Burnham MPO-IQ84 oil water boiler

jesmed1

My plan to convert our Weil-McLain WGO-5 oil boilers to gas conversion burners hit the wall yesterday when a chimney inspection by a trusted local chimney sweep confirmed that a new metal liner would be needed. The cost of the liner plus the fact that I can't even get a heating contractor to come give us a quote means that option is pretty much dead.

So I'm looking down the road to when one of the boilers fails and needs replacing. They're way to big for our actual heat load, which is about 44,000 BTU/hr per boiler at zero degree design temp. The options are:

Weil McLain WGO-2, 86,000 BTU/hr gross output
Buderus 115GS/W3, 85,000 BTU/hr gross output
Burham MPO-IQ84, 74,000 BTU/hr gross output

The Weil-McLain is a reliable well-known quantity, the same boiler as we have now but with fewer sections.

The Buderus is also reliable and well-known, and our oil company has installed both Weil McLains and Buderus.

I haven't heard anything about the Burnham MPO-IQ84 though. On paper I prefer it because it has a slightly lower output closer to our actual needs, and the IQ control system lets you do things like program a circulator post-purge to get some of the residual heat out of the boiler after shutdown.

Does anyone have experience with these Burnham MPO-IQ boilers and the electronic control system, and would you recommend them?

Steamhead

That's a nice boiler. But you'll still need to re-line the chimney, no matter what boiler you use.

DJD775

I have a version of the MPO re-badged for Ferguson but it has a standard aquastat instead of the IQ controls. I have no issues with the boiler but be aware that the current AFG burner specs were updated to increase the oil pressure from 150psi to 180psi so the gross output is essentially the same as the Buderus now. Mine came setup for 150psi but it runs so much smoother at 180 psi.
https://www.ferguson.com/product/proselect-force-boilers-force-residential-oil-boiler-84-mbh-forceoil084egbhdr/8090258.html?searchIndex=11

jesmed1

Steamhead said:

That's a nice boiler. But you'll still need to re-line the chimney, no matter what boiler you use.

OK, thanks. Hopefully we can get many more years out of these Weil-McLains, so my research may be a little premature, but better to be prepared when the time comes.

jesmed1

DJD775 said:

I have a version of the MPO re-badged for Ferguson but it has a standard aquastat instead of the IQ controls. I have no issues with the boiler but be aware that the current AFG burner specs were updated to increase the oil pressure from 150psi to 180psi so the gross output is essentially the same as the Buderus now. Mine came setup for 150psi but it runs so much smoother at 180 psi.
https://www.ferguson.com/product/proselect-force-boilers-force-residential-oil-boiler-84-mbh-forceoil084egbhdr/8090258.html?searchIndex=11

OK, thanks. I wasn't aware of the Ferguson brand.

DJD775

jesmed1 said:

DJD775 said:

I have a version of the MPO re-badged for Ferguson but it has a standard aquastat instead of the IQ controls. I have no issues with the boiler but be aware that the current AFG burner specs were updated to increase the oil pressure from 150psi to 180psi so the gross output is essentially the same as the Buderus now. Mine came setup for 150psi but it runs so much smoother at 180 psi.
https://www.ferguson.com/product/proselect-force-boilers-force-residential-oil-boiler-84-mbh-forceoil084egbhdr/8090258.html?searchIndex=11

OK, thanks. I wasn't aware of the Ferguson brand.

The Burnham version is more readily available but a wholesaler near me had the Ferguson version available at a deep discount.

STEVEusaPA

I have a pre IQ MPO. Love it. But it requires positive pressure over the fire which you’re not going to get from a conventional chimney, even with 2 draft regulators. You’ll probably need to get someone in there that knows what a neutral pressure point adjuster is, otherwise you’ll be posting about a boom on startup.
I'd recommend energy kinetics boilers. Some models, no chimney needed (vented thru the wall) or chimney can be used as a chase, but I doubt you’ll get 6 pipes from 3 boilers in the existing chimney.

jesmed1

STEVEusaPA said:

I have a pre IQ MPO. Love it. But it requires positive pressure over the fire which you’re not going to get from a conventional chimney, even with 2 draft regulators. You’ll probably need to get someone in there that knows what a neutral pressure point adjuster is, otherwise you’ll be posting about a boom on startup.
I'd recommend energy kinetics boilers. Some models, no chimney needed (vented thru the wall) or chimney can be used as a chase, but I doubt you’ll get 6 pipes from 3 boilers in the existing chimney.

OK thank you. Didn't know that about the positive pressure requirement. Our heating guy raved about the Energy Kinetics he installed for his family, but it may be too pricey for us. We'll probably stick with the Weil McLain or Buderus.

Steamhead

jesmed1 said:

OK thank you. Didn't know that about the positive pressure requirement. Our heating guy raved about the Energy Kinetics he installed for his family, but it may be too pricey for us. We'll probably stick with the Weil McLain or Buderus.

Don't be so quick to dismiss the EK boilers. They are some of the best.

jesmed1

Steamhead said:

Don't be so quick to dismiss the EK boilers. They are some of the best.

OK thank you. Unfortunately it seems pricing is hard to find for them, and I know we're not allowed to discuss prices here on the forum. I'll ask our heating guy about them next time he comes.

EBEBRATT-Ed

I would go with the Weil McLain a proven design. Anything made by Burnham is suspect to me. It may be (the Burnham) the best boiler on the planet but I have see way to many Burnhams in Massachusetts both steam and hot water that only lasted 10 years or so. I have no clue weather it is a water quality issue or what it is. But Burnham was the hot item in Ma. back in the 90s and 2000s previously HB Smith owned the market (they used to be made in Westfield) and Weil McLain had a good share but the Burnhams failed faster than anything else which on steam is one thing if they were not maintained or were neglected but way too many hot water boilers failed.

I know of a High School with 4 Burnhams all on hot water and they started failing10-12 years out and another school in the same system with 3 that have all been replaced except for 1 with a slow leak kept for an emergency spare. All their equipment was well maintained.

It just left a bad taste in everyone's mouth

JMHO

jesmed1

Thanks Ed. I'm in MA too, so I'll avoid the Burnham, which seems to be cursed here. Our oil company guys like Weil McLain and Buderus, so it will probably come down to those two.

bburd

Burnham boilers from that time did not like high chloride levels in the water, which are a problem in much of southern New England. They made design changes to mitigate this in steam boilers by eliminating pins above the water line, but a lot of contractors and owners got burned and are going to be cautious.

Have you considered installing high-efficiency gas boilers that can vent through the building's side wall, eliminating the need for the chimney?

Steamhead

bburd said:

.......Have you considered installing high-efficiency gas boilers that can vent through the building's side wall, eliminating the need for the chimney?

I wouldn't do this. Sidewall venting adds moving parts which will require service. Regular servicing is more complicated. And all parts for these boilers are proprietary and often take over a week to arrive. Not a good situation in the dead of winter.

jesmed1

Steamhead said:

bburd said:

.......Have you considered installing high-efficiency gas boilers that can vent through the building's side wall, eliminating the need for the chimney?

I wouldn't do this. Sidewall venting adds moving parts which will require service. Regular servicing is more complicated. And all parts for these boilers are proprietary and often take over a week to arrive. Not a good situation in the dead of winter.

I have considered high-efficiency boilers but ultimately decided against them for some of the reasons Steamhead mentioned, plus we don't have a good place for the sidewall vent. Also, this is a 4-unit condo building in which the only person who knows anything about heatings systems is me, and I may be gone soon. And I would not want to leave my neighbors and future owners at the mercy of finicky high-efficiency boilers. The people here just want things to work with minimal attention, and the Weil-McLain/Beckett AFG combination we have now has been totally trouble-free for the 10+ years I've been here.

So IMO, the best option for this building is dirt-simple 86% efficient cast iron boilers like Weil-McLain or Buderus, where there's minimal electronics and other bits to break. Reliability and ease of service/repair trumps efficiency in this case.

EdTheHeaterMan

OK thank you. Didn't know that about the positive pressure requirement. Our heating guy raved about the Energy Kinetics he installed for his family, but it may be too pricey for us. We'll probably stick with the Weil McLain or Buderus.

It might be the lowest price boiler compared the cast iron boilers like Burnham, Weil and Bud. You see the design of the boiler (low mass) and the design of the control system (post purge wasted hot water out of the boiler into the last zone that called for heat) will cost you less to operate. How long are you going to live in the home after you install the new equipment? if it is 10 year or so... then you will be paying a lot less for the system and the oil or gas that goes into the system.

It's like the old General Tire commercial. You are going to pay one way or the other. Finance the difference and use the fuel savings to make the payments.

EdTheHeaterMan

I looked at your original post and see this

I do maintenance for a 4-unit condo building. We have 2 Weil Mclain WGO-5 oil boilers and burn about 1200 gallons of oil a year total.

Are these two boilers in separate buildings? Because if they are in the same building, you could look into piping the two systems together and only using one of the boilers. the other one could be a backup.

If the buildings are close together, you may also be able to run a supply and return pipe underground between buildings. You won't be the first to do that.

That may cost less that purchasing new boilers and you will have a back up if one goes down.

OR are you saying that one WGO 5 is too large for the one building and you happen to have two of them in the same building?

jesmed1

EdTheHeaterMan said:

I looked at your original post and see this

I do maintenance for a 4-unit condo building. We have 2 Weil Mclain WGO-5 oil boilers and burn about 1200 gallons of oil a year total.

Are these two boilers in separate buildings? Because if they are in the same building, you could look into piping the two systems together and only using one of the boilers. the other one could be a backup.

Same building. There's a partition wall running down the middle of the building, with 2 condo units per side. One boiler heats the left half of the building, the other boiler heats the right half. The basement has no partition wall, so the boilers sit side by side down there and share the chimney.

That suggestion of piping both sides of the building together and running off one boiler has been made here by you and other pros, and it's a good thought. We might do that if/when one boiler breaks down. We could then manifold the 2 supplies and the 2 returns together and run them off the remaining working boiler.

EdTheHeaterMan said:

OR are you saying that one WGO 5 is too large for the one building and you happen to have two of them in the same building?

That too. Even if one WGO-5 broke down and we piped both loops into the second WGO-5, that remaining WGO-5 would have almost 2x the heat loss in this building on a zero degree day.

So yes, our installed heating system of two WGO-5's has almost 4x the capacity we need on a zero degree day...it's massive overkill.

EdTheHeaterMan

So here is the boiler setup you have. (not sure about the radiator type but that does not matter)

This shows 2 over sized boilers doing half of the building each

If you use a standard Primary/Secondary design where the primary loop traverses the two Boiler rooms. each system can be a secondary loop with a system circulator using the same thermostat you have now.

Each boiler can be a secondary loop that feeds the primary loop with heat for both zones. only one boiler needs to operate at a time.



Three pumps, some copper tubing and a Zone control relay might be a lot less than a new boiler. And the savings can start this season.

Steamhead

EdTheHeaterMan said:

So here is the boiler setup you have. (not sure about the radiator type but that does not matter)

This shows 2 over sized boilers doing half of the building each

If you use a standard Primary/Secondary design where the primary loop traverses the two Boiler rooms. each system can be a secondary loop with a system circulator using the same thermostat you have now.

Each boiler can be a secondary loop that feeds the primary loop with heat for both zones. only one boiler needs to operate at a time.



Three pumps, some copper tubing and a Zone control relay might be a lot less than a new boiler. And the savings can start this season.

This.

STEVEusaPA

Who’s paying for the oil?

jesmed1

Thanks Ed, that is terrific! It might even be easier than you drew, because there's no partition wall in the basement, so the boilers sit side-by-side in the same space by the chimney.

I'm going to ponder your drawing overnight and come back at you with some questions tomorrow. Meanwhile, here's a pic of our setup.

EBEBRATT-Ed

I agree with the primary secondary but not piped like that. See the attached. You want both boilers to get the same mixed return water temperature. You don't want one boiler heating the other boiler or affecting it's return water temp. Plus with my method you have two boiler pumps and two system pumps. i saved you a pump

jesmed1

@EdTheHeaterMan and @EBEBRATT-Ed, What about this diagram? What I'm thinking is to disconnect the boiler on the left entirely, drain it and leave it dry as a spare when the right boiler fails. When that happens, remove the right boiler and slide the left boiler over into the right-hand position and plumb it up.

So we just pipe the supply and return from the left boiler over to the right boiler with tees, and reposition the circulators. And add a zone valve on each loop.

I understand that, when both zones are calling for heat, zone 2 might be getting more hot water than zone 1 because of how the zone 1 supply tees off horizontally while the zone 2 supply rises vertically, but that may not matter. If one zone gets heated more slowly, that will change when the other zone's thermostat is satisfied and closes its own zone valve. The balance doesn't have to be perfect. Maybe add an adjustable balancing valve on the vertical S2 riser just in case.

The horizontal and vertical runs in my diagram aren't exactly to scale, but they do reflect the actual geometry of the pipe layout and where the zone valves and circulators would be. What do you think?

jesmed1

STEVEusaPA said:

Who’s paying for the oil?

The 4 unit owners split the cost of oil 4 ways. We burn about 1200 gallons per year. This season is probably going to be a $5,000 oil bill.

Steamhead

EBEBRATT-Ed said:

I agree with the primary secondary but not piped like that. See the attached. You want both boilers to get the same mixed return water temperature. You don't want one boiler heating the other boiler or affecting it's return water temp. Plus with my method you have two boiler pumps and two system pumps. i saved you a pump

Would this be an issue if only one boiler is being used at a time?

STEVEusaPA

If your actual design load for the entire building is 88k, there are a number of triple pass boilers that can do that with a ODR, and a buffer tank. Run the emitters off the buffer, with ODR, let the boiler re-charge the buffer.
If you like redundancy, then 2 similar sized boilers, ODR on the buffer, lead/lag rotating control.
No reason to do all that double boiler piping.

jesmed1

STEVEusaPA said:

If your actual design load for the entire building is 88k, there are a number of triple pass boilers that can do that with a ODR, and a buffer tank. Run the emitters off the buffer, with ODR, let the boiler re-charge the buffer.

Yes, if we were doing a clean sheet design, but we don't have the money or the need for a new boiler and buffer tank at the moment. (My question at the start of this thread was about what new boiler to get *eventually* when the need arises, but then Ed suggested tying both loops together using our existing boiler(s), which is an efficiency improvement that we might be able to afford to do right now.)

So now the question is how to make an incremental minimum-cost improvement that makes maximum use of what we have. Which is two perfectly good WGO-5 boilers.

What about the schematic I posted above, where we pipe the second loop into the right-hand boiler so that we're running both loops off one boiler, and leave the left-hand boiler idle as a backup when the right-hand boiler fails? The logic is that one boiler heating both loops will be a little more efficient, and then we have a ready backup when the first boiler fails. Then swap the second boiler into place. Then when that boiler fails, we can upgrade to a new single boiler.

EdTheHeaterMan

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.

jesmed1

EdTheHeaterMan said:

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 OK, I see your point. A few questions:

(1) All supplies and returns are 1" copper coming out of the boilers. Could we stay with 1" copper for the primary loop? That would make all the tee connections easy, but then both loops are limited by the same 1" copper in/out of one boiler, which now needs twice the flow rate when both loops are running at the same time. Is this OK?

(2) Why do the primary loop tees need to be so close together (12" or less in your diagram)? Right now the supplies and returns coming out of the boilers are about 22" apart from each other.

(3) Is it OK to leave a boiler idle for a full year? I'm thinking about possible fuel clogging in the copper tubing that runs from the tanks, under the concrete floor, and over to the boilers.

(4) Would we not need zone valves if we do the primary/secondary loops the way you drew it? If not, why not?

EdTheHeaterMan

@EdTheHeaterMan OK, I see your point. A few questions:

(1) All supplies and returns are 1" copper coming out of the boilers. Could we stay with 1" copper for the primary loop? That would make all the tee connections easy, but now both loops are limited by the same 1" copper, which now has twice the flow rate when both loops are running at the same time. Is this OK?

No. (or maybe) The primary loop must be large enough to handle the load of both radiator systems. 1" pipe can move about 80,000 BTUh. If both systems add up to 80,000 or less then you might be OK. But to be safe I would pipe the Primary loop with 1-1/4" copper. get yourself some 1-1/4" valved flanges for the circulator and eight 1-1/4" x 1" copper tees

(2) Why do the primary loop tees need to be so close together (12" or less in your diagram)? Right now the supplies and returns coming out of the boilers are about 22" apart from each other.

For primary/Secondary systems to work properly, you need to have the least amount of pressure drop between the supply and the return of the secondary loop. That way the water will not flow into the unused loop because the pressure difference between the supply and the return. A Flow check may be needed in the event of a ghost flow, however properly designed, there will be no need for them.

(3) Is it OK to leave a boiler idle for a full year? I'm thinking about possible fuel clogging in the copper tubing that runs from the tanks, under the concrete floor, and over to the boilers

Usually there is no problem, but you can do a swap over every month if you feel that might be an issue. It's your system to take care of. You set the rules.

(4) Would we not need zone valves if we do the primary/secondary loops the way you drew it? If not, why not?

No. See answer to #2 above.

Look at these posts:
https://www.heatinghelp.com/systems-help-center/why-closely-spaced-tees/
https://www.heatinghelp.com/systems-help-center/primary-secondary-pumping-on-a-one-pipe-hot-water-heating-system/
https://www.heatinghelp.com/systems-help-center/primary-secondary-pumping-with-multiple-boilers/

This might be a better piping design based on both boilers being in the same area. My first diagram might be problematic for the second system on the primary loop. I believe with the oversized boiler there will be more than enough heat to over come that problem, but when it coms time to replace that boiler with the correct size, Then the oversize advantage will be gone in favor of a more efficient heat source. So lets plan for the future.

jesmed1

EdTheHeaterMan said:

This might be a better piping design based on both boilers being in the same area. My first diagram might be problematic for the second system on the primary loop. I believe with the oversized boiler there will be more than enough heat to over come that problem, but when it coms time to replace that boiler with the correct size, Then the oversize advantage will be gone in favor of a more efficient heat source. So lets plan for the future.

@EdTheHeaterMan Thank you Ed, this is all very helpful.

So does that mean in your new diagram, when both WGO-5's fail and a new boiler must be installed, the whole primary loop goes away, and the new boiler gets plumbed directly into the single red and blue supply and return?

jesmed1

@EdTheHeaterMan Ed, here's my interpretation of your last schematic. I've left the existing circulator pumps on the boiler returns in the hope that they can stay there. All the existing copper is in fact 1-1/4", not 1" as I mistakenly said earlier, so the new 1-1/4" primary loop will tee easily into the existing 1-1/4" copper. And I've shown valved flanges on either sides of the new pumps as you suggested. Does this look OK?

EdTheHeaterMan

I have tweeked your diagram just a little. Although I originally did a few little improper piping things, this will correct them. One is not to have the two system pumps point at each other and exit by way of the branch. My mistake because it was easier to to draw it that way. The other change is the Expansion tank location. You want to make one spot in the system that will have the hottest water and the lowest pressure.. The only way to do that is by pumping away from the expansion tank and putting that at the boiler supply. So as close as you can put the expansion just past the boiler supply tee (where the hottest water is) and have the primary loop pump just after that (that will be the lowest pressure in the system) You have created a place where the most air bubble will collect in the system. And get a new diaphragm type tank. Don't use the open type tank

If you put a micro bubble air eliminator in that spot, you will create a system that will constantly purge air just by its design. There is a 45 minute section of my old Hydronics class that I taught that explains why this will happen. So that is why I did the two changes.

Your primary pump location was placed between the boilers. that makes it great for air removal on one boiler but a disaster for air removal on the other. put the pump after both boilers, that way you can have the best design when either boiler operates

jesmed1

@EdTheHeaterMan OK, thank you. A few questions:

(1) I see how you changed the relative positions of the secondary pumps, and you said it's because they shouldn't be facing each other on that teed line. What bad things happen otherwise?

(2) I assume the blue line going off to the right past the expansion tank is the makeup water line and pressure regulator?

(3) I think I see how to do the electrical controls: a Taco 2-zone relay with the "TT" switch terminals wired to both boiler "TT" terminals, and with a manual switch allowing either boiler "TT" circuit to be selected, but not both simultaneously. That gives us manual control over which boiler to run, and ensures that both boilers can't run simultaneously by accident. Then the boiler 110V circuitry stays the same, and each boiler controls its own circulator as usual. The secondary loop pumps are controlled by the 2-zone relay. The only bit I haven't quite figured out is how to switch the primary pump on/off. It has to come on whenever either zone is active, but the 2-zone relay doesn't have a switch function for that. Any suggestions?

Overall it looks very doable, and I'm trying to get a local plumber to come take a look and price it.

Roger

Great comments, all. I know I’m a little bit late to the thread, but if you’re interested, it seems like keeping one boiler as a back up and installing a System 2000 Frontier EK1 would handle the load and substantially cut energy consumption.  Both would inject into the primary loop to improve heat distribution and allow manual back up to the old boiler if it were ever necessary. The 1200 gallons per year reinforces 60 to 70,000 BTUs per hour on design day, so capacity is not issue. With thermal purge built into the system, oversizing is not a factor either.  A Resolute would work nicely if you are interested in quiet sidewall venting with polypropylene. 

If you’d like to find out more or need assistance with pricing, please PM me or call us at (908) 735-2066.
Best,
Roger

jesmed1

@Roger Thank you, I would love for our condo association to be in a position to buy a new Energy Kinetics boiler. Unfortunately we don't have the funds or the immediate need right now, so we're trying to squeeze as much incremental improvement as we can from our existing WGO-5's. But when we do have to buy a new boiler, I will definitely look into the Energy Kinetics options.

Roger

Thank you, @jesmed1 - good luck with all and let us know if we can help. 

Best,
Roger

EdTheHeaterMan

(1) I see how you changed the relative positions of the secondary pumps, and you said it's because they shouldn't be facing each other on that teed line. What bad things happen otherwise?

I added two scenarios in this picture where you push the water together so both flows smash together head on and leave out the branch. This creates a little more turbulence than if you were to use the flow from the branch being added to the flow straight through the tee. There would be less turbulence that way. Noise and additional restriction might be the result of the Bull Head Tee design. Click on the screenshot below

(2) I assume the blue line going off to the right past the expansion tank is the makeup water line and pressure regulator?

YES

(3) I think I see how to do the electrical controls: a Taco 2-zone relay with the "TT" switch terminals wired to both boiler "TT" terminals, and with a manual switch allowing either boiler "TT" circuit to be selected, but not both simultaneously. That gives us manual control over which boiler to run, and ensures that both boilers can't run simultaneously by accident. Then the boiler 110V circuitry stays the same, and each boiler controls its own circulator as usual. The secondary loop pumps are controlled by the 2-zone relay. The only bit I haven't quite figured out is how to switch the primary pump on/off. It has to come on whenever either zone is active, but the 2-zone relay doesn't have a switch function for that.

Any suggestions? The Zone Pump control has a set of terminals for that if you purchase the correct one. The SR503 EXP. has extra primary circulator contacts that will operate on any call for heat. It has more zones that you need but it has the feature you need. I have faded out the sections of the control you will not use.Click on the second screenshot below

Overall it looks very doable, and I'm trying to get a local plumber to come take a look and price it.

jesmed1

EdTheHeaterMan said:

I added two scenarios in this picture where you push the water together so both flows smash together head on and leave out the branch. This creates a little more turbulence than if you were to use the flow from the branch being added to the flow straight through the tee. There would be less turbulence that way. Noise and additional restriction might be the result of the Bull Head Tee design. Click on the screenshot below

@EdTheHeaterMan OK thank you. I'm a little confused because the secondary pumps are pumping away from each other, not towards each other, so wouldn't the flow for the supply go into the tee through the branch, then split and go out each leg of the tee towards each pump?

EdTheHeaterMan

jesmed1 said:

@EdTheHeaterMan OK thank you. I'm a little confused because the secondary pumps are pumping away from each other, not towards each other, so wouldn't the flow for the supply go into the tee through the branch, then split and go out each leg of the tee towards each pump?

You are correct, it is not as critical on the Tee fitting where the pumps are pulling from the branch and out one side or the other. It is just a good habit to have in case you change directions for some reason. Your plumber will understand, if he is any good.