Help with Lochnivar Wall Hung system design

[BPIAuditLongIsland]

I am hoping with the knowledge on here I can find someone on long island who can do the system design for me, or help me through this online.

Over the next few years I want to completely change over my home from an energy wasting nightmare to an energy efficient comfortable home. Due to budget constraints and logistics, I also need to do this in pieces.
Current home:
1511 sq ft home built in 1927with flat roof. stucco exterior 1 pipe steam heating system with 1 zone of slant fin and a standalone 40gal hot water.
1238 sq ft of that is balloon frame 9' ceilings with no insulation over a full basement with no insulation again 9' ceilings
273 sq of that is platform frame with R-13

Finished home ~2500 sq ft putting 2nd story on main portion of home. Insulated all with spray foam.
Lochnivar WHN055 boiler with a 60-80 gallon indirect tank, 30-80 gallon boiler buddy, feeding mix of cast iron radiators, cast iron baseboard, and radiant heat. Total of 5-7 zones
My friend is a plumber, and will be assisting with the install, but unfortunately he does not have a clue as to how to properly install a condensing system, nor do I know of any local plumbers who do either. I see 5 heating systems a week due to my job, and have yet to meet a heating contractor that does not install a system 2-5 times to large due to "fear of callbacks".

I would like to start off with installing the Lochnivar WHN055 boiler with a 60-80 gallon indirect tank, 30-80 gallon boiler buddy, onto 1 zone of slant fin, 1 cast iron radiator I will be installing in the basement, and the 1 indirect zone to start. My current hot water heater is on its way out, and i need to add a heating zone to the basement, as well as i need to get this slant fin zone off of the steam boiler.

Thanks in advance

 

[Dana]

Is there wood sheathing on the exterior of the studs, with tarpaper on the exterior and a vented air gap to the stucco?

If not describe the stackup- just filling those stud bays with insulation (any type) could destroy the framing if the stucco doesn't have good drying mechanisms. There are often ways around the problem, but it varies with the actual construction.

Spray foam is on the expensive side- there are cheaper ways to air-seal, and you would still need to use other stuff (acoustic sealant caulk is good) to air seal the other seams/joints in the framing & sheathing such as between the bottom plate & subfloor, subfloor & band joist, doubled-up top plates etc. If you go with spray foam for the cavity fill, use open cell foam not closed cell, since the performance of closed cell is severely undercut by the thermal bridging of the framing. Going with 2x4 framing and damp-sprayed cellulose or open cell foam on the cavities, and 2" of foil faced rigid polyiso on the exterior costs less than 2x6 framing with closed cell cavity fill, but has about 1.5x the performance at the same wall thickness. The 2" rigid + 2x4 wall is about R23 "whole wall" after thermal bridging, compared to ~R14 for a code-min 2x6 wall with R20.

You may or may not need the Boiler Buddy, depending on the amount & type of radiant heat and the thermal mass & size of the 5-7 zones. The min-fire output of the Lochnivar WHN055 is about 10,000 BTU/hr, so it can manage some fairly small zones without short-cycling. The higher performance the building envelope, the less benefit you get out of micro-zoning, so if you make the upper floor reasonably high-R you can single-zone it.

The heat load @ +15F (the 99% outside design temp of L.I.) of the basement even without foundation insulation is probably between 10-15K, but it'll be under 2K if you put an inch of rigid foam on the foundation walls, with a 2x4 batt-insulated wall trapping it in place as the code-required thermal barrier against fire. If you're using a surplus antique radiator for the basement, find a big'un that has large volume, to guarantee that the boiler won't short cycle.

Ideally you'd like the smallest zone to be able to emit 10,000 BTU/hr with 110F water (where the WHN055 is hitting it's stride with mid-90s efficiency), or have sufficient thermal mass to not short-cycle, with no more than 3 burns/hour when serving just that zone. That would save you the cost & complexity of the Boiler Buddy. If you insulate & air seal the original part of the house (including the foundation) and install tight low-E storms over the antiques then put U0.25-ish windows and a high-R walls on your second story the whole house load is probably going to be under 25K, maybe even under 15K. Chopping that up in to 7 zones means the average zone will be only 15% of the minimum-fire output of your boiler, and the smallest zone may be 5%. It's probably better to keep the zone counts down, which will automatically keep the mass & radiation per zone higher. At a minimum you'd be looking at three zones (basement, first floor, new floor), but holding the line at 4 zones is probably reasonable.

 

[Sponsor]

 

[BPIAuditLongIsland]

I am not sure if there is any sheathing under the stucco, the stucco itself is in degrading condition, I will most likely have to rip it all off and restart.

I own a spray foam rig, so the expense is not as much of an issue as it is for most, but yes, it is still on the expensive side. I was planning on doing open cell full stud bay on the interior, as well as rigid iso boards on the exterior if i have to rip off the existing stucco. Roof deck will be 9.25" full stud bay of the same open cell. For the basement walls I might do 1-2" rigid iso with just an empty stud bay, as I am not a fan of fiberglass in any way.

For my basement right now I just picked up a 18 section @ 25" height cast iron radiator similar to the type i have upstairs, not the largest thing in the world, but its definitely not small.

That is a good point on zones that I overlooked, so then yes keeping it to 3 zones + the indirect will be my goal. Possibly a 4th if I ever want to add a snow melt zone/heat exchanger.

Does the boiler buddy add complexity? I have no doubt on the added costs, and being able to fully utilize my condensing boiler without one would be great, but from the diagrams I have seen it looks like it is pretty simple and straightforward. Then again this is the area that really has me stumped, zone design, circulator sizing, P/S loops etc.

Another thought, thoughts on using my old 40 gal DHW tank as a buffer until I can get around to replacing the slant fin zone with something with more mass?

 

[Dana]

The Boiler Buddy is just an expensive high-mass hydraulic separator. While plumbing a mod-con for hydraulic separation has it's merits, on small systems it's often possible to design it to pump direct, saving the cost of the hydraulic separator and the extra pump, and saving on pumping-power operating cost to boot. (Some manufacturers will void the warranty if plumbed without hydraulic separation, even if the design math shows it's not necessary. I don't know if Lochinvar is one of those.)

At your likely pumping flows using an un-wired electric hot water tank as a massive hydraulic separator rather than a Boiler Buddy works. (On higher-flow systems the 3/4" connections could become an issue.) Pulling the drain-valve port and teeing into that as the return side, and teeing out the hot-output for the supply-side to the radiation, capping the cold feed tends to work best, since it avoids using the dip-tube (which can and will eventually fatigue and break off.) Keeping the stub to the Tees as short as possible, and keeping at least 8" of straight pipe on the arms of the tee matters too. Some folks prefer to plumb to the heater element ports rather tees- I don't have a strong opinion either way as to whether this is a meaningful functional change when dealing with smaller boilers like the -055.

 

[BPIAuditLongIsland]

How does this look?

Everything would be done using 3/4" copper. Come spring I will be changing over the rest of the 1st floor over to hot water, converting the existing steam radiators and tying them all into zone 1. I will keep the buffer in place until I can place more radiation in the basement / zone 2.