68 year old Monoflo system: Keep or Replace?


  #1  
Old 05-03-21, 10:02 AM
F
Member
Thread Starter
Join Date: May 2021
Posts: 2
Received 0 Votes on 0 Posts
68 year old Monoflo system: Keep or Replace?

My son and his wife own a 68 year old, 1.5 story cape in Concord, NH that's been weatherized. The heating system includes a 35 year old standard oil boiler with upright cast iron radiators and 1" main / 1/2" branch copper monoflo distribution. It's time for at least a boiler replacement. If the masonry chimney is continued to be used it will need a liner.

Given the costs, efficiencies, and adaptability involved, would it be better to start fresh with an entirely new HE natural gas system with entirely new distribution, adapt a HE system to the existing monoflo distribution, or settle for a standard efficiency boiler (oil or NG) that will require a stainless steel chimney liner?
 

Popular Reply

 
05-04-21, 02:35 AM
Steamboy
Steamboy is offline
Member
Join Date: Jan 2017
Location: USA
Posts: 561
Received 12 Votes on 9 Posts
Combine this information with what you learned on "heating help" and I think you get your questions answered. That mono-flo system is great and the cost to replace a good working boiler will never be paid for by the fuel savings.
 
  #2  
Old 05-03-21, 10:48 AM
2
Member
Join Date: Jan 2014
Location: USA near Boston, MA
Posts: 1,214
Received 105 Votes on 90 Posts
I would go with a standard efficiency atmospheric boiler and keep the existing distribution. HE boilers cost more, need more maintenance, are harder to troubleshoot and really do not provide a greater overall HEATING efficiency (just boiler efficiency.) Heating efficiency will be determined by a correct boiler size and controls (including outdoor reset, draft damper, etc.) to provide the right amount of heat to offset the losses at various outside temperatures.

Before buying any replacement boiler do a heat loss calculation. (See sticky links at top of thread list in this forum.) Given that there have been (or should be) insulation, window, draft leak, etc,. improvements over the years you will probably not need as large a boiler as you are replacing. I replaced my 160K BTU oil boiler in 2013 with a 140K BTU NG atmospheric before doing a heat loss calculation. I could have gone a size smaller (90K BTU) and still would have satisfied the 72K BTU load that my house actually needs. (The calculated amount has been confirmed by actual NG usage over the past 7 years.) You can estimate your actual load from the amounts of oil or NG consumed in recent years if you have that information.

The cost of a standard atmospheric boiler AND the SS chimney liner should be about the same cost as the HE boiler alone. Either type can serve a mono-flo system.

Also look into any rebate program that your NG supplier may have.
 
Fungo21 voted this post useful.
  #3  
Old 05-04-21, 02:35 AM
S
Member
Join Date: Jan 2017
Location: USA
Posts: 561
Received 12 Votes on 9 Posts
Combine this information with what you learned on "heating help" and I think you get your questions answered. That mono-flo system is great and the cost to replace a good working boiler will never be paid for by the fuel savings.
 
Fungo21, gilmorrie, hvac01453 voted this post useful.
  #4  
Old 05-04-21, 09:12 AM
D
Member
Join Date: Apr 2014
Location: us
Posts: 1,148
Received 61 Votes on 57 Posts
Avoid New Expensive Replacements

DH has similar 1957 system with original boiler. In 1970 used 1800 gallons of oil. At end of 2020/2012 winter will use 600 gallons.

Would replace original boiler only if it developed irreparable leaks. Is 86% efficient at 350 F stack temperature.

Have never had issue with original clay pipe lined chimney. A stainless steel liner might feed corrosive condensates back to boiler.

DH split single zone 1" copper main line, monoflow system into 8 zones, 5 thermostats. One Grundfos Alpha 2 circulator for 6 zones and small for ones.

Bought for $100 on eBay, like new Beckett AFG retention head burner. Is fired at 63% of boiler original BTU rating. On coldest winter day system run 8 hours or 1/3 of day. If gas prices dropped below oil would slip in 4” gas conversion unit. Used it during 1970's oil crisis.

Typical monoflow hydronic heating system with baseboard or other elements require water temperature of 140F to 180F .

New high efficiency boiler ratings are based on water exiting at 80 F. Little would be gained from installing HE type which have typical 10 year life span and maintainence issues.

Old cast iron boilers do not have establish life span and are often needlessly replaced.

Fungo21 son could easily modernize the system with zones, modern, adequately sized burner, outdoor reset aquastat and auto stack vent. Greedy, incompetent professionals often promote expensive programs that bring new problems.
 
Fungo21 voted this post useful.

Last edited by doughess; 05-04-21 at 10:27 AM.
  #5  
Old 05-04-21, 02:11 PM
S
Member
Join Date: Oct 2013
Location: United States
Posts: 3,235
Received 85 Votes on 79 Posts
Steamboy is right on point. Have personally had monoflo since 85 without incident.
 
Fungo21, gilmorrie voted this post useful.
  #6  
Old 05-04-21, 06:56 PM
F
Member
Thread Starter
Join Date: May 2021
Posts: 2
Received 0 Votes on 0 Posts
doughess: "Have never had issue with original clay pipe lined chimney. A stainless steel liner might feed corrosive condensates back to boiler."

The clay liner is shot. It's an exterior chimney, and the liner is likely be original to the house / 68 years. If not the boiler condensate, it was never capped and the freeze thaw eventually flakes/crumbles the clay.
Would a drip T between the chimney and boiler be enough to stop condensate feedback?

 
  #7  
Old 05-04-21, 07:46 PM
D
Member
Join Date: Apr 2014
Location: us
Posts: 1,148
Received 61 Votes on 57 Posts
In 50 years have not seen any sign of chimney condensation. Any condensation would fall to clean out area below where boiler horizontal line enters chimney and just drain in to ground. Might call it drip trap.

A screened chimney cap keeps out squirrels and debris from trees

Monoflow system works great. Just put good Watts auto vent on each element.

Grundfos Alpha2 circulators with auto sensing pressure control, eliminate many multi zone system issues. Left it powered on automatically adjusts to changes as zones open and close. No need for zone end switch wiring and circulator controller.
 
2john02458, Fungo21 voted this post useful.

Last edited by doughess; 05-04-21 at 09:03 PM.
  #8  
Old 05-05-21, 08:40 AM
D
Member
Join Date: Apr 2014
Location: us
Posts: 1,148
Received 61 Votes on 57 Posts
Look on condensation in chimney as multi step process.

First ...Hot flue gases condense on cold chimney walls.

Second ... Hot flue gases vaporize condensation and moist air is carried up an out chimney.

Third ...Continue flow of hot gases heat walls of chimney above condensation temperature.

Forth ...As weather get very cold, long boiler runs heat chimney walls above condensation temperature.

Condensation is another “fear” button contractors push on customers to increase profits. Sulfuric acid concentrate in your chimney! spend $ to protect your home.
 

Last edited by doughess; 05-05-21 at 10:52 AM.
  #9  
Old 05-06-21, 07:10 AM
rbeck's Avatar
Member
Join Date: Jul 2007
Posts: 2,511
Received 13 Votes on 10 Posts
Retired after 42 years in the industry I feel the same about a monoflo system. They are good systems. You do not mention if the monoflo system is cast iron radiators, cabinet convectors or some type of baseboard. This is a determining factor on boiler choice and near boiler piping.
If you use a cast iron boiler and the system is CI rads you will need to pay attention to near boiler piping to protect against condensation in the boiler, vent pipe and chimney. With copper tube baseboard the need pretty much goes away unless you add OD reset..
If you choose a HE boiler no need to worry about condensing the boiler and use Primary/Secondary piping. I will agree the boiler requires more maintenance and more expensive parts. Sizing is always important today with lower water volume CI boilers and even more critical with HE boilers.
Most heating systems with OD reset, contrary to belief can operate at temperatures down to 120F during the shoulder seasons. Cast iron rads can be operated below that many times as low as 100f.
HE boilers are great for this reason and CI boilers would require good boiler protection.
All boilers CI or HE boilers are tested at 140f supply and 120f return temperatures (DOE testing Requirement). If your water temperature increases the efficiency goes down and if your water temperature decreases your efficiency goes up. When a HE boiler is in condensing mode you will gather btu's out of the flue gases and add to heating the home which is not done with the CI boiler. A HE boiler also modulated so most of the winter your boiler would be firing usually less than 50% of rated input if the boiler is properly sized. While the boiler is modulating the boiler efficiency is higher.
In my travels across the country the last 22 years doing tech training and visiting job sites I have noticed that the further West I went I saw more internal chimneys, this means a 4 walls of the chimney are warm in the living space. On the East coast most chimneys are exterior chimney, at least one wall of the chimney is on an exterior wall. I have seen many chimneys destroyed by floe gas condensation. There are may signs of effervesce (do a search of chimney effervesce) on the outside of the chimneys it gets so bad sometimes. I have seen puddles of water on the floor or collected in big tubs below the integrated draft hoods to collect the water.
the minimum flue gas temperature entering a chimney I have always heard and lived by was 350F. New CI gas boilers will normally be between 230f and 260f thus a need for a chimney liner. AT boiler efficiency's at 84% and higher by code the liner must be stainless steel.
As the fed's keep raising boiler efficiency my OPINION is chimney vented boilers as we know them will go away at some point and only sidewall boilers will be allowed.
So to sum it p choose CI boiler and maybe consider a sidewall vented boiler that allows combustion air to be brought into the home and connected directly to the boiler, watch the near boiler piping or a HE boiler and bring combustion air in and connect directly to the boiler piped primary/secondary. Either way your system is good and for any reason of either comfort or appearance I would not change away from the monoflo system.
I do agree if you keep the same system use a variable speed circulator. They use less electric and the water flow changes as the water temperture changes so these circulators also control flow better. Dependent on manufacturer they they work of Delta-P (pressure) or Delta-T (Temperature) which is what I prefer.
 
2john02458, spott voted this post useful.
  #10  
Old 05-06-21, 08:55 AM
H
Member
Join Date: Nov 2002
Location: Massachusetts
Posts: 1,851
Received 1 Vote on 1 Post
upgrading

upgrading to a retention head low mass boiler is as far as one should go. HE is a salesmans dream. They are expensive, breakdown more often, (service calls) and replacement parts are way up there, good for service department. If you have lots of money to do the exact same job, namely making hot water, be my guest (sucker)... Thats like buying a new car for $40,000 because you dont want to wait for your existing car to break down, maybe $1,200, although it never, or rarely has... both will get you to work safely. The price you save on fuel is miniscule compared to the maintenance costs involved. get an 80% CI low mass boiler. I have a 117.000btu Pensotti CI boiler, with a Riello oil burner and its been running since 93 without any issues. I replaced the Field 5" power venter once with a SS units becaused the steel one rotted off, till it fell apart. I oil it twice a year...I have a garber spin on filter with a vacuum gauge, and havent drawn any vacuum in two years so far. so I dont change it. My efficiency is about 82%. I have an indirect 40G DHW zone so I dont maintain a minimum boiler temp like a tankless requires. My average for an 1920SF colonial is averaged to about 2.2 gallons per day throughout the year. If NG were available in my area, that would be a cheaper alternative. Then if you have a NG power generator, your all set during an outage. I have a gasoline generator and then found out I had to scamper around looking for gasoline when we had an outage that lasted for several days. The gas stations had no power to run the pumps= no gas and huge lines to the ones that did. If I had it to do over again I would have got a diesel generator and ran a fuel line off my indoor heating oil tank...Oh well, hindsight....
 
  #11  
Old 05-06-21, 02:58 PM
D
Member
Join Date: Apr 2014
Location: us
Posts: 1,148
Received 61 Votes on 57 Posts
An issue for Fungo21 to consider in evaluating various solutions is oil versus gas fuel.

In 1970's oil rose from 0.15 cents per gallon to $3.00+. DH bought and installed $150 gas conversion unit with 4” tube to replace Beckett AFG oil burner

When oil became cheaper that gas, plugged Beckett AFG burner back in. Maybe will have to switch again.

Rather the buying a new gas only boiler, might consider oil now, and converting to gas at later time. Gas utility promotions often preclude units that can be converted.

Supplyhouse.com has many types of gas conversion units.. Here is one:

https://www.supplyhouse.com/Beckett-...version-Burner

DH had similar experience to hvac01403 trying to buy gasoline for generator. during week long power outage in region. For $100 converted generator to natural gas with installation of air horn adapter on carborator air inlet. Is fed natural gas from valve activated by intake manifold vacuum. Another way, more complex way is with dual fuel carburetor.

https://www.aliexpress.com/item/3292...5c7b4c90914232
 
hvac01453 voted this post useful.
  #12  
Old 05-10-21, 03:36 PM
rbeck's Avatar
Member
Join Date: Jul 2007
Posts: 2,511
Received 13 Votes on 10 Posts
Be careful when converting boilers from oil to gas. Some oil boilers cannot legally be converted to gas. If the oil boiler has not ever been tested for gas it should not be converted to gas. Check the Installation instructions or call the manufacturer and verify it can be converted. I know some installation manuals say not to convert to gas due tot having the certification. Conversion gas burners are sold but not always certified by the boiler manufacturer.
So what happens if it is converted and there is an issue at some point and there an issue. You are responsible and the insurance company is not responsible to pay. Most boilers are negative draft boilers and some are positive pressure boilers. If not certified for gas the main question is will the boiler seals hold up to gas products of combustion.
 
  #13  
Old 05-10-21, 07:15 PM
D
Member
Join Date: Apr 2014
Location: us
Posts: 1,148
Received 61 Votes on 57 Posts
Most gas conversion units to replace oil burner have electric blower to produce draft, just like oil unit. When installed a draft gauge verifies proper setting.

To limit liability, manufacture's place all kinds of things in literature that are not valid in states with limited liability laws. We have all had experience with manufacture's denying responsibility.

Many professionals have a whole library of “fear” buttons to push on consumers. Some posts also have them.

DH does not worry about “certification” or insurance company issues.

DH life is simpler, more reliable and economical without the pro's. Became a DIYer because of pro's failures.
 
  #14  
Old 05-11-21, 01:31 PM
rbeck's Avatar
Member
Join Date: Jul 2007
Posts: 2,511
Received 13 Votes on 10 Posts
Doughness, I am just glad as a retired contractor with 42 years in the HVAC industry that I would have been smart enough to not follow some of your advise. I have seen many problems where HO's did their own work and not aware of either codes or enough knowledge of heating systems where there have been issues that have caused property damage/loss and even deaths.
I have also seen applications where licensed contractors did not follow the installation manual or codes cause the same issues as above.
Draft is not the only issues that can be an issue if converting to gas.
You stated, "DH does not worry about “certification” or insurance company issues" if you do inferior work due to negligence or lack of knowledge and nothing ever happens life is good, but if you have a problem your life will change forever.
About a 2 decade's ago we had a situation in our area where a contractor moonlighted a boiler on the side. He did not install a pipe on the relief valve terminating close to the floor. Children were playing in the basement when the ball they were playing with rolled over near the boiler. Just so happens the relief valve blew off and scared the poor girl face for life. He lost everything he owned. Yeah, forget insurance company issues, certifications, installation manuals and codes.
 
  #15  
Old 05-11-21, 02:18 PM
H
Member
Join Date: Nov 2002
Location: Massachusetts
Posts: 1,851
Received 1 Vote on 1 Post
An article I read in the JLC

A plumber got sued for not installing an anti scald valve in the 80s when a mother left her infant in the sink to answer the door, her son used the fauset to rinse his hands and didnt turn the HW off all the way. The infant got scalded. The mother was at fault for negligence right???
The courts found the plumber at fault because the technology existed although not required by code. It was also inspected and signed off on. They sued everyone in sight.Before the incident happened, the apartment has been sold and re-rented out by several people. They came back to hold him liable years later. Now thats a plumber that followed code, what about the one that doesn’t?
 
  #16  
Old 05-12-21, 01:19 PM
rbeck's Avatar
Member
Join Date: Jul 2007
Posts: 2,511
Received 13 Votes on 10 Posts
I read about a death in a basement bedroom in Texas caused by CO poisoning probably 10 - 12 years ago. The reason the contractor cut the vertical height of the draft hood by about 6". CO skyrocketed and the worst happened. All draft hoods are a certified distance from the top of the boiler to the Bell on the draft hood. No draft hood can be altered in any way. The draft hood setup two things, how much secondary air is brought into the combustion area to control CO and also helps control the temperature the boiler starts condensing.
 
hvac01453 voted this post useful.
  #17  
Old 05-12-21, 08:21 PM
D
Member
Join Date: Apr 2014
Location: us
Posts: 1,148
Received 61 Votes on 57 Posts
Subject of this thread is about keep or replacing 68 year old monoflow system. DH has similar 63 year old system that work great, is very reliable and economical to operate.

DH recomended keeping 68 year old system.

Many subsequent posts are off on tangential issues

Here is post on thread topic DH #4: Fungo21 son could easily modernize the system with zones, modern, adequately sized burner, outdoor reset aquastat and auto stack vent. Greedy, incompetent professionals often promote expensive programs that bring new problems.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: