bulbs lit!--NBC
MistakesThanks. I just saw an interesting stat. If medical misdiagnosis would be a disease it would be the sixth leading cause of death in the US. We all make mistakes. The key is to admit and learn from them.
DHWInstalling a $900 circulator under waranty will make anybody learn real fast!- Joe Starosielec
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