Burnham MPO-IQ84 oil water boiler

jesmed1

@EdTheHeaterMan Thank you, that is excellent. I will try to get a plumber to come price this out. I really appreciate all the time you spent answering my questions. I'll come back when we get this plumbed up and let you know how it's working out.

Do you have any guess as to what we might expect to see in the way of reduced oil consumption with only one boiler running? Also, what size expansion tank should we use? Current non-diaphragm tank is 40 gallons. I used an online tank size calculator inputting 200,000 BTU/hr boiler output into cast iron radiators, and the calculator gave me an Amtrol SX-30V 14-gallon tank. That's much smaller than our current 40-gallon non-diaphragm tank, but that may be way oversized like everything else.

OuterCapeOilguy

I'm a big fan of the Weil-McLain Gold equipped with Carlin EZ-1 burners. That said, I have yet to run into a 2-section Gold; smallest ones I encounter are the WGO-3 and WTGO-3. Lots of WM Golds here on the outer Cape; a couple of years ago I replaced the burner, fuel system and combustion chamber on a 1996 model, first year they were made. Still running nicely.

jesmed1

@OuterCapeOilguy That's just about the vintage of our WM Golds. In the 10 years I've been here, we only needed one new combustion chamber. The Beckett AFG's hum along nicely, no problems. They're nice boilers. I just wish they were 1/3 the size!

EdTheHeaterMan

Never a fan of any pin boiler. Even the American Standard's from the 1960s. The clean out brush would get stuck between the pins. More than once I have had to cut off and abandon a clean-out brush inside a boiler. Maybe next year I can pull it out, after a year of baking in that flue passage. Great idea for absorbing more heat from the flue gasses. Lousy idea for maintenance.

I liked the Buderus with the big front door for the chamber and the flue maintenance.

Never installed an EK boiler until one of my former competitors changed from oil to gas and removed the EK System 2000. I got it for free and installed it for one of the gal’s that worked for me. When I saw the process and the design I was sold on the concept. Too bad for Roger I sold my business and retired soon after that.

You can keep WM gold and Utica and all the rest. The Crown Freeport and Freeport 2 were much easier to clean. Almost like the old coal conversions from back in the day.

OuterCapeOilguy

EdTheHeaterMan said:

Never a fan of any pin boiler. Even the American Standard's from the 1960s. The clean out brush would get stuck between the pins. More than once I have had to cut off and abandon a clean-out brush inside a boiler. Maybe next year I can pull it out, after a year of baking in that flue passage. Great idea for absorbing more heat from the flue gasses. Lousy idea for maintenance.

I liked the Buderus with the big front door for the chamber and the flue maintenance.

Never installed an EK boiler until one of my former competitors changed from oil to gas and removed the EK System 2000. I got it for free and installed it for one of the gal’s that worked for me. When I saw the process and the design I was sold on the concept. Too bad for Roger I sold my business and retired soon after that.

You can keep WM gold and Utica and all the rest. The Crown Freeport and Freeport 2 were much easier to clean. Almost like the old coal conversions from back in the day.

There's a lot to be said for the triple-pass boilers like the Buderus and EK. If I ever need to replace my WM WGO-5 (at age 71, it will likely outlast me), I'd probably go with an EK-everything I've heard about them is really positive.

EdTheHeaterMan

OuterCapeOilguy said:

There's a lot to be said for the triple-pass boilers like the Buderus and EK. If I ever need to replace my WM WGO-5 (at age 71, it will likely outlast me), I'd probably go with an EK-everything I've heard about them is really positive.

Awh fiddlestix @OuterCapeOilguy ... You don't look a day over 70

jesmed1

EdTheHeaterMan said:

This would actually be better
The expansion tank on the supply pipe at some point. Then both circulators pumping away from the expansion tank. Flo-Chech valves are a better choice over a Zone Valve, since you already have 2 pumps.

I propose the primary/secondary because the changeover from one boiler to the other is done with a switch or a switch and a valve. Get ready for the inevitable, you can even swap boilers from year to year. #1 on odd years and #2 on even years.

Why make more work for the future. And when will the swap be needed? When it is the most inconvenient time. When you barely have time to go over there and flip a switch, you will need to cancel your daughter's wedding, or postpone your uncle's funeral, to replace a boiler.

@EdTheHeaterMan If we plumbed it this way, would we need higher-head pumps to overcome the added head from the Flo-Check valves? We now have Taco 007's.

EdTheHeaterMan

NO

jesmed1

EdTheHeaterMan said:

NO

OK, thanks!

EdTheHeaterMan

If you want to understand how pump head works there is a section in this booklet that will explain ot in easy to understand terms. https://s3.amazonaws.com/s3.supplyhouse.com/product_files/108119-Reference Guide.pdf
It starts on page 7. Pump Head has nothing to do with the building hight

jesmed1

EdTheHeaterMan said:

If you want to understand how pump head works there is a section in this booklet that will explain ot in easy to understand terms. https://s3.amazonaws.com/s3.supplyhouse.com/product_files/108119-Reference Guide.pdf
It starts on page 7. Pump Head has nothing to do with the building hight

@EdTheHeaterMan Thanks Ed. Very informative. So using the pump head rule of thumb in that pamphlet, I figure our longest run is 100 feet, then add 50% (I assume for fittings) to get 150 feet. Then multiply by 0.04 to get 6 feet of head. Then looking at the curve for our Taco 007 circulators, I get 14 gpm at 6 feet of head.

That's without Flo-Chek valves. The Flo-Chek spec sheet says to add 48 feet of equivalent pipe length for a 1-1/4" diameter Flo-Chek. Adding that 48 feet to our original 150 feet gives 198 feet, which I'll round to 200. Now multiplying by 0.04, I get 8 feet of head. Then the Taco 007 is circulating 8 gpm. So we would drop from 14 gpm down to 8 gpm by adding the Flo-Chek. Am I doing the math right?

EdTheHeaterMan

Yes. Every system has a friction curve. This is an example I used in my seminar.
It shows the Taco 007 pump curve in a system with zone valves. If only one zone is open then the system curve is different than if all zones are open. Where the system curve intersects the pump curve is what is actually happening. So, if you are needing 8 GPM to operate your 80,000 BTU NET boiler and that falls below the pump curve at the system head requirement, then you are good to go (within reason). If you have a pump that is too large then your system curve will intersect at a point where the flow will be too fast and you will experience noise and premature equipment failure (pumps, valves, pipe erosion etc.)

jesmed1

@EdTheHeaterMan OK, thank you. Our boilers are running at about 150,000 BTU/hr gross output now, so assuming a 20 degree delta T, that would imply a flow rate of 15 gpm. I don't know what the actual delta T is, but I'm getting some pipe thermometers tomorrow to monitor supply and return temps, albeit rather crudely.

I do have a thermal imager, but I've found the readings can be thrown off by the differing emissivities of metal surfaces, so I don't quite trust it yet for copper pipe. I have read that it can be made accurate on copper pipe by wrapping with black vinyl tape of known emissivity, and then plugging that known emissivity value into the imager; I may try that too to calibrate the pipe thermometers.

EdTheHeaterMan

Your boiler has 3 numbers for BTU
Input is what you size the gas pipe by or select the oil burned nozzle and pressure
Gross Output or sometimes called DOE output. This is close to the steady state combustion efficiency number. For example a 100,000 input boiler that has an efficiency rating of 80% would have a 80,000 Gross Output. It was introduced in the 1970s in order to compare boilers and furnaces when those EPA and DOE yellow stickers started to show up on heating equipment and MPG on cars.
AHRI Net or I=B=R Net on older boilers, is the number you use for sizing your pumps, the radiators and to match the heat loss of the building. That number is usually about 15% lower So the 100,000 BTU input might have a NET output of 68,000.

So in your case you may only need 13 GPM to move 129,000 BTUh. But you need to look at the actual radiators. What is the capacity of the loop or the zone? That may only be 25,000 for one zone, and 40,000 for another zone and maybe 30,000 for the third zone. So, if all zones call at the same time your pump may need to move 10 GPM .

You need to look at the whole system and see what the requirements are for the lowest common denominator.

If you have enough radiators to emit 200,000 BTU of heat but your boiler is only able to make 129,000 BTU NET output, then the pump must be able to move 13 GPM so the boiler does not short cycle on the Limit control. Likewise that same boiler on a system with only 100,000 BTU of radiation connected to the system needs only to move 10 GPM, but the burner will cycle on the high limit because your system can't get rid of all the heat the boiler can make.

But I like that you are starting to understand the concepts Keep researching Keep learning.

jesmed1

@EdTheHeaterMan Thank you for all your help, Ed. I really appreciate it!

jesmed1

@EdTheHeaterMan

Some test data from today on a 45-minute boiler run:

BTU input rate: 165,200 BTU/hr input
85% efficient
So 140,420 BTU/hr gross output

Measured delta T = 12 degrees
Implied flow rate = 23 gpm (=140,000/60/8.33/12)
Circulator is Taco 007
Chart for Taco 007 shows 23 gpm is max at zero head (we have a lot of large 2" pipe)

This seems like a high flow rate (though no noise) and a low delta T. And since boiler is cold start, the high flow rate floods the boiler with a lot of cold water. Should we switch to a Taco 008 with lower max flow rate (15 gpm at zero head) which would increase delta T to around 18 degrees? This would also make sense for the future when we install smaller boilers, as delta T will go down again.

EdTheHeaterMan

Should we switch to a Taco 008 with lower max flow rate

No. You need to partially close a valve to create more restriction. (Globe valves or gate valves are better for balancing. A ball valve will do in a pinch). The large pipes and the elbows and the boiler and the other pieces of the system that the water is flowing thru will create some friction. Your system has its own curve based on the amount of flow thru it. (I refer you to this comment https://forum.heatinghelp.com/discussion/comment/1764008#Comment_1764008) If you were to plot that on the pump curve then the point where the system curve intersects the pump head curve is what is actually happening. The 007F is one of the most common pumps used in the residential boiler market. As a result of this, it is also the lowest cost pump on the market. You might find that the 008 pump is more expensive because it is less common, and therefore the economy of scale for that pump has not lowered Its price.

The lower cost pump (007) will work just fine. Besides ...and it has a license to kill and what is the AHRI Net or. the I=B=R NET of your boiler. That is the number you should be using. Not the DOE Gross. You always use the NET for sizing stuff. click spoiler for details

This post is way too long to re-hash this stuff
Heat loss of building = AHRI NET
Pump Size based on AHRI NET
Pipe Size based on AHRI NET
Radiator size based on individual room heat loss
Then add all the radiators together and you will = AHRI NET

Next point: You measured a 12° ∆T when the system was operating... Was it operating at steady state efficiency? That happens after the boiler has run non-stop for about 5 minutes and the water temperature is no longer increasing. Was the water temperature increasing during this test? If it was increasing during the test, then you were not at steady state yet. The boiler may only be putting out 128,000 BTUh NET if you are firing it at 1.20 GPH firing rate. (which I hope you are, if not lower) This is from the WGO-5 Series 3. Your boiler may be a Series 1 but the numbers are not that far off.
It indicates that the NET is only 129k when the input is 168k
Base your calculation on the 128 or 129 (or some other NET Number) depending on what series boiler you are using and what firing rate you actually have. Then after you get more accurate numbers to plug into your calculation you will be closer to what you actually have.



Lets try this: 128,000 / 60 / 8.33 / 12 = 21.3 GPM and the temperature in the boiler keeps rising. That means that the pump is moving less than 21.3 GPM, maybe more like 13 GPM. That means at 12° ∆T you may only be moving 78,000 BTU (what the pipes and radiators can handle) to the radiators and the boiler will keep getting hotter until it reaches the high limit setting. Then the burner will be cycling say 36 minutes on and 24 minutes off every hour (or 6 minutes on and 4 minutes off 6 times every hour) Let's look at that calculation: 78,000 / 60 / 8.33 / 12 = 13 GPM This makes more sense to me!
But these are only guesses from the “armchair quarterback” When you get into the coldest days of winter you can do the timing test along with the ∆T test and know the actual nozzle size and pressure then have the combustion analysis to determine the real steady state efficiency when it is operating during one of those short cycles in January.

This is more that you expected... But every time you read that TextBook and every time you get another concept under your belt. It will let you understand the next concept. I tell a story about how I learned about Hydronics in my 20s here. It took 3 years and I was not done yet: https://forum.heatinghelp.com/discussion/comment/1679684#Comment_1679684

jesmed1

@EdTheHeaterMan OK, thank you. Some answers to your questions:

1. We have the WGO-5 (not the -5RD) downfired with a 1.0 nozzle running 140 psi, actual input 1.18 gph. So that's 165,200 BTU/hr input, running at 85% efficiency, so 140,420 BTU/hr gross output, and 119,357 BTU/hr NET I=B=R after the additional 15% reduction. So I will use the 119,357 BTU/hr NET I=B=R for sizing as you said.

2. It's impossible to get these boilers to run at steady state, because they (and the radiation) are so oversized for this building that even during the -10 degree polar vortex with 40 mph winds last February, the boilers ran only about half the time, and the water temperature never got above around 150 degrees. So the boilers never, ever, hit the high limit. 99% of the time, the water temp at the boiler gauge doesn't exceed 140 degrees when the thermostat satisfies.

3. So you're correct that, during my 45-minute run, the water temp rose slowly (while maintaining a 12 degree delta T all during the 45 minutes.) But as I described above, it's virtually impossible to get the boiler to hit the high limit, because we'd probably need to run it for about 2 hours continuously, and massively overheat the condo units in the process.

4. I understand what you're saying about the pump moving less than 23 gpm, and now that makes sense. I couldn't understand how the system would have zero head. We do have gate valves on all the branches, so I could close them partially as you suggest. If I experiment and slowly close those valves a bit at a time, I can creep up on a new target delta T. What delta T should I target? 20 degrees?

5. We also have a massive amount of radiation, again much more than we need. We have 480 sq ft of cast iron radiator per boiler. Most of the time our water temp doesn't exceed 140. At that temp, cast iron rads emit 90 BTU/sq ft, so that's 43,200 BTU/hr. That happens to be roughly the design heat loss for that half of the building at zero degrees. So you can see why our water temp never gets very high. The radiators can radiate sufficient heat with water temps 140 and below. If the water temp ever got to 180 degrees (with 170 BTU emitted/sq ft), we'd be radiating at 81,600 BTU/hr for that half of the house, which is almost twice our design heat loss. So we never get close to that water temp, and as a result, the boilers never hit the high limit.

PS--I enjoyed your learning story. I think you're the new Joe Flash!

EdTheHeaterMan

2. It's impossible to get these boiler to run at steady state, because it (and the radiation) are so oversized for this building that even during the -10 degree polar vortex with 40 mph winds last February, the boilers ran only about half the time, and the water temperature never got above around 150 degrees. So the boilers never, ever, hit the high limit. 99% of the time, the water temp doesn't exceed 140 degrees when the thermostat satisfied.

Then you are at steady state at about 5 to 10 minutes in to the cycle. The fact that the thermostat(s) are satisfied before the limit temperature is reached means that you have more radiation than you need (you already know that) and the boiler temperature at 130° to 140° is more than enough to satisfy the thermostat(s) in order to cycle off for more that 30 minute per hour will be to your advantage when you do the primary loop and take the radiators off as secondaries, and the boiler off as secondaries. You may even get the boilers to operate at a higher temperature with a little tweaking of some valves. This will reduce the time that the boiler is operating with a flue gas condensation issue.

Have you got prices for the repipe yet?

jesmed1

EdTheHeaterMan said:

Have you got prices for the repipe yet?

I drew up a bill of materials and costed that all out, with a Taco 3-zone control as you said, 3 new circulators, valved flanges, expansion tank, micro-bubble air eliminator, etc. After costing out the materials and telling the other unit owners that the plumber's labor cost would probably equal or exceed the materials cost, they decided to wait until one boiler fails and then make all the plumbing mods at that time. So I'm back to square one, trying to optimize what we have now. It sounds like partially closing some gate valves to get the delta T up is probably the best thing I can do at this point.

The one thing that concerns me with that is the balance between the first floor and second floor units. There are no zone controls and no thermostats in the second floor units. Somehow the flow is balanced enough that the upper floor units stay around 68 degrees, and I don't want to upset that balance. I worry that by closing some gate valves I might throw that balance off.

EdTheHeaterMan

Follow up: Based on your latest information, you do not want to do this piping design, unless you want your boiler to rot away from flue gas condensation. Having both systems on one boiler will cause the water temperature to rise even slower.




Your system will operate below 130° most of the time. You will need to have a bypass installed in order to keep the boiler return temperature high enough. I have posted the low temperature system instructions form both the Series 1 and the Series 3 WGO boilers. The diagrams are from the Series 1 WGO I/O manual. Take note that they are insisting that you use Primary Secondary and a bypass valve to control the boiler temperature at a higher temperature. See valve # 7 on the diagram. Your original installer failed to follow those instructions.



It seems that Weil McLain has a magic number of 140° minimum boiler return temperature. By looking at the photo of the boilers you posted, there is no bypass.

jesmed1

EdTheHeaterMan said:

By looking at the photo of the boilers you posted, there is no bypass.

There is definitely no bypass. That explains a lot. They just plumbed each boiler straight in with a supply a return, and a circulator.

But guess what? After 25+ years of running below 140 degrees, the boilers are still in good condition. The pins are all still there, and the boiler techs keep saying we might get another 5-10 years out of them. So despite totally ignoring the plumbing instructions, few or no bad consequences seem to have resulted. Also, the chimney terra cotta liner is fine.

jesmed1

EdTheHeaterMan said:

Follow up: Based on your latest information, you do not want to do this piping design, unless you want your boiler to rot away from flue gas condensation. Having both systems on one boiler will cause the water temperature to rise even slower.

OK, we may be back to square one and eventually just get two somewhat smaller boilers and leave them on their own loops.

EdTheHeaterMan

No. You need to partially close a valve to create more restriction.

jesmed1 said:

EdTheHeaterMan said:

Have you got prices for the repipe yet?

I drew up a bill of materials and costed that all out, with a Taco 3-zone control as you said, 3 new circulators, valved flanges, expansion tank, micro-bubble air eliminator, etc. After costing out the materials and telling the other unit owners that the plumber's labor cost would probably equal or exceed the materials cost, they decided to wait until one boiler fails and then make all the plumbing mods at that time. So I'm back to square one, trying to optimize what we have now. It sounds like partially closing some gate valves to get the delta T up is probably the best thing I can do at this point.

The one thing that concerns me with that is the balance between the first floor and second floor units. There are no zone controls and no thermostats in the second floor units. Somehow the flow is balanced enough that the upper floor units stay around 68 degrees, and I don't want to upset that balance. I worry that by closing some gate valves I might throw that balance off.

.

Do not close down any valve on the system as it is piped. That can cause other problems unless you install a bypass somewhere. You should tell the other members of the condo assn. that the boilers are installed incorrectly and therefore wasting fuel and causing premature failure of the boilers for as long as they are operating at that lower temperature.

jesmed1

EdTheHeaterMan said:

Do not close down any valve on the system as it is piped. That can cause other problems unless you install a bypass somewhere. You should tell the other members of the condo assn. that the boilers are installed incorrectly and therefore wasting fuel and causing premature failure of the boilers for as long as they are operating at that lower temperature.

OK, I will leave all valves open. I have told the members that the boilers are oversized and therefore running inefficiently. However, since the boilers have survived 25+ years with surprisingly little or no ill effects, they aren't interested in spending any money until/unless a boiler breaks and needs to be replaced. I have been trying to find low-cost efficiency improvements, with little success.

The only other thing I can think to do is install Field Controls automatic vent dampers. Those are relatively inexpensive and reportedly do keep a lot of warm air from being sucked up the chimney after shutdown.