Click here to Find a Contractor in your area.
In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Need to contact us? Visit

Weil McClain GV-5 Series 1 w DHW wiring

dvizzdvizz Member Posts: 39
I have a wiring arrangement on my WM GV-5 series 1 boiler with a WM Combo 30 DHW tank I would like to upgrade. I am considering a Taco SR 506 Switching Relay. I currently have 4 zones which are controlled by 4 separate thermostats 4 Taco circulators and 4 Honeywell zone valves. The boiler has a circulator which comes on whenever a zone is calling for heat in concurrence with the heat zone circulator. The boiler maintains a temp. of 130 deg with a high limit of 180.

When the DHW aquastat calls for heat the boiler mounted circulator runs and a three way valve opens allowing boiler water to flow to the Combo 30 but shuts off flow to the line feeding the zones. There is a relay mounted next to the transformer for the boiler control voltage and this relay starts the circulator when the control voltage going through the aquastat calls. I've posted photos below and would appreciate some direction on rewiring the system controls. I understand the thermostat and pump wiring but am not clear on the aquastat boiler circulating pump wiring. I basically want a priority for the DHW so the zone pumps don't run when the DHW demand is shutting off the 3 way valve to the heat zones. The concern I have is the transformer mounted on the boiler and the transformer attached to the SR 506 conflicting.


  • icesailoricesailor Member Posts: 7,265
    edited March 2014
    3 ways:

    Is this Deja voux all over again?

    It would be easier to remove the three way valve and pipe the boiler with a primary/secondary system like they do for a Munchkin, with an indirect and install the 506 controller. Set the zone valve to have the water heater on priority.

    The GV Series 1 boilers I had worked fine with the priority switch OFF.

    What is that miscarriage of wires in the left hand picture?  I think I met that person once. Or was where he had been before. Argo made zone switching relays back then, You didn't need a 3-way to make that boiler run. Someone knew better than the manufacturer.
  • dvizzdvizz Member Posts: 39
    edited March 2014
    Weil Mclain GV-5 Series 1 w DHW wiring

    What your saying is remove the 3 way and install a zone valve on the return side coming out of the indirect. The aquastat on the indirect will control the zone valve and the WM internal mounted circulator through the Taco SR 506. Would the aquastat wiring connect to Zone 6 Priority on the SR 506? What about the zone valve wiring for the indirect zone valve, where is that tied in?
  • icesailoricesailor Member Posts: 7,265
    Wiring & piping:

    I don't know how much you want to put into this boiler.

    By removing the bad thermostat, you lose the cold protection it was supposed to give but lost. And still doesn't have.

    If I remember, you wanted to get ODR or something from the heating zones. You can't do that now without serious damage to the boiler from cooler waters condensing inside. It may already be damaged.

    However, there is a way if you are interested. I don't know your capabilities and you might need the services of the people that removed the thermostat/valve.

    Use a Taco "I" series 4-way mixer and install it in place of all of the zone piping. It becomes a primary loop of a primary/secondary system. One side of the 4-way is the primary and through adjustments of DIP switches, will give you boiler protection and ODR. Both of the heating zones get connected to the other ports of the 4-way valve. You will need a separate circulator for the heating zones that will work in conjunction with the primary circulator when it is calling.

    Because the 3/way zone valve is "Either/Or", you might be able to leave it as is. I'm not there and I can't tell if it is. If it is "Either/Or", the zone valves could be connected to a Taco 503 or 504ZC Zone Valve controller. The hot water indirect heater gets connected to the priority zone. When no call for the indirect is present, the valve is closed for the primary water to go to the indirect and the boiler won't run. If you get a call for heat, the zone valve(s) open and water flows through the primary circuit, through the closed 4-way, and back to the boiler. You should add two closely spaced tees and a circulator (007) to the heating secondary. The 3-way to the indirect is closed for water to go through the indirect. The 3-way MUST be closed to the indirect when there is no call and the water is all directed back to the boiler. The zone valve is connected to the Priority zone and the switch is ON. If the Taco 404 ZC closes the heating zone valves on a priority call, the primary circulator must still be able to run unless all valves are closed. If the indirect calls, Priority should take over and close the two heating zones, but open the indirect zone by transferring the primary circuit through the indirect and back to the boiler, It is sort of a take on what Munchkins do with a Vision Controller. Its either through the indirect or through the heat zone.

    I'll probably have to add to this. I have to go.
  • dvizzdvizz Member Posts: 39
    edited March 2014
    Weil Mclain GV-5

    Does the boiler maintain a low temp set point when there is no call for heat from the room stats and the indirect aquastat is satisfied?
  • icesailoricesailor Member Posts: 7,265
    edited April 2014
    Cold Start:

    Yes, it does. When it gets the call, the "I" series stays closed or partially closed until the boiler water starts to come up. It then modulates the water going into the outlet side of the valve. The primary side/boiler side can go as high as it wants to. The system water for the heat side is modulated. When the indirect calls, it doesn't pass through the valve, but by it and back to the boiler, If the present 3/way is a "Either/Or" valve, when the non priority call is made (heat), the valve is closed to the indirect. If the indirect calls, the 4-way loses power because of the priority call and no water goes into the heat side. IMO, it's a form of hydraulic separator, another take on primary/secondary. You need a circulator on the primary side to pump water through the boiler. Another one on the secondary side of the heat side of the 4-way. I can't tell you the exact way to pipe it because I'm not there. It sounds like the guys that fixed your thermostat are competent. They should understand the concept. If they figure it out and make it work, they should get excited to see how it flows and works. Like I said, its a variation on how Munchkins are piped with a vision controller. Modulated heating water, high limit water to the indirect.

    The only other question is do you want to spend money on such an old boiler? I consider them Bomb Proof and might do it. I'm just asking.

    You actually don't need to add a circulator to the primary side, there's already one there. The internal one. Sort of what Weil-McLain did on the Series 3 &4 with the added circulator. Remember, what you are accomplishing is to stop any damage that the lack of the thermostatic by-pass provided. Which was a quick warm up of the boiler to prevent boiler condensation. The boiler will remain hot when running. Just the heat side will modulate. There are a lot of things you can do to play with boiler and system temperatures, but the 4-way will be the brains of the operation.

  • dvizzdvizz Member Posts: 39
    edited April 2014
    Weil McClain Boiler Question

    This boiler has provided 8 years of faultless performance up until this year when I started feeling cold baseboard and hot water issues, which were magnified by the extremely cold winter. After the mixing valve was taken out a few weeks ago the performance has been on par with how I remember the boiler to have worked in previous years. The system was installed in 97 and we are the second owners of the house, so I don't have any knowledge of why the system has 4 Taco circulators and 4 Honeywell zone valves. I think the system is working fine now aside from the Furnas zone relays snapping closed when the room stats are calling for heat. That picture showing the bad control wiring is taken under the floor in our hallway, so I can hear the contactors when they operate, it's pretty annoying. That's why I wanted to replace them, but found the Taco SR 506 won't control the zone valves. I think I'm going to stay with the 3 way valve as is, as removing the mixing valve has given me plenty of hot water for the heat zones and indirect. Prior to that, system return water was bypassing the boiler and flowing out again. Based on the WM service faulty mixing valve bulletin; water temp. maintained above 130 deg should not be a concern for condensation. Is there anything else I should consider?
  • dvizzdvizz Member Posts: 39
    Cold Start

    I'm getting water coming from the bottom of the stainless elbow sealant connected to the combustion chamber. The temps have risen around here and the boiler has not cycled during the day when the set back thermostat temp. set at 66 deg. has been maintained.

    I had the mixing valve removed a couple of weeks ago based on SB0401R1. The system has been working great up until a few days ago. I initially suspected the condensate drain tube being clogged but last night I took the front cover off and could see water dripping from the bottom of the elbow where the sealant connects it to the boiler. The second page of SB0401R1 lits a piping bypass installed with a adjusting valve to compensate for the removed mixing valve. Is this an option?
  • dvizzdvizz Member Posts: 39
    Water and Piping

    That's a lot of info for me to get my head around. Could you explain it with an illustration so I can understand it better.
Sign In or Register to comment.


It looks like you're new here. If you want to get involved, click one of these buttons!