Need some assistance with my radiant/radiator/DHW design

beardley

Hello,

My wife and I have taken on the task of building our own home. We're all framed and enclosed and we're ready to really get working on the radiant. Fortunately Julia works for an architectural firm and she tagged one of her colleagues to help us design a system. Unfortunately he left the company, and we've been left with a 3/4 designed system. To add insult to injury, we had already purchased the boiler and storage tank, but not the rest of the components. So here's the deal, we have our zones laid out and the heat calcs done, but I'm not nearly qualified to design the rest of the system. I attached our zone layout, which has changed some, and I'm thinking needs to be tweaked further. So here we go

-House is in the Syracuse NY area, so reasonably cold.
-1400 finished sq' between 2 floors
-Walls are R35 strawbale (different topic all together!) and R60 in the attic, so very well insulated
-Air seal was a strong focus, so its a pretty tight place.

Boiler we own = HTP Elite FT 55
indirect DHW = HTP Superstore 45

The zone drawing shows 7 zones, which given some of the heat loads, I really think thats too many. In my mind, I've already combined zone 1 and 3, and I'm thinking about tossing the downstairs bathroom on that zone as well. If I do that, I'm down to 5 zones. *Note, zones 6 and 7 on the drawing will have cast iron radiators, not floor heat, so they will be a higher temp.

I'm thinking if I can get it down to this, I could use the Taco ZVC406 to control the 5 heat zones, and use 6 for the DHW. What is over my head right now, is what is the best method for attaining the 2 different temps for 6 and 7 vs. the floor zones? I've seen mixing valves, and injection valves, but I've just not fully grasped how that should work. What else am I missing? The boiler will be set up with an outdoor reset, and I truly want this system to be as highly efficient as possible. That fact that its a strawbale house should tell you that much. So please, guide me. Tell me what other info you could use to get me down the right path.

Regards,
John

Gordy

What is the heat load calc? Can't be much.

Zman

None of the text came through on your drawing. How will the tubing be installed? What type of cast iron rads?

Gordy

I thought it was just me on the text.

Gordy

Problem I already see is the multiple zones with low loads. Unless you have an absurd design day that boiler will short cycle unless you use a buffer tank. Even with out the zoning possibly, but need some heat loss numbers.

beardley

That file is weird for some reason I've not figured out. It has to be opened in adobe reader of the text is messed up. The heat loads for each zone are on the bottom of the file.

beardley

Gordy,

That's what I was thinking as well, which is why I want to combine basically the whole first floor into one zone. Think it will be even better to combine further?

SWEI

beardley said:

I attached our zone layout, which has changed some
...
The zone drawing shows 7 zones

All of which have the same tube spacing and require the exact same temperature? Something may be off there.

zones 6 and 7 on the drawing will have cast iron radiators, not floor heat, so they will be a higher temp.

This is a straw bale house. Why on earth would your floor tubing need 159°F water and your CI radiators need a higher temp than that? Another likely red flag. Is the tubing embedded in concrete? Is there insulation under the concrete? Something seems off here.

I'm thinking if I can get it down to this, I could use the Taco ZVC406 to control the 5 heat zones
...
The boiler will be set up with an outdoor reset

Outdoor reset (properly implemented) and on/off zone control are not generally a good match. Which way is south on your drawing? Is there proper shading and use of passive solar gain? I would start with two zones -- one for the rooms that have southern exposure and one for the rooms that do not. Make sure you specify low-e glass where you need it (west, north, and east walls) and avoid it where you don't (south walls.)

Gordy

Got off the ipad

Wow 19324 total load.

20* deltas on the floors tube 8" OC.
159* supply temp.

I agree with Kurt some issues. here.

Again type of Radiant floor panels.

Snowmelt

I would keep all 7 zones, your right on the mixing valves bring the temperature down. If I was you I would get a local supply house to do a heat calc. How far are you from nj?

Gordy

So you already purchased the boiler?

Gordy

Snowmelt his total load is 19324 btus about what I expected for the construction. The ft 55 is over twice the size needed at design temp.

What I question are the water temps. With out knowing type radiant panel design hard to make a call right now.

You could heat that place with candles.

Snowmelt

I think that's why they will need a storage tank added to the system, but have to do the math.

beardley

It's going to be a staple up 1/2" PEX over 1" board and 3/4" wood floor. Full dim 2x10 so I'll have plenty of insulation below.

Gordy

Over the top is out of the question. It would really drop the water temps and increase efficiency. Your trying to push through all most an R 2 worth of wood. I still think those temps are high though.

beardley

Not a surprise but they originally had the 85 spec'd because "I'd never run out of hot water". Based on the heat load of 19k I know that boiler is oversize. We have a garage planned in the future, so part of the reason I was ok with it is knowing I'll be able to expand and cover that w/o a lot of capital is a good thing.

Gordy

is there extruded plates with the radiant installation.......I hope.

beardley

We've not yet acquired that part of the system, so we'll just say yes

beardley

And yes over the top is out of the question at this point of the build.

Gordy

The spect supply water temps makes me suspicious that no plates are figured in the calculations. Your load is on average 14 btus a SF.

Gordy

beardley said:

And yes over the top is out of the question at this point of the build.

I always ask a mod/cons highest efficiency comes with the lowest possible return temps. Radiant offers that as an emitter.

beardley

Honestly the supply temp made me nervous as we're putting down hardwood, and my understanding is that it's more susceptible to temp swings. We're going with a narrow flooring to reduce the cupping risk.

Zman

Since you have not bought anything, I would like to talk you out of in floor radiant. I have never stepped on a hardwood floor and even noticed the heat. With your super insulation, you absolutely won't notice it.
If it were mine, I would put in Runtal panel radiators with TRVs and constant circ and odr, put a buffer tank on the boiler on pipe for domestic priority. Each room will have individual control and the system will be super efficient.

Gordy

I agree with Carl. Pipe the rads home run, and the trvs are your zone control. Your wasting money on that radiant with hardwood, and such a low load. Like Carl said you wont even notice you have a radiant floor. or not.

Gordy

There comes a time when radiant does not make sense if an optimal installation method can't be achieved, or the loads are so low there is no noticeable benefit.

Ceiling radiant could be a viable option depending on what construction phase you are in. I have it, and it is every bit as efficient, even better than floor radiant. You don't have to be disappointed about not feeling warm floors, and you don't have to worry about floor finishes. You would be running extremely low water temps in plated design. Cost compared to rads would be maybe more though.

SWEI

Still curious about solar orientation and gain. Is there a woodstove or a well-designed fireplace in the house?

Around here, with that kind of heat loss, I would likely be recommending an electric resistance boiler (and our electricity costs 5-6 times what our natural gas does.) Where is the house located? Are you on NG or LPG?

beardley

So radiators are a challenge. Because the exterior walls are strawbale, there are no studs to attach anything to because they're buried in the straw. Any radiator would have to be free standing, like the planned cast iron ones for the 2nd floor. The home is in upstate New York a little north and west of syracuse. The house is oriented to the south with large windows facing south and a minimum number on the north. We do have a woodstove (woodstock keystone) and realistically it's going to carry much of the load, but we want a system that can truly be a primary and keep the place very comfortable w/o the Woodstove. No NG out where we are, it's LP country.

beardley

So I'm quizzing the "boss" on the radiator options. Carl you mentioned runtals, but is there any reason a cast irons wouldn't work? Again, they have to be free standing because of a lack of interior framing members. If we were to go down this route, would it be possible to keep one radiant zone for the Kitchen/bathroom? They will be tiled, not hardwood. Still over the 1" pine boards.

I really appreciate your guys help on this. We've had nothing but bad luck on advise from anyone local, so your opinions are valuable. Given the nature of the home, efficiency is priority #1 for me.

Snowmelt

What you said is fine, just do the bathroom and kitchen with radiant and rest of house with rads.

Ironman

I like the suggestion of panel rads with TRVs. We do that type of system regularly and customers are amazed at how comfortable and efficient they can be. Mounting is not an issue: I generally use Buderus panel rads and you can get an optional floor mounting bracket for them. I would think that Runtal, Myson and Pensotti would have that option too.

As far as the bath and kitchen go, look at using an electric radiant grid and possibly a toe kick in the kitchen if wall space is not available for a panel rad. The toe kick can be connected to the HYDRONIC side of the indirect to avoid creating a micro zone. This gives it the buffer capacity of the indirect. Or, you can connect a small radiant zone with a mixing valve the same way.

For constant circulation with TRVs, use a Grundfos Alpha or Wilo Star circ and you won't need a pressure bypass valve which would probably cost more when you factor in the cost of a standard wet rotor circ like a ups15-58 or 007.

Zman

You could absolutely do it with some infloors in kitchens and baths combined with cast iron rads. It would take some homework to get the rads sized and add the TRV's.
I do think you could make runtal work.They are not very heavy and just require a couple solid mounting points. Other things to look at would be heated towel bars and heated countertops.

beardley

Ok sounds like we're getting somewhere. The kitchen and bath are 272 sq ft combined and both on the north side of the house. I'll take a deep look around for radiators today. As we hadn't planned on these, space is a concern, and also appearance. The home has a. Are natural feel between the timber frame and plastered walls, so we're not going to slap on some fin tube to get it done quick.

So in this scenario, would I still run the system constant on with outdoor reset? The rads will be controlled by the TRVs but what would we be looking at on the floors? Just good old tstat in the space? I planned on floor probes because of the Woodstove overriding the air temp.

Zman

The TRV will determine whether the radiator heats. You may want one central t-stat for when it is very warm out.
The panel radiators are low mass and can react very quickly so should not get fooled by the wood stove as your floor heat would.

beardley

Yea I get that for the radiators, just questioning the remaining floor zone in the kitchen/bath. I would probably use one of those nest Tstats to go with the TRVs

hot_rod

There are a lot of nice free standing radiators available. I like the look of some of these Jaga. or their in floor convectors, some of them work nicely down around 100f supply.

Runtal has some nice bench style that may fit somewhere.

Towel bars in baths can add plenty of BTUs.

http://www.jaga-usa.com/jaga-products

beardley

OK, so I went over all of this with my wife, and although we were really hoping for warm floors, it seems based on the advise given here, we're better off with a system that will function better. So we're thinking we want to keep a floor zone in the kitchen and bathroom downstairs. We're fine with this being 1 zone to cut back on the short cycling issues. We like the US boiler slenderized cast iron radiators, and thing those do two things. 1)Fit our aesthetic, and 2)don't take up a ton of floor space.

So looking back at the loop drawing I attached in the OP, I'm thinking we take circuits
A-2, A-5 and A-4 and keep those as floor heat. A-4 would be wood flooring, but I'm thinking it would be good to add that load. (correct me if I'm wrong here) I would then install cast irons in the following spaces

-Bedroom (zone 4) 3560 Btu/hr
-Living room (Partial of zone 1, circuit A-3) 2679 Btu/hr
-Dining room (partial zone 1, Circuit A-1) 3400 Btu/hr
-Hallway (zone 3) 1656 Btu/hr
-2nd flr bedroom (zone 6) 2607 Btu/hr
-2nd flr bedroom (zone 7) 2849 Btu/hr
-2nd flr bathroom (zone 5) 1598 Btu/hr (we may do a towel warmer instead of the cast iron)

Thinking about potentially putting one in on the upstairs landing, but I don't think we'll need it. If I did, Runtal makes a neat looking tube radiator that can be built into a railing. We'd probably go with something like that, and not a free stander.

So this leads me to determining water temp going to these and also then what size I need. Is there an optimal water temp? because you guys are recommending a constant on, should I shoot for a lower temp? I think I have the sizing calculation figured out based on the specs from US boiler, but correct me if I'm wrong here.

zone 4 example 3560 Btu/hr.
We'll use an avg. water temp of 160F
Heat emission chart shows 130 Btu/hr/sqft
3560/130 = 27.4 sqft.
Size chart shows 18 sections for 19" high, or 14 sections for 25" high

Is my math right there?

Zman

Life is going to be much simpler if you run the whole thing at the same temp. The high efficiency boiler is only efficient at lower return temps.
I would pick a supply temp around 130 degrees on the coldest day then pick a radiant floor assembly and other radiators based on that temp.
If you really want to understand this (and make your head hurt) read this. http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0CC4QFjAC&url=http://www.duluthenergydesign.com/Content/Documents/GeneralInfo/PresentationMaterials/2013/Day1/hydronics-siegenthaler.pdf&ei=n_rtVO-5DJb-yQTstoGoCQ&usg=AFQjCNG-mwgHIVRzTtOWpD3FlhMY_5-g9Q&bvm=bv.86956481,d.aWw

RobG

Have you already purchased the boiler? If not I think SWEI's idea of an electric boiler with that kind of heatloss would match the load much better. You can still do OAR and upfront and maintenance costs are much less. Piping is a breeze as well.

beardley

Rob, boiler is already purchased, along with the superstore 45.

Carl, that presentation is hugely informative. I'm the type of person that needs to know why, and this does that. I'm on my phone at work, but page 126 seems like a good starting point for me.

For the water temp, 150 is the lowest on the chart, so I'll give them a call and see if they have a figure at 130. Does my math above for the size look right?