Radiant Heating Not keeping up

[turbosl2]

System/House Specs:
New Construction
3000sq ft single story (above grade)
2000sq ft lower level (basement)
Bryant BW9 Boiler (Set temp ~175)
1/2" Pex (orange/red color)
Aluminum Diffusers installed at doorways
6 Zones (Argo Controller) w/ 6 valves
Single Circulator pump
Brass Manifold w/ball valves (no flow meters)
Hardwood & Tile throughout
Spray foam at all sill plates
Bat insulation under all floors

My father in law is having some issues with the radiant heat keeping the house warm. Its new construction and the house was originally designed with forced air, then radiant heat added later. The system was designed and installed by him. All rooms above grade do not seem to reach target temp (68), they consistently remain 1-6 degrees under. Outside temps are -10 right now. The zones are not all equal 300ft runs, some are 2-3 times longer runs than others. It appears the longest run (great room, kitchen, study) is 67 which is closer to the boiler. The Master bedroom and bath are at 62, this is the farthest run from the boiler but a shorter run overall compared to the great room. All valves are open at this point

 

[turbosl2]

Pics attached, no way to throttle the zones

 

[Sponsor]

 

[Jadnashua]

The head pressure on 1/2" pex gets pretty high on a long run, limiting the flow. It also means that the return water will end up lots cooler than shorter runs.

If I understand your description, there aren't diffuser plates along the entire runs?

Is the pex embedded in the floor or staple up?

It's generally good to limit each loop to about 200' so with the flow, you can get moderately even heating. You also want to have the origin of the loop at the exterior wall so the hottest water is at the potentially coldest location.

Do you have return temperature sensors? If so, what are your typical return temperatures? FWIW, if embedded, 175-degrees is way too hot. If staple up, it may be what you need.

What is the spacing of the tubing?

 

[turbosl2]

The head pressure on 1/2" pex gets pretty high on a long run, limiting the flow. It also means that the return water will end up lots cooler than shorter runs.

If I understand your description, there aren't diffuser plates along the entire runs?

Is the pex embedded in the floor or staple up?

It's generally good to limit each loop to about 200' so with the flow, you can get moderately even heating. You also want to have the origin of the loop at the exterior wall so the hottest water is at the potentially coldest location.

Do you have return temperature sensors? If so, what are your typical return temperatures? FWIW, if embedded, 175-degrees is way too hot. If staple up, it may be what you need.

What is the spacing of the tubing?

The runs in some area are pretty long, much longer than 200’, maybe even 3-4X in the great room and master which is on the other side of the house from the boiler. The pex is staples up with diffuser plates only in certain locations, doors...etc. sits under the floor between the joists. I guess 6” spacing between tubes 16” OC floor joists. The thing is the manifold was custom made from the heating company that installed the boiler. There are no flow controls or meters or temp gauges just at the boiler. You can see this custom hobby in the pics. No way to tell anything except watch the boiler temp rise to 175 then drop to 140 every 5 mins.

 

[Dana]

I've seen worse looking DIY designs, but I've seen better too.

Getting the heat into the PEX is one thing, but how is the heat getting out? Is the entering water temperature on the PEX the full 175F (which implies suspended tube) or is it mixed down? (Doesn't appear to be.)

There appears to be a boiler bypass branch tweakable with a ball valve (circled in red). Was that to keep the delta-T on the boiler within spec? What is the entering water temp at the boiler under current operating conditions?

What pump is that? It looks potentially undersized for a high flow system. Six zones at 1 gpm per zone adds up to some real flow.

With all of that uninsulated plumbing and 175F water temp I'll bet the boiler room is the warmest place in the house. It shouldn't be.

 

[Jadnashua]

Trying to get flow through 6-800' of 1/2" tubing and expecting it to dissipate much of any heat in the process isn't going to work well, as you've discovered. You can have multiple loops in the same room, controlled by the same thermostat, but trying to do it in one, super long one isn't going to work well. The heat won't be even as the end of the loop will be much cooler than the beginning, and that assumes you're getting much flow through the loop. Not being able to balance the flows between loops may or may not be a main issue, but it becomes one most of the time if they are not equal length. Pex transfers heat much better if it has diffusion plates or, it is embedded in a conductive material (like mortar underneath tile). Underneath the subflooring without diffusion plates with hardwood on top of it, the wood acts like an insulator - it's not a great conductor, and isn't a great thermal mass. There's a little bit of art and a lot of science to make radiant work well and be efficient...seem to have broken most of the rules. Not everyone is qualified to design a reliable system.

What is the return water temperature?

 

[turbosl2]

Here is what I know at the moment. There is no mixing valve. The valve circled in red I closed, it was arbitrary adjusted, closing the valve brought the temp in some parts of the house up from 52-62. There are runs in some zones much longer than other. I think about 4500-6000 total foot of pipe over 6 zones. I was informed that the great room zone valve (ball valve before actuator) was closed this morning to 45deg, the temperature in every zone hit its target temp of 68 later today. The joist cavities are all insulated under the subfloor, I believe some with some sort of reflective insulation. Not sure to be honest. I cannot tell the return temp without going over and shooting it with an infrared thermometer. There are no temp gauges or flow control valves, just that manifold in the pic with a temp gauge on boiler. I mad I had to guess the return temps are pretty high because if a zone is running I can barely grab the return pipe ball valve. If zone is off it’s warm but not like when running. I am not sure what circulator pump that is. I can get any information that is needed. Unfortunately I am looking at ideas to work with what you see in the pics. The entire house is Sheetrocked so in the boiler room I can make changes but that’s about it. The boiler room is not the warmest in the house but it’s not cold. I guess 66 def where house is 68

 

[turbosl2]

You guys have been a great help so for, i really appreciate it.

I made some mistakes in info above. The ENTIRE system has diffuser plates. The plates are finned and pex snaps into it.

The system was designed to be the sole heat source. The forced air was installed for AC but an entire furnace was installed as a backup due to minimal added cost.

Center valve is now closed completely. All rooms seem to be maintaining their set temps now that the largest run (great room, study, kitchen) was throttle back on the ball valve.

No setbacks, constant 68deg

Even though all rooms reach target it appears the system still continues to call for heat on all zones and boiler continues to run, cycles on and off every 2mins or so. ~175, 2mins go by and it hits 140 (temps at boiler), lights, heats to 175...process continues. All zones running. I will get temps with infared thermometer tonight.

Circ Pump:

TACO Model V007-F5
1/25 HP
.71Amp
3250RPM
125PSI max
240deg Max
Class F

Should i install a 6 zone flow control manifold and thermal storage tank. If so which one is recommened?

 

[Dana]

What are you referring to by "diffuser plates"? Are they the finned convectors like UltraFin?

Two minute burns at a 50% on/off duty cycle at 10+ burns/hour are efficiency robbing boiler-wearing short cycles, but that's what happens when you throw a ridiculously oversized 200 KBTU/hr boiler at the problem. It will probably still short cycle on zone calls after the other flaws are rectified. The whole-house heat load of a 3000' house with a 2000' basement might not be much more than the min-fire output of the Bryant BW9. (That's enough boiler to theoretically keep my antique sub-code 2400' above grade 1600' basement home at 70F even when it's absolute zero outdoors.)

It needs more flow into the zone plumbing and through the boiler and a single Taco 007 just ain't gonna cut it. Without doing the math on it it's hard to say exacly which monster sized pump is going to work here, but on a system using zone valves an ECM drive smart pump operating under constant pressure control may be the cheapest way out. Plumb the boiler primary/secondary using the existing -007 as the primary pump, and something much beefier for the secondary driving the radiation. You can use closely spaced tees as the hydraulic separator.

^^This primary/secondary diagram is using separate pumps per zone. In this system a big ECM drive pump driving the red plumbing located near the tees, replacing the individual secondry pumps with zone valves would be the equivalent architecture.

I hate to just throw out random suggestions for parts that cost more than $500 without doing the math, but the Taco Viridian 3452 can probably handle this.

 

[Dana]

Regarding the secondary pump, that may be too much pump. Do the math.

Alternatively, plumbing it primary/secondary and replacing each of the six zone valves with a Taco oo7e per zone (which will probably require a different zone controller), might be cheaper/better if you're going to just punt without doing any math. Earlier revisions of the 007e pumps can be had for about $100 (new) on the secondary market.

I misunderstood the minimal specs out there on the BW9 boilers. Which version of the Bryant BW9 is installed (looks pretty big, but maybe the 50KBTU/hr version is the same sheet metal as the 200KBTU/hr version? Either way it's short cycling as operated now, but might not be so bad once the gross errors are fixed, assuming it's a smaller version. A massive hydraulic separator (instead of closely spaced tees) can probably suppress the short cycling sufficiently on the BW9-050 or BW9-075, but it would need a large buffer tank to manage the -200. According to this document there is only 2.6 gallons (~22lbs) of water in the smaller ones, 3 gallons (~25lbs) of water in the bigger ones, which isn't a lot of thermal mass to work with.

What is the size and spacing of the finned convectors? Run the rough math of how much heat emitter you have (on each zone) using this guide. I believe the water temperature numbers are average water temp across the loop, not the entering water temp.

 

[turbosl2]

What are you referring to by "diffuser plates"? Are they the finned convectors like UltraFin?

Two minute burns at a 50% on/off duty cycle at 10+ burns/hour are efficiency robbing boiler-wearing short cycles, but that's what happens when you throw a ridiculously oversized 200 KBTU/hr boiler at the problem. It will probably still short cycle on zone calls after the other flaws are rectified. The whole-house heat load of a 3000' house with a 2000' basement might not be much more than the min-fire output of the Bryant BW9. (That's enough boiler to theoretically keep my antique sub-code 2400' above grade 1600' basement home at 70F even when it's absolute zero outdoors.)

It needs more flow into the zone plumbing and through the boiler and a single Taco 007 just ain't gonna cut it. Without doing the math on it it's hard to say exacly which monster sized pump is going to work here, but on a system using zone valves an ECM drive smart pump operating under constant pressure control may be the cheapest way out. Plumb the boiler primary/secondary using the existing -007 as the primary pump, and something much beefier for the secondary driving the radiation. You can use closely spaced tees as the hydraulic separator.

^^This primary/secondary diagram is using separate pumps per zone. In this system a big ECM drive pump driving the red plumbing located near the tees, replacing the individual secondry pumps with zone valves would be the equivalent architecture.

I hate to just throw out random suggestions for parts that cost more than $500 without doing the math, but the Taco Viridian 3452 can probably handle this.

Yes this is the type of diffuser plates, fully insulated as well. So if my takeaway from your suggestion is correct it would be NOT to replace the custom manifold shown in the picture with one that has flow meters/control & gauges but to increase the primary pump size and use the current 007 as a boiler circulator? Your believe is there is not enough flow due to the long loops. Was also thinking of adding a 50gal thermal storage tank ($900-1500) to reduce the cycles. I am not familar with radiant heating so forgive me with all the questions and i do appreciate the advice. We will make whatever necessary changes just want to make sure it will at least help. Increasing the flow through all the zone valves will help deliver more heat or will it cycle the boiler even more?

 

[turbosl2]

Regarding the secondary pump, that may be too much pump. Do the math.

Alternatively, plumbing it primary/secondary and replacing each of the six zone valves with a Taco oo7e per zone (which will probably require a different zone controller), might be cheaper/better if you're going to just punt without doing any math. Earlier revisions of the 007e pumps can be had for about $100 (new) on the secondary market.

I misunderstood the minimal specs out there on the BW9 boilers. Which version of the Bryant BW9 is installed (looks pretty big, but maybe the 50KBTU/hr version is the same sheet metal as the 200KBTU/hr version? Either way it's short cycling as operated now, but might not be so bad once the gross errors are fixed, assuming it's a smaller version. A massive hydraulic separator (instead of closely spaced tees) can probably suppress the short cycling sufficiently on the BW9-050 or BW9-075, but it would need a large buffer tank to manage the -200. According to this document there is only 2.6 gallons (~22lbs) of water in the smaller ones, 3 gallons (~25lbs) of water in the bigger ones, which isn't a lot of thermal mass to work with.

What is the size and spacing of the finned convectors? Run the rough math of how much heat emitter you have (on each zone) using this guide. I believe the water temperature numbers are average water temp across the loop, not the entering water temp.

Ok i will check the math. Boiler is BW9-150, 150k BTU input 135k BTU output. I am not familiar with a hydraulic separator. You do not recommend a 40-50 gal storage tank. Maybe you could help me understand the principal of short cycling. To much heat loss to quickly throughout the floor? From what you believe is going on it seems there is not enough flow through the system and a flow control manifold will only hurt? This could be why when the main part of the house was throttled and the remaining 5 zones all equalized?

 

[Dana]

A hydraulic separator allows the flow through the radiation to be a different rate from what's flowing through the boiler. When you have 6 zones on a system the radiation flows are going to vary quite a lot, but with a separate pump to guarantee a minimum flow through the boiler on a loop that intersects the radiation loop, the boiler no longer has to handle the full flow of the radiation. That intersection can be a device, or closely space tees. If the tees are too far apart the flows can interact a lot. Most buffer tanks can be plumbed to behave as the hydraulic separator but not all.

Using high volume hydraulic separators such as a Boiler Buddy can add enough thermal mass to the system to tame short cycling, but you have to do the math.

Short cycling occurs when the boiler is putting more heat into the system than the radiation is taking out. When that happens the temperature rises to the high limit, causing the burner to turn off. How fast that happens is a function of the total thermal mass (mostly the water weight) in the zone(s) + boiler, and the difference between BTUs-in to BTU-out. I'd have to bury my nose in the manual for that boiler to see what if any adjustments there are to the temperature swing that it allows, but if adjustable it needs to be set to the maximum temperature differential between high-limit & refire to lengthen those burns as much as possible. The way it's going the boiler won't last 10 years, it might not even last 5 without repairs/replacement of the ignition components. It should be doing 3 burns per hour at most.

A 150K boiler for a new 3000' house + basement is just plain ridiculous (that's enough to heat an uninsulated house that size with single pane windows) , and even with 3000 square feet of of Ultra-Fin at the high temp spacing the radiation can deliver AT MOST about 2/3 of that boiler's output even if operated as a single zone. A reasonably tight code minimum new construction house of that general description would have a heat load of maybe 45-55,000 BTU/hr at the 99% outside design temperature, 65K if the house design is over-glazed and has a gazillion corners, bump-outs dormers etc. The boiler's output is getting on to 3x the likely heat load, but the radiation isn't even capable of emitting the full output even after fixing the flow issues.

At 175F out, 155F back , 165F average water temp Ultra Fin should be able to deliver about 30 BTU/hr per square foot, and with no heat transfer plates on the staple up section the performance will be similar. (With stamped sheet metal heat transfer plates you'd be able to get more than 50BTU/hr out of the staple-up, perhaps enough to cook your feet on the tile sections if running 175F water.) If it's 2700' of active heated floor (subtracting out 10% for stairwells, cabinets & furniture, etc) that's a hair over 80,000 BTU/hr, which in most houses that size would be more than plenty. But that's still woefully shy of 135,000 BTU/hr of boiler output, so even operated as a single zone the boiler is going to cycle (a lot.)

A flow control manifold won't hurt, but it's not "the" solution. Without anything to balance the flows when multiple zones are calling for heat the lowest-head zones are going to be hogging the flow but not delivering as much heat as the longer loops would at even half the flow. Guaranteeing at least SOME flow on the longer loops is why no-math brute-forcing it with separate pumps can work. Until then it's worth trying to adjust the flows with ball valves (globe valves are a bit better at that), but you don't really have enough pump to really do it, and when just one zone is calling for heat you won't have enough flow through the boiler to prevent flash-boil. Six 1/25 HP -007F5 pumps is overkill at about 1/4 HP total, but it'll get you there. The ECM drive 007e is overkill too, but not as much, and even a six pack of those draws only about as much power as the 007-F5 you're trying to run the whole thing with.

So let's say you install a 50 gallon buffer (about 400lbs of water) and have 60,000 BTU/hr of excess heat going into the system, and the differential on the boiler is a 10F swing. The 60K/hr is 1000BTU/minute so the temperature will be rising 1000/400lbs= 2.5 F per minute. A 10F swing would then be a 4 minute burn, which is fine.

But then say just one of the six zones is calling for heat, emitting 15,000 BTU/hr. With 135K of heat going in that's 120,000 BTU/hr of excess heat, and you're back to the 2 minute burn, which isn't great, but at least the numbers of burns will go down. It's probably enough buffer, but without doing the math who knows?

When I micro-zoned my place I designed it heating system to have the zones sipping from a 48 gallons of buffer served by a modulating burner, but even at max-fire I'm not putting in heat at even half the rate the BW9-150 is delivering, and there are still some operating conditions where it delivers ~3 minute burns.

Don't just throw hardware at it- do the math, or hire somebody who knows what they're doing to design the fix. Start with a zone by zone, room by room heat load calculator. (Using loadcalc.net or coolcalc.com are fine as long as you make aggressive assumptions on air tightness and R-values. They'll still overstate the load, but not by 2x.) From there you can take a look at the existing radiant and figure out what water temp it's going to take at some reasonable flow (>0.5gpm), do the math on the amount of tubing in each zone to know how much pump it takes to get that flow, and keep on working out the details on what changes need to be made, but as importantly what changes DON'T need to be made.

 

[turbosl2]

This really helps. Tonight i will get the numbers with all zones operating to see the delta T across the in and outlets, as well as boil cycle times and exact temps. I will then spend some time over the next few days to estimate the heat loads in each of the six zones based on a rough order magnitude on what was installed in the floor and estimate the head loss in each zone(loop) as well. You are most likely very close with your estimates.

150k BTU boiler seems huge to me. We def dont mind making any changes that we can (boiler room changes that is, not able to tear the sheetrock out of the entire house to change the loops). I just get lost when it comes to what to do with the values after i get the heat loads and how to apply them to what changes should be made (e.g. larger pump, smaller pump, buffer tank...etc). I can figure most of it out based on reading and learning, which is what i plan to do. Your scenario above really helps but i would like to be sure i have all the info and get back to you. I will start with the data mentioned above and report back, as well as perform calculations on my own

 

[turbosl2]

Attached are the Delta T values with all zones calling for heat. Its a little hard to read but seems legible.

Also, the ultra fin is perpendicular to the floor joists 24-30" OC. We are in the process of drawing out the rooms and calculating the BTUs. They seem to indicate installation in this mannor but i am worried it will not deliver the heat to the floor beyond a standard day...such as the -10 we had the other day. http://www.ultra-fin.com/wp-content/uploads/2015/06/Ultra-Fin2013manual-WebHi.pdf

BTW, do the flow manifolds control flow as pressure drop/head loss changes. E.g. If one small zone calls for heat vs all 6. Will a manifold keep each zone at .6GPM if thats where we set it, or is the setup such that you open all zones, balance the flows to the .6gpm and then if one zone calls for heat that zone will be getting a ton more flow than the .6GPM in our case because the head loss is diff in each loop. Wasnt sure if the manifold is used to fine tune a system with the assumption each loop is within 10%. I ask because in this case each zone is considerably diff lengths and your idea of individual circ pumps makes much more sense no matter what the heat load is.

 

[turbosl2]

Dana,
What are you thoughts on this data. We are still performing calcs on heat load

 

[Dana]

Dana,
What are you thoughts on this data. We are still performing calcs on heat load

Nice scrawl- are you in medical school?

At a supply temp of 157-158F you'd typically be looking at a delta-T of 15F-20F, give or take on most systems, or a return temp of about 137F- 142F, if it's getting the requisite amount of flow. (At a supply temp of 180F it would be more like 20-25F deltas, at 140F supply 10-12F.)

The Baseboard zone has a 26F delta (= not enough flow)

The LLB zone has a 10F delta (= higher than optimal but not crazy over pumped flow)

The MBRB zone has a 27F delta (= not enough flow)

The MBR zone a 28F delta (= not enough flow)

The Main zone a 31F delta (?) (= not enough flow)

The Guest zone a 23F delta (= not enough flow)

Seems to be a theme here.

While it's possible to design systems with high delta-Ts on the radiation that still work, it's pretty clear that this system not getting enough heat into the rooms at those 23-31F deltas, and that can be improved with higher flow.

Throttling back the LLB flow with a ball valve to get it in line with the others keeps it from hogging the overall flow output of the -007, but it's clear you won't be able to fix this by just a few ball valve tweaks.

The 31F delta on the Main zone means the average water temp (AWT) on that zone is 15F cooler than the entering water temp (EWT). Reducing the delta to 15F with a higher flow increases the AWT by 7-8 degrees from about 150F to about 157F, which would result in about a 15% increase in radiation output. Whether that's enough to actually heat the zone depends.

Most boilers aren't rated for more than about a 50F delta-T on the boiler itself, which may require cracking that bypass branch ball valve open a bit. Measure it, right at the output port and return port on the boiler itself. Then measure it again after 15-20 minutes of operation with just the Main zone calling for heat.

If the tubing is accessible without demolishing anything, adding more finned convectors on the finned convector sections or adding sheet metal heat spreader plates on the staple up section can get more heat out of the tubing and into the floor. Unless the flow is also increased that will also increase the already fairly high delta-Ts (which is fine), but more heat out is the goal, not some magic delta-T rule of thumb.

 

[turbosl2]

Nice scrawl- are you in medical school?

At a supply temp of 157-158F you'd typically be looking at a delta-T of 15F-20F, give or take on most systems, or a return temp of about 137F- 142F, if it's getting the requisite amount of flow. (At a supply temp of 180F it would be more like 20-25F deltas, at 140F supply 10-12F.)

The Baseboard zone has a 26F delta (= not enough flow)

The LLB zone has a 10F delta (= higher than optimal but not crazy over pumped flow)

The MBRB zone has a 27F delta (= not enough flow)

The MBR zone a 28F delta (= not enough flow)

The Main zone a 31F delta (?) (= not enough flow)

The Guest zone a 23F delta (= not enough flow)

Seems to be a theme here.

While it's possible to design systems with high delta-Ts on the radiation that still work, it's pretty clear that this system not getting enough heat into the rooms at those 23-31F deltas, and that can be improved with higher flow.

Throttling back the LLB flow with a ball valve to get it in line with the others keeps it from hogging the overall flow output of the -007, but it's clear you won't be able to fix this by just a few ball valve tweaks.

The 31F delta on the Main zone means the average water temp (AWT) on that zone is 15F cooler than the entering water temp (EWT). Reducing the delta to 15F with a higher flow increases the AWT by 7-8 degrees from about 150F to about 157F, which would result in about a 15% increase in radiation output. Whether that's enough to actually heat the zone depends.

Most boilers aren't rated for more than about a 50F delta-T on the boiler itself, which may require cracking that bypass branch ball valve open a bit. Measure it, right at the output port and return port on the boiler itself. Then measure it again after 15-20 minutes of operation with just the Main zone calling for heat.

If the tubing is accessible without demolishing anything, adding more finned convectors on the finned convector sections or adding sheet metal heat spreader plates on the staple up section can get more heat out of the tubing and into the floor. Unless the flow is also increased that will also increase the already fairly high delta-Ts (which is fine), but more heat out is the goal, not some magic delta-T rule of thumb.

HAHA, its my Father-in-Laws handwriting.

We will throttle back the LLB, it makes sense because that room is the smallest, on the same level (LOWER LEVEL BASEMENT) as the boiler and is about 5x10'. The baseboards are already throttle on a ball valve but obviously are a MUCH longer run around the entire basement perimeter (again, same level as boiler) but these really don't need to put out a lot of heat since its all sub grade. I was worried the 007 pump is to small and taking your advice looked at the 0012. The theme of low flow seems to be common and there is a sht ton of piping in series for many of these areas of concern. We are calculating that now but its only an estimate. Again the Ultra fin is 32" give or take OC but the house is new construction with spray foam sills and very tight, maybe this doesnt warrant alot of ultra fin and pipe...not sure yet. I know he didnt just throw the piping in and did some math so there must be a reason it was installed like it is....but the long unequal loop runs is just a function of not following standard installation methods. Cant change that now.

So maybe this is a dumb question but the high delta T is not an indication that all that heat is going into the floor?E.g. not a good sign? We want lower delta Ts by increasing flow? Some of these rooms are throttled now (again ball valve). The big hitter that seemed to work was shutting down the flow on the "MAIN". This covers the kitchen, dinning room, great room, hall. Its a massive zone and with that full open none of the other zones hit their target temps on a -10 day. More pump is the theme here, lower Delta Ts?

 

[Dana]

The high delta-T just means that enough heat is leaving the tubing to drop the temperature, but doesn't indicate where that heat is going. With even R13 insulation between the tubing and the ceilings below it's typically less than 10% of the total going into the "wrong" heating zone.

Dribbling along at 0.5 gpm = 250 lbs/hr and a 30F delta-T you're looking at 30F x 250lbs/hr= 7500 BTU/hr. Bump that to 2 gpm (1000 lbs/hr) and a 10F delta-T it's 1000lbs x 10F= 10,000 BTU/hr, 33% more heat.

Your pumping head may or may not be too high on the Main zone to even hit 2 gpm with a reasonable sized pump, but do the math. The Taco 0012 is only good to about 15' of head, more of a high-flow/modest head type of pump designed to push Niagra falls type flows through fat plumbing. The 007 is good for only 10' of head but lower flow. Calculate the pumping head on your longest tubing runs at 1 gpm & 2 gpm using this quick & dirty online calculator. (<< only to ballpark it) . At 2 gpm 300' of half inch is over 10' of head, even if perfectly straight- you may be able to squeak better than 1 gpm out of a Taco 007, but not 2. With the 0012 you'd be able to get better about 2-2.2 gpm on a 300' loop.

This is why it's easier to get there brute-forcing it with an individual pump per zone. The shorter-tubing zones might still be fine sharing a pump, but probably not the longer zones. Smart ECM drive pumps that display the gpm can be very useful for dialing these things in, but they're pricey.

The maximum advisable gpm on half inch PEX is 2.3 gpm, so you'd still be good to go on the higher-head loops, but would have to throttle back the lower head loops. With 6 zones you don't need or want more than about 12 gpm of flow total. For less money than the 0012, the Viridian 2218 is a higher head/lower flow type pump that can probably handle this, and can be tweaked in several ways to deliver enough to each zone without delivering too much. At 10' of head it can deliver about 10gpm, whereas the 007 is gasping to deliver 2 gpm even at 9 feet of head which is why all your longer zones are starved for flow. (With apologies for the less-considered Viridian 3452 random monster pump earlier), a Viridian 2218 operated under delta-T control on the manifolds would almost certainly make a reasonable secondary/radiation pump on this system if you're keeping the zone valves and doing the radiation with a single pump. Even at max speed it draws less power than the 007, but under delta-T control it will throttle back to even lower power (and lower gpm) when zone valves close, which avoids the over pumping issue with lower head zones. There will still be manual zone-flow tweaking to throttle back the lower head zones, but you'll be starting from an easier place.

And you'll still want to set up the primary loop with it's own pump, and probably a massive hydraulic separator to tame the short cycling.

The heat loss of basement rooms in house with a code-min full height foundation wall insulation are pretty tiny, so even throttling that down to 0.5 gpm or less may still heat those rooms, and it's usually easy to add more baseboard if/where necessary to do it.

Clearly if the boiler is short cycling not even half the boiler's potential output is going into the zones. The only way of getting more into the zones is higher flow. Once you get the flow into the radiation high enough to actually heat the place at the 99% outside design temp (assuming that's even possible with the radiation design) it will be time to address the short-cycling. With more heat going into the zones the burn times will lengthen, but probably not enough to fully suppress the short-cycling on this way-oversized boiler.

Using an electric water tank as the hydraulic separator works fine at 10-12 gpm, using the upper and lower heating element ports as the primary loop connections (boiler output goes into the top heating element port), and the cold & hot connections (or the drain and hot connection) as the secondary side connections. (Think of it as a really FAT closely spaced tee.)

Using the existing Taco 007 to drive the loop through the tank to the BW9-150 will run at about 8-10 gpm , or 67-83lbs per minute when it has just the pumping head of the BW9 to deal with. At 135,000 /BTU/hr = 2250 BTU/minute and 67lbs/minute flow there would be 2250/67= 34F delta T across the boiler, which is fine. At 83lbs/minute the delta-T across the boiler would be 27F, which is also fine. If in practice the delta turns out to be less than 10F the boiler flow can be throttled back to deliver more. If it's over 50F at the boiler a bigger primary pump is called for. The curve indicated on page 6 seems odd, almost as if the axis' are mislabeled, but at 8' of head there's 9 gpm of flow, which is in the right range for the Taco 007, which delivers about 8gpm at 8' of head.

Is the UltraFin laid out with tubing ~32" on center perpendicular to the joists, with a fin in every joist bay? Or is the tubing parallel to the joists, with fins 36" on center?

 

[turbosl2]

The high delta-T just means that enough heat is leaving the tubing to drop the temperature, but doesn't indicate where that heat is going. With even R13 insulation between the tubing and the ceilings below it's typically less than 10% of the total going into the "wrong" heating zone.

Dribbling along at 0.5 gpm = 250 lbs/hr and a 30F delta-T you're looking at 30F x 250lbs/hr= 7500 BTU/hr. Bump that to 2 gpm (1000 lbs/hr) and a 10F delta-T it's 1000lbs x 10F= 10,000 BTU/hr, 33% more heat.

Your pumping head may or may not be too high on the Main zone to even hit 2 gpm with a reasonable sized pump, but do the math. The Taco 0012 is only good to about 15' of head, more of a high-flow/modest head type of pump designed to push Niagra falls type flows through fat plumbing. The 007 is good for only 10' of head but lower flow. Calculate the pumping head on your longest tubing runs at 1 gpm & 2 gpm using this quick & dirty online calculator. (<< only to ballpark it) . At 2 gpm 300' of half inch is over 10' of head, even if perfectly straight- you may be able to squeak better than 1 gpm out of a Taco 007, but not 2. With the 0012 you'd be able to get better about 2-2.2 gpm on a 300' loop.

This is why it's easier to get there brute-forcing it with an individual pump per zone. The shorter-tubing zones might still be fine sharing a pump, but probably not the longer zones. Smart ECM drive pumps that display the gpm can be very useful for dialing these things in, but they're pricey.

The maximum advisable gpm on half inch PEX is 2.3 gpm, so you'd still be good to go on the higher-head loops, but would have to throttle back the lower head loops. With 6 zones you don't need or want more than about 12 gpm of flow total. For less money than the 0012, the Viridian 2218 is a higher head/lower flow type pump that can probably handle this, and can be tweaked in several ways to deliver enough to each zone without delivering too much. At 10' of head it can deliver about 10gpm, whereas the 007 is gasping to deliver 2 gpm even at 9 feet of head which is why all your longer zones are starved for flow. (With apologies for the less-considered Viridian 3452 random monster pump earlier), a Viridian 2218 operated under delta-T control on the manifolds would almost certainly make a reasonable secondary/radiation pump on this system if you're keeping the zone valves and doing the radiation with a single pump. Even at max speed it draws less power than the 007, but under delta-T control it will throttle back to even lower power (and lower gpm) when zone valves close, which avoids the over pumping issue with lower head zones. There will still be manual zone-flow tweaking to throttle back the lower head zones, but you'll be starting from an easier place.

And you'll still want to set up the primary loop with it's own pump, and probably a massive hydraulic separator to tame the short cycling.

The heat loss of basement rooms in house with a code-min full height foundation wall insulation are pretty tiny, so even throttling that down to 0.5 gpm or less may still heat those rooms, and it's usually easy to add more baseboard if/where necessary to do it.

Clearly if the boiler is short cycling not even half the boiler's potential output is going into the zones. The only way of getting more into the zones is higher flow. Once you get the flow into the radiation high enough to actually heat the place at the 99% outside design temp (assuming that's even possible with the radiation design) it will be time to address the short-cycling. With more heat going into the zones the burn times will lengthen, but probably not enough to fully suppress the short-cycling on this way-oversized boiler.

Using an electric water tank as the hydraulic separator works fine at 10-12 gpm, using the upper and lower heating element ports as the primary loop connections (boiler output goes into the top heating element port), and the cold & hot connections (or the drain and hot connection) as the secondary side connections. (Think of it as a really FAT closely spaced tee.)

Using the existing Taco 007 to drive the loop through the tank to the BW9-150 will run at about 8-10 gpm , or 67-83lbs per minute when it has just the pumping head of the BW9 to deal with. At 135,000 /BTU/hr = 2250 BTU/minute and 67lbs/minute flow there would be 2250/67= 34F delta T across the boiler, which is fine. At 83lbs/minute the delta-T across the boiler would be 27F, which is also fine. If in practice the delta turns out to be less than 10F the boiler flow can be throttled back to deliver more. If it's over 50F at the boiler a bigger primary pump is called for. The curve indicated on page 6 seems odd, almost as if the axis' are mislabeled, but at 8' of head there's 9 gpm of flow, which is in the right range for the Taco 007, which delivers about 8gpm at 8' of head.

Is the UltraFin laid out with tubing ~32" on center perpendicular to the joists, with a fin in every joist bay? Or is the tubing parallel to the joists, with fins 36" on center?

Thanks for the info we will look into increasing the flow. Now to dial back the flow in other zones there is no flow meters. We are just ball parking it with trial and error. Would a manifold with flow meters keep the flow in all zones equal as the head changes and diff zones open, assuming we went with a single pump. I will look into the pump you mentioned and how it’s controlled.

The pex is perpendicular to the joists 32” OC with a ultra fin in each joist bay, joist bays are 16”OC