Grundfos UPS3

[The Omen]

My system is based around a Glowworm Ultimate 50ff some thirty years old. Over the years I have worked on it many times and always managed to solve problems, thus i have an extensive supply of parts. However after all this time finally the Grundfos pump gave up. I replaced it with a Grundfos UPS3 pump. This seems to be working OK. The boiler also starts up OK but after 5 minutes shuts down and stops power to the pump. Often the overheat is tripped. Wait a few minutes and the exercise can be repeated.
My thoughts are that there is no water circulation even though there is a new pump. My suspicion is that the two valves which I closed to replace the pump have not opened properly. The system is thirty years old and I am aware that the two valves to shut the water off are no longer available and there are rumours that some of them are problematic. Those supplied today are gate valves. I feel mine are the problem type as they operate as a regular tap, so there must be a washer. which after all this time ..........
I hate the prospect of draining the system but for me filling the system is always a major problem. Can anyone confirm my suspicions?

 

[terryplumb]

Can't you close both valves ,remove the pump ,and open each valve to ensure they pass water when opened ?
Without pics of your set up we are working blindly.

 

[The Omen]

Can't you close both valves ,remove the pump ,and open each valve to ensure they pass water when opened ?
Without pics of your set up we are working blindly.

That is an idea, at least I could have a look and verify the valve type. Maybe it is a gate valve but it did feel like a tap valve as I felt I was compressing something when I shut the valves. Of course gate valves do break but you are aware all is not well as the operation becomes too easy and never stops.Bit worried about turning them on though. water everywhere

 

[terryplumb]

Show us a pic of pump and valves. Big towel over the pump valve and a short opening of the valve would quickly tell you if it opens !

 

[ianmcd]

why did you change the pump in the first place ?

 

[The Omen]

why did you change the pump in the first place ?

The original one was showing zero ohms resistance and the boiler PCB fuse had blown

 

[The Omen]

Show us a pic of pump and valves. Big towel over the pump valve and a short opening of the valve would quickly tell you if it opens !

 

[The Omen]

Have not got a camera and needless to say no mobile phone. In a few hours when I can get access to the boiler I will follow your suggestion and tell what I find. Unfortunately I assume I have blown the boiler thermostat while playing around, fortunately I have a couple more.