Hydro air vs. furnaces

paul1976nj

Hello! I currently have a 5,000sf house in northern NJ with two single-stage 90% furnaces both located in the basement, and old matching single-stage A/Cs (one serves downstairs, one serves upstairs).

Very bad duct design, insufficient supply air, lack of return air, etc. Also supplies and returns are placed unsymmetrically in very aesthetically unappealing places. The ductwork is the biggest problem and it all needs to be replaced so it not only works a lot better, but also looks better!

I am putting three additions on the house totaling 1,200sf, which will make the total house 6,200sf. (Normal living area, not including basement or garage.)

I am therefore about to invest in a total HVAC redo from scratch, and I don't want to make a costly mistake! I've been researching like crazy for months, watching YouTube videos, etc. I've finally found a really good contractor, but there are so many options, pros and cons, etc. so I could really use some expert advice!

Downstairs has four distinct living areas with different sunlight exposures and so I really need 4 zones downstairs. Having four separate systems downstairs would be too much A/C even when using the smallest-sized systems (unless I went with single stage which I don't want), so two systems each with 2 zones (to create 4 zones total downstairs -- 2 on each system) looks like the way to go.

Upstairs has two distinct living areas (master suite and the rest of the upstairs) so I really need 2 zones upstairs. Upstairs is a little too big to be served with one 5-ton zoned A/C system, so two separate systems (non-zoned) is the way to go up there.

Attic is uninsulated (insulation is on the floor). No equipment currently up there.

That said, the biggest question I'm struggling with is the heat. I feel like hydro air is a much higher-end, more elegant, and more comfortable solution. I have a huge problem with the house too dry in the winter currently with the furnaces. Also to be honest I love the way two boilers (cascaded) with an indirect tank and all the beautiful copper piping, zone valves, circulator pumps, etc. look down the basement -- it would be a real work of art. I'm putting quality finishes in my house so I don't want an entry-level HVAC system. (Doing radiant in floor heat would be a budget-buster though, and I don't like the way HWBB looks.)

However I'm afraid about hot water freezing in the attic. I've read that glycol solves this but that it also shortens the life of the system. The idea of putting something harmful in a brand new, expensive system scares me.

Also, the consensus seems to be that if I go hydro air, I can't use communicating thermostats, which rules out inverter A/C (which I really want), unless I go with Bosch (since they use non-communicating thermostats), and I don't want Bosch. Too many things I don't like about it from my research.

That pretty much forces me into only using two-stage A/C if I want hydro air. If I want inverter A/C, then I pretty much need to use furnaces. It's much colder here than it is hot, so I do feel that heating should be the priority. The A/C works fine in the summer except during the mid/late afternoon on hotter days, and it maintains humidity just fine. (Two-stage A/Cs that are a bit larger capacity than I've got now should solve that, while maintaining the low humidity on the first stage.) Whereas the heating is a nightmare. The house is freezing in the winter and the gas bills are outrageous. Investing in a better heating system I feel should be the priority.

If I go the furnaces route, I wouldn't have to worry about about anything freezing in the attic if I put 80%s up there. However only York makes 80% modulating and my contractor said they are not available right now at all. Which means I could only have two-stage up there. I like everything matching for consistency so if I did two-stage in the attic, I'd rather do two-stage 90%s in the basement even though I really want modulating.

I just don't like the idea of furnaces at all. It seems like the cheap way out, and I hate the idea of four fossil-fuel burning furnaces plus a water heater. Boilers seems better, and then later when air-to-water heat pumps become more prevalent, I could dump the existing boilers and use that instead to be all electric. (I looked into VRF for heating and cooling but I hate the way they look having to sit way up on high stands.)

All this said, do you recommend hydro air? If so, how do I deal with the uninsulated attic and glycol issue? And also is it better to use an air handler built for it like the Trane TAM9 with matching Trane hot water coil, or a generic variable speed air handler like York or First Co. and separate generic hot water coil? I don't understand how a variable speed air handler that's not communicating would know how to ramp its blower speed up and down.

Also on the A/C side of things, even getting many brands' 2-stage A/Cs is hard (can't get any York 2-stages at all right now). This is so crazy. Options are very limited. I'm leaning towards the Trane TAM9 air handlers and Trane XR17 two-stage straight-cool A/C, with two boilers in a cascade configuration and indirect hot water tank. Four air handlers, 2 of which are zoned (so 6 thermostats), and a total of 5 hot water zones (4 air handlers + the indirect).

I'm just scared because this is such a large investment and I want to make sure I make the right choice. I read about tons of aluminum evaporator coil leaking issues with the Trane, I hate the way the Bosch (which everybody is pushing right now) looks up on those ridiculous stands and how they don't make an actual 2 or a 4 ton unit and you have to use dip switches to limit the capacity, and how Bosch doesn't make a variable speed air handler, etc. Part of me thinks just use 80% furnaces in the attic and eliminate the worry... if I could actually get the York 80% modulatings I would strongly consider that, but I can only get 2-stage up there, so I'm hitting roadblocks at every turn. I feel like the simpler I keep the system, the better. But I at least want 2-stage A/C with variable speed blowers.

Sorry this is such a long post. I need to make a decision on all this by next week as construction is about to start, and I just don't want to make a very expensive mistake. Any advice would be greatly appreciated.

Many thanks,

-Paul

ChrisJ

Many like hydroair.


If it was me and I was stuck with duct work and no form of radiation I'd use a decent 2 stage furnace.  I just don't see enough benefit to warrant all the extra needed for hydro air.

Hot_water_fan

I feel like hydro air is a much higher-end, more elegant, and more comfortable solution. I have a huge problem with the house too dry in the winter currently with the furnaces.

Hydro air will not change this whatsoever unfortunately. It’s more expensive but not higher end really. It’d be useful if you were using air to water for both heating and cooling, but you’re not there yet. 

Inverter driven heat pumps (with furnace backup if you like) seem to meet your criteria well - lower emissions, variable speed, etc. You can get away with the minimum efficiency furnaces in this scenario because they’ll stay off for the majority of the winter. 

Are you sure the upstairs needs 5 tons? It could be ductwork issues. 

Upstairs is a little too big to be served with one 5-ton zoned A/C system, so two separate systems (non-zoned) is the way to go up there.

TAG

The problem with hydro air is the control ... there is no great way to modulate the water temp and match the fan speed. If you had other hot water going on in the house .... like high temp radiators and wanted to add on hydroair for a new addition --- that could be a plan. Starting out new and just doing hydro ... plus making domestic hot water .... not the route I would take.

Having done quite a few old house rehabs -- the key is air sealing and insulation. In my case I have always use foam .... but -- the goal is to get the loads down for AC and Heat. Proper envelope may not be sexy .... it's the key to comfort and long term cost savings. Better envelope makes for smaller loads and smaller equipment to match those loads --- this makes for smaller ductwork. It's all easier to install -- that's less cost for materials and labor. Win/Win/Win

With today modulating equipment, a matched furnace and AC would be ideal. I have used the Carrier Infinity equipment for almost 20 years now. The infinity furnace is fantastic and matched to the 5 speed heat-pump makes for a great system. The infinity zoning controls are as good as they get. The key again is that envelope .... My last project is a rehab of an old stone structure with an addition and it has over 4K of SF on 3 ton of AC in PA. You want to do 5T in one part of your house !! ---and two more systems !!

Get a professional room by room load on the property and get an overall envelope load so you know what the max total you really need. Don't be guessing with old rules of thumb --- like 500sf per ton. Manual J/D/S -- this way you know what ductwork sizes are needed as well.

I always zone my projects -- I would rather have a single properly zoned system vs two non zoned as the two almost singles always are oversized. You may need two because of the ability to run ductwork in a big odd house -- I have had to do it. FYI - The guys that zone .. do a lot of it and the other guys are afraid of it. It not very hard especially with the new variably equipment like the infinity ... I normally make the smallest sone 25% above the lowest CFM rating of the equipment. Don't put a system in an unconditioned attic .... that a loss of 40% right there.

Mini splits can save you in very odd spaces. Gas or HP water heater

Hot_water_fan

the key is air sealing and insulation

Bingo! Air sealing is how you prevent dry air. Notice how you’re not concerned about the furnace freezing in the attic? That’s because it doesn’t remove moisture.

ChrisJ

Hot_water_fan said:

the key is air sealing and insulation

Bingo! Air sealing is how you prevent dry air. Notice how you’re not concerned about the furnace freezing in the attic? That’s because it doesn’t remove moisture.

No it doesn't.
But the burners do produce condensate.  Is freezing a concern for such systems?

Hot_water_fan

@ChrisJ that’s why he said only 80% efficient furnace in attic. Anyway, plenty of ways to deal with that. The important point is that it’s not forced air that dries out a house - it’s incoming cold, dry air. The furnace/hydro air whatever doesn’t remove moisture 

ChrisJ

Hot_water_fan said:

@ChrisJ that’s why he said only 80% efficient furnace in attic. Anyway, plenty of ways to deal with that. The important point is that it’s not forced air that dries out a house - it’s incoming cold, dry air. The furnace/hydro air whatever doesn’t remove moisture 

No it's definitely not forced air, though I'd bet bad duct work and a drafty house would tend to do it more than a radiant system.

But.
My house with steam heat runs about 20% in the winter.  My dad's house he built in 2007 with forced air and no humidifier runs about 40% and it's 10F cooler where he is.  My house is very leaky and his isn't.  

It actually seems like a really tight house may even need a dehumidifier in the winter to stop windows etc from sweating.   My dad's do when it's below 0 out.   When it's -20 his pvc fresh air intake frosts in the conditioned basement.

paul1976nj

Wow, such good and helpful advice. Keep it coming! LOL.

I'm afraid to mess with the attic insulation. It's a truss roof system so I couldn't just move the bats from the floor to the rafters because they wouldn't fit. I'd have to use spray foam, which I got very pricey estimates to do and I think it looks really messy. Also I'm afraid to fix something that isn't broken - there's currently no moisture issues up there and I'm afraid I'll start having them if I seal the attic.

The common consensus so far seems to be that hydro air is a waste of money and won't work any better or be more comfortable than furnaces. I thought however that two modulating boilers heating four hydro coils plus domestic hot water would use a lot less natural gas than four furnaces - and be an easy drop-in replacement later for when air-to-water heat pumps become more prevalent (so I wouldn't have to replace all the furnaces, only the boilers - or just keep them and make them backup, and make the new one primary).

I feel more comfortable with 6 separate systems not zoned, rather than 4 of them with 2 zoned. But unless I went the Daikin Fit route which goes down to 1.5 tons, it'd be overkill on A/C. And I don't know if the Daikin Fit communicating controls could work with a hot water coil or if that could be rigged up to work as the emergency heat instead of electric heat strips. So the two downstairs systems being zoned is probably best. The advice seems to be to get another load calc done upstairs and see if one 5-ton zoned would be enough. We kept coming up needing more like 60,000-66,000 BTU upstairs (and a 5-ton system only actually gives you about 54,000).

So then would I be more comfortable with communicating inverter heat pumps paired with say two-stage furnaces, or communicating inverter A/Cs paired with modulating furnaces? But I can't put modulating furnaces in the attic, and I can't run that much additional ductwork from the basement to the second floor. (If I could somehow, that would be ideal - to just have it all in the basement.) Hmmm, maybe I can. There's already several runs going up there, I just would need more (and to fix the bad locations of some, which is tricky because of beam placement).

I really appreciate all the input. This will have me way better prepared with the meeting with my contractor on Monday.


Big

Hot_water_fan

But unless I went the Daikin Fit route which goes down to 1.5 tons, it'd be overkill on A/C. 

There are many small capacity ducted variable speed options. Mitsubishi, Fujitsu, etc. 

I thought however that two modulating boilers heating four hydro coils plus domestic hot water would use a lot less natural gas than four furnace

Nope. Best you could do is match performance. Heat pumps are the most efficient way to use natural gas to heat right now. 

paul1976nj

Hot_water_fan said:

But unless I went the Daikin Fit route which goes down to 1.5 tons, it'd be overkill on A/C. 

There are many small capacity ducted variable speed options. Mitsubishi, Fujitsu, etc. 

To pair with a furnace or hot water coil for backup heat?

Hot_water_fan

To pair with a furnace or hot water coil for backup heat?

Not sure about that. Do you need backup heat? 

paul1976nj

Hot_water_fan said:

To pair with a furnace or hot water coil for backup heat?

Not sure about that. Do you need backup heat? 

I'm in northern NJ, up high on top of a mountain. It's 10 degrees cooler up here than it is just 5 minutes down the mountain when I go into town. It's often near zero degrees F out late at night. The existing furnaces just drink natural gas at night during the winter, and my natural gas bills are sky-high and only getting higher. And the house is still freezing because of all the windows and serious lack of supply air and return air. The ductwork is so bad, that's why I want to rip it all out and redo it properly.

I know VRF heat pumps work down to like -4. But I fear they'd have to be crazy oversized in order to be able to effectively do that. Contractors who have come here who sell and are familiar with VRF have all been nervous about me not having a secondary source of heat that's natural gas-based (more than just electric heat stripis). And since they're all communicating systems with proprietary controls, I don't know how they'd marry up with hot water coils. With Daikin furnaces, they sure would. I could use Daikin's VRV Life systems paired with Daikin 2-stage (or even single-stage since it'd just be backup) furnaces upstairs (80s) and downstairs (90s). Not sure if Mitsubishi (which my contractor of choice sells) has anything like this.

TAG

They put 80% units in attics years ago because they were non condensing and there was nothing to freeze. You piss away 40 to 50% of what heat or cool you make putting a unit in an unconditioned space. Also -- any leak in the ductwork or imbalance with move the pressure point and introduce more outside air into the envelope. It's one on the worst things you can do IMO.

I can't fathom putting 4 systems in a house of 6k sf. Today, the infinity style furnace is fully modulating -- the output matches the load and the fan is fully variable. The 5 speed compressor has just that 5 speed.

You need a load done .... Carrier unit will go down to 25% of rated output. The fit is just a VS system .... just like the others. It just uses an Asian style condenser like a mini .... vs our traditional upright design.

With natural gas .... you want to use the gas. Our electric is expensive and even a 3+ COP does not save over natural gas

Hot_water_fan

Mitsubishi (not VRF) makes ducted hyper heat units that work much colder than -4. It doesn’t sound like the contractor has a handle on the heat loss yet, which is concerning. There are good reasons for gas backup, but not knowing the heat loss isn’t really one of them. 

paul1976nj

My natural gas is so expensive!

Right now I have 2.5 tons upstairs and all the ductwork is in the basement coming up in the interior walls, and the A/C struggles badly upstairs even on days in the 80s, and I am adding 420 additional square footage upstairs. Having new systems in the attic (which every single contractor without exception has recommended), I don't see how I could make do with less than 5.5 or 6 tons upstairs, given there will be some loss with it being in the attic.

Downstairs currently has 3 tons, two rooms with lots of windows struggle very badly to stay cool or stay warm enough in the winter, and downstairs is getting 780 additional square footage (and lots of windows in the two new rooms, with no second floor above them). Every contractor has told me I need a total of 6 tons downstairs and between 5.5 and 6 upstairs (ideally 6).

I've been researching this for months and next week I have to make the decision that I'll be living with for the next 20 or so years, and will be costing 6 figures. So I'm kind of panicking last-minute here about going the wrong direction. Two boilers with hydro coils and 2-stage A/Cs with variable speed air handlers seemed more "tried and true" and befitting a quality home (based on so many fine homes in CT, MA, etc. being done this way - and my climate here is pretty similar to theirs). It's interesting that I'm getting such different opinions, which I appreciate immensely!!!

ChrisJ

paul1976nj said:

My natural gas is so expensive! Right now I have 2.5 tons upstairs and all the ductwork is in the basement coming up in the interior walls, and the A/C struggles badly upstairs even on days in the 80s, and I am adding 420 additional square footage upstairs. Having new systems in the attic (which every single contractor without exception has recommended), I don't see how I could make do with less than 5.5 or 6 tons upstairs, given there will be some loss with it being in the attic. Downstairs currently has 3 tons, two rooms with lots of windows struggle very badly to stay cool or stay warm enough in the winter, and downstairs is getting 780 additional square footage (and lots of windows in the two new rooms, with no second floor above them). Every contractor has told me I need a total of 6 tons downstairs and between 5.5 and 6 upstairs (ideally 6). I've been researching this for months and next week I have to make the decision that I'll be living with for the next 20 or so years, and will be costing 6 figures. So I'm kind of panicking last-minute here about going the wrong direction. Two boilers with hydro coils and 2-stage A/Cs with variable speed air handlers seemed more "tried and true" and befitting a quality home (based on so many fine homes in CT, MA, etc. being done this way - and my climate here is pretty similar to theirs). It's interesting that I'm getting such different opinions, which I appreciate immensely!!!

You're heating a 5000sqft mansion it doesn't matter what you do it's not going to be cheap.  That's a large space to heat.

How is your electric bill for air conditioning?

paul1976nj

I'm prepared to invest what it takes to get a properly done system that is energy efficient, doesn't rely needlessly on excess fossil fuels, balanced, can keep the house at setpoint, and also looks good! My electric bill for A/C even with almost 20 year old original single-stage units is shockingly cheap, even though the A/C runs constantly (especially upstairs). Like a couple hundred bucks a month in the summer, seriously. It's the gas heat that's a killer, like around $600 in January and February.

Hot_water_fan

Two boilers with hydro coils and 2-stage A/Cs with variable speed air handlers seemed more "tried and true"

Quite the opposite - hydro air is extremely uncommon. Probably <1% of houses have it, and it’s usually because they had existing radiators. It’s fine, it’s just complex and unnecessary for most situations. 

Every contractor has told me I need a total of 6 tons downstairs and between 5.5 and 6 upstairs (ideally 6)

That’s concerning - they’re guessing. If 2.5 tons isn’t working, why is the answer to jump to 6? 12 tons for 6000 sqft in that climate is extremely high. 

Hot_water_fan

It's the gas heat that's a killer, like around $600 in January and February.

How many therms in January and February? That’s actually not that bad. Your heat loss might be lower than expected 

paul1976nj

It's currently 2.5 tons upstairs with all basement / interior wall ductwork, and I'm adding 420sf more plus the new ductwork is going in an uninsulated attic. The A/C is currently way undersized up there.

It's currently 3 tons downstairs, and I'm adding 780sf more, and both new rooms will have a lot of glass and no conditioned space over them. The A/C is currently undersized down there as-is, as two existing rooms with a lot of glass are extremely warm. The also heat struggles badly on cold nights on both floors, but especially downstairs in the rooms with a lot of glass.

Every contractor has said I'm way undersized on A/C currently and have insufficient supply and return air, especially in the rooms with a lot of glass. For whatever that's worth.

Hope this info helps. Also regarding the most recent heating season gas bills with two 90% furnaces in the basement (single stage) for the existing 5,000sf (prior to adding the additional 1,200sf):

December bill = 158.2268 therms
January bill = 311.3304 therms
February bill = 402.9480 therms
March bill = 337.3514 therms
April bill = 271.2180 therms
May bill = 163.6866 therms

Thanks!!!

TAG

Have you looked into getting an energy audit .... NJ used to have a fantastic clean energy program. Unfortunately they modified it and it not as good.

You need to get a blower door test done and a proper load done. Pay someone to do it if you can't get an audit done. What't the average temp through the year .... if you are 10 degrees cooler than my place in NJ it's obviously going to cost more to heat and less to cool.

House layout and design .... a wall of windows and the ducts on the other side is never going to be comfortable. Having a $600 bill in the winter with an 80% system and leaking house is quite possible.

NG has gone up but it's still cheap in relation to what it has been at some points in the past 30 years and much cheaper than oil and propane currently

paul1976nj

I had multiple contractors here who said they would do a Manual J and Manual D, but then they either disappeared (after telling me they were probably too busy to do the job until the fall which is way too late), or just point-blank told me they were too busy to do the job during the summer and told me to find somebody else. Others refused to do one, and also refused to help me with the rebates on the high-SEER inverter equipment. I'm down to a core group of very responsive contractors at this point to choose between who all have lots of 5-star reviews nearby me, but they don't seem to have the advanced knowledge about these more complex systems that the larger companies who dropped out did. In order to get the job done, I'm going to have to go with one of them (I need to sign a contract next week to stay on schedule with the builder).

Hot_water_fan

Rebate programs often cause more headache than they're worth.

Your usage shows 1643 therms used over six months. Ignoring all non-heating gas usage for now, that means you used 1478 therms for heating (after 90% efficient furnace). Over about 4400 heating degree days, that's only 33,370 Btus/HDD. On a day with an average temperature of 0 (probably colder than your design temperature), that means you'll use 33,370 x 65 HDD / 24 hours/day = 90kBtu per hour on the coldest day for the existing structure. Maybe 105kbtu including the additions? What'd they say your heat loss was?

clammy

In my experience hydro air is usually a 2 birds one stone deal , mostly to save money on installation and heating and cooling cost are at a higher energy uses . If you go w furnaces in the attic then your stuck w 80 % furnaces plain and simple. Using 90 u will build a conditioned space for the to occupy which won’t be cheap and a simple electric fan unit heater to keep me h room above freezing . There arguments on both sides . Personally I’m not for hydro air aside from all the up sides you hear . I feel way to much heat is lose through the duct work in attics even w proper air duct sealing and r 8 duct wrap all flex r 8 and all ceiling supply and returns cans being sealed and insulated . As w all air based heating and cooling systems most if not all the important issues are in the installation and are in the details which most over look being they require time ,skill and some basically caring enough about the overall quality of what your putting your name or companies name on which usually leave a great difference in quality ,lower quality work equals high operational and maintenance cost .
Personally i am a wet head even though I ve been in the Hvac field for getting close to 40 years I see more over all eff in hot water systems especially when It comes to trying too fit duct work where no one wants to lose a square inch at which point I ve had enough w nonsense and let some one else hack a roo it in . Being possibly in your area I can say w all surety and honesty good luck finding real Hvac quality workmanship aside from the as usual drive by installs . Professional Hvac installs don’t happen by luck or cheaply they like all things in life require a well though out plain ,a layout and realizing mechanical things get the biggest priority not a super kitchen or bath and when they dont get any priority and are cheaply installed the occupants are usually living in discomfort w high energy bills until they cry uncle and move and complain in between .
Wish u the best luck and peace
Clammy

TAG

Odd buildings require some thought .. lots of glass or rooms open on three sides have different loads. Equipment sized correctly to give long run times makes for a more comfortable house -- that's why multi speed and modulation adds comfort.

You have to get the ductwork correct. zoning should not scare people --- in fact it often makes poor ductwork better as it's able to run low and long if you get the multi speed equipment.

paul1976nj

The contractor I'm leaning towards most strongly is primarily a York dealer, but also sells Trane, Rheem, and Mitsubishi. So as far as brand goes, I need to go with what he sells. I know that a properly-designed system with not as high-end of a brand will work far better than a top-tier brand not installed correctly. Nobody here seems to recommend hydro air, which has been very helpful to hear so it is definitely making me reconsider on that.

Unfortunately with the equipment shortages, I can't get any of York's inverter or modulating equipment right now, or even their 2-stage A/Cs or variable speed air handlers. Not sure if I can get Trane's inverter or modulating equipment either, but can at least get their 2-stage equipment and variable speed air handler. If I can't get the Trane (which would be my preference, as would have been the York since they make 80 modulatings but apparently not right now!), but I can get all of Rheem's full equipment line, do you think their inverter heat pumps paired with 2-stage 80s in the attic and modulating 90s in the basement would be best? Or perhaps Mitsubishi Hyper Heat units with 6 small indoor air handlers (one for each zone) and electric strips for backup?

paul1976nj

One other question: I need a new water heater, and the house is too big (and am adding too many new bathrooms with the additions) to be served by a standard water heater, and everyone who's been out here also doesn't recommend tankless for various reasons. Boiler with indirect tank seems to be the best way to go. So that's part of the reason I'm considering hydro air. Also the Trane TAM9 air handlers seem to be designed for hydro air and can intelligently vary the blower speed up and down. If that all sounds good, having them be in the attic is my only remaining concern. Will glycol solve that? If so, how does it "shorten the life of the system"?

Hot_water_fan

One other question: I need a new water heater, and the house is too big (and am adding too many new bathrooms with the additions) to be served by a standard water heater, and everyone who's been out here also doesn't recommend tankless for various reasons.

Get a high capacity tank with a large burner, not a Home Depot special. Easy! No need for a boiler. 

You need a competent heat loss. You might need zero furnace/boiler backup, so you’ll be fine with modulating heat pumps, with or without resistance backup. Worry less about brands at this point. 

paul1976nj

I am working on having a proper heat loss and load calculation done ASAP to assist me and the installing contractor in making the right decisions, prior to any work being started. That is the message I'm getting loud and clear here over everything, and I really appreciate it! I will make sure that happens!

Hot_water_fan

I expect your heat loss is under 120kbtu based on that gas usage. Bigger is worse! 

EBEBRATT-Ed

@paul1976nj

The first thing is windows, doors and insulation. This will keep you investment down.

2. Accurate heat loss and heat gain..don't oversize the equipment!!!!!


Use Hydro air, you can get air handlers with both a heating coil and an ac coil. If the sizes don't match up by an air handler sized for cooling and install heating coils in the ducts. This would help with zoning.

Use a brazed plate heat exchanger to keep the glycol only in the attic piping and out of the boilers

TAG

hydro air was the the back up heat thought on my last project. With full radiant and boiler/ indirect it seemed like a natural. Just use the boiler and add on a hydro coil to the HP's air handler. When they priced it all out the cost to do the matching carrier furnace was not much more and I had no control issues with trying to integrate the hydro air. The house is propane and I wanted something other than the hp if the floors were off -- not a full time house yet.

Decisions often come down to cost and possibilities. Years ago with needed high temp flues and running far flung gas lines -- hydro was used as it was a cheaper install for an up and down install. Furnaces advanced overtime with more and more modulation --- hydro stayed the same needing high temp water keeping the boiler from condensing. I never ran into anybody using a boiler with ODR running a VS blower ... maybe someone makes the controls.

Basic 80% equipment and single stage AC is about the same comfort as the hydro ... it's on/ off equipment.

Can you use any of the existing equipment? Does the new layout allow ductwork to tie into any of the old equipment? it just not that hard to zone a trunk off of a furnace and control it.

I have done old houses where ductwork for proper heat was impossible ... there I did have to had various type of hot water.

paul1976nj

@EBEBRATT-Ed : How does using a brazed plate heat exchanger to keep the glycol only in the attic piping and out of the boilers work? Could you describe in layman's terms how this is accomplished, so I can understand the configuration?

@TAG : I thought hydro air would be a lot more money than furnaces, but surprisingly the quotes came in with it only being a small amount more, with the benefits of also being able to heat domestic hot water and not having to buy a separate new water heater like I'd have to with the furnaces. When taking that into consideration, it's almost the same price as furnaces. Now it is a bit more if I use the Trane TAM9 air handler, but I understand that's because that's a more advanced air handler that is smart enough to be aware of the presence of the hydro coil (because it can come from the factory with it installed), and for the Vortica blower to intelligently vary its speed with the water coil. Not sure other variable speed air handlers can do this as well?

If the hydro air route was a lot more money, I'd be reluctant to go that way. Also if I could get 80 modulatings in the attic I'd be more open to furnaces. But I don't want to deal with trying to put 90s up there or totally redoing the attic insulation. And I don't want basic 80 equipment.

The existing equipment can be re-used, it's working just fine. I was wondering if it'd be possible to just add a third system in the basement, zone all three systems, and have nothing in the attic. Ductwork changes would be needed of course, but that's not as expensive to do. The trickiest thing is getting additional supply and return runs up to the second floor from the basement. I'd have to tear open a lot of walls on the first floor. And I also have the issue of bad register placement upstairs because of limitations with where floor joists are, etc. - although perhaps some of that could be fixed.

Jon_blaney

Hydro air lets you get the air handler anywhere you want. You are spending a lot of money on this addition. Get the design to include space outside the attic for the heating equipment. High velocity air is you solution here. Central air handler, and small ducts in the ceiling.

TAG

The cost of the indirect will be more that doing a simple tank.

Maybe someone will comment on the Tam9 unit if you ask in another thread .. how does it work with multi-speed heat pumps?

IMO you want some form of gas heat when it gets cold ..... so you want to have ductwork for heat. For AC in an odd spot there are always mini split solutions for those strang places

GW

I read half then started skimming- that was long! I didn’t read any replies. Bear in mind you’re asking for hvac advice on a mostly hydronics page. Bear in mind not all guys tackle this larger stuff you’re describing. Not all guys do AC. A heating guy and hvac guy- not necessarily the same (putting it mildly) 

You CAN have communicating stats with air handlers- curious why you think otherwise. I have done carrier and Bryant comm systems with hot water coils. But as you indicated- comm stuff is severely short on inventory- best of luck. 

Also- no perfect answer to your question. Always some pros and cons. Just opinions to be offered 

Attic concerns- build rooms for the ahu systems. I don’t have any pix in my phone but I’d be happy to take some pics of my mech room in the attic. I have geothermal but same applies. In my several decade of being in the trades, I’ve never seen any attic mech rooms as decked out as my (can you tell I’m quite proud of it). 

I have a mech room in the basement too, boiler stuff

humidity- are you gonna tighten your home with all the dough flying? No reason your home should be drying out in mid winter—get that thermal envelop buffed up

5 ton for the second floor? Seems very excessive. I hope your hvac guy dials you in 

might you consider Mitsubishi or some mini system? May be the ticket if you’re thinking micro zones (my definition is under 500 sq feet). Mini ducted systems are more popular than ever 

Sounds like you’re gonna drop some serious dough- your hvac guy—-I hope he’s awesome because you’re kinda marrying him —so to speak. I click quite well with all of my customers, yet once in a while (extremely rare) I have a bumpy personality that pops out of nowhere. Could be a spouse. Could be a change of ideology as to what should e a “free trip”. I hope you like this person you hire (so to speak). There are not tons of guys that can easily and properly service all the technology you’re about to install 

Gary 

EBEBRATT-Ed

@paul1976nj

You can google a plate and frame hx. It's just a heat exchanger and has 4 pipe connections. Boiler water supply and return is on one side of the HX and glycol system on the other side. See attached.

You can download all the caleffi manuals on their web site. See page 17 of the attached for "brazed plate heat exchangers"