Adding Economizer to GV90+4

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RKP

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I recently had a GV90+4 installed. It was somewhat of a winter emergency as my old Burnham boiler had started leaking and it was discovered that the cast iron portion was disintegrating.

I tried my best using fin tube measurements and old heating bills to downsize the boiler, since the plumber just wanted to install similar input. My old boiler was 198,000 BTU input and the new is 104,000 BTU, so I cut it almost in half. Still I'm observing short cycling and probably could have gone to the GV90+3.

I'm running on the internal circulator of the GV90+, with three zones using Taco zone valves. Zone 1 is 1st floor, zone 2 is second floor, zone three is indirect hot water with a SuperStor 60 gal tank. I was able to watch and measure some cycles on low single digit nights. With constant zone calls I saw cycles with 1-3 minute burns and 5-6 minute round trip. The IBC is programmed for a fixed 20F drop. I verified that there was no way I could change this with Weil-Mclain (had to pretend to be a plumber or they wouldn't even talk to me). So if I had Max temp set to its high limit of 200F, the boiler would fire until that was hit, then flame would shut off. Boiler temp then falls to 180F (200-20), and purge/fire cycle then starts up. I estimate this would give me 10-12 cycles of suboptimal burn per hour.

I was able to manually simulate a 50F swing by setting the Boiler max temp to 170 so that it's cycle would start at 150, then after burn started, I would set the max temp to 200. For the few cycles I observed doing this, I got 5-8+ minute burns and 18-20+ minute cycles. This would be much more ideal, with 3-4 cycles per hour I'm assuming.

The boiler's max temp low limit is 140F, so I think I could give something like the Intellidyne HW+ maybe 60F to play with safely, and I like that unit's simple setup. My questions are: Is the Intellidyne HW+ still available, and secondly, the GV90+ has a built in IBC that is doing a few things, like running a bypass curculator to protect the cast iron heat exchanger for example. I'm not sure how to wire the HW+ in, or if it's even possible to. If any other details about my setup are needed, let me know. Thanks in advance.
 

Fitter30

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What did your btu's come to with your heat emitters? What else did u upgrade windows ,doors and insulation in the last 20 years + to cut capacity? I'd want the return water temp below 130° for condensing. 7 pass boiler without talking to the factory personally wouldn't td above 20-25° and worry about the economizer now. Know how to extend your run times by adding a 60-80 gallon tank to the system. If Dana chimes in he will have some more ideas.
 

RKP

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Fin tube is emitting approx 25,000-30,000 BTU/hr per zone/floor, plus whatever the indirect hot water pulls. Gas bill analysis also came out to ~60,000 BTU/hr. House is 17 year old construction, with no upgrades to the original construction, 2,500 sq ft.
 
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RKP

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60,000 BTU x 1.4 = 84,000 BTU which is output of the new boiler.
 

Fitter30

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60,000 BTU x 1.4 = 84,000 BTU which is output of the new boiler.
Boiler in the basement? That 84k is taking into the account the boiler and piping losses are not taken in consideration. Being in the basement all heat is used most residential system piping isn't insulated heat is going everywhere not just going to the heat emitters.
 

RKP

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Yes, the boiler is in an unfinished full basement.
 
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