Large Restoration Project

Jed_2

Hi, all. I'm wrestling a bit with a large, 6800 sq.ft., 3 story National Registry Project where the entire interior is being gutted. Restoration will involve exterior being maintained, but interior will undergo a complete remodel. Load re-inforcing, partition remodel (many partitions will not be replaced, creating a fairly open floor plan), and entire envelop re-insulated (lathe & plaster ripped out). The new heating/cooling system will be Hi-Velocity SpacePak, powered by two semi-redundant boilers, and 5 SpacePak WCSP-D Air Handlers. The Cooling system will be driven by a SpacePak ICSD-120 indoor air-cooled water chiller (as long as we can get the air intake/exhaust figured out). The heating Load is 275,000 BTUH; and the cooling load is about 8.5 tons.

My dilema is whether to add heating coils to the air handlers, or try to operate the system as a switch-over. Piping would be P/S in either case, just whether or not to add independent P/S circuits. What brings this question into focus is the existence of wide and very open stair wells between all floors (ceilings are 13', 12', and 11' respectively for the three floors). Zone interference? This must be done right the first time. Correct strategy is a must.

I'm asking for wisdom I may not have for this.

Regards,

Jed

Constantin

I'm just a homeowner but...

... since I just am going through a complete historic gut job myself, I thought I'd chime in.

For one, I would consider radiant floor heating. Not only is it more efficient, it also heats large, well insulated homes very well and very evenly. Not having twenty AH's running at the same time helps retard the movement of air in the place and hence the tendency for everything to infiltrate up and out.

Depending on what system you're specifying, you may discover that a radiant system has a small marginal delta in up-front cost that the customer may be willing to accept.

Anyway, to come back to your previous question, you could consider fitting the AH's with secondary heaters, or you could simply run the piping and leave the access to do so at a later time, if necessary (i.e. a insurance policy). Then install a 2-stage thermostat and have the AH's kick in whenever the primary means of heating the place does not keep up.

greg_7

I may be out of line here, but why does everybody seem to be so eager to dump the radiators?

My 1910 house is over-radiated and warm, thanks to those ARCO behemoths.

What about Burnham Base-Ray cast base board as an option?

Brent_2

2 pipe or 4 pipe

The obvious is with a 2 pipe system you can not have heating and cooling at the same time. With a normal house this shouldn't be a problem but I don't know your project. I guess you have to examine what is going to happen at the changeover temperature. i guess I would run wiring from each zone to the mechanical room so I know if a zone is calling for heating or cooling. If you have a 2 pipe I would look at shutting down the heating system above 65° OAT and no zones calling for heat. I would include a delay timer of maybe 30 minutes where the cooling system could not start right after the heating system shuts down. You don't want 140° (or whatever I'm assuming HW reset) hot water dumping into the chiller. You can check to see what the highest EWT the chiller will tolerate.
I guess it comes down to costs. With 4 pipe you have a second coil in each unit, twice the piping thru the building to the air handlers, and a second zone valve at the air handlers.
With 2 pipe you have changeover valves in the mechanical room and a more complicated control system.

brent

Constantin

By all means...

... keep the radiators, if you have them. As you pointed out, most of them are way oversized WRT the heating load they have to carry in a well-insulated house. However, not every homeowner is lucky enough to have period castings standing around, crying to get used.

For example, our house was stripped of the gas lighting, the coal stoves, etc. that used to illuminate and heat it. We were left with a hot-air heating system that didn't work very well and a couple of register covers that don't appear older than the 1950's.

In other words, we had no infrastructure worth saving. Thus, we were happy to choose radiant heat since it's unobtrusive, efficient, and very comfortable.

dconnors

Hi-Velocity

Most require hot water temps in the 200 degree range. what a waste when its only 30-50 outside. go with Rads. and modulate the water temp to the outside temp or use variable spped air handlers.,

Jed_2

4 pipe it is

Brent, you hit it on the nose. Shoulder months, and wait a minute (if you don't like the weather, this is Maine). Plus the stack effect of the large stair wells. Cooling could be called for on upper floors, while the first floor may be o.k., until the open circulation takes hold, then some heating could be needed zonally. T'stats could be set to manual for individual control. Hot water temps to coils don't need to 200°F, but flow needs to be correct.

Existing radiators are all Steam only rads, and the steam boiler is "outa here".

The concensus of respondants is "go radiant". In this project, which I confess to not supplying adequate info, is not the right strategy. Most of the wall space will be filled up with book shelves, and supplemental heat would be required. Significant supplemental, given floor construction and heat loss, would be needed. While budget is not an issue, design sensibility is. RH and environmental issues are priorities. You could say mix RFH and Hi-Velocity, but let's not get too carried away here. And then there is DHW! No, I think the 4-pipe is the way to go. SpacePak even has introduced a nice PurePak recessed air cleaner for the return grilles.

Brent, I follow your reasoning, but I don't understand the "second zone valve" comment. Each coil would have a circulator. We could even use Taco VS series, per coil. No variable speed blowers available. Can you elaborate?

Jed

Constantin

Call me crazy...

... but I still have not seen a good reason why radiant floor heat should be out of the question. In a well-insulated, home it'll provide even heat with an unbeatable efficiency. Then optimize the AC system to cool the home.

I have yet to see an AC system in a home that works just as well cooling the place as it does heating it. Inherently, design choices have to be made about duct sizes, duct balancing etc. that result in sub-optimal performance in one season or both, starting with the position of registers and ending with the induced air currents in the home.

In our home, the forced-air heating system went out and was replaced by radiant floor heat. Even in cold weather with the windows open, the place is warm, and incredibly even-heated. No stacking effect that I can detect. Plus, you could always pull out hot, stagnant air up there with an HRV and blow fresh warm air back in on a floor lower.

The AC system is conventional but was split into two units to provide cooling on all 4 levels while minimizing ductwork chases (considering that a Victorian doesn't have chases). Most of our ductwork runs inside 4" interior walls, with some closets shrinking somewhat to accomodate return ducts. Every room has a return, every register location has been optimized for cooling.

So, if budget truely is not of concern then at least give your clients the option to go RFH. OTOH, it seems like you've already made up your mind, oh well.

PS: For some truely out of this world efficiency in heating and cooling the place at the same time, consider going with a GSHP and install a desuperheater. Not only do you get the DWH hot for free during the summertime, it'll also heat and cool the house at the same time for almost nothing.

Lastly, you could consider a ceiling-based radiant heating/cooling system like the stuff from Karo. Then, your duct requirements shrink considerably since you only have to worry about removing latent heat in the cooling mode. Your water-based chiller would be compatible...

However, such an innovative system would require a level of building sophistication that is probably outside your reach. As intrigued as I was about it, playing beta-tester with advanced technologies in my own house is not my idea of fun either. In the EU on the other hand the technology has been been proven and more people have experience with it...

Jed_2

But, in this home

Radiant WON'T heat the place. GSHP?, get real. This is in a residential neighborhood in central Maine.

Ceilings will NOT be touched, as crown mouldings and ceilings will stay in place. Ceiling radiant is not an option.

constantin, you obviously don't know much about Hi-Velocity. 2" Supplies, 9" Trunks, which can be integrated by floors, since there will be 5 distinctive Zones, or AH units. This is a Hydro-Air heating-Cooling system, not combination "scorched-air/cooling". There is a difference.

Insignificant Latent heat heat in this home!

Jed

Weezbo

are there speed drives made for the space pack?

Constantin

Interesting...

... on the one hand, this is going to be a well-insulated historic home, on the other hand, radiant floor heat can't keep up? When I insulated the exterior walls in my home, the infiltration went for a tailspin and design-day heat-losses approach 16BTU/ft² at -15°F. In a 1872 Mansard with 6 foot historic windows and all that jazz.

So, from my perspective, something doesn't add up. Does this home have 16' wide French doors, glass walls, or somesuch? Since you've apparently done the heatloss calculation, what is the worst-case design-day heatloss per square foot?

For that matter, don't discount a GSHP outright just because you're building in downtown Augusta or whatever. Deep vertical stacks have been bored even in places like NYC. If they can do it... of course, NYC doesn't have ignious bedrock right under most of its surface either!

... and I have been to several homes with high-velocity systems. The funny thing is, I could always tell which rooms were heated with radiators or radiant floor heating vs. the ones on a hydro-air zone. That doesn't make me special or the installer of the Hi-velocity system incompetent, I simply didn't feel as comfortable in the rooms with Hi-vel systems as in ones that had other (hydronic) means to heat them.

The big trump card that high-vel. manufacturers seem to always trot out WRT their 2x colder ΔT coils is superior latent heat removal... not a problem in your neck of the woods, it appears. Thus, you'll have to upsize your system to remove enough sensible heat. IIRC, in SEER terms, high-velocity AH have lower HX efficiency than comparably-equipped low-velocity AH as a result. But I am happy to be wrong.

I also happen to prefer the permanence cleanability of insulated metal ducts over the plastic socks that Unico, et. al are selling. Perhaps your solution can offer cleanability and high efficiency, perhaps neither is a design consideration.

So, while I agree that a hydro-air system will give you better air temperature control than a furnace, I don't think that using a hydro-air coil is necessarily an insurance policy for even heat, comfort, etc.

Naturally, feel free to disagree. Best of luck with your project. May your ceilings and crowns last longer than ours did (despite our best intentions). Considering the structural work you're describing, maintaining ceilings and crown-work will be pretty challenging.

Brent_2

4 pipe

I was thinking for a 4 pipe system you would have (5) 3-way valves for CW, & (5) 3-way valves for HW. With a 2 pipe system you would have (5) 3-way valves.
I guess since you are using pumps you will have 5 pumps for CW & 5 pumps for HW (plus the system pumps).
Don't forget you have to insulate every inch of chill water piping so you won't be able to run it in existing walls.
I am assuming the manufacturer recommends having a CW storage tank to increase loop volume.

brent

Paul Pollets

My 2Cents

Having done many a historic remodel, I'd be looking to use wall panel radiators, if wall space allows. The HV HW coils can be used for supplemental, but I would try and shed the major heating load to radiators, with cast iron B/B as a 2nd choice. Especially in Maine, you'd feel the difference with radiators vs. air side coil heating.

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Jed_2

60 gallon

is what the manufacturer recommends. And all CW piping (HW as well) will be insulated. Large, open basement to run primaries. There is absolutely no wall space for C.I. bsbd or panel rads. Majority of space will be taken up with book shelves. I haven't done the flow analysis yet. But, I'm considering 45-50°F chiller leaving temp, with about 10-12°DT. And the AH trunks will be GR8 Red Round fiberglass, with R8 insulation. Radiant analysis required between 32-37BTUH/SQ FT (kitchen area vs. great room). Walls, while being stripped and re-insulated, are 3-1/2", so R-11 it's going to be. The first floor Great Room alone has 483 sq.ft. of glass&doors, and is about 1720 sq.ft., with 13' flat ceiling.

Will t'stat on manual be o.k. to set room temps if there is zonal interference?

Jed

p.s. Weezbo: no variables for blowers available