Only six zones?

DeathValleyDog

I'm designing a new hydronic heating system for my house, and it looks like I'm going to have 8 zones, with mostly radiators, but in-floor in certain rooms (like the bathrooms ... because who doesn't like that? )

But I can't find any zone controllers that do more than six zones. Is there one out there, or would I just use more than one------like a 4 and a 4, or a 6 and a 2?

[Note: obviously not a pro, just a hard-core do-it-yourselfer. I built a hydronic heating system for my old house nearly 20 years ago, back when Munchkin boilers were all the rage. Looks like the industry has come a long way since then ]

Zman

You can just gang them together as you suggest

kcopp

8 zones is a lot... how many sq feet is the home? I would caution you about micro-zoning..... this will cause the boiler to short cycle. Not a great situation.

hot_rod

The Caleffi relays gang together with a 3 conductor thermostat wire, upper right connections, as many as you need.
DHW priority is always zone 1 on the first box.
They all need 120V supplied of course.
Unique to the Caleffi ZCR is the 3 configurable pump outputs, for multiple temperature systems, indirects, etc.

DeathValleyDog

kcopp said:

8 zones is a lot... how many sq feet is the home? I would caution you about micro-zoning..... this will cause the boiler to short cycle. Not a great situation.

It's technically two homes, as we're converting about a 900 square-foot section of a 4000 square-foot home into a distinct and separate mother-in-law unit.

How would you define "micro-zoning"?

With my current plan, each zone is a defined space that can be closed off by a door. Bedrooms and bathrooms are each their own zone, and the larger, open space of the kitchen/living room/dining room area (in both the main house and the MILU) are just one zone each as well. They'll probably have more than one heating loop each (again, using wall radiators) but are definitely just a single zone with a single thermostat deciding when heat is called for.

I also have an office that used to be bedroom, but we took down the wall that separates it from the living room in the main house, so it's more of a nook now, and it will also be included in main living area zone.

So those are my "zones". Any rooms/areas that can't be separated from each other by a closed door are a single zone.

Have I effectively avoided "micro-zoning" or am I not understanding the definition?

And I'm honestly asking without pretense. It's been quite a while since I built one of these things, and I'm here to learn

STEVEusaPA

I'd recommend getting you plans over to someone who designs hydronic systems.
First of course is a complete heat loss.
Then they will do all your calculations on something like Wrightsoft and provide you with piping diagrams, tubing lengths and call outs, near boiler piping diagram, flow rates, and equipment call out.

DeathValleyDog

STEVEusaPA said:

I'd recommend getting you plans over to someone who designs hydronic systems.
First of course is a complete heat loss.
Then they will do all your calculations on something like Wrightsoft and provide you with piping diagrams, tubing lengths and call outs, near boiler piping diagram, flow rates, and equipment call out.

Thanks for the recommendation, but half the fun is figuring it out and designing it. That's why I'm here

The other half is building it, and (most of) the system I designed and built 20 years ago in my old house is still providing the folks who bought that place with warmth.

I say "most of" because they did finally replace the old Munchkin boiler ..

Alan (California Radiant) Forbes

If one bedroom or bathroom is zoned on it's own, that's microzoning. Not the end of the world, but you have to keep that in mind when you're planning your boiler room so that your boiler doesn't short-cycle like crazy. Add a buffer tank. Caleffi has some good information here.

hot_rod

One definition of micro-zone could be a btu load of the smallest radiator lower, maybe much lower then lowest turndown of the boiler.

You can find mod con boilers that turn down to about 7,000 btu/hr.
Most of the better mod con boilers brands and models have a whole range of settings to help eliminate short cycling, ramp delay, anti cycling time out function, output limiting, etc.
Read up on those features when you boiler shop.

If you have a building with multiple uses and rooms sometimes micro zoning is not avoidable. A room by room or zone by zone load calculation is your friend to prevent an inefficient problematic short cycling boiler. the more calculating and planning before you shop and build the better the results.

A high volume boiler or buffer tank are other good options.

DeathValleyDog

hot_rod said:

A high volume boiler or buffer tank are other good options.

Navien-240E is the current plan for the boiler.

I'm a bit limited on space in the boiler room, so not a lot of room for a buffer tank. I could maybe fit a small 25 gal, but it would be tight.

Alan (California Radiant) Forbes

Will this boiler be heating 900 [] or the entire 4000 []? You can't really choose a boiler until you know the demand and you won't know the demand until you do the room-by-room heat loss calculations.

Do a search on this website, "Navien 240E", i.e. without the hyphen to give you some more background on the boiler.

HVACNUT

Do P/S piping and outdoor reset. You're still micro zoned but that will help. Tekmar had a zone board that would stack the heat calls until they all called and all ran at the same time. I don't know if it's still out there. 

EdTheHeaterMan

The buffer tank does not have to be in the boiler room. Try to keep it close but it can go under the steps or under a bathroom sink with an oversized vanity cabinet. place it in a closet with a box over it. You are just adding some volume to reduce short cycling.

hot_rod

I've been able to get a stubby 25 or 35 under the boiler in a tight space restriction. it depends a bit on how the venting works out. A hydroseparator and associated piping can add a couple three additional gallons.

I'd like to try one of these 300 Viessmann on a micro zoned systems, they have some fluid content and also some mass (weight). Maybe they are crazy expensive? I don't hear much about them.

The HTP tank type, Voyager, Phoenix, were great for micro loads.

DeathValleyDog

Alan (California Radiant) Forbes said:

Will this boiler be heating 900 [] or the entire 4000 []?

The entire 4000, so effectively two complete homes.

On the DHW side of it that means: two kitchens w/dishwashers, two clothes washing machines, and a total of four full bathrooms. Also one outside shower, and an outside kitchen as well (probably no dishwasher for the outside kitchen tho, just a sink)

So there will be fair amount of demand. That's why I'm leaning towards the big Navien.

hot_rod

Most of the water heater manufacturers have formulas for sizing DHW.

Back when, we assumed 20 gallons per person per day. Or 20 for the first 15 for additional family members. With low flow faucets I'd guess more like 15 per day, 10 for additional. This was for tank sizing.

Tank temperature matters. running a tank at 140 or 150 and mixing to 110 will extend drawdown. it also shortens tank life expectancy!

Any high flow faucet or multiple shower sprays will throw a wrench in the works for combi or instantanous type dhw appliances. I think code compliant showers are 1.5 gpm now. A couple high flow heads or body sprays could use the entire tankless or combi output.

At some point the occupants get used to the amount of dhw that is provided
Back in my ski bum days, 6 of us got by with a 40 gallon tank in the rental homes.

DeathValleyDog

HVACNUT said:

Do P/S piping and outdoor reset. You're still micro zoned but that will help.

The Navien has an internal pump, and all the design examples show that as powering the primary loop, if I'm understanding it correctly. Also comes with an outdoor temp sensor, and a programable Outdoor Reset Control mode on the unit. So it seems like I'll be good on that

SuperTech

A buffer tank is the answer if you have lots of small zones. If you have a mod con it can help keep the boiler running more efficiently and condensing more. If you have a cast iron boiler the buffer tank can be used to help avoid flue gas condensate formation and other issues from short cycling.

DeathValleyDog

hot_rod said:

Back in my ski bum days, 6 of us got by with a 40 gallon tank in the rental homes.

I bet those were some short showers

Hey Hot Rod, you being the Caleffi guy: I'm doing the calcs for what size buffer tank I might need to deal with my potential short-cycle situation with all my tiny zones, and I'm curious what determines the "allowable temperature swing" in the buffer tank.

Using the formula on page 28 in the issue of Idronics that Alan Forbes so graciously linked to above, I'm coming up with only 14 gallons if I plug in a 20 deg allowable swing. Change that to 10 deg, and of course it doubles.

What factor(s) determine what that "allowable temperature swing" should be?

Note: my numbers are based on the Navien modulating down to 18,000 btu with my smallest zone needing 3,300 and a minimum cycle time of 10 minutes.

hot_rod

The input to the tank could be as wide as you want, even a 60° delta. One goal with a buffer is maximize that drawdown time.

Charge the tank to 180°, pull down to 120° or whatever the lowest SWT your system can use, with a mixing valve or outdoor reset controlled valve.

With a mod con you may not want to run much more than a 140° tank temperature to keep it condensing and as efficient as possible. So 140 down to your lowest useable SWT. That is why I keep promoting low design supply temperature. It maximizes the buffer, keeps the mod con running 90%.

With conventional boilers, wood, pellet, solar, we charge the tank to 180F or more to lengthen that off cycle.

You are on the right path, just keep juggling the numbers to best suit your design, and pocketbook

DeathValleyDog

hot_rod said:

... just keep juggling the numbers to best suit your design, and pocketbook

Oh, I'm definitely juggling. I feel like there's a constant soundtrack of circus calliope music running through my brain

I was looking at some other threads on the forum where someone had added a buffer tank to a system with a Navien combi-boiler specifically due to micro-zoning, and came across one from Feb of 2019.

Both you and Bob B. (Ironman) had commented about potentially not having any sensors at all in the buffer tank, and just using it as extra mass.

If I was going to go that route, how do you feel about 4-pipe vs 2-pipe? Based on what I read in Idronics I'm leaning toward 2-pipe, but I might be missing something.

The Navien comes with an outdoor temp sensor and the option to use ODR (although it kinda looks like an afterthought ... maybe just a recent addition to the product? I could be wrong) but it doesn't appear to have any other "system sensor" options to monitor the buffer tank temp.

hot_rod

You could just install a simple setpoint control to run the buffer tank. I think you could use the air handler contact, wire an electronic controller like this. Depends if you want to maintain the tank hot, or enable on a heat call.

I prefer the two pipe buffer, simple piping, easy to source or modify an off the shelf tank.

DeathValleyDog

hot_rod said:

Depends if you want to maintain the tank hot, or enable on a heat call.

Not sure which way I'm going to go yet. Still trying to learn about all the factors I need to consider.

We're in a pretty mild climate. Rarely gets above 100F in the summer and very rarely drops to freezing in the winter. There will probably be a solid four months when heat won't be used at all. The house is also quite well insulated.

Still figuring out exactly how all of that plays into it, but I'm sure it does.

DeathValleyDog

The good news is that think I figured out a spot for the buffer tank.

EdTheHeaterMan said:

The buffer tank does not have to be in the boiler room. Try to keep it close but it can go under the steps ...

There will be a staircase only about ten feet away from my tiny boiler room, and I was always wondering what (if anything) I was going to put under it. Now I know

Thanks, Ed

hot_rod

nice to put a drainpan under tanks also, pipe to floor drain if possible.