Ask Caleffi
Ask Caleffi
#23 How can I protect a boiler system from condensation?
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Straight from the Ask Caleffi Podcast studio, Greg and Dan dive into boiler protection. Let's face it when high-temperature, mid-efficient boilers condense... it's a mess! How can that be prevented? Greg and Dan talk about solutions, including a "Swiss Army Knife" approach. They discuss how the ThermoProtec thermostatic mixing valves work and where they should be piped with steel, cast iron, and copper tube style boilers to ensure that they automatically control the return water temperature, preventing condensation of water vapor contained in the flue gas. Familiar with a soot vac? Don't forget maintenance!
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[Music]
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welcome to ask Caleffi the podcast that
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dives into real life problems that
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plumbing and hvac technicians face in
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the field we're your hosts from the
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caleffi tech support team i'm greg tubbs
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and i'm dan ferkus welcome we look
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forward to sharing some stories from our
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tech calls and using our background and
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expertise to make your days a little
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easier hey we're back
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coming at you from the ask luffy podcast
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studio how you doing dan i'm doing good
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today thanks greg yeah so we're going to
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talk a little bit about boiler
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protection valves today
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uh obviously you're not going to see
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them much at all you shouldn't see them
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at all on any of your modulating
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condensing boilers no you won't find
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them there but you know there are a lot
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of mid efficient boilers out there that
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are still continuing to be installed and
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there's certainly applications for them
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yeah anything that's a copper fin tube
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cast iron whether it's fired off of oil
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natural gas lp
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or even wood boilers for that matter
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right well and you look at you know high
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temperature systems like you mentioned
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you know that the copper fin tube or
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cast iron you know baseboard or
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radiators
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you know those are systems running you
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know 160 180 degrees or or so and
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you know you can put a condensing boiler
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on them yeah absolutely and it's done
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all the time but
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you really don't get the the efficiency
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out of a condensing boiler unless it's
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running in that condensing mode right
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and you want to avoid those situations
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when you've got an older cast iron
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boiler right you know or copper fin tube
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boiler because you know what happens
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when they condense it makes a mess right
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yeah so you need you know you look at
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your lower temperature applications and
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you know that's where
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you know
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the modulating boilers are a great fit
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um but initially trying to heat a system
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up or heat a building up
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you know you don't you're right you
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don't want to risk condensing that cast
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on your boiler you're going to throw a
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shock at that boiler right you will 100
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every every day of the week yeah so we
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but we have a couple options for that
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yes we do we have the 280
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and the 281. yeah 280 being a basic
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just thermostatic element in it uh
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at thermostatic bypass bypass valve
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essentially it's a mixing valve
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right for to prevent condensing yeah
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those are great two options on those you
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know you typically you're you know we
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always say your cast iron boilers you
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don't want to return water back to them
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below 130 degrees or that block will
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start to condense right
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so we have two options we have 130
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degree and 140 degree option right and
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then we've got kind of a
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swiss army knife approach
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that incorporates a pump in the 281
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series right yep the 281 is going to
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have the pump built into it the 280
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you're going to have to have you're
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going to have to size and add your pump
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right but that 281 will have the pump
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built into it provides you know similar
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protection similar applications
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130 or 140 degree
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option as well right now we also have
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replacement cartridges available so some
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will actually call and order
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a different cartridge if they want a
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lower or a higher temperature yeah we
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have a cartridge 115 degree cartridge
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and we have 160 degree cartridge and
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then we have replacement 130 or 140
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degree cartridges so you can take them
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apart you can maintain them you can
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replace the cartridge rather than
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replacing the whole valve
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when we look at the two options you know
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the 280 is going to
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be a higher flow than the 281 because
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the 281 has the pump sized and
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installed with it
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uh the 280 you're going to be
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providing your pump um it's not going to
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have a check valve in it like the 280
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one would have um so it is a higher flow
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option
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yeah you don't have the resistance of a
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pump being in the way a check valve
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right so that 280 without the pump is
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gonna flow a bit more right
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so when you look at how they work i mean
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they're designed you know again for
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boiler protection so when you first
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initially fire your system up that water
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is going to be starting to heat up
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so it's going to be it's going to be
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cooler water so the bypass is going to
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be open in the bypass mode so it's going
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to be taking that supply water running
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it right back through the return side of
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the boiler creating a small loop which
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is going to start to come up the
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temperature relatively quick
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right
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when you look at that again 130 or 140
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degree thermostat we'll say
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yo you pick the 140 degree thermostat so
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you have the 140 degree element in it
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once that water temperature
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hits 140 degrees that bypass is going to
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start to open up and send that water out
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to the system and continue to bypass so
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it's going to do both it's going to say
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okay the water is above the condensing
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mode for the boiler condensing
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temperature right so it's going to start
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to open up to your system right so it's
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actually essentially
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moving up and pinching that bypass loop
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between the supply and the return off
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and allowing it to flow more out to the
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system and come back through the return
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right
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of the boiler yeah exactly
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um once that water gets 18 degrees above
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that it's going to be completely open to
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the system so it's going to close the
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bypass off correct so that 140 degree
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thermostat
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at 158 that baby's going to be closed
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off it's not going to be pulling
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pulling water from the return or from
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the supply to the return anymore it's
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just going to be all system water yep
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now it's going directly out to the
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system so you've just protected that
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boiler from getting return water coming
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back and condensing exactly um and then
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that 281 is going to work in a similar
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similar
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yeah operation similar operation
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so we get a lot of questions about
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piping these don't we we do yep and pump
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locations pump location is big with
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these honestly it's got to be on the
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return pulling water
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pushing water back into the boiler
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pulling water through the valve yeah we
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have a nice diagram you know in in the
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install manual showing the operation but
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greg's right you got to have that you
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got to have the pump pulling through the
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mixing valve so it's going to pull down
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through the bypass
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pumping through the boiler as that
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bypass starts to close it's going to be
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pumping now out to the system and coming
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back through right and we've got guys
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out there that want to kind of buck the
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system so to speak well it's not i can't
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pipe i i i don't have the room to pipe
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it you're going to have to unfortunately
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make room for this to work properly
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right i've had a handful of guys well i
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piped it in the other way because that's
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the way it worked you know i had room
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for it
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and it doesn't work well there's reason
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why it's not working it's it it's not
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gonna if if you don't pipe it the way we
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show you in the diagram right yep it's
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not gonna sense and register temperature
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and
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and react as it should if you're not
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pulling water through that valve sure
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and but
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this is where the 281 kind of makes it a
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little easier
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it does for an installer is the pump is
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there where it needs to be
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and it's going to work properly
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when installed properly but you don't
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have to worry about sizing the pump
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correct yep but again lower flow
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applications because you know you're
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going to have some
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your flow limitations with the thermal
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block and that factory installed pump
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where the 280 is going to have
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less restriction it's going to work at a
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higher flow rate right
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realistically well i think we're looking
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at about
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10 gallons a minute two feet ahead with
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with that 281 yeah on high yep on high
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speed so and again you're not you don't
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need to move a high velocity of water
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here anyway you're just
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pulling a little bit out to try and
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prevent condensation and add boiler
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block right exactly protect that protect
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that
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system
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man i can i can think of one boiler i
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would have loved to have seen that on i
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spent hours once i think it was probably
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three or four years into being a service
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technician
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and
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i go to this house
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very strange people
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i i've never seen so many antiques stuck
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in one area
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and
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their boiler was down
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you know
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i go down in there they you know don't
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look don't touch okay go in
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from now on you're going in and out the
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bilco door all right fine because i
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don't think i would have made it out of
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that house without tripping and falling
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on something right go down into the
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basement he moved all of his antiques
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from around the boiler clearly it had
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not been serviced in a long time
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and they keep the temperature really low
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like 60 degrees in the house
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right it's all cast iron radiators with
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an oil-fired burnham boilerplate
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yeah so you know where this is going yep
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it kept tripping out on reset
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the the classic well i only pressed the
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reset button twice
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sure you did sure you did sure you
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didn't twice twice after the first two
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or three or four times you pushed it
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twice before i got here and it didn't
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start so that's why i'm here exactly
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exactly
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so i go in and this was the first
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experience ever having to use a soot saw
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oh oh yeah
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so i start to dejack at the boiler and i
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mean the smoke pipe was nothing but
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sweat
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yeah get into it pull the hood off and i
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can't see through the heat exchanger
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it's literally like tar right
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so i call back to the shop tell them hey
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i'm going to be
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a couple hours here what couple hours we
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don't have that kind of time you know
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it's what do you do what do you do i
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mean it's 20 degrees it takes that time
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it's the first cold snap of the year and
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we're running around right we're you
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know we got four tacks and we're all
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busy 10 deep yep so
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look
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we'll see if see if they're willing to
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replace it
09:50
well one they don't have natural gas in
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the house it's all oil so we're gonna be
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coming back with another oil boiler
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that's not gonna get maintained
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but i'll i'll talk to him that was a
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hard no no go you're not replacing this
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boiler right
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so but it wasn't that old of a boiler if
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i recall you saying yeah it couldn't
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have been more than maybe five six years
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old yeah but not maintained ever right
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so i go at it with a saw
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to get this nasty stuff out of it
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finally get to see in daylight in
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probably two of the sections out of the
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five sections that were in this in this
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boiler
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and
10:27
the homeowner's coming down are you done
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yet are you done yet no
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i mean this is this is what it's going
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to be it's going to take a long time 25
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done yeah
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it takes a long time to get that out
10:38
when it's that it's literally like tar
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it's right it was sticky the the
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soot vac hardly did anything you know i
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took the top layer of dry stuff off and
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the rest was just goo yep
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so
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that's where one of these valves would
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have helped prevent that that and some
10:54
some maintenance obviously yeah
10:56
obviously something was out of tune with
10:57
that but the combustion side right so
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but no you're right i mean you start
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seeing
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you know five six
11:05
eight year old boiler heat exchangers
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failing mid efficient boilers you know
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with those heat exchangers failing i
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mean pretty good odds it's you're
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condensing that block right and then
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those things will last forever they will
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installed and maintained correct it's
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crazy how long a cast iron efficient
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boiler will last so when you start
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seeing a you know heat exchanger
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failures or multiple heat exchanger
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failures
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pretty good odds you're condensing that
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block yeah and that can lead to not just
11:37
sorting up
11:38
and you know problems with combustion
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and high co levels but
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i've even seen it where it causes the
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the block to pop or crack and leak
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so
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by all means i mean this is a huge a
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huge deal to install one of these i
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think i think so yeah
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well i think that covers it pretty well
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greg yeah it certainly does uh you got
12:02
any more questions feel free to hit us
12:04
up yeah give us a call anytime we
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appreciate your calls send us an email
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12:09
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right
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12:15
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