New Boiler Install & Design Question(s)/Feedback

[logan1211]

Hi all! I've been a sponge lately on everything hydronic. This place is a wealth of knowledge and I hope not to annoy.

We're doing a very large house addition (3900 sq ft) and as part of this installing a Central Boiler Classic Edge 750 with 1 1/4" Thermopex running inside.

We'll essentially have 3 "zones" more or less that I'm looking to heat from the OWB.

Zone 1 - Existing house. This will simply be a water to air HX
Zone 2 - First floor addition radiant (2204 sq ft)
Zone 3 - Second floor addition radiant (1700 sq ft)

I've gone back and forth now so many times on what this system will look like. FWIW, each one of those zones listed above will have their own air handler for AC/Propane furnace as a backup heat as well.

I'm on the fence about just open system the whole thing, primary loop, secondary loops with zone pumps/valves (depending on primary circulator/head loss) or hydraulically separating.

1. Design "Open": A few more detailed calcs needed, but I think this would meet the demands adequately. Primary loop, secondary loops, etc. One question I haven't been able to wrap my head around here. How do secondary loops/circulator pumps impact the primary loop circulator pump? Is it just a matter of making sure all my secondary circulatory pumps GPM totals less then primary circulator?

2. Design "Closed" : I'm REALLY liking the design of running 1 1/4" Thermopex to an indoor indirect 120gal tank. Looking at some numbers, and with 180* boiler/entering water temperatures, the recovery rates and continuous rates can be pretty impressive. From there then, just having a closed system off the tank with circulatory pumps/zone valves for each zone and calling it good? Obviously sizing based on head, GPM, etc.

I'm generally a big fan of keeping things simple, but I can appreciate efficiencies.

Anyone have any thoughts, advice, necessary reading here to help out? Appreciate y'all in advance!

 

[E Yoder]

Is this radiant in a slab? Mixed down? That affects flow rates pulling off the primary loop.
I personally would do all open with one primary loop, with secondary loops to each zone. Would be pretty simple. If piped properly secondary loops do not affect the primary loop flow rate as they kick on and off.

 

[maple1]

Is it just a matter of making sure all my secondary circulatory pumps GPM totals less then primary circulator?

I don't think that is a big factor. A secondary loop could flow a lot of GPMs while pulling little off a primary loop.

 

[Jacon Construction]

Hi all! I've been a sponge lately on everything hydronic. This place is a wealth of knowledge and I hope not to annoy.

We're doing a very large house addition (3900 sq ft) and as part of this installing a Central Boiler Classic Edge 750 with 1 1/4" Thermopex running inside.

We'll essentially have 3 "zones" more or less that I'm looking to heat from the OWB.

Zone 1 - Existing house. This will simply be a water to air HX
Zone 2 - First floor addition radiant (2204 sq ft)
Zone 3 - Second floor addition radiant (1700 sq ft)

I've gone back and forth now so many times on what this system will look like. FWIW, each one of those zones listed above will have their own air handler for AC/Propane furnace as a backup heat as well.

I'm on the fence about just open system the whole thing, primary loop, secondary loops with zone pumps/valves (depending on primary circulator/head loss) or hydraulically separating.

1. Design "Open": A few more detailed calcs needed, but I think this would meet the demands adequately. Primary loop, secondary loops, etc. One question I haven't been able to wrap my head around here. How do secondary loops/circulator pumps impact the primary loop circulator pump? Is it just a matter of making sure all my secondary circulatory pumps GPM totals less then primary circulator?

2. Design "Closed" : I'm REALLY liking the design of running 1 1/4" Thermopex to an indoor indirect 120gal tank. Looking at some numbers, and with 180* boiler/entering water temperatures, the recovery rates and continuous rates can be pretty impressive. From there then, just having a closed system off the tank with circulatory pumps/zone valves for each zone and calling it good? Obviously sizing based on head, GPM, etc.

I'm generally a big fan of keeping things simple, but I can appreciate efficiencies.

Anyone have any thoughts, advice, necessary reading here to help out? Appreciate y'all in advance!

You need hydraulic separation. You can use a large buffer tank, or closely placed tees, or buy a hydraulic separate device.
See this attachment it’s excellent
I installed a similar system as what you described. Used a closed system and a 120 gallon buffer tank for separation and storage.

 

[sloeffle]

@Medic21 posted some pictures awhile ago of his setup, I believe he's doing something very similar. Might want to search for some of his older posts.

 

[peakbagger]

My usual plug for a free on line course led by the hydronics guru John Siegenthaler courtesy of NYSERDA on how to install biomass boiler systems. https://www.heatspring.com/courses/...ficiency-biomass-boilers-sponsored-by-nyserda

If you want to get into more detail John has a much more extensive course (equivalent to a college semester) which includes some great software for designing a system rather than guessing is here (not free) https://www.heatspring.com/courses/mastering-hydronic-system-design. I heve been doing industrial piping for 35 years and I learned a lot of hydronic specific stuff.

The problem is that most of these systems are getting installed based on old designs that might have worked once but no one has actually designed them. Once stuff is poured into concrete its lot harder to do it right.

John does monthly articles in PME magazine and has done so for many years,I think a lot of them are archived online.