Weil McLain Ultra Problem

robert griggs

I have a 3 year old weil mclain ultra 105 boiler I installed.  The problem that just started in the last 2-3 weeks is that only one zone will run at a time.  In the morning, the upstairs zone gets to 67 degrees, while the downstairs will drop to 62-63 degrees.  Both zones are set at 67.

The downstairs will not come on until the upstairs zone stops calling for heat.  It is only in the morning that this problem is occurring. 

This morning the problem was the opposite- downstairs was running and upstairs was at 63.   The boiler never had priority on it.  It is a basic two zone system with copper fin baseboard.

Once the heat comes on, it works great- no other problems. Nothing has changed on the system since it was installed. I am the only one who ever touches it. The only thing different from when it was installed is one thermostat was replaced about a year ago.  Both tstats are honeywell 4000 digital programmable tstats.

Any ideas what to look for or where to go?

Thanks for your help,

dano415

simple stuff first

Hello--I'm not an expert, but I did install a ultra 80.  I'm assuming your using the U-control

to operate the zone valves.  I would first check the simple things; make sure the zone valves are operating correctly(turn on both thermostats and make sure both zone valves are completely open--check the temperature of the supply water temp. right after the zone valves and then throughout the system(at the baseboards).  You might need to buy a

devise to measure water temp.  I wouldn't bother with a tridictator--it can get expensive.





It sounds like the U-Control might be defective, but check the obvious first.  Disconnect the outdoor sensor(if installed) and see what happens.  Let me know the outcome. 

I'm not that impressed with Weil Mclain.  My boiler arrived with bolts missing, etc., but they

do honor their warranties--I've been told.

robert griggs

No zone valves

I used circulators with flo-checks.  I have not connected the outdoor sensor yet. Temps at baseboards are hot when it does come on.

It is working just like a priority does- but it is not and has never been wired that way.

Thanks for the help.

Jean-David Beyer

Were Ultra-3s out already three years ago?

'I'm assuming your using the U-control to operate the zone valves."



I have a W-M Ultra 3 boiler with U-control. It came with all the parts, including boiler circulator, pressure relief valve, supply and return temperature sensors,  outdoor temperature sensor, all needed bolts, etc. Not supplied was a LWCO, but my contractor supplied one of those; or a condensate pump, but my contractor supplied one of those too.



I think the U-control came out with the Ultra-3 series a little over a year ago. The Ultra-2 series uses a control called PhD (for "Precision Hydronic Data") that is far less flexible. My guess is that the O.P. does not have a U-control at all, so there is no need to figure out how to debug a U-control.



How are the thermostats wired to the circulators and the boiler? Are the thermostats connected to a relay box, such as a Taco SR502? If so, maybe the priority is turned on and one zone locks out the other.

Tim McElwain

The older Ultras

used a Honeywell MCBA control. Do you have the Installation and Operating manual?