Suggestions for improving radiant design.

RxRoy

Hi Everyone,

First I have to say--I am so glad to have stumbled upon this site. I have read through the last 100 pages and have learned a lot, from obviously knowledgeable people. Thanks to all!

I am designing/installing a radiant floor heat system and was hoping for your suggestions for improvement. I have read through Siegenthaler's book and all my calculations are based off the formulas in his book.

About the project:
--1800 square foot, 12 year old ranch home in southern Wisconsin built on top of a gravel drumlin, woods on 3 sides
--Design heating load = 53,196 Btu/hr (53,300 per SlantFin calculation--was surprised it came out that close)
--Walls R-18, 2x6 walls, blown cellulose, full brick exterior (effective R-value, taking into consideration framing losses)
--Ceiling R-41 blown cellulose
--Basement walls 10" concrete not insulated (planning to install 2" rigid insulation this summer to exterior of walls), partially exposed (insulated to R-18 at exposed area)
--Basement floor 3-4" concrete with tubes, 1" rigid insulation underneath, 1" air gap on slab sides (badger basement water proofing)
--Full unfinished basement with 5 loops of NON-barrier (Rehau Raupex) 1/2" tubing (12 OC in 750 sq ft, 16 OC in 1050 sq ft). This was installed in 2003 when I didn't know enough to question the tubing choice...
--Upstairs is mostly 3/4" plywood sub-floor with 3/4" oak on top (2" width). Bathrooms and laundry room are linoleum. Bedrooms are carpeted for now.
--ThermoFin C heavy aluminum plates 8" OC under entire first floor with 1/2" Uponor HePex (loop length varies from 175 to 222 feet)
--4 zones (5 Caleffi manifolds), 2 temps (higher temp for underfloor, low temp for slab)
--Triangle Tube Prestige Solo 60 (propane) mod/con
--The existing forced air heating / cooling system is available for supplemental heat.
--Not planning to use boiler for DHW.

Attached is my schematic and much more information about the system and components.

My specific questions are:
1. Is my piping design reasonable and as simple as possible?
2. Since the basement tubes are non-barrier I was planning to use a brazed plate heat exchanger to isolate that circuit. Is using a 3 way Taco motorized mixing valve with outdoor reset the best way (fewest things to go wrong) to control the temp of the basement zone?
3. I was planning on using floor sensors on all 4 zones for more responsive control and to keep the hardwood safe. Good idea or better way?
4. I was planning to tie the basement circulators together--both on and off at the same time. Is there anything wrong with running them that way?
5. Do you think the boiler has enough output? The next size up is 76,000 Btu/hr which can fire down to a minimum of 19,000 Btu/hr (which I think is over-capacity).
6. Any suggestions for controlling everything? I don't think the boiler can run 4 zone circulators off it's control.

I also attached an Excel file that I made to determine loads, operating temps, etc.

Thank you to everyone who is still reading. Even more thanks to anyone who replies!

Roy

Zman

Wow,
You have a great start!
The non barrier tubing is not a big deal with the TT60. I have done these by just swapping out the provided circulator with a stainless one. You will also have to eliminate the other ferrous materials including using an expansion tank rated for potable water.
If this were mine, I would have one (stainless) alpha circulator and 3 zone valves take care of the higher temp upstairs zones.
I would eliminate the heat exchanger and associated parts and use one alpha (stainless) and a smart mixing valve for the lower temp basement slab. I would set up the mixing valve so that it modulates to hit your outdoor reset target and so that it utilizes a "boiler protection" mode. A big cold high mass slab will drag down the boiler temps during startup. This will cause the higher temp upstairs zones to be starved for heat. Boiler protection mode will remedy this.
If you are careful with the water temps, I would not bother with floor sensors.
Your boiler sizing looks perfect.
The boiler cannot control all this on it's own. You will need some 3rd party controls. A control that will manage the mixing valve and modulate the boiler accordingly would be best. I would take a look at Tekmar Controls. They also have t-stats that can provide indoor feedback and optional slab sensors.

A very nice start,

Carl

RxRoy

Zman, thanks for the reply and the suggestions for improvement. Your system seems much more simple. I attached a new schematic--Is this how you meant? Would the basement circuit also need a check valve on the return (off the main header)?

Will the single stainless Alpha have enough head to circulate the upstairs zones all at once?

I'm wondering about the efficiency of your suggestion versus my original system. Is it more efficient to run more ECM circulators at a lower wattage or fewer ECM circulators at higher wattage? Or would it come out the same either way? Are the zone valves a significant source of power consumption?

Any suggestions from anyone else?

Thank you,
Roy

NRT_Rob

Carl absolutely nailed that analysis, that was a pleasure to read. Though I do like floor sensors for MINIMUM temp sensing, ensuring minimum foot comfort in between "required" heat demands, I totally agree they should be unnecessary for floor protection if due diligence is done regarding water temperature specificiations.

I've pushed 7,000 sq ft houses with single alphas. It can certainly be done. Your house will be fine with less.

I have grown to love Taco Sentry zone valves for low power use and low flow restrictions. Those valves with an alpha is as efficient as residential zoning gets these days.

Zman

Roy,
That is what I had in mind.
As Rob said the alpha is plenty of circ for your system.
You do not need the check valves on the zones. You will need the check valves that come with the alpha circs.
Using the I-series instead of the full blown tekmar will work and save you money. You just want to set the second ODR curve in the boiler to match the one programmed into the I Valve.
The Tekmar setup works better for controlling indoor temp overshoots and is much more "elegant"
Carl

RxRoy

Thank you both for your advice. This project has been on hold for the summer while I dug a moat around my house to insulate and water proof the foundation. I also installed a whole house dehumidifier.

I've spent a lot of time thinking about your suggestions and have more qustions.

1. I was planning to use a SEP-4 dirt/mag/air separator on this system so I posted to the Caleffi website to see if the internal walls of the unit are bare steel, which it is. They suggested I add an oxygen scavenger to the system, but still use the SEP-4. My questions are: Should I us something else (non-ferrous) instead? Or should I use some kind of oxygen scavenger (if so what brand is your preference)? Is the water going to turn the tubing brown? Hot Rod, please chime in!

2. I am now considering a Lochnivar Knight 44,000 btu mod con instead of the TT. I like the venting options, controls, and manual better. The output is slightly less than the TT, but I don't feel enough to worry about. Does anyone see a compelling reason not to use the Lochnivar instead?

3. I am still struggling to figure out the best way to control this thing. If I were to use Tekmar controls, what would you suggest? What components would be needed (Like Tn-2 house control, wiring center, and thermostats?) I don't really understand how the boiler controls and basement mixing valve integrate with the Tekmar. Does the Tekmar basically render the boiler controls useless? Could the Lochnivar handle everything by itself without the Tekmar controls?

I certainly appreciate everyone's comments!
Roy

SWEI

Is there any old iron pipe, radiators, etc. in the system? Any black pipe in the new system? Buy a lined expansion tank and you could probably skip the magnets (though they really don't add much to the unit cost.)

Not sure I've seen a 44k Knight?

Great controls, no need for the Tekmar IMO.

Mark Eatherton

Any time you have non barrier pipe in a system, you shouldn't have any ferrous components in the water stream. Oxygen scavengers are a chemical that requires long term maintenance program. I agree with the others that it is easier to go all non ferrous components, and keep the pH in check and maintenance. Quite honestly, for R19 walls, I'd expect a lower load per square foot, like around 20.

Are you planning to use this boiler for DHW? If yes, you might want to consider a larger boiler unless you have total control over the demand. (no large voulme tubs or simultaneous showering/washing machine loads)

Kudos on doing your home work first. Avoids having to come back and figure out why it won't heat at design condition.

ME

RxRoy

There are no radiators or any iron pipe in the system. Just pex tubing and copper pipe. This is the boiler I was considering.

http://www.supplyhouse.com/Lochinvar-WHN055-44000-BTU-Output-Knight-High-Efficiency-Boiler-w-Fire-Tube-Heat-Exchanger-Wall-Mount

I assume it can be converted to propane.

Its too bad I couldn't open up the SEP-4 and use the guts. I could easily fabricate a stainless housing of the same dimensions...

Zman

The Knight's control will do what you need.
You have to buy an add on control module and it can control a motorized mixing valve.
That is a very nice boiler.

SWEI

Boilers are generally identified by their firing rate, so most of us would consider that a 55k boiler, capable of delivering 51k into systems we design.

The insides of both the SEP4 and quality CI pumps are coated (typically epoxy, powder coating, or some kind of cataphoretic voodoo.) With no other iron in the system, I would install a lined expansion tank (Amtrol RX series or equivalent) and sleep well at night, even without magnets.

Separate brass Caleffi bits are not that expensive either.

RxRoy

"Any time you have non barrier pipe in a system, you shouldn't have any ferrous components in the water stream. Oxygen scavengers are a chemical that requires long term maintenance program. I agree with the others that it is easier to go all non ferrous components, and keep the pH in check and maintenance. Quite honestly, for R19 walls, I'd expect a lower load per square foot, like around 20."

There is a fair amount of glass in my house, which increases the heating load. I agree with not wanting to add oxygen scavengers, which means I should scrap the idea of using the SEP-4. Maybe I'll still make a stainless hydraulic separator and just use the brass Caleffi air/dirt separator instead.

"Are you planning to use this boiler for DHW?"

I don't plan to use the boiler for DHW.

"You have to buy an add on control module and it can control a motorized mixing valve."

This is the mixing valve I was considering. This has the control module on it I think?

http://www.supplyhouse.com/Taco-I075C3R-1-3-4-3-Way-Outdoor-Reset-I-Series-Mixing-Valve-w-Sensor-5203000-p

"Boilers are generally identified by their firing rate, so most of us would consider that a 55k boiler, capable of delivering 51k into systems we design."

That is good news. It should definitely be OK then.

"The insides of both the SEP4 and quality CI pumps are coated (typically epoxy, powder coating, or some kind of cataphoretic voodoo.)"

That's what I was hoping, but I posted on the Caleffi Website and they said it was bare steel. Scroll to the bottom comment on the link below to see their reply.

http://www.caleffi.com/usa/en-us/blog/do-i-really-need-magnetic-dirt-separation-my-hydronic-system

Do most of these radiant systems end up with brown water after a few years, or will the water stay pretty clean?

Thanks everyone for the replies--this is great stuff!
Roy

hot_rod

I could find some mesh for you if you want to build you own.

Here is a stainless version someone posted on the wall many years ago. Clever corner layout, and belly band.

The composite mesh we use needs to be loaded in after the welding, so a removable top is required. Or use stainless mesh. I may have some of that also, as the larger welded steel seps and discals use stainless.

SWEI

RxRoy said:

"You have to buy an add on control module and it can control a motorized mixing valve."

This is the mixing valve I was considering. This has the control module on it I think?

http://www.supplyhouse.com/Taco-I075C3R-1-3-4-3-Way-Outdoor-Reset-I-Series-Mixing-Valve-w-Sensor-5203000-p

Only if you need two separate simultaneous reset curves and do not want to buy the Lochinvar box.

"The insides of both the SEP4 and quality CI pumps are coated (typically epoxy, powder coating, or some kind of cataphoretic voodoo.)"

That's what I was hoping, but I posted on the Caleffi Website and they said it was bare steel. Scroll to the bottom comment on the link below to see their reply.
http://www.caleffi.com/usa/en-us/blog/do-i-really-need-magnetic-dirt-separation-my-hydronic-system

I'll have to defer to Bob on this one.

Do most of these radiant systems end up with brown water after a few years, or will the water stay pretty clean?

That basically depends on the presence of iron and the amount of oxygen ingress.

Rich_49

Get yourself a nice Caleffi air separator and call it a day . Nothing ferrous there . Nobody needs P/S anymore for the most part . Since everyone is throwing names and the like around , look at this link . i have then humming away right now at right around 1 gpm through the Hx . If it looks interesting open the manual and take a look . Finally , a true modulating condensing boiler that does not need some flow through the HX that would suggest it's low end is a myth .

http://www.htproducts.com/literature/UFT-brochure.pdf ., You can also use both top and bottom S & Rs simultaneously .