INDIRECT HELP!

adambuild

Hi Wallies,

Replacing a leaking Amtrol 80-gallon indirect with a TT Smart80. Current boiler is 206000btu ouput and piping is 3/4" with a zone valve for the indirect, but I can replace piping with 1" and plan on using a Taco IFC circ. Which circ should I use?

Thanks in advance, Adam

Ron Jr._3

Hey Adam

Here's the .pdf for the Smart series



http://www.triangletube.com/documents/2/Smart%20manual%20.pdf



Looks like 1 1/2 inch is recommended for the boiler connections . 1 inch will work too , at a lower recovery rate I'd assume . How many baths do you have ?



Not sure about circ sizing . Hopefully some pros will chime in .

CMadatMe

Piping

Recommended pipe size is 1-1/2". Now the pump question with a question. Are you giving the indirect have priority over the heating zones? This is very important and if not your should. The best I can come up with based on the manual is 2' of head for the tank. YOu mostlikely need a pump that can cover a samll amount of head such as the 007 but gpm is still needed to be asertained.

Brad White

I take it that you are using

Fig. 7 in the TT Smart manual, (circulator dedicated to the DWH loop)?



Reason I ask is, you did mention a zone valve and want to be clear that you are not replacing the main circulator. A dedicated circulator I think is best because the flow rate vs. the heating side would differ too much.



As to the pipe size, I would go by the manual which, as Ron Jr. said, is 1.5".



In order to select a circulator, you need to know the flow rate required and at what temperature drop. But also the pressure drop of the boiler, intervening piping, fittings and valves and the DWH heater itself. Being tank in a tank, the DHW heater probably has a minimal pressure drop, so that leaves the boiler and piping to deal with.  Do you have that information or the make of the boiler?



If fairly close-coupled, the piping, valves and fittings might run 2 feet of head if sized at conventional friction rates and flows.



Flow rate: Shall I assume that 100% of the boiler output will be directed to the DHWH? This would make this a short task rather than dragging it out.



 If 206 MBH that would be 20.6 gpm assuming a 20 degree drop. (That, my friend, will reinforce using 1.5" pipe right there). 



If you really do need 80 gallons (who am I to say, but feel like asking anyway), your load to heat that volume by 90 degrees (50F in and 140F out), requires about 60,000 BTUs. If the boiler gives it all to the process, that 206 MBH will heat that tank in about 17.5 minutes from a cold tank and will trim it/top it off in less of course.



Given a 20+ gpm flow rate and some presumed pressure drops, I am thinking that a Taco 0011 IFC or a 0014 IFC would be in the range. These will handle that flow rate at between 7 and 9 feet of head, but lesser pumps do not even make the flow rate. This is just a preliminary suggestion and we have to know all of the factors to get the real pressure drops.

adambuild

Thanks

Thanks all! Yes the DHW will have priority and the main circ serving the ZV's will stay. I would like to add a dedicated circ fotr the new TT Smart80 but can only boost the piping from 3/4" tp 1". Under these circumstances, which Taco circ would you use? Thanks again!

Brad White

When you say that

you can only boost the piping to 1", why is that? I am suggesting that you COULD get 20 gpm through a 3/4" port and it would scream a bit and erode, but that would be silly.



So what you are left with is a longer recovery time. That in turn has me asking, why 80 gallons?  What is your HW demand?



Also is your DHW priority enforced by a 3-way valve?



My last house had a 1" feed to a 45 gallon indirect (HTP SuperStor with a higher pressure drop), but still, it worked and we never ran out of hot water.



So you have a 3/4" pinch point and can go to 1", so far so good. What is your boiler pressure drop? And if we give your DHWH say 7 gpm but not your full boiler capacity, unless you have a diverting valve too. If it is just "biggest pump wins and the others are shut off", your boiler delta-T will rise. If 206 MBH and 7 gpm, expect a 59 degree delta-T on that water. May not be pretty. You may want to re-think your limitation or that 100% of the boiler will be on-task.

CMadatMe

Do they not Sell

Do they not sell 1-1/2" pipe where you live? Why are you saying you can only use 1"?

Basically you can get 9gpm through 1" pipe. That gpm is based on a standard 20 degree delta t. This means you can only give that indirect 90,000 of the 200,00 you have sitting there. Where does the rest go. Up the chimmney. As Brad asked why an 80 gallon? If I was a betting man I would say this is not a single family residence.

adambuild

Thanks

Thanks for the benefit of the doubt........ It so happens it is a single family house with ten kids, six bathrooms and a tight budget. To pipe the indirect with 1.5" will mean a major repiping job that the homeowner can't really afford. I didn't do the original installation, I'm just a nice guy trying to help some folks in a bind by keeping the price down without sacrificing too much performance.

CMadatMe

Six Bathrooms

Pipe it 1-1/2". They are going to either pay the utility/oil company for the extra burned fuel to keep up making hot water or you for doing it right. They may even save money on domestic compare to what they were spending if you size that pipe correctly. Then your good deed would really be seen.  Where are you located?

Ron Jr._3

6 bathrooms and 10 kids !

Wow , they really do need the big tank !



Any chance you could post some pics of the boiler and indirect ? Maybe we can figure out a way to break into the piping to increase it to 1 1/2  ........



If it is indeed very hard to repipe the existing pipework , what about increasing it to 1 1/2  where you can do it more easily ? I'm assuming the boiler supply and return piping is all 1 inch ? I wonder if it'd be worth increasing the size of the indirect piping to 1 1/2 if the system piping is smaller .............

adambuild

Thanks!

Not to beat a dead horse........... If we can only bump piping up to 1" which circ would you use? If the client can somehow pay to repipe to 1.5" which circ would you use? Thanks in advance, Adam

CMadatMe

The Pump

If your dead set on the 1" I would use a Grundfoss 15-58 on speed 2 but without seeing the job and knowing the boiler that's a guess. Could you please tell us where you are.

Bob Bona_4

If it was

me, and was locked into the 1" piping, it would be a Grundfos 15/58 speed 3, on priority. Any shortcomings in flow rate would most likely be masked by the sheer volume of the tank. Just expect longer recovery after a deep drawdown, and most likely using a little more fuel from the longer run time.

Otherwise, it would be 1 1/2 or at least 1 1/4 pipe with a 0010 Taco. 

adambuild

Location

Sorry, job is located in Northern New Jersey.

CMadatMe

Then I'll help you and this family out

E-mail me. I'm in your neck of the woods. Would be more than happy to help this family out.