Solder type

What type solder to use on Weil McClain CGA-7

  • 50/50

    Votes: 0 0.0%
  • 95/5

    Votes: 2 100.0%
  • stick with steal

    Votes: 0 0.0%

  • Total voters
    2

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Cpeters

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In replacing my old Burnham 140,000 btu 65W unit with a new Weil McClain CGA 7. The Burnham was originally a oil burner converted to gas. Is 50/50 the solder of choice or should I use 95/5? I've used 50/50 for hot water heaters years ago before the law changed.
 

Dana

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If you haven't already taken delivery on it, it's unlikely that your heat load is anywhere near the 175,000 BTU/hr DOE output of a CGa 7 (or the old Burnham, for that matter). Getting the boiler sized for the load is the key to higher comfort and higher efficiency, and this is the opportunity moment for getting it right for the next 20+ years. Is this boiler going into a poorly insulated 10,000 square foot house or something? (That's nearly 5x the heat load of my antique 2400' 2x4 framed house @ 0F.)

I vote that you not use melt ANY solder until you nail down the actual load, unless it's already too late to ship it back.
 

Cpeters

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If you haven't already taken delivery on it, it's unlikely that your heat load is anywhere near the 175,000 BTU/hr DOE output of a CGa 7 (or the old Burnham, for that matter). Getting the boiler sized for the load is the key to higher comfort and higher efficiency, and this is the opportunity moment for getting it right for the next 20+ years. Is this boiler going into a poorly insulated 10,000 square foot house or something? (That's nearly 5x the heat load of my antique 2400' 2x4 framed house @ 0F.)

I vote that you not use melt ANY solder until you nail down the actual load, unless it's already too late to ship it back.

Dana, thanks for the reply. I have a 2700 sf 1977 yr built home. I multiplied 2700x50 (region factor (NJ) to get 135,000 btu.
I'd rather go over than under. I was leaning toward the CGA-6 just because it was (50lbs.and 1/2 gallon) less. I don't want to undersize though.
Better to go over than under.
 

Dana

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Most 2 x 4 framed 1970s vintage houses have real heat loads in the 13-15 BTU/hr per square foot range @ +10F (the 99% outside design temp for New Brunswick) That would be more like 40,000 BTU/hr, not 135,000 BTU/hr.

Using a 50 BTU/ft ratio is truly insane. That would be about right for a heavy canvas tent in an NJ climate. Even an UNINSULATED house with only single pane windows, no storms would still be under 35 BTU/ft.

Case in point, my 2x4 framed ~2400' + 1500' conditioned basement 1.5 story bungalow with 1980s vintage storms over the original 1923 double hungs came in at a bit under 49,000 BTU/hr @ +5F when I first moved in back in the 1990s, and that was with R13-R15 in the attic, and NO wall insulation. With some insulation upgrades (including foundation insulation) and some air sealing it's still WAY below current code min, but it's now in the 35K range @ +5F. Trust me, this is no super-insulated specimen- it has many thermal envelope improvements to go before I'm done, and I'll never get it up to even IRC 2012 code min.

It's NOT better to be oversized by more than 1.4x (according to ASHRAE standards), and AFUE testing presumes no more than 1.7x oversizing. At 5x oversizing you'll reap both much lower efficiency AND much lower comfort. (That is, unless you think it'll actually get down to -150 F, a temp not seen in NJ even during the last ice age. :) ) So using the 15BTU/ft WAG and a 1.4x oversizing factor that comes to about 55-60,000 BTU/hr, and that's still probably overkill if the place has had any window, air sealing, or insulation upgrades since 1977.

You'd have to undersize by a LOT for it to become a comfort issue.

If you have a fuel use history on the place we can prove an upper bound on the real heat load using the old boiler as the measuring instrument. What was the last gas bill's fuel usage and the meter reading dates that it covered and your ZIP code? (For weather and outside design temp data purposes only.)
 
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Cpeters

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I'm in zone 3 close to zone 4. Zone 3 calcs at 45 per sf. So I could probably go with the CGA5 or CGA6. I always feel like I should err on the side of
caution. So is 50/50 good enough? Thanks
 

Dana

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I'm in zone 3 close to zone 4. Zone 3 calcs at 45 per sf. So I could probably go with the CGA5 or CGA6. I always feel like I should err on the side of
caution. So is 50/50 good enough? Thanks

Whose zone map are you looking at, and whose (utterly insane) rules of thumb are those? (Code min houses in Fairbanks AK typically come in at about 25 BTU/hr per square foot of space at -50F using ACCA Manual-J methods of load calculation.) This is truly off the deep end.

My antique place has a 5F colder outside design temp, probably has crummier windows too, and I'm a but under 15 BTU/ft-hr if only counting the above grade part, about under 10 BTU/ft-hr if I count the insulated-conditioned basement. I'm radiation constrained to about 44,000 BTU/hr at the water temps I'm running, and it only lost ground on the radiant-floor-only zone when it hit -15F a couple weeks back (it bottomed out at about 60F in that room, which has WAY too much window to floor area.)

If you have a heating history on this place (and I think you probably do), you don't have to guess or use some rule of thumb based on the square footage. The boiler itself becomes the measuring instrument. Take the measurement, THEN upsize by a factor of 1.25-1.4x if you think there's too much error, and you need to err on the side of caution.

Heat load is not a function of the square footage of floor area, it's a function of total exterior surface area, the construction type (U-factor/R-values), air leakage rates, and the temperature difference between indoors & outdoors. The shape of the house matters, as well as it's construction. But even a paper-thin (literally heavy kraft paper) walled house with an average shape and size with only single pane windows would not have a heat load of 45 or 50 BTU per square foot at NJ type outdoor design temps.

I'd be willing to bet real money that you don't even have enough radiation/baseboard to emit heat into the house a rate of 175,000 BTU/hr ( or the original 160,000 BTU/hr) at the boiler's maximum output temperature. With most baseboard type heat emitters you'll get at most 600-650 BTU/hr per running foot of baseboard, lets push that to an unrealistic 700 BTU/ft-hr. To emit 160,000 BTU/hr would then take (160,000/700=) 229 feet of baseboard. (That's a foot of baseboard for every 12 square feet of living space.) A more realistic output of 550 BTU/ft-hr would take 291 feet. No matter how big the boiler is, the amount of heat that the radiation can deliver is bounded.

How much radiation do you have? If it's baseboard, add up the lengths, multiply by 600BTU/hr and that's that ABSOLUTE upper bound for DOE output of any boiler you should be considering. But even that is probably going to be 2x overkill, and if it's broken into zones you'd be losing a lot to short-cycling if you went that big.

If zoned, break it out by the length in each zone, since that affects boiler sizing decisions too.
 

Tom Sawyer

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Either 50/50 or 95/5 is fine. It's sometimes hard to find 50/50 these days
 

Dana

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Unless the house has a very complicated shape you probably don't have even 200' of exterior wall suitable for installing baseboard , which means even the CGa -5 is going to be oversized for the radiation (and 2.5-3x oversized for the likely 99% design heat load.)

If operated as a single zone and you have more than 150' of baseboard the CGa-4 might do OK, but realistically your load is probably covered by the CGa-3 with margin even at absolute all time record low temp in NJ. The CGa-3 has enough burner to maximize the heat output of 90-100' of baseboard.

If it's broken into multiple zones and the 99% load as calculated on a fuel-use basis is on the order of 40,000 BTU/hr, it's covered by the CGa-25, which would be the right choice, even if it isn't huge margin.
 

Cpeters

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I went to the supply house to get prices on Weil McClains. As you said, he told me to measure the baseboard with fins on it, add it all up and multiply by 600. So I did and came up with 258 linear feet of finned baseboard. So I need 154,800 btus (CGA-6) using the baseboard method. The sf method comes up with 2,612 x 45 = 117,000 btu (CGA-5). My assumption is I'm using input btus x unit efficiency (approx. 83%).
 

Tom Sawyer

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So I haven't given you advice yet but I'm going to now. The last thing you want to do is waste your money on a Weil McLain CGA series boiler. If you have that much radiation available, go with a high efficiency, condensing boiler. Find something that is available in your area. Do a K factor gas use and size it for that load. The CGA is a waste of your money.
 

Cpeters

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So I haven't given you advice yet but I'm going to now. The last thing you want to do is waste your money on a Weil McLain CGA series boiler. If you have that much radiation available, go with a high efficiency, condensing boiler. Find something that is available in your area. Do a K factor gas use and size it for that load. The CGA is a waste of your money.
My father was a plumber and when I was a kid they didn't have labor cheaper than me. I loved those buckets of asbestos to put around the
smoke pipe, just add water. The CGAs are a lot like the old boilers, easy for dinosaurs to understand.
 

Dana

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I went to the supply house to get prices on Weil McClains. As you said, he told me to measure the baseboard with fins on it, add it all up and multiply by 600. So I did and came up with 258 linear feet of finned baseboard. So I need 154,800 btus (CGA-6) using the baseboard method. The sf method comes up with 2,612 x 45 = 117,000 btu (CGA-5). My assumption is I'm using input btus x unit efficiency (approx. 83%).


You don't NEED anything like 600 BTU/hr per foot! That's just the maximum amount of heat that the fin-tube can reasonably expected to deliver, thus anything beyond that has absolutely no benefit, only down side. It's a terrible way to size a boiler, since it increases the cycling & standby losses.

You also don't need anything like 45 BTU/ft^2-hr- that's literally THREE TIMES what's typical for real heat loads on that type & vintage of house in your area, and much higher than most houses in Alaska. Even if your house has no insulation what so ever your load isn't going to be that high, though it might be more than half that.

What you need is a boiler that covers your actual load with reasonable margin, and runs fewer longer more efficient burn cycles. The smallest boiler that covers your load will do that.

Tom Sawyer's "Do a K factor gas use and size it for that load." is absolutely the right thing to do, which is what I've been saying using different terms. A K-factor would be the how many heating degree-days are covered by a single therm of gas (HDD/therm) with the existing system. From that one can derive the approximate heat load using simple napkin arithmetic. There are multiple recent threads where I've spelled out exactly how to run those calculations- it's not hard, and doesn't take a lot of time.

With a wet-finger to the wind I'm saying it's probably going to come in at about 40,000 BTU/hr. It could be as high as 55,000 BTU/hr (if the place is in rough shape) or as low as 35,000 BTU/hr (or lower if you've gone hog-wild on thermal upgrades), but there's no way in hell that it's anywhere near 117,000 BTU/hr with the windows and doors closed.

Assuming the WAG of 40,000 BTU/hr is anywhere close to reality, with 258' of baseboard that divides out to 155 BTU/ft-hr, which means you probably have enough baseboard to run a condensing boiler at 95% efficiency all season long, even at temps cooler than the 99% outside design temp. Tom Sawyer usually isn't much of a modulating-condensing boiler fan, but his advice here is dead-on: "If you have that much radiation available, go with a high efficiency, condensing boiler."

But if you're going to ignore that advice, at least size the dinosaur to the actual load, as measured by fuel use, not some rule of thumb from Mars that has no bearing on Earth reality, or to the absolute maximum possible output of your existing excessive baseboard. Outside design temps in my area are 0F to +5F, and the per-square foot rule of thumb heating hacks tend to use 25 BTU/ft for houses like yours, 35 BTU/ft for 19th and early 20th century antiques with empty wall cavities. Those 25 & 35 BTU rules reliably oversize by at least 1.5x, and often more than 2x. The customer never gets cold, but they're not doing them any favors- they're buying too much boiler, and end up less comfortable for it.
 

Tom Sawyer

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I get excited when someone actually has enough radiation to support condensation and high efficiency because 99% of the time, it's some schmuck trying to put a condensing boiler on 45' of baseboard and then bitching when the damn thing short cycles itself to death.
 

Dana

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They're out there- especially with the micro-zoning crowd!

Beyond all reason cpeters seems to believe his heat load is something like 117,000 BTU/hr, which would be pretty far out of the condensing range with 258' of baseboard.

Here's what the lipstick on bathroom mirror math says:

Most of NJ is in zone 4A, part is in zone 5A, but a typical NJ climate is about 5000 heating degree days. Assuming the heat load at +10F is 100,000 BTU/hr (not 117K), in 24 consecutive 10F hours would add up to (65F-10F=) 55 base 65F heating degree days, over which the heating system needs to supply (100,000 x 24= ) 2,400,000 BTU.

That's (2,400,000 BTU/ 55=) 43,636 BTU/HDD, or (/100,000 per therm= ) 0.43636 therms/HDD.

Assuming his retrofit gas burner on the ancient oil boiler is delivering 75% AFUE (probably a stretch, but maybe), it would then be consuming (0.43636 therms/0.75= ) 0.5818 therms/HDD

So over a 5000 HDD season the boiler would burn through (5000HDD x 0.5818 therms/HDD= ) 2909 therms per year, just for space heating, not counting the domestic hot water.

Is he really using something like 3000-4000 therms/year?

I doubt it.

The only way he's going to burn through 3000 therms /year in NJ is by leaving some windows open 24/7. A fairly leaky 2600-2700' house might go through 1500 therms/year in that climate, but a reasonably tight house would be using about 1000 therms/year (give or take a couple hundred, depending on how much hot water is being used.)

With a condensing boiler instead of the decrepit piece of scrap iron it would use 600-700 therms/year.

With a right sized cast iron boiler it would be ~750-850 therms/year, but with the ridiculously oversized new hunks of iron being discussed such as the CGa-5, -6, or -7 it would again be ~900 therms/year or higher. The oversized cast iron wouldn't short-cycle with that much radiation, but the standby losses would be about the same as the standby losses of the existing boiler.
 

Cpeters

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They're out there- especially with the micro-zoning crowd!

Beyond all reason cpeters seems to believe his heat load is something like 117,000 BTU/hr, which would be pretty far out of the condensing range with 258' of baseboard.

Here's what the lipstick on bathroom mirror math says:

Most of NJ is in zone 4A, part is in zone 5A, but a typical NJ climate is about 5000 heating degree days. Assuming the heat load at +10F is 100,000 BTU/hr (not 117K), in 24 consecutive 10F hours would add up to (65F-10F=) 55 base 65F heating degree days, over which the heating system needs to supply (100,000 x 24= ) 2,400,000 BTU.

That's (2,400,000 BTU/ 55=) 43,636 BTU/HDD, or (/100,000 per therm= ) 0.43636 therms/HDD.

Assuming his retrofit gas burner on the ancient oil boiler is delivering 75% AFUE (probably a stretch, but maybe), it would then be consuming (0.43636 therms/0.75= ) 0.5818 therms/HDD

So over a 5000 HDD season the boiler would burn through (5000HDD x 0.5818 therms/HDD= ) 2909 therms per year, just for space heating, not counting the domestic hot water.

Is he really using something like 3000-4000 therms/year?

I doubt it.

The only way he's going to burn through 3000 therms /year in NJ is by leaving some windows open 24/7. A fairly leaky 2600-2700' house might go through 1500 therms/year in that climate, but a reasonably tight house would be using about 1000 therms/year (give or take a couple hundred, depending on how much hot water is being used.)

With a condensing boiler instead of the decrepit piece of scrap iron it would use 600-700 therms/year.

With a right sized cast iron boiler it would be ~750-850 therms/year, but with the ridiculously oversized new hunks of iron being discussed such as the CGa-5, -6, or -7 it would again be ~900 therms/year or higher. The oversized cast iron wouldn't short-cycle with that much radiation, but the standby losses would be about the same as the standby losses of the existing boiler.

I have to put those new hang on the wall units in with blue and red plastic pipes. Easy to install, but give it some time and we will see which gets the most mileage. I see lots of plumbers installing pex like copper pipe with fittings, connections and branches behind sheetrock and tile walls. Time will tell.
tell.
 

Dana

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If it leaks a ton of air, maybe it's 45K, but it would be fix-able.

You're not required (by law or convention) to plumb a mod-con with PEX, or to micro-zone the hell out of it with a maze of blue & red spaghetti streaming out of manifolds.

Sweat copper connections to mod-cons and the near boiler plumbing are the rule, not the exception. I can't recall ever seeing the near-boiler plumbing on a mod-con done in PEX by a pro, but I've seen a few pictures (even on this forum) where DIY hacks did it in PEX.

You don't even have to hang the mod-con on the wall- there are plenty of floor-mount modulating boiler options if that's preferable:

lochinvar-knight-boiler-replacement-ayer-ma.jpg
 

kbrill

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95-5 is the best choice for everything except the zone valves

Zone valves should use a lower temperature solder like 50- 50 and heat applied very sparingly.
 
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