New radiant system

thfurnitureguy_4

Being done now. Thanks for all the input

thfurnitureguy_4

New radiant system

Getting started on a new radiant system. The plan is to use Pex Al Pex in the joist bays under the wood and lam. flooring (about 1/2 of the house) and use modern Euro style pannel radiators in the bedrooms with carpet.The bathrooms would have a mix of towel warmers and radiant floor. The question is about zones and controls. I need advice on where to zone or if to zone. We would be using the whole house when were there and only keeping above freezing when were not there. (for weeks at a time) We were advised that since the AC is also being replaced It may be a good idea to use a heat pump system to do the "Keep from freezing" heating and use the radiant as a backup during that mode.
With the 3 types of emitters how do you balance the rooms? I would like to use an efficient boiler for this and have oil as the only fuel. What kind of choices would work well for this? What would you pick as for pannel Radiators, TRV, Outdoor reset and boilers? Hope to start getting bids on this this week and any help would be great. As always thanks for any input on this.

Brad White_9

Balancing Emitters

The most effective way to balance emitters of different types is by varying temperature to them, not flow to them. Much more linear than volume to output ratios, so mixing stations of some sort are required for each "flavor". At a minimum, floor radiant would have one temperature and radiators another. If your radiant floors have different coverings (tile versus concrete versus staple-up with or without carpet, etc.) you will want to sub-divide those also.

Towel warmers and panels are to me the same type, but panels have more convective output.

For freeze protection I would not be so "electrically dependent". Heat pumps do not work well in power outages- in fact they do not work at all

A mild glycol solution would be best. Noble No-Burst or any good quality inhibited propylene glycol. Not too rich especially if you use a condensing boiler. The surface boil off in the tubes gives a moan which I have heard described as a banshee in the piping.

Unknown

I disagree. You can balance water temps to radiators and radiant floors without doing a seperate temp for each.

And zoning within the same emitter type is driven by your heat load calculation and living patterns, not just floor coverings. That carpeted bedroom at 60 degrees may need the same water temp as the extremely restricted floorspace tile bathroom at 70 degrees. Or, not!

Mike T., Swampeast MO

Heavy conduction plates with the underfloor?

Zoning has much to do with layout. Rooms with permanent opening of 4' or more to others effectively become one room and it makes little sense to divide them into individual zones. TRVs do their own "zoning" so the point is moot with them. If the radiant spaces are mainly open to one another a single radiant zone should suffice. The baths may be the exception as people frequently prefer the baths warmer than other spaces. With careful engineering of the panel you can have the baths on the same zone as the rest of the radiant spaces yet still producing a generally warmer temp. Otherwise, a separate "baths" zone (t-stat probably in the master) could be used. You could also consider FHV (floor heat valves similar to TRVs) for the bathrooms.

Towel warmers can present a problem--particularly if you want warm and fluffy towels year round and yours is not a climate where space heating is used nearly continuously. Running a boiler just to satisfy a few towel warmers is very inefficient. You might want to consider oil-filled electric for the towel warmers. Whatever you do, don't just hook the towel warmers into the DHW system in series with a shower.

Using a heat pump to "keep from freezing" may well be effective in moderate weather--in cold weather you'd probably be better off using the boiler system. Being away for weeks at a time in the winter gets a bit spooky with a hydronic system unless you use antifreeze--don't forget that such MUST be monitored and maintained! If you use a good freeze warning system and have a close friend/neighbor that it can telephone (via a land line) you might forego the antifreeze.

Brad White_9

Temperature versus Flow

Firstly there is a presumption that emitters are properly sized by heat loss calculation and are proportional to the heat loss. Different floor coverings do require different temperatures unless the densities of tubing are designed for the common water temperatures. So many variables in construction. Example: If a staple-up job between joists with plates, you have limited choices, only so much tubing and plates. Being common to all floors the most effective variable you have to work with is a different temperature for each mass or floor covering. Volume modulation lacks proportional response.

Yes, you can increase or decrease your emitters to suit a single common water temperature, of course. Another discussion.

I never said that you could not; the question I chose to answer was, "what is the best way in my opinion ("how would I"..)"

I maintain that temperature is the most effective not the only way. Also panels may want to respond faster for pick-up (being an apparent vacation home) and the radiant would respond appropriately more slowly or act as a base-line.

Here is why temperature is a more effective means than volume, relative to emitter output:

When you reduce volume in a given emitter by say, 50 percent, you will still have approximately 90 percent of your output. You may double your delta-T across the emitter which only reduces the average water temperature by half of the former difference.

Example:
1.0 GPM at a 20 degree Delta-T, 180 in/ 160 out / 170 average.

0.50 GPM at a 40 degree Delta-T. 180 in/ 140 out / 160 average. Ten degrees drop for 50% flow reduction. Not a lot of reduction in output for the effort, and little range left for further reduction. Then you get laminar flow and other pheonomena to thwart heat transfer.

Now. let's put temperature modulation to work for us: Take that volume control valve as an injection mixing means to a secondary circuit: The supply water temperature can now vary between full boiler supply (or design emitter maximum) and near room temperature (emitter minimum where heat ceases to flow).

When you see a graph of flow versus output it is a flat top curve rapidly dropping only below 50 percent turndown, sort of a hockey-stick. Temperature versus output is decidedly linear, hence better.

Not the only way.

Respectfully always,

Brad

Unknown

Different floor coverings require different water temperatures IF your per square foot load is equivalent. Your 25BTUs/sq ft bath with its tubs and sinks and tile floors though, may need the same temp as your 15 BTUs sq ft bedrooms with carpet, especially if you want different room temps. That's all I am saying there. Floor covering variation is just one variable of several there.

Varying temperature is undoubtably "ideal". It's also undoubtably expensive to add additional mixing systems, and increases your system complexity, giving you even more points of failure. Multiple temps is fine when necessary, but personally I would jump through serious hoops to avoid it on most projects where I would rather the person put money into a better boiler, emitters, or insulation and guarantee comfort by properly sizing radiators for whatever temp you are working with, if possible.

Brad White_9

We agree, Rob

More than you realize. Yes, I do follow the KISS principle wherever possible. As simple as possible, not simpler.

Brad

Unknown

Well smooches to you too brad kiss kiss!

Brad White_9

Just respect me

in the morning, Rob.

thfurnitureguy_4

Heavy conduction plates

I'm going to guess that a conduction plate is a plate that contacts the radiant tube and spreads the heat over an area under the sub floor. (correct me if I am wrong). I was considering a pex-al-pex tubing system inside the joist bays. This would use a foil backed foamboard insulation below the tubes and I believe no plates. Could you comment on this technique. The goal is to keep this as simple as possible, but I would like it to heat as well as the fin tube BB I'm replacing.

Unknown

This is a very weak system that runs at high temperature. Depending on your heat load, it may or may not even work. Step one is always make sure the heat load calculation is done, room by room. That unlocks the info you need to make good decisions.

JimL

I agree with Rob. Get an accurate Load worked up first. If your going underfloor, I would use plates. Lower temps and a much more efficient method of transferring the heat. Why run water temps at 150, 160 or higher? Don't let anyone convince you that the plates don't make that big a difference. They do. As far as the foam board goes, we typically put in R-19 or as much fiberglass as we can while maintaining a 2" air space. There are some valid arguments that the foil will lose some of it's effectiveness over time due to dust accumulating on it. I personally think the fiberglass is a little less labor intensive than trying to fit the foamboard snug in the bays. I would use foamboard on the rings though and foam fill any gaps. JM$.02. Jim

Weezbo

i saw a new Gravity boiler today! *~/:)

it comes in four sizes up to 40K BTU's it just looks so low tech i love it

it is oil:) the smallest one is 6,800 BTU's ...:) it is non electric:)

that might fill the bill, furniture guy, for the "keep from freezing part" *~/:)

the pinner boiler burns .035->.o79 gallons per hour...

the largest burns from.122->.399 GPH

thfurnitureguy_4

how does it light?

no electric? How does it start up?

Would it be better to go above the sub floor in the hardwood section of the house? if so what brand of plates. Do you need to use all of the fillers between the pipes or is there a pre fab type setup? House is in plywood now, no flooring. I would DIY the hardwood (being the wood guy and all)

Brian (Tankless)

April 1st has

come & gone Wheeze :O)

The oil tank has to be mounted say, 250 ft higher than the boiler, and the blower and ignition are solar powered. Am I close, or is it still April fools day?

I'm back off to the wild & wooly frontier town of Cameron, LA. No stores, gas stations, pubs, girls, nothing, just work & sun & mosquito's

Later guys.

Brian.

Weezbo

Take alook at Toby oil control valve,

or Nordic stove ,non electric Oil Heat...i think this comes in two types one is convector has a small chunk of "baseboard convector "that comes with...

Weezbo

It is ,so ...plain Jane *~/:)

i think it is about as dumb a gravity heater as a guy could imagine:) ok a Guy half hot on the 4th of July over worked under paid thinking ' whats The easiest way to heat my Yacht Ketch or Yawl, that i will never own?'

And BANG! There it is ))

the thing looks so anti tec it could have been designed by iron age man

i just think it has some uses that just scream for low to no tech, Trappers camp(small cabin),boat,pinner remote miners camp some place that needs portable heating appliance and want Radiant Boy scout tent for the scout masters:)

"Ok Kids ,lash up the he pex on the blue foam and go put up the ;freezing cold, leaky, twelve man tent for use guise "

See how well i use the English language ?...when i want to?:) did you see