Ideas to cut boiler room cost when a LOT of 1.5" black pipe is involved?

Ferrythecat

Detailed diagram attached.

Looking to replace most/all the boiler room. Nothing in the design is exotic, though it is a bit 1955 old school in that it is 1.5" black pipe, 2 zones, ~100' in each direction, reverse return.

Doesn't really matter, but since I am sharing it is a ranch house, boiler in basement, total lift from top of boiler to radiators is less than 5'.

Here is my question. A 1.5" thermostatic valve for boiler protection is ~$1300. The radiator

style by ESBE or Caleffi (under $300) only go to 1.25". The hydronic separator at 1.5" also isn't cheap, but less than that dang mixing valve.

The boiler, indirect water heater, TACO RMB and 400' of 1.5" pipe are not going to change. In light of that, can anyone propose a more cost effective solution? Does anyone know a vendor who makes a protection valve in 1.5" that is a bit more price effective? Any favorite brand of hydronic separator that I might want to consider?

Any obvious gaps/mistakes in my plan if I were to simply spend the money?

Feedback and ideas greatly appreciated.

BTW, LOVE LOVE LOVE the forum. I read the old thread for fun and education.

Thanks,

CK

heat_thoughts.pdf

Kaos

88k does not need 1.5" pipe, so as long as the near boiler piping is not complicated with lots of elbows, you can go way down. You need about 9 GPM through the boiler which you can do with 1" pex.

You can put the boiler pump on the return pumping into the boiler, makes it easier to prime and keeps it a bit cooler.

hot_rod

what size boiler?

At the most those 3/4 bb loops would be 4 gpm each, 12 gpm could be handled with 1-1/4”

I used to buy Wheatland Tube MegaThread

It is the thinnest walled steel pipe that can be threaded, so ID is larger for a bit more flow, compared to sch 40 steel. Lighter to carry and work overhead

It is commonly used for fire protection piping, makes the hydraulics calculate better.

Made in the USA also, so the threads don’t rip like some import stuff

Could be more $$ however ?

mattmia2

if you do the math on the maximum bypass you need and the maximum the common valves can provide you will find if you can use those valves with reducers (or 1.25" pipe since your load doesn't appear to need 1.5" pipe). if you think about loads and where things tee off you can bring some sections down to 1". there tends to be a big jump in cost between 1" and 1.25".

Though it likely won't last as long, if you have gas available a mod con with the right controls built in could simplify and could reduce cost in a number of ways. It would have odr built in, can find models with different curves for different zone calls, would not have issues with return temp.

was this a gravity system originally?

i want to make sure this isn't a monoflo system you didn't identify as such?

unless it is monoflo and you need the flow for the diverter tees, you can reduce the pipe where it connects to the existing system piping to a size that will carry the heat loss of that section, assuming you have a way to balance it.

Jamie Hall

@Kaos is absolutely correct on this: you don't need 1 1/2 inch pipe everywhere.

There is no harm to keeping the inch and a half out in the wilderness there. If it doesn't have to come out, don't take it out.

However, near the boiler — in fact everything out to the manifold line outlets — can be smaller. I haven't run the numbers; @Kaos maybe right at 1 inch. The thing to keep in mind with pipe size is that it is limited more by keeping the velocity reasonable; variations in head loss (so long as they too are not much worse than moderate) can be handled by choice of pumps.

Now he suggests using PEX. Um… well… I personally am not really happy with PEX on the supply side of a boiler (comes to that, I'm not really happy with it on the returns, either). For domestic hot water, no real problem. The reason is that on the boiler side of the mixing valve, if one is used, there is a very real possibility that you are running very close to, if not over, the maximum rated temperature of PEX — 200 F. I just don't care to push my materials that hard.

Copper is more expensive, granted, and somewhat harder to work with — but I'd use copper.

Ferrythecat

Agreed the 1.5" is super overkill, BUT that 400' of 1.5" is already installed. Been in place since 1955 or 56. That part is not changing, way to much work, even with pex. Consider it thermal buffer.

I know I showed 4 and 3 loops, but that was just representative that the 2 sides are different. Actual # is probably 7 and 5 + the radiant.

If I were doing a total re-pipe I would probably 3/4 pex to each room all of a manifold, but not going to happen.

Boiler protection is a real concern, especially with the DHW. That tank needs ~115% of the boiler output to sustain continuous 140 degree output. Granted that isn't realistic, but it is what the math shows.

This is why I am looking for creative ideas. Upping the boiler output for a theoretical future whirlpool isn't necessary. But when the mixing valve and separator cost the same as the boiler I start scratching my head thinking I should do something different.

I COULD in theory down size to 1 or 1.25" on the primary loop, but I admit I am not sure how the separator will like that. I suppose I could call Caleffi.

Other ideas?

CK

Ferrythecat

Woops, @Jamie Hall got a comment out while I was writing mine.

I personally also like to keep my PEX a feet away from the boiler. When I see someone running PEX directly to a gas fired hot water heater I always wonder how many days until it gives way. Never seems to, but won't do it on my watch.

But it sounds like Jamie is saying dropping to 1.25" or check the #s and maybe 1", and then adaptor my way back to 1.5" for the long runs and it should be OK. Yes, more velocity in the boiler loop, but the runs around the house won't change. Certainly would save $. This is basically what I was looking for idea wise. Just looking for that extra confidence that it shouldn't mess anything else up.

Oh, NOT monoflow BTW.

Thanks,
CK

mattmia2

The us code rating of pex is 200f. the rating from the engineering data is a curve with temp and pressure that brings you well above the temps you'll have in residential hot water at the pressures you'll have in residential hot water.

That being said, the fittings and combinations of fitting's you'll need to use pex is likely far more expensive than using fewer fittings that do more of what you need in one fitting in black iron or copper. Pex tubing is les expensive but the fittings are more expensive and more limited and most of your cost is in fittings in near boiler piping.

You can size the piping to the existing piping by the output you need from those sections, the existing pipe size is irrelevant. I still don't understand why it is as large as it is if it wasn't previously gravity.

ethicalpaul

there is a very real possibility that you are running very close to, if not over, the maximum rated temperature of PEX — 200 F. I just don't care to push my materials that hard.

Surely there is already a safety factor in the rating. Is another lower safety factor required to be added by the end user? Do we not trust the engineers who came up with the pex rating?

mattmia2

They stop at 210f but it is clear it would withstand what you would see in a residential domestic heating system barring any failures that would also damage other components:

ChrisJ

https://forum.heatinghelp.com/discussion/comment/1829955#Comment_1829955

Many on this forum feel they're superior to engineers.

Jamie isn't one of them, but I felt it needing mention.

Waher

Propress copper on the hotter side of things transitioning to once past the tempering devices? That’s usually what I see instead of black pipe or brass in hydronic installations now. High temperature Pex does have some use in solar thermal systems.

PC7060

@Ferrythecat - second what @Jamie Hall recomended. Use copper to tie from new boiler to existing mains. Leave majority of not all of existing pipe unchanged.
This is example from converted gravity system with 80KBTU modcon piped with 1” copper into 2” iron pipe. The pump and expansion tank are connected to topside of boiler in a pumping away configuration as @hot_rod recommended.

Ferrythecat

Thanks all. The easy out for me here is to do the boiler loop in 1" and then the long distribution runs will bump up to 1.5" as they are today. I really just wanted someone more experienced than I am to confirm I wouldn't be shooting myself in the foot.

No gas available and no desire to bring in propane, so no mod-con.

No clue why originally 1.5". Not likely to have been gravity in the past. House was a 1955 build (well into the age of circulators) and a rather high end custom build for the time. Most likely this was a combination of over engineering and maybe a desire to lower velocity/noise. Practically speaking what I like about it is that it heats the basement. Of course when I did my heat loss calculations on the house it really threw me for a loop, but it is convenient. I need to dig out the old Crane CI baseboard design book. Maybe it was what they recommended at the time.

Now to go think about what might I change in light of all this.

CK

hot_rod

https://forum.heatinghelp.com/discussion/comment/1829957#Comment_1829957

oxygen ingress goes up with higher fluid temperature also

leonz

You would be much further ahead by installing a hot water buffer tank and piping the hot water output to the base of the tank then pumping away from the top of the buffer tank to the heating load.