Boiler temperature; adjust? - Weil-McLain GOLD GV series 4

[2apart]

Just had a new (replacement) Weil-McLain Gold GV series 4 boiler installed. This unit heats fluid that is piped thru a basement floor.

The old unit, that rusted out (15 years old), had a lower outlet temperature. That unit supplied fluid at about 120F into the floor. This new unit is up around 140F.

I assume that the oulet temperature, at 140F, is related directly to the boiler inlet temperature; it's the same circuit. I'm guessing.. I don't have a schematic. My desire to reduce this temperature is based on increasing the boiler efficiency.

The user's manual says that the GCM (the units controller) mixes return water (cooled by the floor) and by-passed boiler output to maintain 140F temperature into the boiler sections, "to guard against condensation even if the return water is as low as 6oF". Fluid returned from the floor is around 60F.

My questions are these.

Can the boiler inlet temperature be adjusted?

Would it be more efficient to lower the boiler inlet temperature?

Would lowering the temperature to, say, 120 be a good idea?

What is the reason to avoid condensation? Doesn't the condensate just flow into a drain?

[Oscar_Lives]

Just close the gas valve off a bit until you get the temperature you want.

[Nathan In Montana]

i understand the reason behind your comment, but do you _really_ want to potentially bare the burden of this liability?

[Oscar_Lives]

Here, bare THIS!

[Steve Scott]

The reason for the 140 return temp is to prevent damage to the boiler. If that doesn't concern you lower away.

Or rip out the WM and install a mod/con boiler. They're specifically designed for low return temps. The Buderus GB142 will give you up to

98% when it's c>Just had a new (replacement) Weil-McLain Gold GV series 4

[Bubba]

Nope! Only 98% when it is in a low temp application. In other words, around 75 to 80 degree outlet water temperature. "You gotz to read the fine print" Bubba

[Bubba]

You have a little bit of information but dont know what to do with it. What you might want to do is ask yourself why a boiler rusted out in only 15 yrs when it should have lasted 25, 30, or 40 yrs or more. Oversized boilers and improperly installed boilers will rust like crazy. "It aint rocket science you know?" Bubba

[Nathan In Montana]

giving a harmless bullshit response is one thing. giving a potentially hazardous bullshit response is another matter entirely. at best its completely irresponsible.

[Oscar_Lives]

going to an alt newsgroup for responsible advise seems somewhat irresponsible as well.

Seems this is a question for the manufacturer or a qualified technician...

[Steve Scott]

[Nathan In Montana]

i agree with you _completely_. however, should one take you seriously and follow your advice causing damage to life or property, a strong case could be made against you. in todays litiguous society, its something to think about.

[Anonymous]

Do you guys actually think you could be held responsible for anything you say here? I am from Canada so our laws differ, but I know I couldn't be held responsible for anything I say on the internet, even if it leads to death or injury. It's up to the home owner to use due diligence, and it's the homeowner who is ultimately responsible for anything that happens. In my province the homeowner can work on his own gas equipment, so long as his house is not aatached to another..hahaha

-Canadian Heat

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[Bubba]

Steve, I dont think you understood what Im talking about. Now Im not familiar with the Buderus but we've used the Weil-McLain high eff condensing boilers. Weil-McLain rates theirs at something like 98% eff too but its NOT. Not unless you are using it in a specific low temp application. I looked on the Buderus site. Its not very detailed. All it says is the boiler is either 97, 98 or 99 % efficient depending on the size. Typically, that rating is for the most extreme type of install. For example: If you use this boiler in a system where it heats the closed water loop for a McQuay water source heat pump system. It only heats the water in the loop to approx 78 degrees. It doesnt go any higher. Thus they can rate it at a 99% eff unit. When it is installed in the more typical type of installation where it heats water from 140 to 180 degrees in a system using cast iron radiators or base board fin tube then the rating is more in the 92 ish % rating. I didnt see where Buderus makes that distinction but Id bet that is the case. 99% eff on a 198,800 BTU boiler that is putting out

151 degrees at the flue is pure BUNK! At that furnace c>Err, it only condenses in low temp applications, Bubba. FWIW, Buderus

[Nathan In Montana]

absolutely.

[Power's Mechanical]

Yes, but no lower than 140F

Have your contractor install a Tekmar boiler reset control. Keep the min temp at 140F. As the weather warms the boiler temp is lower and vise versa. You can also cycle the pumps according to demand saving even more energy.

No. Didnt you understand the part about condensation? If the boiler water is below a certain point (generally 140F) the outside sections condensate. Thats a bad thing.

It promotes rust and corrosion on your brand new boiler which can also lead to premature and sometimes catastrophic failure.

No. It flows out onto the floor.

[-zero]

I couldn't agree more.

A manufacturer that makes a larger 97%+ HW condensing boiler (s.s. coil in a box) briefly had linked their submitted certification procedures for eff. (not there now and pissed I didn't PDF it) . They used 30-something° inlet water with a pre-mix burner using a Matrix-fiber type cone, perfect ambient conditions, etc.

The verbiage they use now for ALL their heaters is all over the place. "up to 98% eff." "Higher efficiency of 99.1% can be achieved when boiler works with less than full load using lower inlet water temperature."

Well the burner they used for their cert., is listed as OPTIONAL! The standard burner is a Riello. 86.6% combustion eff. in that heater on a good day, at rated output. However all their claims revolve around the high eff. burner numbers. As if that's what your buying. Now they DO show a small chart in their manual with the eff. dropping off to something like 89% with 140° inlet.

But with NO MENTION that this is all with the OPTIONAL BURNER ONLY!!! However, It IS worded in double-speak in a C.Y.A. fashion early on in the manual. Kind of like Where's Waldo.

Bastards.

You've got to watch these manufacturers and there efficiency claims!

This is a good page to start off (good links) into the black-art of "efficiency".

-zero

[Steve Scott]

Go to this link

No tub girls. :) Look to the rated output line. There highest efficiency is with a supply at 122F and the return at 86F. The lowest efficiency, 88.7% is with supply at 176F and return at 140.

122F is plenty to drive most radiant systems unless it's a floor with a thick carpet pad. You could even do panel rads as long as you design for 122 supply.

Agreed and that's why my point to the OP is appropriate. He was complaining about having to maintain a MINIMUM temp of 140. I said to him, "They're specifically designed for low return temps. The Buderus GB142 will give you up to 98% when it's condensing."

I stand by this. The GB142 will delivering up to 98% when it's condensing. To condense you need low return temps. Below 140 qualifies as a low return temp. Will it get you the amzimum efficiency possible? No, but then we don't know what return temp the OP is shooting for. We just know he wants it lower than 140. In fact, he mentions return temps of around 60F. Well below the 86F required for 98% efficiency. My guess is he's heating a concrete slab if he wants a supply of less than 140.

What specifically did I say in this case you find misleading, wrong or disingenuous?

[Steve Scott]

Go to this link

No tub girls. :) Look to the rated output line. There highest efficiency is with a supply at 122F and the return at 86F. The lowest efficiency, 88.7% is with supply at 176F and return at 140.

122F is plenty to drive most radiant systems unless it's a floor with a thick carpet pad. You could even do panel rads as long as you design for 122 supply.

Agreed and that's why my point to the OP is appropriate. He was complaining about having to maintain a MINIMUM temp of 140. I said to him, "They're specifically designed for low return temps. The Buderus GB142 will give you up to 98% when it's condensing."

I stand by this. The GB142 will delivering up to 98% when it's condensing. To condense you need low return temps. Below 140 qualifies as a low return temp. Will it get you the maximum efficiency possible? No, but then we don't know what return temp the OP is shooting for. We just know he wants it lower than 140. In fact, he mentions return temps of around 60F. Well below the 86F required for 98% efficiency. My guess is he's heating a concrete slab if he wants a supply of less than 140.

What specifically did I say in this case you find misleading, wrong or disingenuous?

[Bubba]

Radiant will probably do. My part of the world deals with 180 most of the time with homes that have a mix of copper fin tube baseboard radiation and cast iron radiators in the same home. At some point, someone said, "Eww. Those big ol radiators look horrible. Rip them out and install those small pretty looking baseboard radiators."

I guess this is where you are confusing me. It IS a condensing boiler. It will condense flue gasses if you are heating the water to 180 degrees or to a lower supply temp of 122 degrees. A condensing boiler is a condensing boiler.

So are you saying that the Buderus boiler will NOT condense if the water temperature is above 140 degrees? Maybe this discussion is getting way off track?

Hopefully I pointed that out above. :-)

[Steve Scott]

Got it. A condensing boiler is sort of like a condensing furnace. If the temps the secondary heat exchanger are sufficiently high the furnace won't condense. That's pretty unlikely to happen with air. You can make it happen with water though.

If the return is hot enough, and I don't know what the magic number is but I suspect around 160 or so, the condensate drops to about nothing. I think that's why Buderus rates the boiler with higher returns around

88% and 98% with the low return temps. 10% is about the same pickup you get with a gas furnace when you start extract>I guess this is where you are confusing me. It IS a condensing boiler.