Primary secondary piping

World Plumber

I'm replacing a boiler that had been condensating and decided to break in half while sitting idle. I want to use primary secondary pumping on the new boiler. It is one large zone with 3 inch headers. should I use flow control valves? Should I have both pumps come on at the same time or bring the secondary pump on after the boiler warms up?

Mark Eatherton

If it were me...

I'd use a Danfoss Thermic valve.



http://na.heating.danfoss.com/PCMPDF/ESBE%20TV.pdf



Guaranteed success!



ME

World Plumber

the house & boiler

The house has cast iron radiators 1108 sq. feet plus some fins added to piping. The owner decided to stay with oil. The gas company wanted 11k to run the gas line across the street. I'm using a Dunkirk boiler that can be fired from 168k to 280k. I intend to fire at 200k output based on the load.

CMadatMe

Oversized

If that is the sqft of EDR and this is hot water you are way oversized. What's the heat loss?

World Plumber

Thermostatic valve

Mark

I was looking at the primary secondary based on the recommendation of the boiler company of the failed boiler. With the single zone and the thermostatic valve. Am I right in ascertaining that I will only need one pump?

Thank you

      Mark

Mark Eatherton

Go with the left hand drawing...

And put a manual bypass around the Thermic valve, otherwise purging will be difficult.



I've seen your work before. Take lots of picture when you are done.



ME

World Plumber

oversized

I don't think so. The old boiler was firing at 200k in and 185 out and couldn't get the water in the system above 130 degrees. But that's why I choose the Dunkirk over putting the same Peerless back in. I have many firing options. I can go up or down from where it was. At 180 degrees you need the calculation is 199+K plus piping loss. At 150 degrees the load is 187K

Mark Eatherton

How do you figure Chris?

1108 sq feet EDR @ 150 btuH/Sq ft = 166,200 btuH.



166,200 divided by .8 (assumed combustion efficiency) equals 207,750 btuH input.



If the house is 1108 square feet, the boiler IS grossly over sized.



1108 * 50 btuH/sq ft = 55,400 btuH. Nothing like driving a tack with a sledge hammer eh...



ME

World Plumber

Thermostatic valve

Mark:

  Your suggesting the thermostatic valve on the return side? If I push the water with the pump on the supply side will that have any adverse affects on the operation of the valve? For a balancing valve do you suggest a gate valve over a ball valve?

MC

World Plumber

Radiation

1. It is 1108 sq feet of radiation. The building is 92 feet long and 42 feet wide on 2 stories the third story is 72 feet long. The 3 inch mains make a complete loop around the building. I haven't calculated the volume of water.  But it is a lot. I know it takes over 3 hours to fill the system when it is empty.
   
   

Mark Eatherton

No adverse effects.

Yes, on the return side. You are trying to protect the boiler from too low of a return temp.



The actual thermostatic device on the inside of the valve is similar to an automobile radiator thermostatic valve, in fact it has a 1/8" hole in it to allow for miniscule fluid movement to activate the operator and act as a small bypass.



The balance valve assumes that you have high pressure drop emitters on the output side If you have large pipes on the system, pressure drop will be nil, and the choke is probably not necessary. You can use either a gate or a ball. The gate might rattle with the gate being mid throttle range, and the ball valve will have to be closed 90% before it seriously begins throttling.



I usually pipe the purge bypass at least one pipe size smaller than the Thermic.



ME

World Plumber

Thank you

Mark:

     Thank you: That sounds like it will be easer than the suggestion of the s/p by Peerless.

     MC

World Plumber

140 vs 113 degree

Mark:

     With that large of a volume of water do you think the 140 degree would be better than the 113 degree valve?

      Mark

Mark Eatherton

Yes, One pump....

Also, this is a bottom fill, top purge system. You'd need a fire truck to force purge this system. I've used a fire truck for purging a heating system before, and it is not fun...



ME

CMadatMe

ME

Have to eat crow on that one. Your spot on and I know the output. I stopped at 100 in my head and forgot to add the 50.

Unknown

Weeell Chris,,,

perhaps you`re not right,,, like you think of yourself all the time,,,, ;-).

But then again,,, ME is like that too!

Mark Eatherton

The difference in the two...

If it is a German cast iron boiler, you can go with the 113. If it is a North American boiler, go with the 140.



Difference in casting technologies and the ability of the cast irons resistance to corrosion.



ME

NRT_Rob

what does "couldn't get above 130" mean?

with that much water, I would suspect you've got "mass reset" going on here.



that is, so darn much mass that you basically have outdoor reset because the system heats up and satisfies the load before all the water in the system hits a higher temp. the lag in heating because of all the mass slows down the temperature rise, that is.



that means EDR would be way oversized and you'd have a lot of water. Such as you might see with 3 inch pipes, old cast iron, in a building that has been insulated since the radiators were installed.



on the plus side, you can't oversize a boiler on a buffer mass like that.



boiler protection seems like it might be a good idea though.



only if the boiler runs constantly in cold weather and can't elevate water temps... AND THE ROOMS ARE COLD... is it "struggling". if the system just runs cold all the time, that's just mass.

World Plumber

Over 130

Rob; The boiler runs about 3 hours to satisfy a call for heat. The large mass keeps the temperature low. Thus I had a condensation problem. The boiler was rusting away from the combustion side. It rusted out the flue collector box. Lots of rust in the sections each year. The cool water coming back may have contributed to the boiler breaking. This customer accounts for a large portion of my business. So I want to keep it from failing again if I can. My concern now is if I'll have a problem with the back of the building. I had the pump on constant circ with an aquastate shutting it down at 90 That appeased the tenants. I guess I'll be the first to hear if they are cold when I get back to the States. I guess if I get back the the state the previous owner had, I'll have to add a second pump to circulate the water in the system.

NRT_Rob

well

you can't oversize this, with that much mass. so put in whatever boiler you like.



just temperature protect it. Use a variable speed injection system, or a big mixing valve.

Mark Eatherton

Dave....

I am only human. I put my pants on one leg at a time, just like Chris and you. If I make a mistake, like Chris, I fess up. I think it is good of Chris to see the error of his ways, and were it not for the thousands of newbies reading this, I probably wouldn't have made a comment.



Your comment could have gone un-noticed, which is my usual modus operandi.





Reminds me of what my mother use to tell me as a growing child. "If you have nothing positive to add, add nothing..."



Can we get back to educating each other and quit digging barbs?



Peace.



ME

Mark Eatherton

My pleasure...

Always ready to help a fellow hydronicist.



ME

DanHolohan

Dave, please.

This isn't the first time you've taken shots at Mark and I'm trying to understand why. Please contact me by e-mail: dan@heatinghelp.com. 

Unknown

You`re right Mark,,,

and I apologize(not on Dan`s say-so), just my own stupidity.

Please accept,,, my "barbs" wont happen again!

DanHolohan

Thanks, Dave.

And thanks for all that you bring to the Wall. Here's to peace in the valley. 

Mark Eatherton

Thanks Dave.

Keep on doing your great job of educating.



ME

Unknown

Thanks mucho,,

Peace in the valley,,, wasn`t that the name of a song?

Hank Williams Sr. maybe, have to look that up,, LOL. ;-)