New Weil Boiler

corgi11

I just replaced an American Standard ArcoLiner Boiler that was converted to natural gas 1954. The plate said 1 GPH oil 73000 btu output water. I just replaced it with a new Weil 100,000 btu in and 73000 IBR net out.
I live in Chicago suburbs. I ran a modified J calculation and it came out to around 70,000 btu. I have about 100 feet of old Triad baseboard all parallel runs one run for each room all 1/2 inch. With my old heavy boiler it would run for about 30 min and the temp went up to maybe 140 to 150 at 40 degrees out. My new boiler only holds 2.5 gal of water so after about 20 min or less it runs up against high limit and does that until thermostat is satisfied. Pump keeps running until thermostat is satisfied and all runs are very hot. I checked and there is an equivalent pump on the new boiler.
Is this just the nature of the new beast.

HVACNUT

What model boiler?

corgi11

Weil Mclain CGA 4 series 3 Installed 1 month ago.

Steamhead

Sure it's not a HydroStat or other weather-responsive control doing its thing?

jesmed1

Do you know what the actual gas BTU input rate was on your old boiler? Because if the BTU input rate was different on the old boiler after the gas conversion (it may not have been the same BTU that was on the original rating plate for oil input) then you won't have an apples-to-apples comparison. For example, if your old boiler was only getting, say, 80,000 BTU/hr input from the gas conversion, you would expect to see a difference in performance between that and a new boiler that's getting 100,000 BTU/hr input.

corgi11

Old boiler worked fine on oil and gas.I think I have a mass problem. Thank you for your response.

corgi11

No external controls factory stock controls.

corgi11

Same baseboards since 1953 no changes at all.

corgi11

Thank You everyone for your responses. My new boiler holds only 2 5 gal of water. I think my old boiler had so much mass it took a long time to heat up.My old boiler took 4 men to take it out. My new boiler came in with one kid on a hand truck!

Hot_water_fan

Incredibly oversized! 

EdTheHeaterMan

@corgi11, there are some things that are assumed by contributors herein. @jesmed1 may be spot on.

For one thing it is assumed that you understand that the burner may not necessarily have the firing rate that the boiler rating tag reads. That assumption may be incorrect.

For example, your boiler rated at 1.00 GPH oil has a net rating of 73,000 BTUh. This assumes that the nozzle in the burner is in fact a 1.00 GPH nozzle. What would happen if someone put a .85 GPH nozzle in that burner in order to reduce the firing rate in an attempt to save on oil usage back in the 1970s and 1980s? That was a very popular thing to do back then. Now your boiler rating would change from what is on the rating plate to what the new input of 15% less fuel. In your case that would be closer to NET 62,050 BTUh rating.

Next thing to assume is that the gas conversion burner installer looked at the nozzle from the burner and used the orifice that would use only 118,000 BTUh of gas input rather than the 140,000 input of the boiler’s rating plate. If that was the case, then the new boiler you have has an input of 15% more gas than the input of the old boiler.

The installer of the new Weil McLain boiler did you no favor by reading the rating plate of the old boiler to select your new boiler. The only proper way to select the size of a replacement boiler is to perform a load calculation using one of the approved methods, of which there are several. Form 1504WH from the Hydronics Institute, Manual J from ACCA, and there are some that use the actual fuel usage records from the previous years, sometimes called the degree day method.

Now that you have this oversized boiler, You will most likely have to live with it for the next 20+ years. Oh well!

corgi11

Chicago design temp -10, old boiler kept 75 degrees at that temp. Lost 1 degree for every degree colder. Seems the system was designed perfectly.

corgi11

I am asking old vs new problem not design problem that worked since 1954 all most of all my neighbors have same size units. How can it be so oversized if you don't know the size of my house and construction?

Hot_water_fan

Because the boiler can be oversized while the radiation is right sized. No matter how big the boiler is, 100 feet of baseboard has an output limit of about 60kbtu. 

HVACNUT

What are the settings?
Is it large piping and radiators?
There are different piping diagrams in the manual. Which one was used? Maybe it should've been piped primary/secondary.
The CGa comes with a 007 circulator. What circulator was on the old system?
Pics?

EdTheHeaterMan

corgi11 said:

I am asking old vs new problem not design problem that worked since 1954 all most of all my neighbors have same size units. How can it be so oversized if you don't know the size of my house and construction?

by this quote:

I just replaced an American Standard ArcoLiner Boiler that was converted to natural gas 1954. The plate said 1 GPH oil 73000 btu output water. I just replaced it with a new Weil 100,000 btu in and 73000 IBR net out.

It is a well established fact that boilers installed in the 1950s were oversized as a rule. The "Bigger is Better rule" to be exact. And by 40+ years of experience in the oil burner and boiler repair, replacement, and problem solving business. But if you don't believe me, then do the load calculation. if the boiler is within 20% larger that the actual need of the home, then it is the correct size, My guess is that it will be over 60% larger that needed.

If you dont want to do the homework assignment, then just wait for the coldest night of the winter. like when the outdoor temperature reaches 5 or 10 degrees below zero. Then watch the burners on your boiler. They should never shut off if it is the correct size. My guess is that there will be at least a 5 minute off time and a 6 or 7 minute on time while the circulator continues to operate for those cold winter cycles. If the thermostat actually gets satisfied at that low outdoor temperature, then you are way oversized.

You see if you have an actual load calculation of 45,000 BTUh and you put more than 73,000, BTUh in your home, then the burner will stop at some point because the home is no using all that you are putting into the house. This causes on-off cycling. The boiler is least efficient during start up of each cycle. The larger the burner the more cycling. The more cycling the more inefficient operating time. By selecting the size closest to the actual need, you may get a boiler that does not cycle at all, when the outdoor temperature is at design temperature.

But as you say, I can not actually know wht size you should have without knowing the size and construction of your home. But it appears that did not matter to the person that installed your new boiler because they never did the homework assignment. they cheated and put in the wrong answer because they copied the answer from the guy that installed the American Standard boiler.

EDIT: Bottom line... if the gas bill is affordable and there are very few part failures as a result of short cycling, then all is good at your Castle near the Windy City

jesmed1

EdTheHeaterMan said:

If you dont want to do the homework assignment, then just wait for the coldest night of the winter. like when the outdoor temperature reaches 5 or 10 degrees below zero. Then watch the burners on your boiler. They should never shut off if it is the correct size. My guess is that there will be at least a 5 minute off time and a 6 or 7 minute on time while the circulator continues to operate for those cold winter cycles. If the thermostat actually gets satisfied at that low outdoor temperature, then you are way oversized.

This is spot on. I maintain a 100-year-old 4-unit condo building with 2 Weil-McLain boilers that are grossly oversized because the installers used rules-of-thumb with generous margins instead of doing actual heat loss calculations.

When I began suspecting the boilers were way oversized, I did just as you described. I monitored boiler run time on a single-digit-temperature day here in Boston. The boilers ran less than half the time. As you said, if they had been correctly sized, they would be running almost all the time in such low temps.

By calculating our actual heat loss, I found that we're under 20 BTU/sq ft/hr heat loss in zero degree weather. But the boilers are sized for about 50 BTU/sq ft/hr. Now that I know our actual heat loss, next time we need a boiler, we can safely get a much smaller one.

corgi11

So far I have only fired up new boiler on 40 degree day. Will get back to you guys when it gets much colder. But can anyone explain to me why my older boiler never ran up to high limit except at design temp of -10 or colder?

EdTheHeaterMan

corgi11 said:

So far I have only fired up new boiler on 40 degree day. Will get back to you guys when it gets much colder. But can anyone explain to me why my older boiler never ran up to high limit except at design temp of -10 or colder?

The burner was firing at much less than the rated firing rate.

If you have the old burner, you could look at the orifice and see what size opening it is. Sometimes they are marked.

Also, as you suspect, the smaller flame will take longer to heat up that larger amount of water. The thermostat will get satisfied before the smaller burner can heat the water to the limit setting. The longer running cycle is a result of the smaller burner.

Now that you have a bigger flame and a smaller water content, the water reaches the limit temperature much faster. You might find that the rooms may over temperature as a result of this phenomenon.

jesmed1

Your old boiler ran longer, at lower water temps, than your new boiler.

Some of that difference was due to the higher mass of the old boiler's heat exchanger, which took longer to heat up, and some of the difference may be due to the old burner having been downfired as Ed said, which resulted in your new boiler actually having a higher BTU input rate than the old one, even though the rating plates are basically the same.

If it mattered to you, you could add radiators to the loop. That would allow the hotter water to transfer heat to the rooms faster, making the Tstat satisfy sooner, and preventing the water from getting hot enough to hit the high limit switch. But there's probably not much point in that. You're getting heat into the house faster now than you were with the old boiler, so why add radiators? I'm just observing that if you were starting with a clean sheet design, you'd either downsize the boiler or add more radiation so the water temps didn't get so high.

corgi11

Don't you size boiler for design temp in my case -10.
I did modified j calc and ane up with around 68000 btu. 1953s house all vaulted ceilings all brick virtually no i

corgi11

Don't you size boiler for design temp in my case -10.
I did modified j calc and ane up with around 68000 btu. 1953s house all vaulted ceilings all brick virtually no insulation. I could have gotten the smallest boiler weil had it is 20k ibr less BTU then I have now but 20k BTU is only 4 electric space heaters spread over my entire house!

corgi11

Old triad baseboards 6 inch high fins spaced 1/8 inch apart. Steel Covers. Only slots in top front of covers. It takes a long time for the air to convect to start to heat rooms. Water enters at bottom of baseboard makes u turn and exits top of baseboard.
Everybody thank you for your responses.

corgi11

Boiler only holds 2.5 gal water per weil!

EdTheHeaterMan

Actually that old ARCOLiner was much less efficient at making the heat from the flame transfer into usable heat in the radiators. If that old rating plate was from a model 351 that was rated for 1.00 GPH firing rate and has a net rating 73000 BTUh that would mean that the burner flame to water in the boiler efficiency would be about 61% after accounting for the 1.15 piping and pickup adjustment.

The Weil McLain boiler at 100,000 input at 86% efficiency would also have a 73,000 NET rating after accounting for the 1.15 piping and pickup adjustment.

These calculations are based on the fact that a gallon of fuel oil has about 138,000 to 140,000 BTU per gallon. The input of the ARCOLiner 351 is about 140,000 BTUh at 1 GPH oil and a combustion efficiency or perhaps the equivalent of the DOE Output rating of 85,000 to 86,000 BTUh would make that boiler a 61% efficient boiler.

Unless that IBR net rating on the ARCOLiner was for steam. That means that the piping and pickup factor would have been 1.30. In this case, the equivalent of the flame to water transfer efficiency Output might be closer to 95,000 BTUh making the boiler about 68% efficient in converting flame energy to water temperature rise in the boiler.

All this gibberish means is: If the 73000 NET rating was for steam, then the Weil McLain boiler is that much more oversized that the ARCOLiner that was removed.

corgi11

The new weil is rated 73000 ibr net water. This is not a steam boiler. Neither was my old arcoliner. Both hot water only.

corgi11

My DOE rating is 80k btu

corgi11

Yes it was an arcoliner model 351

jesmed1

corgi11 said:

Don't you size boiler for design temp in my case -10.
I did modified j calc and ane up with around 68000 btu. 1953s house all vaulted ceilings all brick virtually no insulation. I could have gotten the smallest boiler weil had it is 20k ibr less BTU then I have now but 20k BTU is only 4 electric space heaters spread over my entire house!

How many square feet is your house? Just curious, because I did our heat loss calculations for a 100-yr-old house in Boston and got a heat loss of just under 20 BTU/sq ft/hr. We have some insulation and upgraded windows, but I was still surprised the heat loss came in that low. 20 BTU/sq ft/hr is decent for modern construction, and very good for an old house.

Your Chicago climate is colder than Boston, and you say you have virtually no insulation, so your heat loss might be around 30 BTU/sq Ft/hr. So if your house is around 2,300 sq ft, that would put you right at your 68,000 BTU/hr calculation. Of course, my 30 BTU/sq ft/hr is just a guess and could be way off, but I'd be interested to know what your actual BTU/sq ft is.

Steamhead

corgi11 said:

No external controls factory stock controls.

@corgi11 , see @HVACNUT 's post above. The weather-responsive feature is built into the main control on this boiler. Try turning the Economy dial to Max and see if that helps. If it's already set at Max, see if it actually gets up to high limit before stopping the burner.

LRCCBJ

corgi11 said:

Don't you size boiler for design temp in my case -10.
I did modified j calc and ane up with around 68000 btu. 1953s house all vaulted ceilings all brick virtually no insulation. I could have gotten the smallest boiler weil had it is 20k ibr less BTU then I have now but 20k BTU is only 4 electric space heaters spread over my entire house!

With a manual J of 68,000 and a net output of the new boiler of 73,000, the sizing is just about perfect. Any suspicion that it is oversized is incorrect. The net output of the next size CGa-3 is 48,000 and you'd freeze to death at -10F.

The reason the boiler cycles at 40F is the fact that it heats very quickly due to the much smaller mass AND the fact that the load at 40F is only 1/3 of the load at -10F.

One additional fact to consider (which is largely ignored) is the wind speed. Get a Chicago day close to design with 40 kt. winds and your heatloss will likely be much more than your calculated 68,000. The house will not maintain 70F. under these conditions with this boiler.

corgi11

My house is 1500 sq ft. All vaulted ceilings 20 ft living room dining room, 10 ft family room. All the rest 8ft. All wooden ceiling Lr & Dr Floor to ceiling windows. Original windows casement on outside 6 in air gap with sliders on inside.Full basement. 10 ft ceiling in den.
Just for grins I helped install the space pack in this house 36k BTU. All Brick house.

jesmed1

LRCCBJ said:

One additional fact to consider (which is largely ignored) is the wind speed. Get a Chicago day close to design with 40 kt. winds and your heatloss will likely be much more than your calculated 68,000. The house will not maintain 70F. under these conditions with this boiler.

This is an excellent point. Here in Boston we had a polar vortex event last January (?) during which temps dropped to -10 overnight and we had high winds. I logged our boiler run times and calculated that our heat loss went up by almost 40% vs a zero-degree day with no wind.

Of course, that was once-in-70-year event, and not something you want to size most furnaces for. But high winds will definitely suck the heat out of a building a lot faster.

corgi11

My wife and I are seniors and we keep thermostat at 75 degrees all winter. An 85 degree differential to design temp. When I did the calc I did it for the 85 degree differential.

corgi11

Floor to ceiling windows in lr and dr have storm windows.

jesmed1

LRCCBJ said:

corgi11 said:

Don't you size boiler for design temp in my case -10.
I did modified j calc and ane up with around 68000 btu. 1953s house all vaulted ceilings all brick virtually no insulation. I could have gotten the smallest boiler weil had it is 20k ibr less BTU then I have now but 20k BTU is only 4 electric space heaters spread over my entire house!

With a manual J of 68,000 and a net output of the new boiler of 73,000, the sizing is just about perfect. Any suspicion that it is oversized is incorrect. The net output of the next size CGa-3 is 48,000 and you'd freeze to death at -10F.

I don't doubt that his heat loss calculation is correct. But it sounds like he doesn't have enough radiation to be a good match with this boiler, because the boiler is high limiting before the Tstat satisfies. He also says it takes a long time to feel hot air convecting up from the radiators, which is another data point suggesting insufficient radiation.

jesmed1

corgi11 said:

My house is 1500 sq ft. All vaulted ceilings 20 ft living room dining room, 10 ft family room. All the rest 8ft. All wooden ceiling Lr & Dr Floor to ceiling windows. Original windows casement on outside 6 in air gap with sliders on inside.Full basement. 10 ft ceiling in den.
Just for grins I helped install the space pack in this house 36k BTU. All Brick house.

OK, so 68,000 BTU over 1500 sq ft = 45 BTU/sq ft/hr. I had guessed 30 BTU/sq ft/hr, but you are using a higher temp differential than most people, and you have high ceilings and big windows.

It seems like your main issue now is not having enough radiation to transfer the heat out of the boiler fast enough, but it's not fatal, just that your boiler will high-limit frequently.

corgi11

Thanks jesmed 1 
These triad baseboards always took a long time to heat up. Old triad baseboards 6 inch high fins spaced 1/8 inch apart. Steel Covers. Only slots in top front of covers. It takes a long time for the air to convect to start to heat rooms. Water enters at bottom of baseboard makes u turn and exits top of baseboard.

jesmed1

corgi11 said:

Thanks jesmed 1 
These triad baseboards always took a long time to heat up. Old triad baseboards 6 inch high fins spaced 1/8 inch apart. Steel Covers. Only slots in top front of covers. It takes a long time for the air to convect to start to heat rooms. Water enters at bottom of baseboard makes u turn and exits top of baseboard.

Then that's the limiting factor in your heating system now. We have old cast iron radiators that heat up fast and allow good airflow. Our boilers are way oversized for the house, but even so, our water temp rarely exceeds 140. Which means we have plenty of radiation, even for oversized boilers.

Your baseboard radiators don't have enough surface area and/or airflow to convect well. So by the time your baseboards start outputting some heat, the boiler is already near high limit.

EdTheHeaterMan

corgi11 said:

The new weil is rated 73000 ibr net water. This is not a steam boiler. Neither was my old arcoliner. Both hot water only.

As you may not realize, the rating plate on the old ARCOLiner was not put on that boiler based on what was done in your home. The rating plate was placed on that boiler based on ALL the possible uses. Do you have a picture of the rating plate of the ARCOLiner? That picture will indicate the IBR net rating. It may say IBR NET Steam 73000. It may read IBR NET water 73000

Here are some examples of different plates that have both water and steam ratings on the same boiler


Your ARCOLiner was able to go both ways.

Your new boiler can not go both ways so your new Boiler will only have water ratings

I offer these tags because your reply assumes that your ARCOLiner rating was a water rating because Yous was a water boiler, But can you be sure the rating was only for water or could it have both and the NET 73000 was not actually water?

corgi11

Old boiler 1gph(140k)BTU 73000 water out was fine for -10 day kept house at 75. 100 ft baseboard set with limit at 205. If you look at slant fin fine line 15 it shows 680 approx BTU ft. I know my baseboard probably puts out more. 

LRCCB Why don't you think a new boiler with 73k ibr net won't work where the old boiler of 73 k net worked? This setup has worked for the 37 years I have owned this house.