Radiant dilemma

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  #1  
Old 01-19-12, 07:47 AM
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Radiant dilemma

Hello-

long time follower of this great forum.

I have a New Yorker boiler 97k Btu http://www.newyorkerboiler.com/pdf/C...out%201-06.pdf . approx 2 years old, 1 zone for the whole house (~2000 sq ft).

I added a rediant loop in a slab(300 ft 1/2 pex) to heat a 285 sq ft space, on a separate circulator with mixing valve (before the circ).

Once up to temp the floor heats the space well, however
as you would expect I'm experiencing short cycling when just that zone is operating.

I have been researching indirect water heaters, and direct fired (i.e. pulling that zone off the boiler) as possible solutions, but l would love to hear what insight the pro's have.

thanks

-ro
 

Last edited by dfor24; 01-19-12 at 07:53 AM. Reason: adding more info
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  #2  
Old 01-19-12, 10:04 AM
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You say that you have one zone for the whole house, but if the radiant section can run by itself, you must have two zones. How many thermostats do you have? If the radiant is on a separate 'stat, adjust the 'stat's heat-anticipator to "longer."

Pictures of your system would help us better undersand your situation.
 
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Old 01-19-12, 10:14 AM
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Apologies,

2 zones, Whole house zone (1) is radiators with circ and stat.


This radiant floor loop is on a (2)nd zone. Mixing valve set to put out 125 F. The zones feed off a 1 1/4 manifold.

That 'stat' remains on for the duration as does the ciculator. Boiler is hitting high limit at 180, comes back again at 150 ish, and around we go.

In essence boiler is too big when this one zone is running on it's own.
 

Last edited by dfor24; 01-19-12 at 10:33 AM. Reason: more info
  #4  
Old 01-19-12, 12:16 PM
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Not a pro here.

However,
IMO, a buffer or an indirect is a much better option than another fired heater.

Boiler Buddy:
Boiler Buddy - Overview

Or less costly, just a low cost electric water heater, (not connected,) in series with the supply from the boiler.
To work as a buffer tank.


Peter
 
  #5  
Old 01-19-12, 12:42 PM
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Appreciate your insight, and the link. I'm leaning towards a buffer solution at this juncture. Want to make sure I leave no stone unturned before I proceed. I'm not keen on another burner either.

-ro
 
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Old 01-19-12, 05:19 PM
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I think this would be more appropriate: Steam Form
 
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Old 01-20-12, 07:51 AM
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Thanks drooplug.

it appears I would need a 50 gal Boiler buddy using this formula Buffer Tank FAQ.


t=10 min
Qh- 80000
qload 7100
dT- 25 f


I have seen varying configurations of how this should be piped in. Buddy specs show supply (on top) and return (bottom). I noted someone from NRT mentioned they only pump supply through the tank so it does not mix thereby partially negating the BTU storage effort.
 
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Old 01-20-12, 10:36 AM
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I noted someone from NRT mentioned they only pump supply through the tank so it does not mix thereby partially negating the BTU storage effort.
I think they mostly do it that way with mod-con boilers.

Peter
 
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Old 01-20-12, 06:15 PM
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At 50 gallons, you might as well get an indirect water heater. It will be a very efficient means to make hot water and the tank will last forever.
 
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Old 01-21-12, 05:58 AM
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Already have a tankless for hot water, so the Buddy is probably the better option. Open to viable alternatives.
 
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Old 01-21-12, 06:27 AM
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What would be the cost difference between the boiler buddy and indirect? The tankless heaters don't last forever and if you do use an indirect, you can switch over to that when it is time to replace. As far as efficiency differences, you are going to have a giant tank of hot water in either case that will be prone to losing heat. I don't know anything about boiler buddies and their insulation, but indirects tend to have lower standby losses compared to traditional tank water heaters. They also have a fast recovery. I don't know what your usage is, but I have a 30 gallon indirect with a similar size boiler as yours. I never run out of hot water while using one shower. Haven't had the chance to run both at the same time.
 
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Old 01-27-12, 09:08 AM
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Droo,

I don't know the pricing difference, having a bear of a time sourcing a boiler buddy.

As for the tankless it's a little over 1 yr old and just performed a flush actually. I expect it to last quite a while with proper maintenance so the indirect would not be used for DHW.

Might have to go with an electric water heater instead (and disable the heating element) for this radiant.
 
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Old 01-27-12, 12:38 PM
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I looked for boiler buddy also, they only sell through distributers, who only sell to licensed contractors, this way they get to double or tripple the price.

I like buffer tanks, but in this case, I think you could make your new pex zone a Slave to your original large zone (Master).

That is: through a relay only allow your Slave zone to heat WHILE your Master zone is heating.

A version of zone synchronization.
 
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Old 01-27-12, 01:02 PM
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That is an interesting approach. I have a taco sr502 now -
http://www.taco-hvac.com/uploads/Fil...2(102-082).pdf

What would I drop in to have the pex slave off the master?
 
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Old 01-27-12, 01:49 PM
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1 relay, like a White Rodgers type 184 SPNO, 120vac coil

Wire relay coil in parallel off of your Master zone circulator terminals on the SR502, so that it energizes when pump is on.

The Normaly Open points of the relay would be wired into a cut of one of your Slave zone thermostat wires, so that your Slave zone thermostat can only call for heat if your Master zone is calling for heat.

PS: this assumes that your heat loss in the Slave zone can be met in the time that your Master zone is heating, averaged across say 8 hrs.
 

Last edited by Buffalobillpatr; 01-27-12 at 02:23 PM.
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Old 01-27-12, 05:05 PM
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Boiler buddy is not the only option. Among others:

Lochinvar: http://www.lochinvar.com/_linefiles/SBT-01.pdf

HTP: Superstor Ultra buffer tank. Basically any of their indirect tanks is available as a buffer tank. Add -B to the model number. Comes with four ports, drain, etc.

Heat-Flo: Hydronic Buffer Tank from Heat-Flo Heating Products
 
  #17  
Old 01-27-12, 07:03 PM
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I found this today, after much digging around.
HOT WATER PRODUCTS LLC SSU-30CB Superstor Ultra Coil Booster Stainless Steel Storage Tank SSU-CB Series MUN SSU-30CB
I don't know how much the shipping might be, but seems like a pretty good price otherwise.


Peter
 
  #18  
Old 01-28-12, 08:15 AM
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Get away from the tankless, make the boiler cold start, install an IWH. You can solve your problem, make domestic hot water, heat the small radiant zone and save money on top of it all. Consider a stone lined tank as it will make more water per boiler input than most tanks, no anode, tank not affected by water conditions.
 
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Old 01-28-12, 04:37 PM
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Excellent find Peter. Thanks to you for the effort to dig that one up. Have brought from KSC before,
all the better.
 
  #20  
Old 01-28-12, 06:13 PM
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There is absolutly no reason to maintain water temperature in boilers today. It is way too expensive. See this link.
Domestic Hot Water Coils....Why Are They Still Being Sold?
 
  #21  
Old 01-28-12, 06:24 PM
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If you did want to go to an indirect.
The Burnham Alliance tanks should be very good.
I believe they are made by Vaughn tanks which is locaated not to far from where i live.
The local Oil Co. guys have been using Vaughn tanks for decades and they say they are great.


Peterr
 
  #22  
Old 01-28-12, 06:27 PM
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Hello RBeck,
I think, maybe that when the OP says he has a tankless, i think he means an independent tankless water heater, not a boiler coil
Something like a Takagi i guess.


Peter
 
  #23  
Old 01-28-12, 08:53 PM
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PeterNH, you are right. Sorry misunderstood. Thanks for straightening that out for me. Tankless coil or tankless water heater are two different things.
I need to pay more attention when tired. ASHRAE was very tiring last week. Chicago has great restaurants though.
 
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Old 01-29-12, 07:43 AM
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Not to worry R Beck we appreciate any time you can give us.
Heard there are really good Greek restaurants there did you eat at one?
Anything new and interesting at the convention?

Peter
 
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Old 01-29-12, 04:01 PM
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You are correct Peter (Navien Tankless). Appreciate all the input.
 
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