Hydronic System Design & Boiler/Piping Control

HydronicComfort

Ok, we are installing a new heating system in a rental property. The old unit was an oil-fired boiler with fin-tube baseboard convection. That system was vandalized, so we start from scratch.

We are installing a gas boiler; initially propane and then to Natural Gas when the gas utility gets around to installing the gas line from the main to the house.

The home is on a slab. We are planning to utilize Viega FostaPex (Pex-Al-Pex) in a series loop configuration for each zone (2). We don't want to trench the slab, so we are open to suggestions as to the best way to run the pex tubing.

The boiler will be a cast iron New Yorker CG-D Series 20 boiler. It's rated at 37.5 BTUH 31K AHRI & 27K IBR. 82.3% Efficiency. 2.5 gallon water content. Has pre- and post-purge control. It will paired with a 50-gallon BoilerBuddy buffer tank and a SuperStor 45 gallon IDWH.

The home has a calculated heat loss of 24,672 BTUH. It will be split into 2 zones; one for the living, kitchen and dining room areas (Zone-1 13,775 BTUH) and bedrooms and bathroom (Zone-2 10,897 BTUH). Programmable thermostats will be employed for each zone. Zone valves will be employed for each zone.

Design temp is for 72-degrees on a 10-degree day. Average water temperature is 140-degrees @ 1 gpm. Zone-1 flow is 1.46 gpm and 10.32 ft head; Zone 2 is 1.06 gpm and 9.6 ft head.

An outdoor reset control will also be utilized. As this will result in return temperatures below 130-degrees at certain times, we'll need a way to control the return temps and keep them above 130-degrees. We understand Taco makes a 4-way mixing valve (IO75T4R-1) to accomplish this and Tekmar makes a 402 control which would control a mixing device, zone valves and allow for separate IDHW control utilizing different supply and differential for both the boiler and IDHW. We believe you must use Tekmar thermostats to work with this controller.

We'd appreciate a few things:

Comments on this design and ways to implement it. We don't want to install a mod-con boiler due to initial cost (~ 3K vs ~1k), life expectancy, reliability and maintenance costs.

A way to calculate how to size each successive fin-tube convector as water temperatures drop in the series of convectors. The sizing in the attachment is based on 140-degree average temperature with no consideration for diminishing temperature as the water travels in series.

A schematic diagram of this layout, if someone has a program to do so, so we can provide it to our installer.
You can find this at this link: http://www.terrylove.com/forums/index.php?threads/hydronic-system-design-boiler-piping-control.58590/#post-432722

I'll try uploading the floor plan and fin-tube convector sizes and location. Z2 R1 is Zone 2 Radiator 1 (the first in that zone series). Scale is 1/4" = 1'.

Thanks!

Rich_49

Hydronic Comfort . I am curious about some assumptions you have made concerning pricing of various technologies . Since prices are not to be discussed in the forum would you contact me privately ? You can install a less complicated more efficient system for quite possibly less outlay than I believe you are looking at . Interested , let me get you looking than come back here for others to comment .

Rich_49

Here is your system . Think more about where you will operate as opposed to the upper end size , you'll never be there . You have a one bath so this will be perfect .
No buffer tank , no indirect tank , no complex controls , no separate air elimination , no dirt eliminator , no special thermostats .
One appliance , 1 zone valve relay , 1 pump , 2 thermostats . Save your money and effort and move along . This is simplicity and elegance from 2 American manufacturers that stand behind their products with no B/S excuses . Use a manifold from Viega to hit each room individually and keep the head loss down , use lower water temps because you don't have to increase them in the beginning of series loops and use the Bumble Bee . If you go series loop you may require the 008VDT and decreasing temps becomes much less of a math headache .
If your tenants pay the bills this will also make it more attractive and charge them accordingly . All for the same or less money than you are speaking of spending .
By the way , I have already verified that these components and labor would cost me roughly 50% less to install in your home . Maybe you can buy better than me ?

http://www.htproducts.com/literature/HTP-Versa-Flame.pdf
http://www.htproducts.com/literature/lp-378.spec.pdf

http://www.taco-hvac.com/uploads/FileLibrary/100-101.pdf
http://www.taco-hvac.com/uploads/FileLibrary/100-68.pdf
http://www.taco-hvac.com/uploads/FileLibrary/100-87.pdf
http://www.taco-hvac.com/uploads/FileLibrary/100-82.pdf

Go ahead gentlemen , let's here your opinion for our new friend .

Rich_49

Please install a Poly propylene venting system if you go this route . It won't take much to get out of the house to an approved area .

Tim Potter

Here is a ton of info:
http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_12.pdf

pg 63 deals with different piping schemes
pg 74 deals with figuring out convector length based on heat loss for specific room

Happy Hunting:

Tim

HydronicComfort

I looked into the HTP product. Nice that it has a built-in buffer tank to help with the oversizing for my system. But otherwise, it's the same old mod-con deal. Hardness, chloride, pH, TDS and sodium standards for water. Annual maintenance including an hour just to service the DHW heat exchanger and flush it with vinegar. 12-year warranty with many exclusions as to why it would not be covered under warranty. So, it really goes back to the reasons I don't want a mod-con: purchase price, reliability, life expectancy and maintenance costs. I believe it's less expensive in the long run to put in a less efficient cast-iron boiler than a mod-con in my system.

Rich_49

Fair enough . My suggestion then would be to simplify the system . Use your boiler , buffer tank (not sure you need a 50 gal ) 20 - 25 gallon would probably be good (HTP SSU20-B, top right corner of brochure) , and indirect . I would also shrink the indirect to 20 or 30 gallons ( SSU20 or 30 ) , store at 140* and use a domestic 1017ASSE mixer ( Taco 5000 series) . This will satisfy faster and perform well in this house with that small boiler .
Get rid of the Tekmar stuff and use the buffer to store 180 - 190* , use the Aquastat in the buffer to fire the boiler when tank reaches 160* , boiler is protected . Use a Taco I Series 3 way ODR valve on the system side of buffer tank . Don't forget dirt and air elimination , I suggest Caleffi DISCAL # 5461 for your application. Just hate to see anybody making it more difficult than it has to be .

http://www.htproducts.com/literature/lp-81.pdf
http://www.taco-hvac.com/uploads/FileLibrary/102-145.pdf
http://www.taco-hvac.com/uploads/FileLibrary/100-100.pdf
http://www.taco-hvac.com/uploads/FileLibrary/102-431.pdf

HydronicComfort

How do you calculate the water temperature drop as it flows through series fin-tube convectors?

icesailor

"" Get rid of the Tekmar stuff and use the buffer to store 180 - 190* , use the Aquastat in the buffer to fire the boiler when tank reaches 160* , boiler is protected . ""


You should NEVER store potable domestic water that hot in a storage tank no matter what you use it for. The hotter the stored water, the faster the tank fails. And it may void warranties because to store water at over 150 degrees (180 degrees) might be considered commercial use application.

I've had 80 gallon Super Stores (Replaced a Vaughan stone lined 80 gallon) that ran at 140 degrees in a 5 bathroom house with dual showers and body sprays that never ran out of hot water when mixed down with a quality mixer.

180 degree water is not only unsafe, it is often illegal unless it is a single point use like a commercial laundry or dishwasher.

icesailor

For shell tanks, the higher the temperature of the water, the faster the tank wears out. That's common knowledge. Just because something is theoretically better, doesn't mean that it is practically better.

People throw the term "Buffer Tank" around like cream for coffee. Indirects can be storage tanks or buffer tanks. This discussion has become so convoluted that I doubt that anyone remembers how it started or what the issue. I certainly don't.

Rich_49

Just so we are clear Ice , a buffer tank is a buffer tank and if I had meant to say use an indirect as a buffer I would have .
What good would a buffer tank connected to a cast iron boiler be if it could not store 180 - 190* water ? None is my guess , and the HTP buffer tank mentioned is in fact capable of exactly that . Please do not mis quote or use what I say in any context other than how it was stated . I have a pretty good command of the English language and say what I mean .
- I do agree that one should never store domestic hot water at 180* , that is why I never write to store at such a temp . My reference was strictly for a space heating buffer tank .

icesailor

You understand that with beer can water heaters being used as Combi units (DHW & Heating) that "Buffer tanks" are being used on Potable water heating systems to run radiant heating zones.

There's nothing new about using Potable Water Heaters for heating buildings. It was a craze where I worked in the early 1960's with oil fired water heaters. There wasn't enough heat to heat the buildings, and you scalded the crap out of yourself in the shower. Then, the water heaters failed.

There was a resurgence of this great idea in the 1990's with using Bock oil fired water heaters as the energy source. They rotted out and leaked. With the installers never to be found again.

What are we calling "Buffer Tanks". A heating storage tank? I've seen some pretty big open storage tanks for Solar Systems that vermin get into.

I'll never be installing one now, but we now have all these "Combi" beer cooler boilers with the thin shell DHW tanks. Before I left, they had already shown up and were leaking. Standard glass lined water heaters leak soon enough. These others go even faster. Buffer tanks are just another way of artificially increasing the flywheel effect of the heat source.

Put a storage tank on an oil fired boiler with a tankless/indirect coil. Call it a buffer tank if you like. Its still a storage tank. Do the same with a Beer Cooler gas water heating boiler, its still a storage tank but it's a band aid on the flaw of the boiler design. Namely to cover up the lag of a boiler to start and them make water.

Put it on a heating only boiler and it is like putting a Band-Aid on an infection. Its still there, just covered up.

If I got all my types and tenses mixed up, I'm sorry. I'm not intentionally trying to put words in anyone's mouth or postings.

Rich_49

If you've been reading what I write and what I use you would know that I do not use beer can anything > I use highly insulated Stainless Steel stuff made in Mass for the most part . A buffer tank is a buffer tank and an indirect is an indirect unless I say that I will use it in an alternative arrangement .

icesailor

Super Stor's (of which I have installed a lot of) are not something I consider buffer tanks. But I've seen some here ask about using them as such. I also installed quite a few Munchkins. The computer program is still installed on this computer.

The manager at the wholesale house that I traded with named them "Beer Coolers" because of the foam cover. They sold a lot of HTP tanks, no boilers except the Peerless Pinnacles. Which ran a whole lot better on the #80's and you had shut down problems because of wind and they were vented 3" and you put a 3" X 2" PVC bushing in the exhaust to give it a touch of backpressure. Or so I discovered when asked to help others that had that problem.

To my sensibilities, a TT type tank with a tank within a tank is still a "Buffer Tank" or whatever you want to call it. A water heater storage tank installed after a Mod Con DHW heater is a buffer thank or whatever you want to refer to it as.

This is my long time experience. Whenever I had to replace a power vented gas water heater, I was always asked about wall mounted high efficiency on demand water heaters like Noritz. I always carefully explained before hand that they might object to the fact that with short or very low draws, they might object to the fact that the water might get cool for a moment while the systems re-aligned their Sun and Stars. So they needed a buffer tank and all the pumps and controls to work it. It would cost considerably more money for the install. And needed room for the equipment under the house because it wouldn't fit in the closet they were gaining.

I never replaced a Power vented tank type water heater with an instantaneous one. My customers weren't cheap. They were careful. I never had to explain something that I hadn't forewarned them about. I see it here all the time. Someone sells and does something that they don't understand. They end up with unhappy customers who want answers. They either can't give the answers, or if they do, they are going to get serious blow back from a customer. So they walk. After a few others, they called me. You must know how much you can learn from the mistakes of others. Its like a free class that you get paid for.

Rich_49

I don't consider SuperStors buffer tanks either , mostly because they are not . The SSU20-B is a proper buffer tank , thus the B at the end of part number . Where in the hell did instantaneous water heaters come from ? They have not been mentioned in this discussion unless I missed it . I hate tankless stuff , big scam if you ask me .

Zman

I have a few questions,
Why are you using 140 degree design temp with a conventional boiler?
Where did you come up with the head and flow numbers in your drawing.
At first look, if you set this thing up with the boiler coming on at 150 and off at 180, you don't need the buffer or the boiler protection loop.
I am just not sure I see the advantage of outdoor reset and buffer and all with a conventional boiler.
Yes, you will prevent some overshooting the t-stat setpoint. With a low mass system is it that big a deal. There really is no efficiency gain.

It is hard to tell with the suspect flow numbers, it looks like you will see a supply/return delta t of less than 10 degrees and the buffer tank would not be more than 20 gallons.

SWEI

Sidestepping the discussion of which boiler here to address the emitters. Is the existing slab insulated underneath? Around the edges? The latter can be remedied, the former can not. An uninsulated slab will waste roughly 30% of your fuel heating the earth. Better to put plates and tubing into ceilings and/or walls by far. Head loss also looks quite high -- consider using more loops of shorter lengths which should roughly halve your pumping costs with but a tiny increase in the first cost.

Chlorides and pH are a big deal for the potable water portion of your indirect. A properly installed and commissioned heating system is sealed and will not need makeup water. When the potable water has issues, we bring in suitable water to fill them.

How long do you expect to be burning LPG? Currently available mod/con boilers are not subject to the problems with older designs you are no doubt seeing online.

HydronicComfort

We picked 140-degree average water temp as a compromise between efficiency and recovery from setback thermostats.

The high head is from running drops to and from attic; that is being changed: we are going to run the piping primarily through dummy baseboard covers.

Yeah, for the living room, the floor represents 20% of the heat loss. It will be padded and carpeted, so actually less than 20% with that included.

The buffer tank is to decrease boiler cycling.

Tekmar controls to have outdoor reset, boiler protection and separate setpoints for heat and DHW. They have been very responsive and helpful with this project.

LPG will just be utilized for a little while until the NG line can be installed from the street.

Mod-cons were initially considered, but due to the lower life expectancy, potential for problematic operation and increased initial and maintenance costs we've decided to go with a conventional cast-iron design, sized as close to the load as we can find.

Can someone inform me on how to size successive fin-tube convectors in series with diminishing water temps?

Thanks!

icesailor

Rich said:

Where in the hell did instantaneous water heaters come from ? They have not been mentioned in this discussion unless I missed it . I hate tankless stuff , big scam if you ask me .

I sort of thought (wrongly) that the old Burkay Commercial gas water heaters that they used in restaurants and laundry's were the first "Instantaneous" water heaters. Next came the almost instantaneous electric water heaters used as booster heaters for commercial dishwashers for the 180 degree water. Give that squirrel enough nuts and it would eat its way through your checkbook any day of the week.

Zman

For figuring the drop from one baseboard to the next you need to figure out how much temp each heater takes from the loop and then look on the manufactures chart to see what the the output will be at the next heater with the new water temp.

If you start with 140 degree water moving at 4 gpm and the first heater produces 350btu per foot and is 8' long.

2,800 btu hrs(8 x 350) / 4 gpm(flow) / 500 (constant) = 1.4 degrees
The next heater would receive 138.6 degree water. You can keep doing this down the line

Or you can cheat and get a little more accurate by using software.

If you can keep the flowrates in the 4 ft/sec range, (4 gpm with 3/4" pipe) the drop is not too bad.

Carl

Tim Potter

HC,
How are thing coming, inquiring minds want to know.
Thanks

HydronicComfort

Ok. Just reworking the fin-tube convector sizing. Going to run the fostapex behind dummy baseboard. At 150-degree supply, return temps come back at 126.86-degrees Z2 and 123.07 Zone 1 at 2.5 gpm rate/zone; 6.84 feet head Z2 and 7.06 Zone 1.

I'm taking the inlet and outlet fin-tube convector temps, averaging them and using that to determine BTU output and room convector sizing. It's quite interesting to see the drop in water temp as it goes in series through each convector. The first convector was reduced in length and the end ones have been lengthened.

Zone 2 will have 37 feet of convector; Zone 1 will utilize 33 feet plus a TwinFlo K42 toe-kick heater.

Also interesting that the Twin-Flo K42 toe-kick heater alone adds 1' of head.

Was planning to use zone valves for zoning. With the above head and flow numbers, I think the Taco BumbleBee pump would work fine.

As this progresses, I would appreciate some assistance in laying out the piping scheme relating to the boiler, 50 gallon buffer tank and 45 gallon IDHW. It will be outfitted with an outdoor reset and separate setpoint control for heat and IDHW. For this, we plan to use a Tekmar 402. BTW, Tekmar have been very responsive to questions we've posed.

It's a work in progress...

Thanks for the help thus far.