one pipe hotwater questios (leo g)

leo g_84

about the velocity needed in a one pipe system using diversion tee's, that is running through old convection radiators. (copper with about 4" metal fins at the bottom of the unit, that sits about 3' high.) the problem is that before these people had their old boiler replaced, they never had problems heating the home.

the new boiler is a larrs coppertube boiler, and the pump is pumping into the boiler, a 15-42F. the far end of the home (about 200' total run) now never gets warm enough.

question 1) is the circ big enough, and if so, i would imagine that i will be moving it to the supply side.

question 2) any idea what btu per foot those old convection rads put out per foot?


thanx!

leo g

Big Ed

No Flow

The B&G 100 was made for the Monoflow system. Sometimes a 007 does not work , you can try a Grunfos or a #100 again. Just a thought and worth a check?Did they installers reverse the flow ?

Steve_35

Size the Piping

leo g: about the velocity needed in a one pipe system using diversion tee's, that is running through old convection radiators. (copper with about 4" metal fins at the bottom of the unit, that sits about 3' high.) the problem is that before these people had their old boiler replaced, they never had problems heating the home.

It's not velocity so much as flow and head required.

leo g:the new boiler is a larrs coppertube boiler, and the pump is pumping into the boiler, a 15-42F. the far end of the home (about 200' total run) now never gets warm enough.

What's the total heat loss (or connected load) on the loop in question? How many monoflo tees? What is the total length of the loop from the boiler back to the boiler and what size is the pipe?

leo g:question 1) is the circ big enough, and if so, i would imagine that i will be moving it to the supply side.

Having it pumping away would be a good idea but I don't think that's going to solve your problem.

Mark Eatherton1

Sounds like...

an air problem to me. One pipe systems are a P.I.T.A. to purge. Shut the pumps off and do a top bleed until no more air comes out, re-fire and see what happens.

With venturi tees, the greater the main flow, the great the branch flow potential.

ME

Earthfire

Circulator location

With a cooper tube boiler like Laars, the manufacturers spec the pump feeding into the heatexchanger so that they have max flow and minimize any chances of flashing and cavitation. Are you getting a 20 deg. temp rise across the heater. If not the flow thru exchanger is of. Might want to try Primary secondary with continuous circulation on the house loop or a buffer tank.

GaryDidier

Flow

I agree with Mark. It is either air in the convectors and or a flow problem. Try a Taco 0010 which is designed as a replacement for the B&G 100.
Gary from Granville

leo g_85

latest

the last installer was nice enough to leave the Laars manual behind. according to the book, the size (160K) boiler that was installed should have pri/sec. which it does not, just a real bad boiler bypass loop. the longest run is about 200 feet, contains 5 convector rads and has 10 venturi tees. the rads are heating, just not hot enough. i could literally hold my hand on the fin and not get burned, this after this zone has been on all night.

it appears to me, that the circ, being mounted right on the return nipple of the boiler, seems to be just swooshing the heated water around the bypass loop, while very little heated water gets out to the system. (the boiler reaches max in about 10 seconds, shuts off,... cycling fast and hard) there is a tekmar boiler control also, but i will remove it, as there does not appear to be enough radiation, for outdoor reset to work .

as for the delta T across the S/R, at the nearboiler piping, it is only about 5*, but if i measure beyond the bypass loop, it seems to be pretty well 20*.

i measured the house today, and am about to do the heatloss, but i think the answer is already quite clear, i am going to have to repipe the system as Larrs says, and use a bigger circ for the system side.

as for air, i'm feeling that there isn't much of a problem that way, as i couldn't hear any, even with my stethascope.

thanx for the replies so far guys.

leo g

leo g_85

no,

it appears by the original zone valves that the installer got the flow direction right.

thanx,

leo g

leo g_85

do you know

of a buffer tank that can take 180* temps?

leo g