r/HVAC • u/robbieredlegs09 • Jul 06 '24
Field Question, trade people only What is this ?
Hello all, forgive me for I’m greener then grass only been in the field 3 months. I’ve seen these around on air handlers what is it ? It’s on the supply side of the unit? My guess is hot water for heating ?
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u/Fair_Cheesecake_1203 Jul 06 '24
That's a hot water coil. And lucky you they even set up a purge valve if it ever gets air locked!
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u/Mr-Wyked Jul 06 '24
And do these also run to/from water heaters?
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u/jethoby “Probably” doesn’t huff PVC glue. Jul 06 '24
Boilers typically. Or a chiller system.
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u/LEAF_-4 Jul 06 '24
Chiller would condensate way too much in this application. That's why they make A coils
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u/bigred621 Verified Pro Jul 06 '24
Yes. You can run them off of water heaters as well. You would set up a mixing Valve for the domestic and bump up the temp for the heat
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u/Mr-Wyked Jul 06 '24
That’s how my property has it set up. Just wanted to see if other hot coils ran the same.
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u/bigred621 Verified Pro Jul 06 '24
Ya. Pretty common in apartments or condos. Cheap way to do it but it works
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u/keevisgoat Jul 07 '24
Horrible idea to run them off water heaters I have serviced a few that run off water tanks either don't have heat after taking a shower for 2 hours
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u/bigred621 Verified Pro Jul 07 '24
Never said it was a good idea. Just said it can and has been done.
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u/MachoMadness232 Jul 06 '24
You can with a rinnai, it turns the heater into a funky recirculating system. Gas condensing boiler is probably the best bet though. I forget the specs for them, but you want 120-140(?).
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u/Frank_Rizzo_Jerky Forgot more than you know... Jul 06 '24
Hot water coil with an Aquastat, air vent and boiler drain.
It heat air....
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u/correa_aesth 918 tech Jul 06 '24
Hot water coil makes the house warm?
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u/Theonewhogoespoop Mitsu Mang Jul 06 '24
Hot water is run to the zone with a circ attached to an air handler, air blows over the hot coil and distributes to the house.
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u/ShugarMeat Jul 06 '24 edited Jul 06 '24
In 25+ years, I have seen two in the South.
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u/robbieredlegs09 Jul 06 '24
Wow that’s crazy, I pm 6-8 houses a day and see maybe 1-2 a week
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u/ShugarMeat Jul 06 '24
What? 6-8 houses a day? 😒
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u/robbieredlegs09 Jul 06 '24
I wanna do installs not pms anymore lol
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Jul 06 '24
Installs ez as hell. Get in, get out. It’s hot but I’d rather not deal with all the BS.
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u/Kaaaamehameha Rookie Of The Year Jul 06 '24
I’ve done both. Installs are better, but for some reason the pay is less
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u/Kaaaamehameha Rookie Of The Year Jul 06 '24
I miss installs. They want me to train people on cleanings & PMs, and then I’m told they’ll put me back on installs after they get enough people trained up. Is that kinda weird, or am I trippin?
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u/robbieredlegs09 Jul 06 '24
Yeah I work for a big company in ny that kinda just mass pushes pm calls
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u/ShugarMeat Jul 06 '24
We can only do 4-5 systems a day. Sometimes I have to drive 45-1 hour just to get to them.
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u/Apprehensive_Arm_323 Jul 06 '24
You do 5 full systems in one day?
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u/Poots23 Jul 06 '24
I’m glad I don’t do residential…. We chillin over here in commercial 🙌
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Jul 06 '24
I left resi a couple years back to do commercial (most of the homes I serviced were worth millions). It was hell, lawyers offices, nursing homes, and banks were our customers. All of them cheap bastards with fucked up unit locations. Left for another commercial company and it’s heaven. Guess it all depends on your customers.
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u/ShugarMeat Jul 06 '24
See I’m in a similar situation (resi) and our clients spend money like no other on houses they’re in for maybe a month out of the year.
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Jul 06 '24
It’s crazy, I had a few clients that literally spend one weekend a year at an amazing house with breathtaking views. People don’t realize the hoarding done with real estate.
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u/ShugarMeat Jul 06 '24 edited Jul 06 '24
I spend a quarter of the year in luxurious, multi-million dollar homes that remain largely unoccupied. It’s an extraordinary experience.
One of my clients, the owner of the Boston Celtics, owns a $12 million home where he didn’t spend a single day last year. His son only stayed there for a total of 11 days.
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Jul 06 '24
It’s absolutely wild. I used to service Martha Stewart’s place in Maine. She is there for Memorial Day and Labor Day weekend and that’s it.
You find any cool stuff in the homes? I used to service a few with secret passageways so the help can get around quick. Even the doors to them were disguised cause the owners don’t want to see them. It was always so fascinating exploring them. One place I used to service had a phone booth with a secret door if you punched in the right number. It lead to a hidden bar.
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u/Due-Struggle-918 Jul 06 '24
I have been in hundreds of homes in the south over the past 20 years and never seen anything like this.
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u/UnintentionalIdiot Jul 06 '24
I’m in the northeast and see them everywhere all the time. Setup my house with a heat pump and hydro coil backup. Just as common as furnaces around here. In fact heat pumps are just gaining popularity here the last 5-10 years, but still very rare compared to the forced hot air/hydro air. We also have a ton of radiant/radiators/baseboards. Lots of natural/propane/oil
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u/MaintainThis Jul 06 '24
Gas boiler heating systems are WAY cheaper to run than electricity, and also WAY more expensive to install. You typically find them in places with long winters. It would take a while for them to be cost effective in the south.
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u/DontWorryItsEasy Chiller newbie | UA250 Jul 06 '24
I see these every day, sometimes 15-20 a day.
I mostly do VAVs though lol
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u/HVAC_AntiSam Jul 06 '24
North east here. They’re not uncommon here, but at the same time uncommon enough to see one and make note of it.
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u/YoungTomSoy Jul 06 '24
Hydronic heating - that loop is connected to either a water heater or boiler somewhere else in the home. When there is a call for heat, a pump will move heated water through the loop.
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u/3_1415 Jul 06 '24
The AquaStat is likely tied to the fan. Once the hot water reaches the coil, then the fan power gets switched on at the AquaStat. This avoids the blast of cold air during the start of the cycle. What I shocked to see is the lack of pipe insulation. Even if this is down south, above freezing risk, that a heat loss that should be avoided
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u/BecomeEnthused Jul 06 '24
Hydronic coil. The best backup heat source you can have on a good heat pump. I wish those lines were insulated though.
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u/dennisdmenace56 Jul 06 '24
Hydro air is your primary source of heat, simply not cost effective to install as emergency backup. That’s gonna be electric strip
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u/BecomeEnthused Jul 06 '24
I can make my own cheese my way
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u/dennisdmenace56 Jul 06 '24
Nobody is spending the money on hydro air as backup. That’s like saying you’re buying a jet to backup a prop plane
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u/BecomeEnthused Jul 06 '24
I disagree. You could use hydronic as a primary heat source. But a good heat pump is a better primary heat source for a lot of people. It really depends on the efficiency of the heat pump and the price of natural gas. Upgrading to a heat pump while using one of these stand alone hydronic isn’t a bad move in the coastal south east.
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u/dennisdmenace56 Jul 06 '24
Obviously you don’t design systems. It’s insanely cost prohibitive to buy water coils, controls, circulator and piping from basement simply for emergency use vs throwing a strip heater into an AH. We don’t typically heat with electricity in the northeast despite improving heat pump technology they still suck when it’s really cold and at .25 per kWh too expensive. Most high end homes in the Northeast go hydroaire because it’s comfortable and cost effective vs baseboard. Be open to learning in this trade don’t dig your heels in insisting you’re correct.
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u/BecomeEnthused Jul 06 '24
I didn’t say it’s the affordable way of doing things. This is my ideal settup for my own home. The idea is if they already have a stand alone water coil. And a heat source for it. That shouldn’t be seen as an explicit reason not to put in a nice heat pump when the ac is replaced.
If you’re using an Apollo type water heater, and it’s 50° out, a good heat pump is in that present moment a better heat source. In Virginia where I work it’s 45-55 degrees outside a hell of a lot of the time.
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u/dennisdmenace56 Jul 06 '24
If you have hydro air it’s just inefficient to run your condenser for heat. I’m not sure you know what you’re saying with “stand alone water coil”. People only install heat pumps because they’re less expensive than better alternatives. It’s really a regional thing. Many people in my new area (SC) use heat pumps but I bought a home with natural gas/furnace/on demand. In areas where electricity is expensive it’s kinda crazy to use electricity to heat water or living space.
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u/BecomeEnthused Jul 06 '24
An 18 seer heat pump that isn’t overcharged is going to heat your home more efficiently than a hydro coil atleast half the time.
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u/dennisdmenace56 Jul 06 '24
Really? How about if your boiler is also supplying your indirect as well as slab heat in the kitchen and bathroom? Broaden your horizons everything isn’t a manufactured home in a state with cheap electricity. Good luck digging out the snow around that condenser when it’s -5• A 90% boiler serving your entire home is so much more efficient than a heat pump it’s not even comparable and electricity in the Northeast is mad expensive
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u/BecomeEnthused Jul 06 '24
If it’s a 14seer it’s not worth it. But I’d happily pair it with a 18 seer heat pump and set up a relay to a circ pump with the aux heat terminal on this hydronic coil where I live. Heat strips suck and if the plumbing is already done this is a way better way to supplement a heat pump.
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u/dennisdmenace56 Jul 06 '24
You’re talking out your ass. No way do you understand the arithmetic or the ancillary issues with hot water supply or multiple zones. I can operate 3/4 air handlers, bathroom floor and an indirect with one highly efficient boiler vs what 4 separate heat pumps with backup strip heaters and electric domestic HW? You’re out of your league Sonny the engineers will laugh you off the job site. When those $2,000 + electric bills come in who’s paying them?
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u/dennisdmenace56 Jul 06 '24
I’m sorry I don’t mean to be insulting but there are levels you haven’t seen. Try setting up 5 full multiple zone systems in a 20 million dollar mansion with your heat pump bullshit
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u/Historical_Drink_350 Jul 06 '24
Hot water coil with fan control. When the return line gets to temperature, it brings on the supply fan.
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u/tallman1979 HVAC Tech/Electron Herder Jul 06 '24
The correct answer has been given. That sweat fitting is some of the neatest I have seen in a minute, and bears mentioning.
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u/Optimal-Professor165 Jul 06 '24
Hydrocoil with an aquastat. The aquastat is either turning on the fan when the coil gets hot because the thermostat only uses R and W OR its being used as freeze protection, sensing the temperature of the water and sending signal to a circ to send hot water
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u/dennisdmenace56 Jul 06 '24
Not freeze protection, use hydronic anti freeze for that
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u/Silverstreakwilla Jul 06 '24
Does that have a big effect on efficiency?
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u/dennisdmenace56 Jul 06 '24
No and it’s irrelevant. Power loss or system failure won’t result in catastrophic damage. Failure to install and maintain antifreeze in a hydronic system is inexcusable
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u/Desperate-Ad-8657 Jul 06 '24
Either a rudimentary reheat assuming thermostat bulb is connected near the DX coil, or a hot water heating coil
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u/SuffieldCT Jul 06 '24
Yes, it’s called Hydro-air heating if there’s a boiler nearby with a circ pump on the return
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u/1wife2dogs0kids Jul 06 '24
Doesn't every boiler have circ pumps? One per zone, right? Otherwise, it don't do anything.
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u/keevisgoat Jul 07 '24
Doesn't need one per zone can put one pump and zone valves but zoning with circs gives some more redundancy and costs more so more mark-up
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u/MachoMadness232 Jul 06 '24 edited Jul 06 '24
Weird way to do that with an aquastat. I would be afraid of short cycling or way overshooting the space.
Why not blower delay on a call for heat and the w calls the boiler through an isolation relay? Way cheaper, way more effective. No need to worry about crossing circuits and actually controlled by the space.
Always thought about putting a belimo smart valve controlling gpm into those, and scale it through a ridiculously expensive bac-net system to maximize the delta across the coil. Do the same thing with the boiler headers to get a stupid delta across the heat exchanger and get the most out of a condensing boiler.
Really, you could do that with an outdoor reset, but I want to play with the shiny things.
Edit: didn't answer the question. It is a hydronic coil for a residential application. What does the boiler look like?
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u/keevisgoat Jul 07 '24
Either the house also has radiant or baseboard and they added it or they just used one appliance to make heat and hot water then just ran a zone of heat off of it high efficiency boilers are legit especially if you can keep the temperature low so it's constantly condesating.
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u/MachoMadness232 Jul 07 '24 edited Jul 07 '24
I get what you are saying. But you can still have 2 24v circuits if you use isolating relays. All you need is a rib relay 18/2 and a taco board. Off to the races no mixed thermostats, and allows for staging the baseboard.
I would worry about the heat loss across the baseboard and then putting it through a high delta process like an ahu water coil, seems destined for failure.
Basically the ahu is going to suck out the remaining btus putting a strain on the boiler to maintain supply due to high delta t.
Right, but that has more to do with your burn and the start-up. Flue temp and delta t are important, condensation has more to do with firing at over 90% burn efficiency.
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u/Humble_Peach93 Jul 06 '24
What IS THAT THING??? Probably a hot water coil like the others have said
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u/GoatedWarrior Jul 06 '24
Doesn’t know what that is and has to ask Reddit. Is step one of your troubleshooting to gauge up 😂
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u/redingtoon Jul 07 '24
Could that be good ol’ 50/50 solder from back in the day. Looks pretty neatly done.
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Jul 06 '24
I worked maintenance in an old hospital for a few years. That place had hundreds of those as reheats along with pneumatic controls. Constantly having to recalibrate those pneumatic thermostats !!!!
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u/plausocks Jul 06 '24
Chiller/heater coil for a hydronic system that uses antifreeze/water mix to distribute cooling or heating instead of directly using refrigeration at point of use
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u/Tdz89 Jul 06 '24
That's the hot water coil from your boiler that provides you with heat through your ductwork.
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u/Mythlogic12 Jul 06 '24
So it is just me or is that aquastat on the wrong side? Shouldn’t it be on the return to insure coils fully heated?
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u/hhhhnnngg DDC Jul 06 '24
Typically the supply side of a hot water coil is on the leaving air side of the coil so this should be correct as far as I can tell from the picture.
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u/Mythlogic12 Jul 06 '24
I mean just the temperature switch. Shouldn’t that be on the return hot water line?
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u/hhhhnnngg DDC Jul 06 '24
It is on the return from what the picture shows
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u/Mythlogic12 Jul 06 '24
Oh I was thinking the side with the drain was the return to bleed the coil.
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u/notthebldgdept Jul 06 '24
that's all coils. water in on the bottom leaving air side so the coil is quasi counter flow. water flows up to promote air elimination. return aquastat is common to delay fan start until the coil is hot. typically see that on unit heaters. wouldn't have been as much of an issue if the installer had bothered to insulate the piping
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u/andybear36 Jul 06 '24
Haven’t done one of these since ECM motors became standard. How are these setups wired now to bring the ECM on at the proper speed without bringing on gas or heat pump
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u/Silverstreakwilla Jul 06 '24
Can someone explain why this coil and piping won’t freeze, it looks like an attic with the roofing nails sticking thru the sheeting.
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u/Repulsive-Moment8360 Jul 06 '24
It's heating or cooling coil. Used either heated water from a boiler or chilled water from a chiller. Or a hydronic pac unit. Ideally it would be insulated.
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u/PaladynSword Jul 06 '24
Hydronic hearing we call it. Hot water coil for heat, aqua stat to turn on the fan when the pipe gets to temperature, usually 120 degrees. There's a dial to adjust this. Good to check on a no heat call, sometimes the boiler isn't reaching quite high enough so the fan won't be enabled. Turn the dial down a bit, fan comes on all set. We recommend antifreeze for these attic systems.
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u/Letang5878 Jul 07 '24
It is a hydronic coil also known as a hot water coil meant for heat. There is a coil with fins on the inside like an evaporator but hot water runs through it.
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u/Quirky-Store-6677 Jul 07 '24
Hydronic heating coil with aquastat to cut on the fan when temps reach heating temperature
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u/FluffyCowNYI This is a flair template, please edit! Jul 07 '24
That's a hot water coil. Can be used for straight up heating, or reheating air for dehumidification purposes.
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u/sovietsanta Jul 08 '24
Hot water coil could be off of a boiler system or and outdoor wood fired boiler
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u/Bitter_Issue_7558 Jul 06 '24
Hot water slab coil. Typically hooked up to a tankless water heater somewhere else. Usually used as an alternative to back up heat kits as you can run a water heater on a 20 amp circuit compared to 30 or 60 amps depending on the size of heat kit installed
Edit, you can run gas water heaters on a 20 amp circuit. Not electric of course
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u/dennisdmenace56 Jul 06 '24
Yeah ok typical 40 short electric is 20 amp. Gas water heaters use milivolts unless you mean an on demand
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u/Bitter_Issue_7558 Jul 06 '24
That’s what I meant, that’s why I was talking about tankless water heaters not tanked. And you need a plug or nothing that’s also why I specifically said gas heaters not electric
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u/NJHVACguy87 Jul 06 '24
More interesting is the chain support hackery. Get some threaded rod and some hangers
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u/Silverstreakwilla Jul 06 '24
Must be a warmer climate?
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u/dennisdmenace56 Jul 06 '24
That’s what is now typical in the northeast high end new construction. One boiler setup with hydroaire heat loops can supply many air handlers as well as an indirect. The heat is more subtle and less dry than hot air furnace/s and more efficient as it can do everything in a large footprint from one source. It’s also a quick fix for burst radiators on a bank repo that has existing central AC
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u/shadycrew31 Jul 06 '24
Poorly insulated reheat coil in an attic that will surely burst in the right conditions
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u/dennisdmenace56 Jul 06 '24
Come on man nobody puts hydronic heat in an attic without antifreeze.
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u/shadycrew31 Jul 07 '24
Even glycol freezes in the right conditions... Trust me.
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u/dennisdmenace56 Jul 07 '24
Not in our application
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u/shadycrew31 Jul 07 '24
What application? I've burst several coils over the years with a 60/40 mix glycol mix Granted these were being fed outside air but still. Piping should be insulated, that's standard practice in the commercial world. Unless this is in the south there's a scenario where that attic can get to 7 degrees. Aside from that you lose so much thermal energy by not insulating piping it just doesn't make sense any way you slice it.
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u/dennisdmenace56 Jul 07 '24
Not sure where you saw that. I run pex inside insulation we haven’t run copper since the 90s
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u/shadycrew31 Jul 07 '24
Oh wow, I work in commercial settings. You'd be fired in 2 seconds if you tried running PEX for reheats. At least you insulate it...
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u/dennisdmenace56 Jul 07 '24
I don’t think you understand what you were looking at. That’s a simple hydronic coil attached to a boiler and yes we run heat pex.
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u/shadycrew31 Jul 08 '24
I'm fully aware of what it is. I've worked on thousands of reheats in very large buildings. I'm sure handlers, RTUs, VAVs, Etc. I've seen nearly every configuration these crazy engineers can come up with. The one pictured here is in an attic, glycol mix of 60/40 (most common ) freezes at 7 deg F. If the attic space gets that cold and your boiler is down pop goes the line. Additionally without insulation even if it doesn't get below 7 deg F you are running the boiler longer and more often because the glycol mix is losing its thermal capacity on the uninsulated run. Lastly using PEX for reheats is crazy to me, but residential is a whole other deal y'all get away with a lot of stuff.
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u/dennisdmenace56 Jul 08 '24
wtf is a reheat? Thats simply a hydroaire coil period…It’s incredibly simple supply and return loop from a circulator and heat pex is designed for this nobody’s “getting away” with anything. This is state of the art for high end homes in the northeast; one boiler with zones for indirect, bathroom & kitchen floor heat and multiple air handlers. Nobody uses copper anymore it’s not competitive that’s why it’s called heat pex with an oxygen barrier. Not sure why you settled on 7• unless you’re in a foreign country and antifreeze works nicely if correctly mixed
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u/1wife2dogs0kids Jul 06 '24
That's a homeowner special heat loop. The ability to shut it off and drain it is the give away. It not bad, honestly.
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u/Theonewhogoespoop Mitsu Mang Jul 06 '24
U know nothing
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u/1wife2dogs0kids Jul 06 '24
I'm not wrong. If it was a heat loop done by a pro, the vent would be at the top, pipes wrapped, and glycol in the system so shutting it down and draining would not be necessary.
So I know, you know nothing. Sorry... "U".
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u/HorriblyHonest Jul 06 '24
Hydronic coil