Recommendation for 90,000 BTU (net) hot water boiler?

delcrossv

Mom's old Crane Sunnyday may be giving up the ghost after 65 years. IBR output is 90k. Looking for a natural gas atmospheric as a replacement. Rear flue would make things easier. Not a low mass system, so would like something with a goodly amount of water in the boiler.

Recommendations?

Thanks!

STEAM DOCTOR

First step would be to figure out what size boiler you really need. That is done by doing the heat loss calculations

delcrossv

90k net works well with the system. Why reinvent the wheel?

If it were short cycling, I'd be with you.

STEAM DOCTOR

Why pay more money for an oversized boiler? And are you sure that it's not short cycling?

HVACNUT

EK-1 Frontier Gas. You don't need a goodly amount of water in the boiler with it. It does just fine with 2.5 gallons.

delcrossv

https://forum.heatinghelp.com/discussion/comment/1810497#Comment_1810497

I'm really sure.

delcrossv

https://forum.heatinghelp.com/discussion/comment/1810501#Comment_1810501

Thanks! Thinking Weil EG-40, but will look into the EK.

delcrossv

Tested system to 25psi, no leaks, so I'll clean her up for another season.

Figured there'd be more suggestions on replacements. :(

pecmsg

I would be surprised a 65 year old boiler is sized properly!

Insulation has been added

Windows and doors replaced

Building envelope tightened.

90,000input is a lot

The Steam Whisperer

You may have seen this before but is work repeating….My previous home was 3200 sq ft on 2 floors, wood frame, with 700 sq ft of glass area. 2800 sq ft was the original 1906 home with about 600 sq ft of original windows with storms. The heatloss was about 45,000 btu/hr. This was confirmed with several seasons of checking gas usage during sub zero temps… 100,000 btu/hr input condensing boiler was running about 50% of the time.

Unless your Mom lives in a mansion, I'd check the heat loss. If it is a high mass system, just pipe it primary/secondary with a supply to return bypass on the boiler loop. Often times all of the boiler loop piping can be 3/4 inch copper in modest homes and maybe 1 inch in larger homes. Makes it really easy to pipe it in. The main loop still needs to be size to the flow rate of the system usually 1 inch in modest homes and 1 1/4 inch in larger homes.

My experience has been: when going from a standard atmospheric CI boiler double the size needed to a properly sized atmospheric cast iron unit of the same rated efficiency, typically the fuel usage drops about 12%.

When it comes to residential cast iron boilers, there doesn't seem to be any particular standouts. Most are lower water content, which works really well if piped as above, since the boiler tends to heat soak on each cycle, drying out the casting if needed during the shoulder seasons. The Weil CG's ( which in my experience is thier longest lived boiler) have really low water content, so they tend to perculate if there's alot of dirt in the system. A Burnham or Dunkirk have a little bit more water.

Definitely don't use a standard efficiency copper tube…they simply cannot handle any low return temps without a lot of damage due to condensation in the heat exchanger.

mattmia2

A fixed temp thermostatic mixing valve might be better than a manual bypass especially given people's propensity for fiddling.

The Steam Whisperer

Yes, I used to use those, but tended to see lots of failures. Once I understood fully how the bypass works, I really don't see much additional benefit from a thermostatic valve on the boiler return. I always pull the valve handles off on our installs.

EdTheHeaterMan

I agree with the Steam Whisperer about getting the valves set just right the removing the handles. I allso tighten the packing nut so the valves cant vibrate to a different position. To be a real nice guy, hang the handles near the valves with a note. DO NOT ADJUST THESE VALVES.

I also agree with doing an easy Whole House Load Calc for your Mom. You should learn how to do them fast and easy. Mom's house is good practice @delcrossv. And it's not like you have not heard this before in your time here on HeatingHelp.com. You might find the EG 30 or the EG 35 will work just fine and save you on the boiler cost and the operating cost. WIN WIN!

delcrossv

@The Steam Whisperer

"Unless your Mom lives in a mansion, I'd check the heat loss. If it is a high mass system, just pipe it primary/secondary with a supply to return bypass on the boiler loop. Often times all of the boiler loop piping can be 3/4 inch copper in modest homes and maybe 1 inch in larger homes. Makes it really easy to pipe it in. The main loop still needs to be size to the flow rate of the system usually 1 inch in modest homes and 1 1/4 inch in larger homes."

I'm liking this idea. It makes the lower boiler water volume less of an issue. (And I get to keep the 3 circs and 4 zone valves on one of them pretty much intact).

Is SlantFin the site with the easy heatloss calc?

The Steam Whisperer

Slant Fin went out of business.. so I wouldn't expect the site to be there anymore. With a high mass system and multiple zones, you really are going to want bypass piping ( or thermostat valve on the return) to help prevent shock to the boiler.

delcrossv

https://forum.heatinghelp.com/discussion/comment/1810808#Comment_1810808

Nuts. Who has the online heat loss calc?

delcrossv

This seems pretty straightforward (danfoss)

delcrossv

Found something on loadcalc got around 60,000btu! 😮

The Steam Whisperer

Yes, pretty simple.

delcrossv

Does the "closely spaced tees" rule still apply?

hot_rod

A good thermostatic bypass mixing valve is nothing more than a tee with a shuttle that moves via a thermostatic element

Really not much more than a TRV with a 3rd port, actually

Very little to fail, maybe crappy fluid conditions cause them to stick and fail?

If so it cannot fail in a closed position, one port or the other will always be open to the mixed port, so deadheading the pump is not possible

Manual valves, just by the definition of the term indicates they are accurate at one flow/ temperature conditions

Ideally a manual valve would be set at thermal equilibrium conditions. Boiler output is matched exactly to distribution.

As the connected distribution always dictates the operating condition of the boiler. Unless you add a control to prevent that condition, a high limit for example. Or a thermostatic device to protect the low side temperature.

If a slug of 60f water comes back from a series of cast radiators, the valve cannot respond or adjust to that condition, better than nothing, but not by much😉

Return 10 gpm of 60f water to a 100K boiler running at 140f, how many gpm would need to bypass to get to a safe condition to the boiler, of lets say 140f rwt. The bypass would need to be 100% open and a supply valve 100% closed under that condition, since no blend of 140 and 60 will get you to 140

Same with a bypass pump for protection.

You can define and predict that rwt at the boiler using the mixed temperature formula. Which is just an extension of the universal hydronic formula. Flow and temperature, two very well known entities in the hydronic world.

The Steam Whisperer

Probably not. Inducing flow into the other circuit probably isn't an issue, especially if you have correct zoning controls on the system.

EdTheHeaterMan

https://forum.heatinghelp.com/discussion/comment/1810493#Comment_1810493

That Sunnyday has a large amount of water in it, so it will not short cycle as much as a replacement boiler with less than 1/2 of the water volume. By replacing the large water content boiler with a small water content boiler, you are reinventing the wheel to a point. So do the load calculation and put a smaller BTU boiler in that home.

EdTheHeaterMan

Closely spaced tees are for Primary Secondary systems so the pumps are Hydraulically separated (one pump dos not effect the other pump)/. Are you thinking you need that for some reason? There are ways to accomplish the new boiler install with only one circulator. Why not look into those?

EdTheHeaterMan

this is another example of running something that old into the ground until you just have to get a new one

https://www.facebook.com/share/r/axncyfniB2q6m6vX/?mibextid=an1DBN

delcrossv

Who makes a large water volume boiler these days? \_O_/