Circulator, Boiler Thermostat or Valve, which one is bad?

[CFLI]

My boiler has been working intermittently even when the hot water tank is full of cold water. My trouble-shooting led me to believe the thermostat in the boiler is what's cutting out the boiler. The trouble is - why does it do that?

I guess two possible reasons, either the thermostat is bad, or water is not circulated to the hot water tank, therefore the overheated boiler.

I listened at the Grundfos UPS 15 50 circulator, and could hear very quiet sound (similar to the electric noise of a huge transformer but much quieter). I am not sure if it is working. Or, it could be working but the Siemens 3PMP V22 valve doesn't open, so no circulation?

The pipe is hot, but the tank is cold. So something is wrong here. How do I know if the circulator or the motorised valve is working?

 

[kevplumb]

View media item 17592
undo the screw marked bleed have a cloth handy

you can see the spindle underneath

to check if the valve is opening lock the lever /slider on man

 

[CFLI]

Thank you for the prompt reply. Let me check the circulator first. Do I need to shut the valve before checking the spindle? Your advice of having a cloth handy makes me think water can come out from there. Thanks.

 

[CFLI]

Kevplumb,

Thank you. The spindle wasn't turning when power is supplied to the circulator. I guess this is THE problem.

I've attached a picture of the circulator. Could someone tell me what are the fittings above and below the circulator? Are they stop valves? I am pushing my luck thinking I may not need to drain the whole system, which is something I don't know how to do...maybe this is out of a DIYer's reach?

Grundfos UPS Circulator

• CFLI
• 18 Sep 2010
• 1

 

[kevplumb]

the fittings are isolation valves

did you try spinning the shaft with power on

and before you start pulling it to bits did you check the pump is actually getting power

 

[D_Hailsham]

The spindle wasn't turning when power is supplied to the circulator.

With the power turned OFF, try turning the spindle with a screwdriver -it may just be stuck. If it turn easily, the pump will need replacing.

Could someone tell me what are the fittings above and below the circulator? Are they stop valves?

Yes. When the slot is across the pipe, the valve is closed. But, as they do not get used very often, they may be stuck; so be very careful. They may also leak around the on/off screw.

 

[CFLI]

No, Kevplumb, I haven't. But I did check the power is up to 240v when no movement was observed. I should try it now.

In addition, the motorised valve seems to have only two positions for the lever. Shouldn't it have three positions? I cannot see clearly due to its position. But I imagine it should have auto, CH or HW. Am I correct?

 

[kevplumb]

But I imagine it should have auto, CH or HW. Am I correct?

no 2

MAN manual

AUTO automatic

 

[CFLI]

Ouch, the spindle was really difficult to turn. It seems to require a special tool. But I did turn it a bit, only about half turn. Then I turned on the power, it didn't work.......

About the valve, what happens when it's turned to manual? Does it flow both CH and HW?

 

[kevplumb]

Ouch, the spindle was really difficult to turn. It seems to require a special tool. But I did turn it a bit, only about half turn. Then I turned on the power, it didn't work.......

About the valve, what happens when it's turned to manual? Does it flow both CH and HW?

only tool you need is a narrow screwdriver

sounds like its seized

when the valve is on man its mid position so yes hw & ch

 

[CFLI]

Kevplumb, thank you so much for all the useful information. You are great. It is all working now. You were correct that pump rotor could stuck. You were also right that turning the spindle a bit could solve the problem. It did. The boiler is working for 10 minutes now, and is still working. I am sure the problem is gone. Thanks soooo much. I really appreciate.

 

[CFLI]

by the way, the first time i turn the spindle, it didn't work. But I did all those again and also change the speed. It worked.

Thank you, Kev.