Recommendation on sizing (replacing original boiler)

[Benphilips]

I am in the process of replacing what seems to be original boiler to the home. It appears to be way oversized at close to 200K btu's.

My home is a 2500sq ft. tri-level home in Michigan (48331), built in 1958 with original wood/storm windows in good condition. Close to 1000sqft of the home is on a crawl, 750sqft is upper and other 750 is lower level on slab. This is a hydronic system with finned baseboard. I measure all baseboards with a total of 140' of baseboards. The system runs 4 zones on circulators. Being mid-century there are many large windows in the home and I took these into account when coming up with a heat-loss calculation of 65K.

I plan to stick with a cast-iron boiler, like Weil-McLain CGA's. Any sizing recommendations would be greatly appreciated.
Thanks,
Ben

 

[Dana]

A heat load of 65K is a lot for a 2500' house, even with a lot of window. Have you verified that load number by correlating fuel use against heating degree-day data from a nearby weather station? If you're willing to share wintertime meter readings I can walk you through that here. Use +4F as the 99% outside design temp (half way between Flint's +3F and Detroit's +5F), which would be close enough.

At an entering water temp of 180F, return temp of 160F (average water temp = 170F) fin tube baseboard puts out about 500 BTU per linear foot, so with 140' of baseboard the most it can emit is 70,000 BTU/hr, which is only 1.08 more than your heat load estimate. If your load is REALLY 65K it means it wouldn't be able to keep up during extended cold snaps and it would be quite cold indoors during Polar Vortex disturbance deep cold snaps.

The biggest boiler that makes any sense at all for that radiation would have an output of ~70,000 BTU/hr. A boiler bigger than that won't heat the place any better- it would just cycle on/off a lot more. If your heat load is actually 50,000 BTU/hr, that would be perfectly right-sized per ASHRAE's 1.4x oversizing above the 99% design temp load. (If your actual heat load (as measured by fuel use) is much lower, it will be more comfortable to go a bit lower on the boiler size.) Among the CGa lineup the closest to the "correct" size would be the CGa-4, which has a DOE output of 88,000 BTU/hr, and an I=B=R net of 77,000 BTU/hr. The next step down would be the CGa-3 which puts out 59,000 BTU/hr (DOE), or 51,000 BTU/hr (IBR).

If the boiler is inside the pressure and thermal envelope of the house (rather than out in an garage on the other side of an insulated wall or something) the DOE number is the most relevant, and that's the only number that would be relevant to a fuel-used base calculation, since the distribution and standby losses can't be separated out using those methods.

The CGa series come only with dumb aquastat controls, which limit the ability of the boiler to utilize the thermal mass of the system for efficiency. With 4 zones the heat load of any individual zone is well below the boiler's output, which introduces more efficiency robbing burn cycles, and may even short cycle (= burns of 5 minutes or less, or more than 5 burns per hour.) Several other vendors are now shipping with smart heat purging economizer controls such as the HydroStat 3250 Plus, etc, which reliably reduce the total burn time while maximizing individual burn times, and lower the average boiler temperature in response to the load for lower standby loss. For a 2x oversized boiler the typical fuel savings is on the order of 10%, but at 3x oversizing or more it can be 15%+, sometimes (rarely) as much as 25%, reducing the efficiency hit that comes with oversizing. The Burnham ES2 series comes with that sort of control- the ES2-4 has very comparable DOE & IBR numbers to the CGa-4. Their direct vented/sealed combustion ESC series is also fitted with those controls, and the ESC-4 may be a better fit to your radiation, at an output of 78,000 BTU/hr (DOE).

Even though you're committed to cast-iron, HTP's mid-mass UFT-080W stainless steel fire-tube modulating condensing boiler is perfectly sized to your radiation, and with a 10:1 turn down ratio can still run at condensing temperatures with no cycling even with zone radiation of only 35-40'. It's also inexpensive- about the same or slightly cheaper than a CGa-4, and since it can use plastic venting can be even cheaper to install. Down-sizing from a 200K boiler to the CGa-4 will require a narrowing chimney liner to vent properly, adding to the installation expense. The UFT series boilers are easy retrofits for cast iron replacement, since (unlike water tube heat exchanger condensing boilers) the pumping head is low, and there is no need to plumb them primary/secondary.

 

[Sponsor]

 

[Benphilips]

A heat load of 65K is a lot for a 2500' house, even with a lot of window. Have you verified that load number by correlating fuel use against heating degree-day data from a nearby weather station? If you're willing to share wintertime meter readings I can walk you through that here. Use +4F as the 99% outside design temp (half way between Flint's +3F and Detroit's +5F), which would be close enough.

At an entering water temp of 180F, return temp of 160F (average water temp = 170F) fin tube baseboard puts out about 500 BTU per linear foot, so with 140' of baseboard the most it can emit is 70,000 BTU/hr, which is only 1.08 more than your heat load estimate. If your load is REALLY 65K it means it wouldn't be able to keep up during extended cold snaps and it would be quite cold indoors during Polar Vortex disturbance deep cold snaps.

The biggest boiler that makes any sense at all for that radiation would have an output of ~70,000 BTU/hr. A boiler bigger than that won't heat the place any better- it would just cycle on/off a lot more. If your heat load is actually 50,000 BTU/hr, that would be perfectly right-sized per ASHRAE's 1.4x oversizing above the 99% design temp load. (If your actual heat load (as measured by fuel use) is much lower, it will be more comfortable to go a bit lower on the boiler size.) Among the CGa lineup the closest to the "correct" size would be the CGa-4, which has a DOE output of 88,000 BTU/hr, and an I=B=R net of 77,000 BTU/hr. The next step down would be the CGa-3 which puts out 59,000 BTU/hr (DOE), or 51,000 BTU/hr (IBR).

If the boiler is inside the pressure and thermal envelope of the house (rather than out in an garage on the other side of an insulated wall or something) the DOE number is the most relevant, and that's the only number that would be relevant to a fuel-used base calculation, since the distribution and standby losses can't be separated out using those methods.

The CGa series come only with dumb aquastat controls, which limit the ability of the boiler to utilize the thermal mass of the system for efficiency. With 4 zones the heat load of any individual zone is well below the boiler's output, which introduces more efficiency robbing burn cycles, and may even short cycle (= burns of 5 minutes or less, or more than 5 burns per hour.) Several other vendors are now shipping with smart heat purging economizer controls such as the HydroStat 3250 Plus, etc, which reliably reduce the total burn time while maximizing individual burn times, and lower the average boiler temperature in response to the load for lower standby loss. For a 2x oversized boiler the typical fuel savings is on the order of 10%, but at 3x oversizing or more it can be 15%+, sometimes (rarely) as much as 25%, reducing the efficiency hit that comes with oversizing. The Burnham ES2 series comes with that sort of control- the ES2-4 has very comparable DOE & IBR numbers to the CGa-4. Their direct vented/sealed combustion ESC series is also fitted with those controls, and the ESC-4 may be a better fit to your radiation, at an output of 78,000 BTU/hr (DOE).

Even though you're committed to cast-iron, HTP's mid-mass UFT-080W stainless steel fire-tube modulating condensing boiler is perfectly sized to your radiation, and with a 10:1 turn down ratio can still run at condensing temperatures with no cycling even with zone radiation of only 35-40'. It's also inexpensive- about the same or slightly cheaper than a CGa-4, and since it can use plastic venting can be even cheaper to install. Down-sizing from a 200K boiler to the CGa-4 will require a narrowing chimney liner to vent properly, adding to the installation expense. The UFT series boilers are easy retrofits for cast iron replacement, since (unlike water tube heat exchanger condensing boilers) the pumping head is low, and there is no need to plumb them primary/secondary.

Thanks for the quick reply Dana...I am basically questioning contractor bids and considering the install myself. Two quotes came back with a CGA-6...what is worst case scenario with the install of this monster? I'd have to imagine it is an improvement of efficiency based on what was in there and would handle a potential addition to our home in the future. I did perform the usage calculation and my monthly usage from 12/15/18-01/16/19 came back with a total of 1114.7HDD. I ended up using +6F for 99% calc. at 65 degrees with a 1.4 multiplier and came up with around 85K btu's.

 

[Dana]

The CGa-6 puts out nearly twice the amount of heat that your radiation can deliver, and is 2x oversized for the fuel-use calculated load. Without smarter controls it's going to burn 8-10% more fuel than the CGa-4 just on the oversize factor issue, 15-20% more if it's short cycling on zone calls.

Zone by zone, how much baseboard is there on each?

You realize you don't even have enough baseboard to emit 85,000 BTU/hr. If the existing boiler is keeping you warm during negative double-digit cold snaps it means the fuel-use load numbers are being skewed to the high side of reality due to the as-used efficiency being so much lower than the nameplate efficiency numbers (an artifact of oversizing and age.)

 

[Benphilips]

The CGa-6 puts out nearly twice the amount of heat that your radiation can deliver, and is 2x oversized for the fuel-use calculated load. Without smarter controls it's going to burn 8-10% more fuel than the CGa-4 just on the oversize factor issue, 15-20% more if it's short cycling on zone calls.

Zone by zone, how much baseboard is there on each?

You realize you don't even have enough baseboard to emit 85,000 BTU/hr. If the existing boiler is keeping you warm during negative double-digit cold snaps it means the fuel-use load numbers are being skewed to the high side of reality due to the as-used efficiency being so much lower than the nameplate efficiency numbers (an artifact of oversizing and age.)

I just re-counted and there is 151' total
Zone 1 (lower level on slab)-39'
Zone 2 (crawl space)-35'
Zone 3 (slab)-35'---not sure if it makes a difference but it's a long run from the boiler to hit these radiators, close to 60'
Zone 4 (upper level)-42'

If i knowingly go over-sized now for future house expansion (addition), what add-on controller would you recommend?

 

[Dana]

Oversizing for some future unknown addition is usually a bad idea. Building the addition to current code minimums (or better) attaching ot the main house on a wall the originally has a lot of glazed area the net heat load can actually go DOWN rather than up (!). If you're doing something like doubling the size of the house, get right-sized mechanicals for the loads of the new addition rather than hacking it onto the older system. Even when it's adding some load, it's usually a lot less than you might think, which is why you have to just buckle down and do a Manual-J or IBR type heat load calculation.

The 151' of baseboard is still CGa-4 territory, since it only emits about 75-76K, and even the IBR net on that boiler is 77K (88K DOE.)

If your going to upsize the boiler, go with a modulating boiler. If the shortest zone in the system is 35' of baseboard a UFT-080W would never short cycle barely cycling at all. Bumping up a size to the UFT-100W would still do OK even though it would do some cycling if ONLY one of the 35' zones were calling for heat, and even then it wouldn't be short cycling. At max-fire when operating above condensing temps it still delivers about 87-88,000 BTU/hr, which is more than your current radiation can even deliver, and probably way more than the whole house load of your new-improved mid-century modern + addition.

 

[Benphilips]

Thanks for all the advice...my only hesitation with a modulating boiler is useful life. I'm not so worried about squeezing out the maximum performance, pay-back is very small on a smaller home.

I've talked with some plumbers working in the field and have been told 10-15 yrs useful life on one. Is this true based on your experience?

 

[Dana]

Thanks for all the advice...my only hesitation with a modulating boiler is useful life. I'm not so worried about squeezing out the maximum performance, pay-back is very small on a smaller home.

I've talked with some plumbers working in the field and have been told 10-15 yrs useful life on one. Is this true based on your experience?

The stainless heat exchanger modulating boilers are much less sensitive to system chemistry than some of the infamous aluminum or cupro-nickel heat exchanger versions of the past couple of decades. The fire tube heat exchanger types are also much harder to screw up than water tube boilers, making them in some regards comparable to cast-iron. (But as the saying goes, the more idiot-proof you make something the more creative the idiots become.) But even an aluminum water tube heat exchanger type modulating boiler can go 20+ years if you check the water (or buffer it), and give it an annual system flush as long as it isn't being over or under pumped, with a delta-T that stays in the sweet zone.

Plumbing & heating contractors who seem convinced that mod-cons don't last more than 15 years are probably not the ones you'd want to install one- seriously! If those are the same contractors who are proposing a CGa-5 or -6 on your system they're pretty much hacks. To find a competent mod-con installer sometimes involves figuring out which boiler or boilers are right-sized for your house & radiation, then soliciting contractor recommendations from the local or regional distributors. The distributors are in a unique position to know which contractors are installing dozens of them with rarely a return or technical issue, and which ones are making dubious warranty claims or tying up the technical help line with questions where the answered is clearly spelled out in the manuals in English, French, & Spanish. The UFT-series boilers are really DIY-able for people who know how to read the manual and ask questions. NY_Rob successfully DIYed one in recent years.

The issues with modulating condensing boilers is sometimes the electronics, sensors going bad or drifting, or the control electronics being degraded by lighting strikes or power surges, etc. It's worth installing some surge-protection/filtering between the boiler and the AC line. That's also true for the smarter controls on cast iron boilers too.

The "pay back" on right sized equipment is more about comfort than the net-present-value-of-future-energy-cost-savings and that's even more so on a right sized modulating boiler under outdoor reset control, which delivers very stable room temperatures. With an oversized non-modulating systems the heat cycles come on fast to heat the room with a hot-flash followed by a longer chill. With a right-sized non-modulating system the duty cycle gets higher when it's colder outside, taking longer to satisfy the thermostat, but it can be set up with a very narrow dead band differential at the thermostat, resulting in shorter cooling off periods for the radiation. It may seem like it's "struggling to keep up", but in fact the system is operating as-designed. With a right-sized modulating boiler under outdoor reset control the duty cycle is VERY high even during the shoulder seasons, and essentially 100% when it's cold outside, modulating the water temperature up as the outdoor temps drop.

It's possible to set up heating systems with cast iron boilers with thermostatic mixing valves under outdoor reset control (Burnham's " IQ " controls have a slot where an outdoor reset adder board that can be plugged in), but those approaches add cost without delivering significant fuel savings. When starting from scratch it's cheaper to just go with a modulating boiler where the outdoor reset controls are standard equipment. The Westinghouse-badged version of the UFT-100w is still under $2K at distributors, which isn't very different from distributor pricing on the CGa-4 and usually cheaper than the CGa-5.

 

[Benphilips]

I ended up doing the install myself and went with the old school tech....CGa-4. The contractors were all over the place.

It is all up and running good with the exception of my pressure. I went from the hanging expansion tank to a newer bladder style, Amtrol 30. My pressure is creeping up beyond the auto feeder setting of 12PSI. I did check the pressure on the tank and it is reading 22psi. Should I lower the tank pressure? Do you think this could be the cause? I do have a shutoff above tank in order to isolate for checking pressure and servicing. See pic below

 

[Benphilips]

The stainless heat exchanger modulating boilers are much less sensitive to system chemistry than some of the infamous aluminum or cupro-nickel heat exchanger versions of the past couple of decades. The fire tube heat exchanger types are also much harder to screw up than water tube boilers, making them in some regards comparable to cast-iron. (But as the saying goes, the more idiot-proof you make something the more creative the idiots become.) But even an aluminum water tube heat exchanger type modulating boiler can go 20+ years if you check the water (or buffer it), and give it an annual system flush as long as it isn't being over or under pumped, with a delta-T that stays in the sweet zone.

Plumbing & heating contractors who seem convinced that mod-cons don't last more than 15 years are probably not the ones you'd want to install one- seriously! If those are the same contractors who are proposing a CGa-5 or -6 on your system they're pretty much hacks. To find a competent mod-con installer sometimes involves figuring out which boiler or boilers are right-sized for your house & radiation, then soliciting contractor recommendations from the local or regional distributors. The distributors are in a unique position to know which contractors are installing dozens of them with rarely a return or technical issue, and which ones are making dubious warranty claims or tying up the technical help line with questions where the answered is clearly spelled out in the manuals in English, French, & Spanish. The UFT-series boilers are really DIY-able for people who know how to read the manual and ask questions. NY_Rob successfully DIYed one in recent years.

The issues with modulating condensing boilers is sometimes the electronics, sensors going bad or drifting, or the control electronics being degraded by lighting strikes or power surges, etc. It's worth installing some surge-protection/filtering between the boiler and the AC line. That's also true for the smarter controls on cast iron boilers too.

The "pay back" on right sized equipment is more about comfort than the net-present-value-of-future-energy-cost-savings and that's even more so on a right sized modulating boiler under outdoor reset control, which delivers very stable room temperatures. With an oversized non-modulating systems the heat cycles come on fast to heat the room with a hot-flash followed by a longer chill. With a right-sized non-modulating system the duty cycle gets higher when it's colder outside, taking longer to satisfy the thermostat, but it can be set up with a very narrow dead band differential at the thermostat, resulting in shorter cooling off periods for the radiation. It may seem like it's "struggling to keep up", but in fact the system is operating as-designed. With a right-sized modulating boiler under outdoor reset control the duty cycle is VERY high even during the shoulder seasons, and essentially 100% when it's cold outside, modulating the water temperature up as the outdoor temps drop.

It's possible to set up heating systems with cast iron boilers with thermostatic mixing valves under outdoor reset control (Burnham's " IQ " controls have a slot where an outdoor reset adder board that can be plugged in), but those approaches add cost without delivering significant fuel savings. When starting from scratch it's cheaper to just go with a modulating boiler where the outdoor reset controls are standard equipment. The Westinghouse-badged version of the UFT-100w is still under $2K at distributors, which isn't very different from distributor pricing on the CGa-4 and usually cheaper than the CGa-5.

New
I ended up doing the install myself and went with the old school tech....CGa-4. The contractors were all over the place.

It is all up and running good with the exception of my pressure. I went from the hanging expansion tank to a newer bladder style, Amtrol 30. My pressure is creeping up beyond the auto feeder setting of 12PSI. I did check the pressure on the tank and it is reading 22psi. Should I lower the tank pressure? Do you think this could be the cause? I do have a shutoff above tank in order to isolate for checking pressure and servicing. See pic below

 

[Dana]

I ended up doing the install myself and went with the old school tech....CGa-4. The contractors were all over the place.

It is all up and running good with the exception of my pressure. I went from the hanging expansion tank to a newer bladder style, Amtrol 30. My pressure is creeping up beyond the auto feeder setting of 12PSI. I did check the pressure on the tank and it is reading 22psi. Should I lower the tank pressure? Do you think this could be the cause? I do have a shutoff above tank in order to isolate for checking pressure and servicing. See pic below

Yes, lower the tank pressure to no more than 3 psi above the system pressure when the system is idle- warm, but not pumping.

With the system at 12 psi and the tank at 22 psi the pressure on the system won't stabilize until the system pressure reaches the tank pressure. With that large of a difference there's effectively zero shock-absorber effect being provided by the tank to ease spikes from closing zone valves, etc, because the diaphragm is pressed hard against the water-side port to the tank. If you set the tank to 14-15 psi and the system idle to 12 psi, the system pressure should stabilize around the tank pressure when the system is operating and hot. There will be some expansion keeping the diaphragm from behaving like a flap-valve on the port, which allows allowing pressure spikes (even pump impeller vibration) to be dampened by flexing of the full diaphragm surface area, not just a tiny patch the diameter of the pipe.

Where is the system pump located relative to the expansion tank & air scoop?

Is that CMU wall behind the boiler a foundation wall or exterior wall?

 

[Benphilips]

Yes, lower the tank pressure to no more than 3 psi above the system pressure when the system is idle- warm, but not pumping.

With the system at 12 psi and the tank at 22 psi the pressure on the system won't stabilize until the system pressure reaches the tank pressure. With that large of a difference there's effectively zero shock-absorber effect being provided by the tank to ease spikes from closing zone valves, etc, because the diaphragm is pressed hard against the water-side port to the tank. If you set the tank to 14-15 psi and the system idle to 12 psi, the system pressure should stabilize around the tank pressure when the system is operating and hot. There will be some expansion keeping the diaphragm from behaving like a flap-valve on the port, which allows allowing pressure spikes (even pump impeller vibration) to be dampened by flexing of the full diaphragm surface area, not just a tiny patch the diameter of the pipe.

Where is the system pump located relative to the expansion tank & air scoop?

Is that CMU wall behind the boiler a foundation wall or exterior wall?

Four circ pumps are to the right of the air scoop, about 6” above it, pumping away.
Foundation wall...boiler is in lower level. The wall is part crawl, part chimney/fireplace in main level. Pic was during re-plumb/install

 

[Dana]

I'll assume the ball-valve at the tank is in the open position once you've fired it up...

Ideally you'd have a foot or more of straight pipe from the last turn prior to the pumps, but you'll be fine. With the 90% turn between the expansion tank and each pump the impeller vibration attenuation provided by the expansion tank is limited, but what you have is about as good as it gets with multi-pumped systems. Looks good!

It's both code and a good idea to insulate as much of that heating system plumbing as possible to a minimum of R3. That could be 1" wall thickness fiberglass, or other materials if fully rated for the maximum water temperature. Box stores almost never carry the right stuff. Grainger carries some, but a local plumbing supply house catering to the HVAC trades would probably be cheaper (or online sources.) It's too often the case that an uninsulated basement boiler room becomes the warmest room in the house when it's 0F outside just on distribution losses. Insulating the pipes is the first and most cost effective system efficiency improvement to make.

But it doesn't end there.

In your cool US zone 5 climate (everything south of the thumb of the MI-mitt) and subsoil temperatures it's worth insulating the foundation walls to current code minimum at some point, which will allow more of the standby and distribution losses in the boiler room to accrue to the space heating rather than the ground or the "great outdoors". That will also reduce summertime indoor humidity issues and "musty basement" a bit too. An 8" CMU wall is about R1.5-R2.

IRC 2018 calls out R15 continuous insulation for basement walls, from the slab all the way up to the subfloor, or the thermal equivalent thereof. There are several ways to go about it without creating a mold farm, and several code-legal but moisture-risky ways too. I can go into that here if you're interested, but it's also been covered on other parts of the Terrylove forum in detail multiple times in the past, if you want to search it out.

Depending on the amount of above-grade exposure on the foundation walls uninsulated basements usually represent 10-25% of the whole house heat load, even when the basement isn't being actively heated. I have a comparable climate to yours and only 18-24% of average above grade exposure. Installing 3" of reclaimed roofing polyiso board (about R17) on the basement walls a decade ago cut fuel use by around 15%, and now the not actively heated basement never drops below 65F in winter.

 

[Benphilips]

I'll assume the ball-valve at the tank is in the open position once you've fired it up...

Ideally you'd have a foot or more of straight pipe from the last turn prior to the pumps, but you'll be fine. With the 90% turn between the expansion tank and each pump the impeller vibration attenuation provided by the expansion tank is limited, but what you have is about as good as it gets with multi-pumped systems. Looks good!

It's both code and a good idea to insulate as much of that heating system plumbing as possible to a minimum of R3. That could be 1" wall thickness fiberglass, or other materials if fully rated for the maximum water temperature. Box stores almost never carry the right stuff. Grainger carries some, but a local plumbing supply house catering to the HVAC trades would probably be cheaper (or online sources.) It's too often the case that an uninsulated basement boiler room becomes the warmest room in the house when it's 0F outside just on distribution losses. Insulating the pipes is the first and most cost effective system efficiency improvement to make.

But it doesn't end there.

In your cool US zone 5 climate (everything south of the thumb of the MI-mitt) and subsoil temperatures it's worth insulating the foundation walls to current code minimum at some point, which will allow more of the standby and distribution losses in the boiler room to accrue to the space heating rather than the ground or the "great outdoors". That will also reduce summertime indoor humidity issues and "musty basement" a bit too. An 8" CMU wall is about R1.5-R2.

IRC 2018 calls out R15 continuous insulation for basement walls, from the slab all the way up to the subfloor, or the thermal equivalent thereof. There are several ways to go about it without creating a mold farm, and several code-legal but moisture-risky ways too. I can go into that here if you're interested, but it's also been covered on other parts of the Terrylove forum in detail multiple times in the past, if you want to search it out.

Depending on the amount of above-grade exposure on the foundation walls uninsulated basements usually represent 10-25% of the whole house heat load, even when the basement isn't being actively heated. I have a comparable climate to yours and only 18-24% of average above grade exposure. Installing 3" of reclaimed roofing polyiso board (about R17) on the basement walls a decade ago cut fuel use by around 15%, and now the not actively heated basement never drops below 65F in winter.

Awesome advice...insulate all heated piping, including the return pipes?

 

[Dana]

Awesome advice...insulate all heated piping, including the return pipes?

Yes, including the return pipes.

I don't off hand remember the maximum temp allowed without insulation in code, but it's way cooler than 130F. Even domestic hot water plumbing is requires to be insulated to R3 on any 3/4" or larger pipes. Under current code any hot water recirculation loop for the domestic hot water needs a minimum of R3, even on it's return, independent of plumbing size. Box stores usually carry inexpensive split R3 polyethylene pipe insulation suitable for retrofitting domestic hot water plumbing.

 

[Benphilips]

Yes, including the return pipes.

I don't off hand remember the maximum temp allowed without insulation in code, but it's way cooler than 130F. Even domestic hot water plumbing is requires to be insulated to R3 on any 3/4" or larger pipes. Under current code any hot water recirculation loop for the domestic hot water needs a minimum of R3, even on it's return, independent of plumbing size. Box stores usually carry inexpensive split R3 polyethylene pipe insulation suitable for retrofitting domestic hot water plumbing.

Final product...thanks again for all the advice and so glad I didn't end up over-sizing. I think its a hard concept to grasp for many regarding bigger is better. My old boiler cycled so much, new one is so comfortable/quite. Insulating piping tonight and chimney liner this week...

 

[Ki23]

Hello!
I also have a tri-level and have installed a new boiler within the last year. I had a 160k btu cast iron and I replaced it with a Lochinvar 80k btu modcon. I have about the same sq ft as you and it keeps up very well. I actually haven't had to use water any hotter than 135F through my baseboards. It's a really nice heat, always warm but almost never hot. Hope this helps you not oversize your boiler. Best of luck