Can you help me with my Hydronic setup?

boopfm523

Sorry for the long post, but context and details help. This is my first post as well. Thanks in advance.

Background:

My hydronic heating stopped working a few weeks ago. It was a debacle finding a competent service provider - meanwhile my house was freezing cold. Finally found one who was awesome. He let me be his apprentice essentially, and he explained a bit how the system worked (for example. my circulator went bad, but I could have had heat by opening the flo check and use gravity for the time being). Anyhow, I'm a guy who likes to learn how stuff works, so this intrigued me. The technician recommended I read Dan's book Classic Hydronics. I quickly consumed that over the course of the next 2 days and found it fascinating. My house is 102 years old. I never once touched the boiler (or anything with the heating system) in the time I've lived here (since 2016) - didn't pay it much attention (so many other things I had to fix, etc). After reading the book and looking at my setup, I've got questions. So figured I'd post here hoping for some help from the experts. I've tried to provide as much information as possible. Hopefully I'm not overly verbose, but some info I've included are:

• photos
  
• a diagram i put together where I tried my best to depict the setup.
  
• a list of all the radiators in the house (where I calculated the BTUs of each)
  
• all the parts with model numbers
  

Questions/Comments:

My general questions/comments are below. But I'm all ears for anything else you experts want to point out or ask.

1. My boiler seems huge, based on the total BTU output of all my radiators. Is this size really necessary? I don't know how much my kitchen's radiant floor plays into the need for this sized boiler, but I also know that boiler was installed 20 years before the kitchen's radiant floor was installed.
   
2. The boiler's temp has been set to 160. My guess is that it is set lower than typical because the boiler is larger than needed for my home - so doesn't have to heat as much?? Does that seem accurate?
   
3. The main circulator pump (the one that went bad a few weeks ago) is on the inbound side of the boiler. The expansion tank comes off the boiler. Reading Dan's book, it is ideal to put on pump on the outbound side of the boiler and soon after the expansion tank. So it seems this pump location is not ideal.
   
4. Is there anyway to know if the water in the outbound pipes go to the 3rd floor first, then work their way down the floors of the house? Or go to first floor first and work their way up, before coming back to the boiler?
   

House Info

• Built in 1920. 3 stories + Basement
  
• Radiator heat mostly. The kitchen (on first floor) has a tile floor with radiant heat underneath.
  
• I moved into the house in 2016. I don't know what was done then. I know the kitchen was updated in 2005, I believe the radiant floor was put in at that time. I assume the radiators were removed from the kitchen when it was redone in 2005.
  

Parts

• Utica - Gas Boiler (1983), J500 B1, BTHU ratings 500k input / 400k output
  
• Bell & Gosset - Circulator, 1/6 HP, PL-36
  
• Taco - Circulator, 1/25 HP, 007-F5
  
• Bell & Gosset - Pressure Reducing Valve, FB-38
  
• Taco - Universal Flo Check, 223
  
• Watts - Pressure Relief Value, M335
  
• Taco - Mixing Valve, 5000-2
  
• Maid-o-Mist - Auto Vent, .67
  
• Bell & Gosset - Drain-O-Tank Air Charger, DT-2
  
• Compression Tank - Don't know make or model. Looks old and I do not think it has a diaphragm.
  

Setup

• Boiler temperature is set to 160 degrees
  
• 17 Total Tubular Style Radiators
  
• The pipes that feed the radiant system look to be 1 inch
  
• The pipes that feed the radiators look to be 2 inch
  
• There is one thermostat that is used for the entire system/house.
  
• Exception to the above is that that radiant floor in the kitchen has it's own thermostat.
  
• The B&G pump feeds the radiators. The Taco pump feeds the radiant floor.
  

Photos/Diagrams/Radiator List:







Example photo of the style of radiators that are found throughout the house.





Thanks all.

hot_rod

At first glance you have an oversized boiler, how many square feet are you heating? It would be nice to have a heat load calculation for the home. The PL 36 is a fairly high head circ for the application. It would certainly be better on the supply side. The gauge on the side of the boiler, what does it read with the pump off, then turned on?

I suspect that PL 36 it may be pushing flow through that mix valve all the time?

aircooled81

Impressive post, very detailed. I'm just commenting, don't have any advisory here. Couple of screws and plumbers tape holding that compression tank-up there for years, love it. Sure, pump away from boiler or relocate compression tank and Make-up water to low side of pump, but need to consider how it would affect the radiant loops configuration. Agreed non condensing boiler, return water below 130*F or 120*F would be bad news. a lot of detail, hope you and your mechanical contractor are able to work it out.

Hot_water_fan

1. The boiler's temp has been set to 160. My guess is that it is set lower than typical because the boiler is larger than needed for my home - so doesn't have to heat as much?? Does that seem accurate?

No - the temp is determined by the ratio of heat loss to installed EDR, not boiler size. If it heats well at 160, great! That means at warmer outdoor temps, it could be lower. Can you share how much gas you use annually? That, along with a general location, can determine what your heat loss is. The lower the heat loss to square feet of radiation ratio is, the lower temp water you can use - so you could run more efficiently . 

bburd

For a hot water system, boiler size is determined by performing a heat loss calculation on the house, taking into account any insulation, window, or other thermal upgrades since original construction. That is a big boiler, but there’s no reason to change it if it still works well and doesn’t leak.

Although current best practice is to pump away from the expansion tank, for many decades the standard was to put the circulator on the return side of the boiler, to protect the pump seals from the hottest water in the system. Modern pumps have better seals. If it works well, there is no good reason to change it until the boiler needs replacement.

If you have 2 inch mains and cast-iron radiators, it was probably designed for gravity flow. You can trace the piping and will probably find it is direct return, with supply and return mains on the basement ceiling. Most of these systems in single-family homes used individual risers to radiators on the upper floors. Systems with main risers to the attic and down flow from there were typically used in much larger buildings. 

boopfm523

Thanks for the responses. I'll look to perform/get a heat loss calculation on the house and pull some of the gas bill information. The Gas and Electric bill gets to be $800 some winter months (most of which is gas).

FWIW, I live in the Guilford neighborhood of Baltimore, MD. The house is cinderblock (stucco outside) with no insulation. Terra cotta roof.

To be clear. I am not actively looking to replace anything with the system (boiler, radiators, etc). I'm just generally curious in how all this stuff works. I enjoy learning and the things I learn now will help me later when needed. For example, if the boiler does break and needs to be replaced. I just went two weeks without heat because the circulator broke and it was 48 degrees in my house. When the guy came to fix it, he mentioned I could have opened the universal flo check and used my systems old gravity setup to circulate the hot water while waiting for a new pump to be replaced. Now I know. Of course if there is anything glaring in the setup that should be improved, that's good to know.

Hot_water_fan

@boopfm523 I’m also in north Baltimore ! Barring extreme supplement heat sources, your boiler is extremely oversized, about 4-5x. This is pretty typical, but more surprising in houses that size. Just keep that in mind for the eventual replacement. Your heat loss is pretty low compared to your radiation too, so lower temps are adequate. When you post some usage data, the important info isn’t the $, it’s the therms. BGE gives us hourly data so you can really dial in the usage by day. 

boopfm523

Here is my Therms usage by month for the past year. This December is lower that it would have been normally. That's because for 13 days in December I didn't have the boiler running b/c of my pump being broken.

Hot_water_fan

Yup that’s typical! In January 2021, your boiler only ran for 116 hours (pretending no other natural gas usage, probably lower), which had an average temp of 36. You’d expect it to run about half the time if it was sized competently. 

boopfm523

Thanks @Hot_water_fan. I'm not necessarily trying to turn this thread into a Heat Loss Calculation thread, but do you mind explaining your response a bit more? I understand how you got to 116 hours (581 * 100,000 / 500,000). But not certain how you came to expect it to run half that time.

I know that month (Jan 2021), had an HDD of 899. But I couldn't figure out the math you used from that to make that expectation.

Sorry, total newbie here.

Hot_water_fan

Think about it on the day interval - a day with an average temp of 65 (HDD base 65 = 0) shouldn’t need any heat. Now Christmas Eve was the coldest day in Baltimore in a long time, and it had an average temp of about 15 (round numbers here). So no heat needed with a HDD = 0, maximum heat needed with HDD = 50. You’d expect a boiler to run nearly nonstop on a 50 HDD, maybe 20 hours to provide a reasonable oversize factor. So a month averaging 35 degrees is 30/50 of the way to maximum heat needed, so you’d expect 60% x 24 hours/day x 31 days/January = 446 hours, or 20% less if you were reasonably oversized. 

If you download the hourly interval bge data, you can plot it to show daily therms vs HDD, and it’s very clear. 

boopfm523

thanks for the details.

boopfm523

One last question @Hot_water_fan. Why is it typical for the homes in this area to have such oversized boilers? Any particular reason that you know of?

My HLC using the gas bill for Jan 2022 was 157,587. My boilers 400K output is 2.5x that. Whenever I do need to get a new boiler, would 1.4x that be good number to use?

Hot_water_fan

1.4x is good! Boilers are oversized all over - there's no real incentive or feedback loop for the installers to get it right.

fentonc

My boiler is about 4x oversized for my house, but the baseboard varies between 6x and 4x the heat loss for a given floor. The baseboard was just installed on all perimeter walls where possible, and then a boiler was installed to match (and generously rounded up). When it came time to replace it, the new guy looked at the old boiler and installed one with the same input BTUh, even though the new one was a little more efficient - this sort of thing seems extremely common with hydronic setups. The installers just have very few incentives to 'right-size' something as few people understand the inefficiency caused by a way over-sized system (installers or users), and they're far more likely to get callbacks for insufficient heat (where 'insufficient' might mean 'can't recover from a 10F setback in 30 minutes') than 'cost me 15% more to run than it otherwise would have.'

boopfm523

thanks for the details everyone. when it's time to replace the existing one, I'll be sure to not do a like-for-like replacement with regards to the BTU output.

However that leaves me with one question on the water connections. I have 2 inch supply/return connections. Looking at boilers online, I don't seem to see those size connections available for boilers with a smaller BTU output.

bburd

Most likely, those 2 inch pipes were designed for gravity flow. Your new boiler will have a circulator, which can connect using smaller piping due to the higher velocity of forced circulation.

Usual practice is to work with a 20° temperature difference through the boiler; then the flow rate is 1 gallon per minute for each 10,000 BTUH of boiler heat output. Pipe size is then selected from charts to keep velocity noise and pipe erosion within acceptable limits.

boopfm523

thanks @bburd - it was designed for gravity glow (it still has the universal flo check). learning about that is what clued me into the fact that when my pump broke last month, i could have opened that flo check and had heat using gravity flow while waiting to replace the circulator pump.

Mad Dog_2

Approx sqaure footage of house?  Mad 🐕 Dog

boopfm523

@Mad Dog_2 ~4,500 Sq feet