manifold

Paul S_3

I will be doing a job I have never done before... Current system is a old two pipe hit water system with column radiators....the highest heat loss in a room is 11,500....customer wants to separate first and second floor on separate boilers....I was originally going to do a two pipe system with one inch copper reverse return....but then someone suggested on this site to use radiant manifolds and connect the radiators with 1/2 pex...has anyone have any experience with this? any tips? Should it be piped in reverse return? And the risers leading to radiators will remain,I will only be removing the Mains.....risers are 3/4"for second floor and 1"for first floor...can I just adapt to those lines with the pex? Thanks Paul s

Eastman

not to hijack your thread

but why do they want a boiler for each floor?

VA_Bear

Customer Request

Does the customer want to shut off a floor completely? If so, consider that the loading will change (adjacent space will no longer be conditioned and will be a heat loss when shut off) and if not, I would consider a high turn-down modulating boiler to give them a higher savings year round and a definite installation and equipment savings up front, even with the higher cost of a mod boiler.

heatman101

No problem...

Did that years ago for a big bed/breakfast....used manifolds and 1/2 hooked to radiators in each room. T-stat in each room controls zone valves on the manifold...works great!!! Just make sure you pipe the boiler P/S.....and you will have no problems.

Also, with the addition of a pump, there is no need for reverse return...

Paul S_3

primary secondary

What happens if I don't pipe primary secondary?....each floor would have its own pump and its own supply and return manifolds....customer is making first and second floor separate apartments....7 radiators on each manifold(zone)....basically when a thermostat calls for heat it will turn boiler and pump on and will heat 7 radiators on its manifold....not getting allot of money for job so really don't want to pipe primary secondary...also using atmospheric boiler thanks Paul S

VA_Bear

Heatman, do you mean...

P/S on the mod boiler or on separate boilers for each floor?

VA_Bear

If you are running both circuits off a single boiler...

P/S is necessary to make sure the boiler sees the flow it needs for correct and safe operation.



Even with two single boilers, I would prefer P/S with a hold on the secondary loop pump until the primary loop comes up to minimum temperature to protect the boiler from shocking, especially since the customer may be shutting down the boiler on a regular basis.

heatman101

P/S.....

I would do P/S no matter what.... that will CYA in case some of the radiators get turned off in the future and water flow drops....I cannot see any situation where I would not do P/S.......a little more work and a few extra $$, will save a ton of headaches down the road!!

heatman101

Yes, yes, and yes....

Good points on all of the above.....

P/S will just make everything so much better with an installation like this...

Running all that cold water from the CI back into that CI boiler will cause it to condensate most of the time it is running....bad news...

Paul S_3

primary / secondary

thanks guys for all your help. I will be doing primary / secondary. do you think one pipe / or two pipe primary/secondary which one would be better? probably two pipe due to temp drop.... and reverse return for the radiators to the manifold would that help with ? Or I wouldn't need it? Thanks Paul S

Zman

Which boiler?

If you are working with a single zone on a bombproof cast iron boiler, I would not do primary secondary unless the manufacture requires it. Cast iron is not very fickle about flows and primary secondary does not magically eliminate thermal shock or low return temps. If temps are a concern, you need a boiler protection loop.

Carl

Jean-David Beyer

not getting allot of money for job so really don't want to pipe primary secondary.

I am not a heating professional, but I did watch the installation of my mod-con boiler and the related plumbing. It seems to me that the person doing the work (he also had a helper) spent about 15 minutes to 1/2 hour plumbing in the closely separated Ts. Some of it was 1 1/4 inch steel pipe, but by the closely spaced Ts it is 1 1/4 inch copper.



I do not know the loaded salary of the installer and his helper, but how much could that come to compared with the cost of the entire job? It seems to me that the main additional cost of going primary-secondary is the cost of the boiler loop circulator. If you add the cost of the loaded salaries and the circulator, I would guess it would be less than 5% of the total job (but since I am not a professional, I may be overlooking something.). Why is primary-secondary installation considered so much more difficult and expensive that conventional installation? Do professionals quote jobs with so little margin for contingencies?

Zman

Unneeded

Primary secondary is a great tool when needed. It's kind of like unnecessary surgery if not.

If he needs anything it is an ESBE valve.

Carl

Paul S_3

Carl

That's what I was thinking.....its a standard crown Aruba cast iron boiler....I really want to shy away from using primary/secondary due too the price of job...customer without a doubt will not dish out any more cash...but I am pretty concerned about low return water temp....I have three pumps on supply of boiler....how can I run a boiler bypass from the three zones...I know it has to be in front of the pumps to divert the water to return.....thanks Paul S

Weezbo

what fuel ?

oil?

Nat Gas?

if oil using a bypass at the boiler with a taco i series setpoint control might be the ticket .

if nat gas a condensing unit would be the ticket.

Oil could use primary secondary with a bridge like an injection loop, 4 way mixer iseries with OR would be good way. protects the boiler and the field side .

with constant circulation , the question arose what if one of the people do not pay the bills then what ? My answer would be that typically after the install , the proud owners are then responsible for maint ,electrical and fuel bills.... not the installer.

To your question about lashing the pex to the return and supply for each floor that would be reasonable on the system side ,....the boiler side though , you would want to get away from the room and only show your copper work and near boiler piping . hosing it into boilers not only looks bad it really doesn't fly due to things like low water , secondary high limits and possible water temp overshoot that might create personal safety issues.

Oh , running pex over and back to a header off a radiant mixing block is sharp , from the individual floors , emitters.

Zman

OP

To the original post. The 1/2" home runs will work well as will reverse return.

If you are trying to do outdoor reset, prevent condensation, or thermal shock, there are piping stratagies for all of these. Non are primary secondary. If you want to do a simple high temp, one zone heat system with a CI boiler, just pipe it direct and be done. Most are designed for a steady state delta t of around 20 degrees. The boiler will come up to temp, burn off the condensate and life will be good.

Carl

Paul S_3

fuel

The fuel is natural gas....the pex will be ran to a manifold in the ceiling which would not be seen after the install...a access panel would be install for future service to access the ball valves on manifold....cannot use condensing boiler....because customer would say to expensive....in this case customer just wants heat to work properly and to have the big cast iron Mains removed....that's the reason for the Pex and manifolds thanks Paul S

Paul S_3

bypass

So should I pipe a bypass after each pump to its dedicated return line? With a full port ball valve in the middle of piping? Thanks Paul s

Weezbo

mains....

ok well , hmmmm...

the 1/2 " pex now are not going to allow the heat to get off the train sort to speak until they get where they are going .

big mains on the other hand act like an emitter in their own right. meaning that they allow some of the heat to get off the train on the way to and from not just when they get to where they are going,.. so this may mean depending on the size and length and complexity of 90's and t' etc,...you may have to put some auxillary heat from the area you took them from ...because some older boiler guys were fanatic about saving a dollar and may have calculated that pipe heat loss to deal with the heat loss of the rooms

Paul S_3

Mains

Adding a baseboard loop in basement to compensate the removal of the Mains....Paul s

Zman

Goals

Paul,

What type of boiler?

One zone?

Carl

Weezbo

Good thinking ...

it seems you definitely have the right idea .

so you will have some thermostats one up one down , a small header couple pinner nat gas boilers done deal .maybe a by pass on the boiler so it becomes satisfied sooner . ,

like that ? a paco temp gauge at the return just after the by pass a ways will let you know what the return temp the boiler is seeing.

heatman101

Bypass will work, but....

Even if you take the handle off the bypass valve......a few years down the road some smuck or Joe owner, comes in and cranks the valve shut or open, not knowing what it was for.......then what do you have??? Not saying what is right and what is wrong.... just saying that there are many ways to skin a cat....but some are better then others.

Paul S_3

for now

For now it is one boiler....it will have four zones two of them will be heating the radiators on the manifolds each with there own pump....the other two will be controlled with one pump and two zone valves....these will be a basic baseboard loop ....so four zones in home.....first floor (radiator)....second floor (radiator)....basement (baseboard).....attic (baseboard)....boiler is a natural draft crown Aruba hot water boiler....what I mean when I wrote for now is in about a year when the customer gets more money....they want to put the first floor and basement on one boiler and the attic and second floor on another...each with there own gas meter...customer rents out the home add two individual apartments and eventually wants them to pay there own gas....which also means one boiler would be grossly oversized....I explained to customer about that Paul s

VA_Bear

Some do and most customers don't know the difference...

... between a good and a poor installation, so they see no reason to spend more than the low bid. Much of that is customer education on both the customer's and the contractor's part in my opinion.



Primary/Secondary systems piping is not significantly more costly, but the primary loop pump and it's components adds a cost factor which is above and beyond the low ball bid.

VA_Bear

Doesn't an ESBE mixing valve...

still need a pump on the boiler side and a pump on the radiation side? No cost savings there and I can hold out the secondary pumps with a simple pipe mounted aquastat until the primary loop reaches an acceptable temperature for the boiler.

Zman

I get it..

OK,

As for the 2 boiler thing, they're nuts. It would be far easier to either put BTU meters on the zones or limit the t-stats.

I still contend that primary secondary will not fix a boiler condensation issue. It is the same water and BTU's, it is just flowing at a different rate. Fast water will make a boiler condense just like slow water.



An ESBE valve will solve the problem, it will require an additional circulator. http://www.danfoss.com/North_America/Products/Categories/Group/HE-HEC/ESBE-Valves-and-Actuators/Thermostatic-Boiler-Protection-Valve/84a52eb4-7041-43d5-8d75-ee4904ce840c.html



A bipass will probably work, it is just kind of a guess and people may adjust it down the road.



I think you need to decide if you have a condensation problem. If you had all baseboard heaters, I would say no problem. The cast iron radiators make me wonder. How many? How big?



It is normal for a cast iron boiler to condense on start up,as it comes up to temp. As long as it burns long enough for the condensation to dry up and go up the flue ,you should not have a problem.



Carl