Two radiators not getting hot

[John.g]

I have checked with the grundfos replace app and it has highlighted the ups3 as a direct replacement for my existing grundfos 15-50x18. if the outputs are matched wouldn't I still have the same problem?

If you post a close up photo of your pump then might be able to get the pump curves but as pointed out above it will only pump the same volumes of water at a much lower head than the UPS3 so far less need for balancing/tweeking lockshield valves if UPS3 installed.
The UPS3 is a direct replacement but you would have to choose different pump curves to give the lower head that your pump is pumping presumably on speed 3?.

 

[Kevin palmer]

If you post a close up photo of your pump then might be able to get the pump curves but as pointed out above it will only pump the same volumes of water at a much lower head than the UPS3 so far less need for balancing/tweeking lockshield valves if UPS3 installed.
The UPS3 is a direct replacement but you would have to choose different pump curves to give the lower head that your pump is pumping presumably on speed 3?.

This is the Pump I have at the moment and you're right it is on speed 3

 

[John.g]

You have done well Kevin, that pump was built in week 34 2000 I think so 23 years, not bad but only a minnow compared to the UPS3., immediately below, which will pump 1.7m3/hr at a 5M head if required, the selectric will only pump that at a 3.3M head.

 

[Kevin palmer]

You have done well Kevin, that pump was built in week 34 2000 I think so 23 years, not bad but only a minnow compared to the UPS3., immediately below, which will pump 1.7m3/hr at a 5M head if required, the selectric will only pump that at a 3.3M head.

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that could well explain things. the house was actually built in 2001 as a 3 bed with a lounge and kitchen. I purchased it in its current state, 5 bed and 4 reception (includes a big conservatory with two big rads) in 2015. Lots of additions, but no update for the pump.
Looks like I will be replacing the pump and trying that.
thanks for the help, if it doesn't cure the problem don't know what I'm going to do!
Here's hoping

 

[Kevin palmer]

Thanks for the Help.
I've purchased a new pump and will be fitting as soon as i can collect it and hoping the isolation valves all work!

Cheers

Kevin

 

[John.g]

You will be lucky if the O rings dont leak on the ball valve spindles. You might find it easier as well to just cut across the securing nuts ( at the two slots) with a junior hacksaw to remove them, if the O rings don't leak you can just buy replacement nuts, they have two slots like in the photo and you can slip them on over the valve flanges, also use rubber gaskets.

 

[Kevin palmer]

Update:

Fitted New ups3 pump, as predicted the valves leaked through the o rings, but luckily I had purchased new ones as that had been expected. All fitted and working perfectly. Considering the house is now twice the size it was when the original pump was fitted in 2001, the old pump hadn't done bad. If only I had asked the question 18 months ago, I could have saved my ears from the MIL

Thanks, once again for your help.

Kev

 

[John.g]

What mode/setting are you running the pump at?

 

[Kevin palmer]

What mode/setting are you running the pump at?

It automatically went to setting three when it started. I left it there, as I was able to turn the boiler down slightly as well. Should I run it at a lower speed?

 

[John.g]

It is set to that, max output, CC3 at 6.5M, by default but you may find that constant pressure CP2 at 4.5M or CC2 at 5.2M will be adequate, its only a few button presses.