Boiler vent challenge - plus new boiler/WH selection help

[Oilhammer]

There's some similar threads on boiler/hot water heater, but it quickly digressed into complicated car discussions.
I have a few different challenges:

Challenge 1: The existing natural draft vent pulls the boiler and the WH up through an 8" single wall then 8" type B for the vert through the house and up through the roof. It functions, but it's in the way of a remodel and needs to be relocated at a minimum. My routing is extremely difficult for a pipe that size. I think I can split them into two until they hit the attic. Maybe I can run ovals and just make a small chase area and still be able to snake through joists and trusses. Looking at charts, I think I can pull off a 6" pipe for the boiler and a tiny one for WH. I'm sure I can switch to a power vent boiler or maybe a high efficiency unit that runs PVC, but that adds complication.

Challenge 2: The boiler and WH both function fine today. The boiler is circa 1963 199kbtu, so not terribly efficient, but it works....and is definitely oversized. I'd rather not spend the money to change them if I don't have to, but the vent question in challenge 1 may force it. At least new boilers are half the size, particularly if I use the load calc and drop to about a 160kbtu. If there isn't a solve for Challenge 1 natural vent, then does a Burnam X-PV8N-T10 make sense? I am at about 5400' of elevation and the current system is hot water baseboard. If I can keep it "simple" I think that's preferred. While the modern Weil-McClains look slick and take up less room, I'm not sure I need the complexity of the computer to avoid a couple hundred dollars a year in gas bill savings. I DON'T want to disassemble a burner every other year and clean it! The WH is a 50gal and probably has another 5 yrs in it. Again for simplicity, not a bad thing to keep it separate from the boiler, but it does seem silly to heat water 2 different ways. The only real benefit I can see to splitting them is that I can keep the passive heat down in the summer (Late May to Sept) by not running the big boiler. Lots of opinions on here about keeping them split for simplicity and that might really make the most sense assuming I can fix the vent issue.

Challenge 3: My wife hates the radiant baseboards. They function fine, but they do limit glass sizing and they collect dust and stain walls. The glass IS the challenge. I live in a mid-century modern with loads of glass in a colder climate. The nice part of the baseboards is that they put heat right at the glass. I'd love to swap out the system, or augment it, with radiant floors. Whatever solution I come up with for Challenge 2&3 above needs to keep this in mind.

Would love advice based on experience, particularly if you WON'T do something again.

Thanks!

 

[John Gayewski]

I would get a new boiler and do radiant floors. A conventional boiler adds complexity to radiant floors as they can't be ran at lower temps. One thing to check is can you heat your structure with radiant floors only. It could be your structure requires more heat than a radiant floor gives at normal temps. With a lot of glass you'd need an accurate heat loss calc.

 

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[Fitter30]

Heres a sizing guide for b vent

https://www.google.com/url?q=https://www.hartandcooley.com/assets/files/c3/hcb_010056_sizingguide_typeballfuelchimney_june2018.pdf&sa=U&ved=2ahUKEwj--f2jnL_4AhWAKkQIHQ6lAnoQFnoECAcQAg&usg=AOvVaw1gGmpA0dvZoQ3Mo1GpJ2ms

If you get rid of the fin tube you will be unhappy. Fin tube is offsetting the glass load by wiping the glass with heat. Being a 1963 house how are the walls insulated? As for as discoloration of walls there like air vents that have stained the area around them. Its not from air from the system its the air turbulence picking up air born dirt depositing on the walls or ceilings. Probably need to pull the covers and vacuum them. Cast iron or steel boilers heating dhw not a big fan keeping a boiler hot all summer to heat the water.

 

[Oilhammer]

I've only had the house a year, so limited experience with how it heats. The dirt on the walls was no doubt from lack of cleaning....she didn't do much of anything. I did notice that the fin tube would pretty quickly change the house from uncomfortable to comfortable, even with little to no insulation installed. At this point I have 6" of spray foam in the ceilings but only old 4" batt in walls....it really is mostly glass though. As much as radiant floors is very appealing for sight lines, I realize I'll lose the fast response but I am worried the cold glass will be a problem without the fins. I was really thinking about moving to a hybrid if such a thing exists. Leave the fin under the big glass sections, then lose it in areas that don't matter as much and use radiant.

I hear you on boiler heating WH. Sounds like many people suggest not doing that. I suppose you mean that running something like a HE boiler would be less of an issue though. I had a "design" put together through PexHEAT and they did a mock up with a sidearm, but definitely not conventional boiler.

Heat loss calcs- On paper, a radiant system can put the BTU's in the house, but living with that might be quite different than what the paper said.

I should also mention that the fins were installed directly to the studs...no drywall or plaster behind them. This resulted in several frozen pipes this winter when I had the heat turned down while away. I'm guessing there may be gaps in the insulation behind there that allowed pipes that didn't circulate enough to freeze up (this section has a Tee with no circ pump, so I suspect flow is low where it froze)

 

[Fitter30]

Condensing boiler might not be a good choice if the return water temp runs above 130° or higher the efficiency drops to 86% doesn't matter what brand. Conventional cast or steel boiler needs to run 130° return water temp. Taco makes a E line of pumps that are very efficient also a outdoor reset control varies water temp based on outdoor temperature.

 

[Oilhammer]

No way to verify that at the moment. I can tell you the boiler was set to about 175 and I can tell you all of the copper supply lines are uninsulated. Many of them rest directly on the concrete wall in the crawl space, and all are supported by bare nails in joist bays. It's a mess. There's so much rework already, that's one of the reasons I was considering starting over. If there was a short/slim fin tube, I could probably convince the wife to go that route. The ones installed are fairly slim, but quite tall.

Have you ever seen a hybrid system? One with high temp baseboards and low temp floor heat?

 

[John Gayewski]

No way to verify that at the moment. I can tell you the boiler was set to about 175 and I can tell you all of the copper supply lines are uninsulated. Many of them rest directly on the concrete wall in the crawl space, and all are supported by bare nails in joist bays. It's a mess. There's so much rework already, that's one of the reasons I was considering starting over. If there was a short/slim fin tube, I could probably convince the wife to go that route. The ones installed are fairly slim, but quite tall.

Have you ever seen a hybrid system? One with high temp baseboards and low temp floor heat?

Yes they exist very commonly. You just need a mixing valve or heat exchanger for different temps. It's adding complexity which you said you didn't want and you'll probably have to pay for someone to design it.

 

[Oilhammer]

Yes, I think I'm into finding a designer or continuing with aforementioned outfit already. I ran heat loss calcs, but there's a certain art to putting a good system together. What I like about this forum is that nobody on here is "selling" me something. My house is complicated and my budget further complicates that in that I really need to phase this in. First order of work is to resolve the venting. If I can't fit oval in and keep the boiler I have, then choosing the right boiler for where I'm going is next.

Sounds like: 1) check sizing (charts say 6" for boiler) and see if oval can fit in the space I have. If not, punt and change boiler out.
2) Determine if traditional or HE boiler (forced air in type B or HE in PVC vent) based on system design.
3) Install vent for #1 or #2, get inspected, close walls up and order the boiler if that's where this has to go.

 

[Oilhammer]

Correction- My current boiler is 290k btu. Not sure how I recalled 199k, but that's way off. It's massive and as I recall, doesn't burn very long unless I'm firing it up cold.

 

[Oilhammer]

Zero progress finding a local consultant to back up my own CAD based calcs. I've now run multiple J calcs just to capture a spectrum. I also cross referenced my figures against existing fin tube BTU figures and I'm pretty close. (Fin tube in place suggests an output of 124-139btu but there's way too much heat in two rooms) If I use a Denver/Centennial outdoor design temp of 4d, I wind up with a total heat load of 107452btu. If I simply take that to 140%, then somewhere around a 150kbtu boiler is what I should be looking for. Giving vent challenges and a future radiant floor, I think a condensing is what the choice should be, but not 100% sure yet.

Question 1: If I decided to put a side arm WH on this, not that I want to, how much larger would the boiler need to be? Total WAG, but seems like a 168 would be about the max. (The pex consultant had sized the side arm boiler to 199btu) DHW just doesn't happen that often, right? I'm hoping to keep the gas 40kbtu WH already here, but I'm not sure I can pull it off.

Question 2: If I move from 100% HWBB to a hybrid radiant floor/hot water baseboard, I suspect I will get greater efficiency out of a condensing boiler. Until I put in the radiant floor, I'm guessing I won't see much efficiency out of the boiler, though at half the BTU of what's there, probably still some level of savings. I didn't find anything that said I "can't" run a condensing water output at ~170d but I know they like return water at 130 or so. I never measured mine, so I don't know what the return temps ever were.

 

[Fitter30]

Do need to oversize a side arm boiler when calling for dhw all the heat go to heating the water not the house. Any condensing boiler return water temp has to at or below 130° for the 95%+ efficiency above drops to 87%. Cast boilers minimum return 140° can go a few degrees lower but l like a safety factor. Any pumps should have a ecm motor. Taco its E series. Combi can run 180° need to check specs.

 

[John Gayewski]

I think he meant to say you don't need to size the boiler based on your water heating needs as they don't run at the same time.

 

[Oilhammer]

That makes sense to me. Instead of 40kbtu to heat water, you have 160kbtu and the overall cycle just takes a few minutes out of the heat cycle. I think there are models that are combi that you can add a sidearm tank to later if need be. That might have to be my route.

Curious, I could search here, but any particular brands that are favorite based on experience and not pricing driven? (ex: I had a discount and a rebate on Certainteed, so there was incentive to push that brand over others. Not that it wasn't a good brand, just that there was heavy bias there for obvious reasons) I'm in a local car club/forum and one of the plumber members was partial to Burnham years ago. Since he was in Colorado, that's primarily what I've been looking at.

 

[John Gayewski]

We use Navien or Viessmann. Although I think Navien has better customer service. I'm partial to Viessmann becuse of the German engineering standards. Plus Germans and Europe in general have been doing hydronics and innovating in that space for many years as it's their most common heating method. Here in the US hydronics was moved to the side for cheaper warm air units in the fifties due to large investments in housing. Effeciant houses wasn't a thing back then they wanted as many as they could build for little up front cost.