I am new to this site and don't know anything about HVAC electrical switching relay with priority for a gas furnace. My question is; If a switching relay with 3 zones is installed on a gas boiler what exactly does it do? For example If you give it priority to heat zones 2 and 3 does it bypass zone 1 completely and render the thermostat control in zone 1 inoperative?

Each zone is controlled by it's own thermostat located in that zone's area of the building. For example, three floors, each floor is a zone, and each floor has a thermostat.

These are not normally wired so that any one is priority. Each stat will call for heat when needed, closing the relay for it's respective circulator pump, separately and independently.

Additional relays and special wiring can give you a "priority zone" if desired, but, this is not standard. Not sure why it would be needed.

Why do you ask about priority?

tkrussell:
Thanks for your reply.
The reason I'm asking about priority zones is because some areas have heat and others do not. To give you more detailed information about the heating system; this is a multifamily dwelling with three floors. The property owner just installed a Burnham gas-fired boiler for a forced hot water radiator system connected to an 80 gal. Superstor Ultra indirect fired water heater. The priority switching system is a Taco 503 (three priority zone) relay switch. From what I can tell the jumpers on the relay switch are not in place to designate a priority zone however I'm trying to understand the system because both the property owner and the gas company that installed the equipment are very difficult to reach or are unavailable. The green "power" light is always on when examining the relay system. I don't think I've ever seen zone 1 light up. Zone 2 occasionally lights up and it seems that zone 3 is always on. There is a thermostat control in each of the two apartments on the first floor and I believe (although I'm not completely sure) there is one more thermostat control on the 3rd floor that controls both the second and third floors. When the thermostat in one of the apartments on the first floor is turned on or turned off it does not seem to have any affect on the zone lights coming on on the relay switch but it does activate the circulation pumps. The radiators on the first floor do not get hot; some of them get slightly warm and others are completely cold even when both thermostats on the first floor are turned up all the way. When the thermostats on the first floor are completely turned off for a long time the radiators in the outside hall on the first floor act independently and get hot. All radiators have been bled twice to eliminate air in the system. So my more detailed questions are 1.) Are the zone lights on the relay switch indicating something other than whether the thermostat is turned on or off in that zone? 2.) Is it possible that the radiators need to be bled more? (The radiators and the water system are very old) 3.) All circulating pumps seem to be working (I can feel the vibration in the pumps and feel the water movement in the pipes) but is it possible that they are not working properly? And 4.) I can't find any instructions on how to adjust the temperature of the hot water. The gas furnace and hot water heater installers told me that the temperature for the hot water is set at 140 degrees. I would like to set it at 130 degrees but I can't find any adjustments on the hot water heater for temperature control and I can't find anything in the literature they left that explains how to adjust the temperature of the hot water coming out of the tap. That's it. Hope you can help.

So there is a property owner, and the installation contractor? Are you a tenant?

I am no heating system expert, only wiring, and I have wired plenty of furnace controls, circ pumps, relays, zone valves, stats, etc. but not up to date on any new controls, systems, methods, etc.

I will help with what I think I can.

If this is a multi-family dwelling, one per floor, one stat on each floor should only control heat on that floor, in my mind.

I found a reference that domestic water heating can have priority over zone heating, but sounds like you have a separate gas fired water heater.or is is just a storage tank, usually these are wired simply as another zone.


The zones with no heat or intermittent heat can be air bound and the air in the lines needs to be removed, or "bleed the lines". But re-reading I see the lines were bled.

All I have to say about that is were they done properly? I have seen lines bled, and because of valve arrangements, etc, water was not pushed through the lines properly, thus not getting all the air out.

On zones that seem to be working, since all the pumps are running, on the supply line going out to each zone, you can feel the copper line is hot, and follow hot line until you find it cold, that is where the hot water is being stopped for some reason.

I went to the Taco website, and it does not recognize the model # 503, so I found no help there. Not a user friendly website. To help better I need to see what controls you have, their purpose, and wiring diagrams.


Boiler temperature will be controlled by the primary burner control, or an aqua-stat. So in one control there is an adjustment.


The installer was the gas company? I don't question that, as this is more popular. I just question if it is the gas utility, they are not available? Gas utilities are usually very responsive. However, if they were hired by the owner, they only need to answer to him.

I saw the question sitting, and I did copy this over at HVAC, and no one jumped in there either, so I thought I would try. I doubt I helped, but gave you some info to get you going in the right direction.