2 zone, prim/sec piping, one zone must have constant circulation.

DougieFresh

just pondering ideas in how to solve a problem before it becomes a problem....i am currently installing a Munchkin condensing boiler, with primary/secondary piping, with two "baseboard" zones. i have to make the first floor zone operate with constant circulation,( pipes run in an uninsulated crawl space, which is very drafty and almost impossible to work in). i am zoning with Taco 007's. here's the question, what other control(s) or device(s) should/could i install that will allow this zone to be isollated from pri/sec piping, without interfiering with other zone??? thanks for the help!

KevinCorr

why?

Why must it be constant circulation?

CMadatMe

It already is isolated

By piping pri/sec you have already created hydronic separation. Zone 1 pump has no influence on zone 2 pump. The only problem with primary/sec is that you must take into consideration that the water temp entering zone 2 is going to be less than zone ones when both zones are callling.

For instance, lets say your system needs 40,000 btus and 4 gpm.  Zone 1's load is 25,000 btu's at 2.5gpm and zone 2 15,000 at 1.5 gpm. Your supply water temp is 180 out of the boiler.

With both zones calling this is what you need to take into condsideration.

Zone 1 will be supplied with 180 degree water at 2.5 GPM. Giving you an approx residential baseboard output of 581 btus a foot

Zone 2 will be supplied with only 167 degree water at 1.5GPM. Giving you an aprprox residential baseboard output of only 500 btus a foot.

Make sure you do a heat loss and that you have enough baseboard for zone 2.

DougieFresh

constant circulation

the reason for constant circulation is to prevent pipes from freezing. it is physically impossible to crawl in this uninsulated "crawl-space". i figure constant circ. would be my safest option. my problem/question is, with zone #1 constantly pumping, when zone #2 calls for heat, im afraid zone #1 may over heat. catch my drift?    doug

DougieFresh

baseboard sized accordingly

i catch your drift. but i am afraid that zone #1(constant circ.) will over heat when zone #2 calls for heat. i did a heat loss calc, and sized baseboard accordingly. i'm trying to figure a way to "isolate" zone #1 from pri/sec piping, as in installing a zone valveon the supply and a balance valve between supply(inlet side of 007) and return line from this zone. let the stat open the z/v in which would allow "heated" water into loop, and the balance valve would be open just enough to allow flow through loop when the z/v is closed( prevent freezing pipes). thanks for your rely(s)   doug

clammy

temperture controller /3 way zone valve

Doug how about a 3 way zone valve on the suction side of your pump controlled by a room stat and a simple outdoor temp sensor that runs the cirulator when temps approaches 32  .When your stat calls for heat it opens the 3 way valve it's end swith makes the boiler ,your will have constant circulation based on outside temp and if need be you an install a aquastat on the return piping for that zone and set it to maintain what evevry temp you feel safe with that won't heat the space but will not let the piping freeze.A simple robert shaw set point controler should work fine to run the circ on out side temp .You will have to iron out a simple wiring diagram but this layout has worked for me in the past peace and good luck clammy

DougieFresh

thanks clammy

thanks for the great idea(s).

Chris S

munchkin

Can you get 180 out of a munchkin?  The one pinnacle I work on goes to 170 max.

I had a similar issue with a hydo air system- we installed a bypass feeding a small amount of water to the loop, just to keep it warm,  then removed the valve handle & put a tag on it for future service men.

Chris

gerry_6

Keep it simple .

Why are you avoiding using glycol?

CMadatMe

Can you provided

A piping schematic of what you are trying to do? Even just a penciled drawing that you could scan and post.

DougieFresh

munchkins stand behind their word!

i have installed at least 35-40 munchkins, all makes and models. never had a problem with the operation. i design my systems to run up to 180, except during dhw priority @ 200. and yes the munchkin does operate up to 200 degree. maybe Peerless or installer "locked" in a min. and max. parameter on the unit you worked on?

DougieFresh

glycol?

munchkin, and as for most ultra high eff. boilers, do NOT recommends using glycol in their boiler. though it would've been nice to do that and take the easy way out.

KevinCorr

freezing

Glycol is for keeping pipes from freezing. Do you keep your car constantly running to prevent freezing?



While your idea can be implemented, you will be wasting energy and making the system unnecessarily complex.

gerry_6

Glycol??

Really     glycol NOT recommended in Munchkin and most high eff.  boilers ?       

    I DONT BELIEVE YOU!

Gerry Alder

gerry_6

glycol

Ok  Im sorry geuss  I should specify the right glycol. Here copy and paste right out of the Munchkin manual.

Use only inhibited propylene

glycol solutions, which are specifically

formulated for hydronic systems.







Use only inhibited propylene

glycol solutions, which are specifically

formulated for hydronic systems.

Slim

Glycol

I've spent a lot of time in the field with a few Munchkin reps, fixing botched installs. Where glycol is concerned, they've all told me the same thing:



1. No more than 50% concentration

2. Make sure its got the inhibitor. (I know most 5 gallon pails of Cryo-Tek -100 come with inhibitor)

scott markle_2

Water temps?

Chris, Can you elaborate? Why would one zone get hotter water than another?



As far as flow rates, the pipes are ignorant of the load, most base systems reach flow equilibrium based on head pressure of pipe distances, and this is unlikely to have any relation to actual loads. Your 15k zone may only need 1.5 gpm (@delt20) but what would stop it from getting the same 2.5 (or more) than the larger zone? In existing systems it's often very difficult to determine the length of pipe on a zone. With no way to measure or regulate flow it's kind of meaningless to be very specific about it. The reality is most systems are over-pumped and or imbalanced in terms of flow rates and actual loads. If when all zones are open, a longer zone should receive less than it's required flow this is generally not a big problem, it's is rare that all zones would remain on together for a extended time,because supply temperatures are generally much hotter than they need to be. Once the zones receiving adequate flow shut off the deficient zone will catch up. Even at design it's rare for a conventional system to have all zones running continuously. This changes when we introduce an aggressive outdoor reset curve . Now the zone of greatest demand will (if the system is calibrated properly) be running nearly continuously in wide rang of outside conditions. Flow balancing becomes more important in this case, and the solution is not a big pump.



One possible issue with the three way zone valve plan, (If I understand it correctly) is that while water is being circulated through the zone (bypassing the heat source) you will be circulating crawl space chilled water through the base, essentially assisting the movement of heat from the conditioned space to the freezing crawl space via the piping.



With the future of energy in mind, there is really no satisfying mechanical solution here, besides fixing the offending pipe work.

scott markle_2

glycol

Even high quality inhibited Glycol heated above something like 180 ( i forget the actual number but it came from a dow rep and it was in the heating range), Will eventually break down and become acidic, it also has a tendency to "weep' from imperfect thread fittings and o-ring seals.



I'd consider isolating it from the rest of the system with a heat exchanger

CMadatMe

I agree with You Scott

On your thoughts. As designers/installers do we not always have to size our systems based on worst case using our heat loss and design parameters? I see everyday more and more mod/cons going in without heat losses and it's going to bite back.

Let's take primary/secondary piping for instance and using the typical 20 degree delta-t. Just about everyone installing mod/cons is using this piping arrangement.

We have a system with a heat loss of 50,000 btu's (5gpm), it has 3 zones with zone valves. Zone 1 has a load of 25,000 btu's (2.5gpm), Zone 2 15,000 btus (1.5GPM) and zone 3 10,000 btu's (1gpm). How do you size the baseboard for each zone?

I size it this way and it is based on all zones calling on my design day (worst case). I have a system flow rate of 5GPM and I hit the first zone. 180 degree water enters at 2.5pgm leaving me 2.5GPM of 180 degree water in between my tees before that zone returns. Water enters the return at 160 degrees at 2.5GPM leaving me a water temp before I enter zone 2 of (2.5x180) + (2.5x160) divided by 5 = 170 degree water at 5GPM. Now, 170 degree water enters zone 2 at 1.5gpm leaving me with 3.5gpm of 170 degree water in between my tees before the second zone returns it's 1.5gpm of 150 degree water. After doing the same calculations I have 164 degree water at 5gpm flowing towards zone 3. I enter zone 3 with my 164 degree water at 1gpm leaving me 4gpm of 164 degree water in between my tees headed toward  zone 3 return. I now have 1gm of 144 degree water returing from zone 3. Using the same formula it gives me my return boiler water temp of 160 degrees.



Each baseboard zone must be sized individually not as a whole. In this case.

Zone 1 Baseboard btu output is 581 per ft so I need 43 feet of board

Zone 2 Baseboard btu output is 508 per ft so I need 30 feet of board

Zone 3 Baseboard btu output is 460 per ft so I need 25 feet of board

Hope this makes sense.



Chris

Kevin_in_Denver_2

Freezing Crawlspaces can be Insulated

ANY crawlspace in continental North America can be made non-drafty and non-freezing with properly designed perimeter insulation.

DougieFresh

thanks to everyones responce

i went with the three way zone valve/control, which is working great. wouldnt glycol make the system more complicated? i think so. doesnt even the best glycol eventually breakdown into an acidic form? i think so.i thank everyone for "deffending" their answers, i went with the least expensive, and not so complicated sollution, as stated above. Doug

DougieFresh

freezing

i park my truck in a heated garage, which has radiant heat, and NO glycol. neither freezes.