Weil McLain GV question

Paul Mitchell

you are talking about is the cross over before the primary loop, max 12" etc. ?? just checking. So I am correct you have the one pump for internal bypass, One pump working this bypass then your system pump.

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Paul Mitchell

Weil McLain GV question

Looking at the installation instructions I notice that they require primary secondary piping when installing with radiators. The paperwork shows a circulator mounted in the main loop for the house. What it doesnt show you is that there are two circs in the boiler...One with some funky piping i guess to provide flow through the boiler. The other would be the system circ if it was baseboard. With that factory piping why do you think they still want yet another circ and not just a bypass?

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Al Letellier

GV

The second circ is the secondary pump to feed the primary loop piping, or the injection pump if you wish. I install a lot of Weils and have wondered this myself from time to time. I also realize the guys in their R&D department know a heck of a lot more about boilers, hydronic flow and engineering than I do, so I just accept the fact this is the way the system works best. I have many GVs out there and have had no problems with the 2 circ set up compared to the old thermostatic bypass on the first generation units.
It's a great little boiler if you like gas heat.

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Paul Mitchell

So Al

As I see it with the GV we have actually three pumps in the system in this situation. Was discussing this with one of the guys and he didnt get it. The injection pump comparison might do it for him.
Thanks

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BobbyG

GV boiler piping

Post: "What it doesnt show you is that there are two circs in the boiler...One with some funky piping i guess to provide flow through the boiler. The other would be the system circ if it was baseboard. With that factory piping why do you think they still want yet another circ and not just a bypass?"

The bypass pump in the boiler is solely to protect the boiler from return water of lower than 140 degrees. Instead of the thermostatic bypass valve they have the circulator controlled by a sensor on the return water line. So don't even consider this as a pump. That being said, they still want a "piped" bypass as the primary safety to protect the boiler from a low temp return with the pump "bypass" being the secondary protection.

Over the last two years I have seen around a dozen Series 1 GV boilers corroded and blocked up flueway because of the acidic condensation from the lack of a bypass in a large mass "radiator" system or low-temp application. That is why they are very cautious about this. It has to do with the flueway and burner being very susceptible to this condition.

The interesting thing is in the Series 1 installation manual it has the "piped" bypass for low-temp applications but not large-mass "radiator" systems. So the installers followed instructions.

BobbyG

In radiator systems I pipe a bypass (short piece of pipe that goes from outlet of boiler to inlet of boiler that includes a ball valve to throttle flow) and only use the two circulators in boiler(bypass & system).

Most of these are gravity conversions with oversized pipe and little friction loss.

The theory is the water coming out of the boiler will be drawn to the nearest circulator (point of low pressure) so the ball valve will have to be closed to restrict the amount of water being short-circuited back through the boiler. It is a way to pre-mix the outgoing (warmer) with the (cooler) return water. It was in the manuals for low-temp applications Series 1&2.

I would take precautions like a thermometer in the return line close to the boiler and take the ball valve handle off after throttling. I haven't had any problems doing it this way.

John (Siggy) Siegenthaler's piping diagrams are now in several manufacturers boiler installation manuals and this is why the piping is shown primary/secondary in the Weil-Mclain GV models.

If you would like a diagram e-mail me your fax number and I can fax it to you Monday A.M.