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Adding an Indirect to an existing Burnham boiler

PickyPro Member Posts: 13
I decided to start a new thread on this subject, I'm new at this and hope it is correct forum etiquette. I copied and pasted my post from another thread here titled :

Glass Lined versus Stainless Steel - Indirect HW Heater started by rsc92


Thanks for the lesson on Recovery Rates. I appreciate your assistance.

I did not intend to hijack this thread, but didn't know if I should start a new one.

The existing boiler is a Burnham. The label on the jacket says "V8

Series low pressure boiler",  Model 85WFH.  D.O.E. heating cap 164,   

196 MBH

I contacted Burnham asking for a manual. They emailed me the pdf version

for the V7 Series, stating that the 85WFH is a warranty replacement

block, jacket , and canopy for the V7 boiler. So, I am assuming the

rating label on the jacket refers to the new block.

Using your lesson in calculating the max. gpm this boiler can produce I

came up with 5.46 gpm (using a delta T of 60) and 4.68 gpm (using a

delta T of 70, well water in CT at 50?).

To do the calculation I used 164,000/500= 328/60= 5.46 gpm for 60 degree water

and 328/70= 4.68 gpm for 50 degree feed water. Did I do this correctly based on the ratings of the boiler?

So, for example, if I chose to go with an indirect like the Triangle

Tube Smart 50, its specs state a boiler output of 140,000 BTU and

Peak/Flow (gal/10 min.) : 65 (6.5 gpm?), the boiler would still only be

able to produce 4.68 gpm with a 50 degree water supply and the max. the

Smart 50 could produce would be 6.5 gpm if my supply water was 70


You stated that an oversized indirect can drag the boiler temps down and

cause condensation if the boiler is not piped correctly. I don't know

if this is a condensing boiler or not and would appreciate any input on

how you would set up an indirect with this boiler. I assume my plumber

will have this knowledge. I'm just trying to learn from others prior to

choosing an indirect and also want to know how best to hook one up.

I am guessing that we will be bypassing the existing tankless coil in

the boiler and that we will add a zone for the indirect. Do you pull the

existing tankless coil and replace it with a cover plate with access

ports and hook the indirect up there? Or, do you just cap the the

existing tankless ports and add a zone valve or an additional

circulator? BTW, the Burnham rep I contacted did state that I would need

to call their inside tech. dept. to ask them these questions.

Right now the existing boiler has one circulator and 6 zone valves. I've

read some articles about making the indirect a priority, but don't

really understand how this is done. Any advice or insights are really



  • Zman
    Zman Member Posts: 6,714

    Your math is correct, assuming you are talking output BTU's.

    Domestic priority means that the boiler will not simultaneously heat domestic water and the home. When it receives a call for domestic it will discontinue heating the home and use all available energy to heat water. This setup will maximize water production but is not needed in all systems.

    As far as preventing condensation there are many ways to do it. Generally you want to bipass the emitters with a certain amount of the boiler water so the boiler temps do not get too low. This can be done with ease valves, mixing valves or circulator controls. If you post a piping diagram, I will offer suggestions.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
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