New modcon boiler with multiple radiant temps

myqhenryt · February 2015

Hi All. First post here as I've found quite a bit of very useful info here in the past. But I can't seem to find guidance on the ideal setup for a new multi temperature modcon setup.

We have a 2100 sqft newly renovated ranch with a basement to be finished in on Long Island, NY. The house is insulated well and is pretty tight -- there's ~R24 in the walls (includes 2 in of closed cell and R15 fiberglass batts) and somewhere around R30 in the roof with open cell. We have an older oil-fired boiler that is on its last legs. I've had a 1000g propane tank installed and have had my eyes set on a Lochinvar Knight (WH-085). I sized this based on a manual-j performed by our HVAC contractor last year along with some info generated from LoopCAD. It's sized a bit high, but the WH-055 might be too small. My thought is the modulating aspect of the boiler will be a benefit here.

The challenge I have is dealing with multiple water temps coming from the boiler for the radiant zones. At this point it looks like I need five heating zones -- 1 low-temp radiant (Warmboard), 1 mid-temp radiant (Joist Trak), 1 higher-temp radiant (Joist Trak), 1 fancoil (supplemental), and 1 baseboard (basement). Ideally we'd have one or two radiant zones, but we had a new addition to the home where Warmboard was a good fit and we have two rooms in the home with R3 floors that require higher water temps. With a delta-t of 20 degrees and a room temp of 70 degrees, LoopCAD has recommended:

Warmboard: 90 water temp
Joist Trak: 116 water temp
Joist Trak (high temp): 135 water temp

I'd like to keep the system as simple as possible, that said are there any options here to reduce the amount of zones and mixing required? The Lochinvar has controls to automatically control valves to mix the water temps (one of the reasons I selected Lochinvar), but this is limited to three zones. My understanding is that water temperatures could be controlled by adjusting flow rates at the manifold circuits, but I don't believe this will have a major impact on temps where the zones above could be consolidated. Note that the Warmboard area is already hooked up to a Mr. Pex manifold, but this is not tied to a boiler yet. Joist Trak has not been installed yet, nor are there any manifolds purchased for this.

Thanks for your help.

bmwpowere36m3 · February 2015

The Lochinvar boiler and Multi-Loop Controller can only handle 3 separate temps... however you could add a separate (standalone) controller and mixing unit (such as a Tekmar) to as many zones or temps you need.

Probably the better approach is to design around 3 or less supply temps. I think it’s been said if the zone SWTs are within 10 or 15* they can be combined.

Radiant floor usually is designed around a delta t of 10*

SWEI · February 2015

Can you increase the amount of Joist Trak to get the design temps down? We work hard to get systems running on one water temp and IME it's worth the effort.

Rich_49 · February 2015

Is the 116* temp area it's own zone ? If so you could just run the 135* through that . When floor surface temp reaches set point thermostat should satisfy and shut down zone , no more flow , no more heat . if is it's own zone it will be fine .

myqhenryt · February 2015

bmwpowere36m3
I've heard that a Delta T of 20 is too high for radiant as this could lead to inconsistencies with floor temps. Is 10 the ideal Delta T?

Good to know about the temps within 10 or 15 degrees. Is this standard practice?

myqhenryt · February 2015

SWEI
No room for more Joist Trak plus I'd really be pushing the loop lengths -- I'd like to keep them under 300 ft with 1/2in pex.

myqhenryt · February 2015

Rich said:
Is the 116* temp area it's own zone ? If so you could just run the 135* through that . When floor surface temp reaches set point thermostat should satisfy and shut down zone , no more flow , no more heat . if is it's own zone it will be fine .

Ideally I'd like both the 116 and 135* temps to be on the same zone as they serve the same area of the house. Should I be concerned that we have an open space with oak floors where the 135* would circulate under half of the room, with 116* under the other half? Seems like an odd design, but half of the room has an area rug, thus R3.

Snowmelt · February 2015

Taco has a good webinar on this subject. If you want to simplify 90 and 116 degree run on one manifold and the higher temp on another zone and just zone it out.

SWEI · February 2015

myqhenryt said:
No room for more Joist Trak plus I'd really be pushing the loop lengths -- I'd like to keep them under 300 ft with 1/2in pex.

More loops more better. I'd shoot for 220' or so depending on the layout. Have you considered using 3/8" PEX? It's far easier to install than 1/2".

Why are you needing high water temps in those areas? We see this all the time in bathrooms due to the limited useable floor space for emitters. The best answer there is almost always to put plates in the shower/bath walls and even the ceiling. I would suggest you set your indoor design temp a bit higher in the bath as well, which makes it even more important to add more emitter surface.

myqhenryt · February 2015

Snowmelt said:
Taco has a good webinar on this subject. If you want to simplify 90 and 116 degree run on one manifold and the higher temp on another zone and just zone it out.

I will check those out. The issue here, or may its not an issue, is that the 90* setup already has a manifold that is 20ft from where the 116* manifold will be. But what Rich noted above, may work where the 116* and 135* zones are combined.

myqhenryt · February 2015

SWEI said:

myqhenryt said:
No room for more Joist Trak plus I'd really be pushing the loop lengths -- I'd like to keep them under 300 ft with 1/2in pex.
More loops more better. I'd shoot for 220' or so depending on the layout. Have you considered using 3/8" PEX? It's far easier to install than 1/2".

Why are you needing high water temps in those areas? We see this all the time in bathrooms due to the limited useable floor space for emitters. The best answer there is almost always to put plates in the shower/bath walls and even the ceiling. I would suggest you set your indoor design temp a bit higher in the bath as well, which makes it even more important to add more emitter surface.

I went with 1/2in as that is what I used with the Warmboard and my understanding is that you can get longer loops with it vs 3/8. My view is to simplify the amount of loops. Right now I have 15 including the three Warmboard loops.

The higher water temps are due to the high r-value in two rooms. We have a master bath with 2 in subfloor, fiberglass waterproofing, thinset, and marble for the floor. Our contractor over-engineered this as the entire room is waterproofed and tilted in one direction to an linear drain on one wall. Unfortunately, adding emitters to the wall and ceiling are not an option. The other room is a living area with wool carpet...same deal with R3. But note that we do have a fancoil to provide supplemental heat. That said, maybe the water temps can be reduced in these areas where the floors are warm but not heating the rooms.

Rich_49 · February 2015

Get rid of the rug , run it all at 116*and call it a day my friend . Rugs are to protect against cold feet .

SWEI · February 2015

myqhenryt said:
Unfortunately, adding emitters to the wall and ceiling are not an option.

Bummer. You haven't lived until you've experienced a "full radiant" bathroom IME.

note that we do have a fancoil to provide supplemental heat. That said, maybe the water temps can be reduced in these areas where the floors are warm but not heating the rooms.

You're getting warmer (pun intended.) Put those BTU's anywhere you can. It will work.

bmwpowere36m3 · February 2015

If you're not totally relying on the radiant floor for heat, then you can run lower supply temps. However you need to do the calculations and sometimes do them a few times over. Start with one supply temp and see if its possible to cover the heat loss given ALL the emitters you have or are willing to install. Usually bathrooms and kitchens are the most difficult for lack of floor and/or wall space.

Like SWEI said, ideally you want one supply temp for all emitters. However the Lochnivar boiler can supply up to three… at the expense of complexity and cost of materials (mixing valves, controls, plumbing).

myqhenryt · February 2015

Rich,
Want to have that conversation with my wife?

Unfortunately the carpet stays along with the over engineered master bath. That said, I'm wonding if I could run all of the Joist Track at 125* (a happy medium temp between 116* and *135) and adjust flow rates for each circuit to output the appropriate amount of BTUs. My initial thought was that adjusting flow rates won't have a major impact, but reading through some of Siegenthaler's stuff makes me think otherwise, unless I'm not properly understanding the math.

bmwpowere36m3 · February 2015

From what I understand it does, but it's not a linear relationship… i.e. half the flow rate does not equal half the BTUs. I think he mentioned something wrt to baseboard and half the flow rate only decreased the btu output by 10% or so (at the same supply temp). I might be wrong.

Seems "emitter" output is more a function of supply temps than flow rate.

SWEI · February 2015

myqhenryt said:
I'm wonding if I could run all of the Joist Track at 125* (a happy medium temp between 116* and *135) and adjust flow rates for each circuit to output the appropriate amount of BTUs. My initial thought was that adjusting flow rates won't have a major impact, but reading through some of Siegenthaler's stuff makes me think otherwise, unless I'm not properly understanding the math.

Lacking the math, but having some experience, I'd say you're close enough that it should work.

Rich_49 · February 2015

Worst thing that can happen is you move the rug to the cold part of the floor . Sorry , I could not pass that up . Agree with SWEI though .

myqhenryt · February 2015

Thanks guys, this was very helpful and has eased some anxiety.

Not sure if I should open a new discussion for this, but in regards to the boiler sizing I'm now on the fence. Our HVAC contractor provided a Manual J&D (using Elite) to size our AC system. The Manual J only provided calcs for the first floor of the house and noted that the heat loss is 42,848 Btuh. I've used LoopCAD and it estimates the heat loss for the first floor at 25,449 Btuh and another 13,149 btuh for the basement. I can share these documents if needed. With taking this info into consideration and knowing that load calcs are performed for rarely occurring conditions, would a Lochinvar WH-055 be a better fit vs the WH-085 which is oversized, but modulates down to the appropriate load?

Thanks again.

bmwpowere36m3 · February 2015

the WHN55 has a DOE of 51,000 btuh... so even that satisfies your contractors calculations. The question comes down to accurately performing the heat loss calcs. That 2100sqft includes the basement?

RobG · February 2015

It is my understanding that the only tubing that can be used with Quick-Trak is 5/16" unless they have changed something that I am not aware of. Take that into account for you flow rates and tubing purchases.

myqhenryt · February 2015

bmwpowere36m3 said:
the WHN55 has a DOE of 51,000 btuh... so even that satisfies your contractors calculations. The question comes down to accurately performing the heat loss calcs. That 2100sqft includes the basement?

Just double-checked some autocad drawings and the first floor of the house is closer to 1900 sqft and the basement is ~1,400 sqft. The HVAC contractor actually used 1646 sqft for his calcs and the LoopCAD uses the more accurate number of 1900 sqft.

myqhenryt · February 2015

RobG said:
It is my understanding that the only tubing that can be used with Quick-Trak is 5/16" unless they have changed something that I am not aware of. Take that into account for you flow rates and tubing purchases.

It's Uponor's Joist Trak which has a 1/2in option -- http://www.uponorpro.com/~/media/Extranet/Files/manuals/JoistTrakHandbook_051.aspx

RobG · February 2015

My bad, I thought I read Quick-TraK.

bmwpowere36m3 · February 2015

myqhenryt said:

bmwpowere36m3 said:
the WHN55 has a DOE of 51,000 btuh... so even that satisfies your contractors calculations. The question comes down to accurately performing the heat loss calcs. That 2100sqft includes the basement?
Just double-checked some autocad drawings and the first floor of the house is closer to 1900 sqft and the basement is ~1,400 sqft. The HVAC contractor actually used 1646 sqft for his calcs and the LoopCAD uses the more accurate number of 1900 sqft.

So ~ 3300 sq ft of conditioned space and a heat loss of ~ 39k BTUs. What is the design temp?

2x6 walls? R30 in the roof cathedral or ceiling joists?

myqhenryt · February 2015

bmwpowere36m3 said:

myqhenryt said:

bmwpowere36m3 said:
the WHN55 has a DOE of 51,000 btuh... so even that satisfies your contractors calculations. The question comes down to accurately performing the heat loss calcs. That 2100sqft includes the basement?
Just double-checked some autocad drawings and the first floor of the house is closer to 1900 sqft and the basement is ~1,400 sqft. The HVAC contractor actually used 1646 sqft for his calcs and the LoopCAD uses the more accurate number of 1900 sqft.
So ~ 3300 sq ft of conditioned space and a heat loss of ~ 39k BTUs. What is the design temp?

2x6 walls? R30 in the roof cathedral or ceiling joists?

Attached are the load calcs I noted before. But offhand, here are some answers:
Design temp outdoor: 10*
Design temp indoor: 70* (although we are happy with 68*)
Walls: 2x6 with 2 in closed cell foam and the remaining batt (R15). I'm guessing this is around R24 total.
Ceiling: R30 open cell throughout the entire roof -- attic is conditioned.
Windows: Low-E glass

Note that Quik Track is mentioned in the LoopCAD doc, but that was used as a place holder for Warmboard -- Warmboard was not an option in LoopCAD

Jean-David Beyer · February 2015

"Design temp outdoor: 10*"

Design temp outdoors here is 14F. It has been down to 0F, and -0.4F (last night) a couple of times this winter. That is quite a bit colder than last year when it went down to 2.8F once. Before that it only went down to 8.9F. I do not know if that is climate change, or just the expected variability of outdoor temperatures.

myqhenryt · February 2015

Jean-David Beyer said:
"Design temp outdoor: 10*"

Design temp outdoors here is 14F. It has been down to 0F, and -0.4F (last night) a couple of times this winter. That is quite a bit colder than last year when it went down to 2.8F once. Before that it only went down to 8.9F. I do not know if that is climate change, or just the expected variability of outdoor temperatures.

Good point. We're actually seeing a similar pattern here the last few years -- colder temperatures as well as tons of snow. That said, I went into LoopCAD and changed the outdoor temp to 0*. The result was a heat loss of 44,628 Btuh for the entire house. That said, I'm still "good" with the smaller sized Lochinvar (WH-055). But I'm not sure if I should trust the LoopCAD calcs over what the HVAC contractor provided with Elite.

Rich_49 · February 2015

The Warmboard will have better output than QuikTrak . There is actually a thermographic comparison showing them next to each other on Warmboard site . Your water temps may be able to come down also due to the construction differences between the 2 panel types . Heda losses will be far lower also .

New modcon boiler with multiple radiant temps

Comments

Categories