too many outdoor resets? (boiler vs mixing valve)

avionator

I'm planning on retrofitting radiant heating using two different methods of installation: underfloor for our main floor (accessible by drop ceiling in basement) and in-ceiling on the top floor (on top of drywall, insulated in attic space).  I know these will require two different temperatures to maintain optimal efficiency and comfort.



I'm planning on using a Buderas GB142-30 with full outdoor reset.  I am going to run seperate Taco Bumblebee circulators, one for each floor. (3 zones upstairs, 4 zones on main floor). 



I plan on setting the outdoor reset on the boiler for the top floor so that it can achieve the higher temps needed for in-ceiling heat.  I know i need a mixing valve for the main floor.  My current thoughts are to use a Taco i-series with outdoor reset.  Would i be able to use a more basic valve?  I'm trying to trim my budget down and the difference would be about $300.  I'm concerned that a standard valve only recognizes one temp setting and would therefore not work with my system.  However, will the i-series reset argue with the boiler reset?



this will be my first installation of this type, ever.  so, be easy on me! looking for any help i can get.

SWEI

I'm not intimate with the Logamatic

but I know for sure that the current generation of Viessmann residential boilers will manage both using the onboard controls.  Lochinvar sells an add-on box for their boilers that will control three outboard mixing valves.

Zman

Options

The best way to do this is to have a controller manage the boiler and the mixing. This way the boiler is always running at the most efficient temp. As mentioned, some boilers have on board capabilities. Companies like tekmar also make (fairly expensive) but really nice external controllers.



What you are describing will work. The disadvantage is that the boiler will always fire to the temp needed for the hotter zone. You will lose some overall efficiency.



If the temp curves for your 2 zones are parallel ( not a high mass and low mass), the cheapest way to do it would be to install a non thermostatic mixing valve on the cooler loop. Once set up, one zone would just lag the other a certain number of degrees. The boiler would be set to the reset curve of the hotter zone.You would still lose the efficiency,. A very low cost solution.



Carl

avionator

re: options

so regardless: it's best to go with an intelligent mixer.  will any outdoor reset mix valve work with a controller?



I'll have to check if the gb142 has onboard controls or if i need to look for a controller.  i hope it's got onboard, or maybe i should be looking at a different option...  i chose the gb 142-30 because it's slightly oversize for my need and has high efficiency ratings as well as good reviews for quality. 

Zman

Buderus

Do you own the buderus?

I am not a huge fan. I believe you will have to use their controls. I find them very counterintuitive. Be especially careful with water quality.

Carl

avionator

no

i do not yet own the buderus, nor have i ordered it yet.  we have good quality water that will (eventually) be filtered.  i looked up that i'd have to use the MM10 control module, but reading through the directions seems a little tricky to get things set up right.



what would you recommend instead?  there is a comparable slant/fin LYNX unit that would save me about $800 (but i don't think it comes with the nice low-loss header unit).



basically i'm looking for something that i as a homeowner could do the install, is roughly 95% or higher efficiency, LP, quiet, reliable and sub $4,000.  minimum BTU output must be 78,000.

Zman

Heat exchangers

It comes down to heat exchanger design.

For years most manufactures were using a stainless steel govanni design. These worked pretty well but required religious maintenance and robust circulators. These exchangers are still used in the lochinar kbn series as well as htp and others.



Buderus introduced the aluminum exchanger around 10 years ago. They had tons of corrosion and control issues in the west. The companies support for the problems was lacking. I know there are plenty of folks that have had good luck with them, in my region you literally could not give one away(I tried a while back).



Triangle tube introduced a stainless fire tube exchanger. It has proven to be a work horse. Lochinar now uses it their whn series. Other manufactures do as well.



Viessmann makes a great stainless steel boiler.



I am not familiar with the lynx. It is aluminum.



Have you figured out the temp difference you need?



The triangle tube 110 will give multiple temps but will default to the higher zone.



Lochinar whn 110 can do mixing with an add on controller.



Are you uncomfortable assembling the near boiler piping? If so this may be a project you need some professional assistance with. Incorrectly installed boilers can be quite dangerous. The combustion needs to be checked and various safety devices need to be installed correctly.

avionator

new thoughts: wm97+

ok, after looking around a bunch i'm now leaning toward a WM97+ 110k btu boiler.  It's got the right price, right output, and a stainless steel burn tube.  zman, thanks for all the great info on materials such as stainless vs aluminum. 

does anybody know much about the Weil-Mclain unit?  sure it's stainless... but is it reliable?  i presume such.  but one should never presume...

anybody know about controls for the WM re: my original question?  Looking to control a seperate temp on a parallell curve.  will the wm97+ do this or do i need a seperate controller?  i can't seem to find any specific to the wm.  tekmar maybe?

Zman

Mixing

The wm has a stainless fire tube exchanger. That's good. The controls look somewhat limited. For the tekmar to be able to control it, it needs to have 0-10 vdc control capability.

You can always use a non thermostatic valve or a taco I valve to temper the cooler zone. You just have to run the boiler at the hotter zones temp.

Have you figured out what temps you need? Depending on your heat loss and design, you may not need 2 temps.

Rich_49

Temps

what are they that you will require ?

avionator

temps

still unsure of exact temps needed, but from what i have found the ceiling mounted radiant should run a bit higher than the in floor.  I've got to go back and look at my heat loss stuff.  looking at the uponor cdm7 it appears the ceiling may need to be about 20 degrees (F) higher than the floor. 



one thing i stuggle with the heat loss is that one area in our largest zone has a 16ft ceiling height whereas the rest is 8ft.  i can't find any calcs that involve a higher ceiling.  any leads?  (my current heat loss estimates are based on simply online whole-house calculators) another issue is that the current master bedroom (ceiling heat install) will become a loft at some point.  I'd wait for the full reno to do the heating but right now the heat in our future babies room really is substandard (poorly designed hot water finned baseboard).  plus, there's always the chance that the addition/reno won't take place... so the "project manager" really wants the upgraded heat, pronto!



I live in a rural area where i can't seem to find any good contractors, so most of this work will be done myself (gas hookups done by local utility contractor).  first guy i brought in told me just to staple up pex loops without heat plates or anything.  a 2nd contractor came in and did a fancy estimate using an ipad.  quote in materials alone was more than double the cost of the materials that i could source (same exact materials!).  another guy did a "heat loss" but jotted down rough dimensions on a notepad, didn't measure windows, didn't ask about insulation. he never even bothered to call back.

i really thank all of you for your help and direction in this.  Once this is finally in place we'll have the best set up heat in the area!

avionator

circulators/valves

as an addendum to the above:

this is one of the reasons i'm looking at the bumblebee and full outdoor reset as well as having mixing valves.  I figure this can compensate for fuzzy math (as well as the unknown insulating envelope in parts of this house) with a flexible design.  we also plan to upgrade insulation and add an addition at some point. flexability is key.

Jean-David Beyer

avionator said:

new thoughts: wm97+

ok, after looking around a bunch i'm now leaning toward a WM97+ 110k btu boiler.  It's got the right price, right output, and a stainless steel burn tube.  zman, thanks for all the great info on materials such as stainless vs aluminum. 

does anybody know much about the Weil-Mclain unit?  sure it's stainless... but is it reliable?  i presume such.  but one should never presume...

anybody know about controls for the WM re: my original question?  Looking to control a seperate temp on a parallell curve.  will the wm97+ do this or do i need a seperate controller?  i can't seem to find any specific to the wm.  tekmar maybe?

I do not have a WM97+, but I do have one of their Ultra 3 units. If its controller is similar to that in th WM97+, you can have one fixed temperature for domestic indirect hot water, and two separate reset curves for home heating. They will not run at the same time. Each of these three has a different priority, so typically you run the domestic hot water at priority 1, since it will run only a short time. Then the other two zones at priority 2 and 3.

The way I do it is to run my radiant slab zone (low temperature) at priority 2 and my fin-tube baseboard zone (medium temperature) at priority 3. It is wired up so that if both the radiant zone and the baseboard zone are calling for heat, they both get heat, but at the lower temperature demanded by the radiant zone. This way the other zone gets some heat even if not as much as needed. The controller will not let any zone hog all the time. The installation manual for the Ultra 3 is very good. I assume the manual for the WM97+ is also good. These are avalable on line as .pdf files. You can download them.

RobG

How do you plan on doing the Radiant ceiling? Hopefully not just laying the tubing in the joist bays and covering with insulation.

Rob