Grant Vortex 26e no hot water

[MickyP10]

Runs for eight mins or so from cold, but can't feel any heat to heat exchanger, then overheat cuts in and boiler starts making rude noises until it cools. Pipes at top are hot. Pump? I've seen a non return valve mentioned, but where is it and how do you test, or is it in the pump?
Heating works, but has its own pump.
TIA

 

[Johntheo5]

I think there's one in the pump but @Exedon should soon inform, check DHW pump running and PHEX clean.

 

[MickyP10]

Thanks for reply. I can feel the pump spinning but have read the impeller can become detached! Also that the pump's no longer available. Is there any point in having a look inside without a replacement to hand?

 

[Johntheo5]

That boiler has total water contents, including the store, of 35.5L, assuming cold as 15C and HI limit stat operating at 100C then it will take exactly 8 minutes to reach that temp assuming a 26kw boiler, so looks as if it is being circulated around the primary circuit?.
My mains is 10C just now so 26kw should give a flowrate of 7.5LPM at 60C or 12.4LPM at 40C, if not allready done so, open all hot taps only to give a minimum flow of say 10.0LPM or more and see does the boiler continue to fire.

 

[MickyP10]

Hi and thanks for reply. I ran it for three mins and all the chromed pipes, exchanger and pump itself were cold. Top outlet at boiler was warming up, which I guess you'd expect if the boiler's ignited. Turned it off again as figured it would overheat again. I ran the hot tap for a couple of mins during that time. Maybe the pump's not running at all and the vibration I can feel is from the oil pump and burner. Apols if I've misunderstood your message. Once it overheats it sounds awful, so I thought I'd cut the test short.

Can I test the pump without firing everything up?

 

[Exedon]

Morning if your getting no flow from main hex into heat store its probably the pump.
Even if its non return valve (rare but not unknown) pump still has to come out as non return valve is screwed to it.
The original pump is either a wilo or grundfos we tend to replace with dab evosta 3 as that can be set to constant curve 3 which is what's needed on that boiler.

 

[MickyP10]

Morning and thank you. I'm told the pump's obsolete and can't speak to Wilo or Grant either as closed for Xmas...

Have you a link to the pump you use, please? I'll order one.

 

[Johntheo5]

Hi and thanks for reply. I ran it for three mins and all the chromed pipes, exchanger and pump itself were cold. Top outlet at boiler was warming up, which I guess you'd expect if the boiler's ignited. Turned it off again as figured it would overheat again. I ran the hot tap for a couple of mins during that time. Maybe the pump's not running at all and the vibration I can feel is from the oil pump and burner. Apols if I've misunderstood your message. Once it overheats it sounds awful, so I thought I'd cut the test short.

Can I test the pump without firing everything up?

With the boiler switched off see what kind of flowrates you are getting from a "hot" water tap you normally use, if the pump isn't running then surprising that the boiler runs for 8 minutes from cold.
You could probably test the pump by running it from a independent power supply, if you have a M.meter you can test for 230V at the pump terminals if you switch on the boiler for a minute or two.

Re replacement pump,
If you look for Dab Evosta 3 60/130 on the various sites, screwfix etc, then you should get one at the best price, 60 is the 6M model and 130mm is the distance between the pump flanges.

 

[MickyP10]

Hiya and thanks
I tried it again and it overheated in about three mins. Hot water flow is very good (although it's cold!)

Is this the pump and is it a direct swap? I wondered if it was too powerful. dhw pump

 

[Johntheo5]

If @Exedon says its the correct replacement, then it is.

Have you tested for 230V going to the pump terminals when you switch on the boiler for a moment or two?.

 

[MickyP10]

Hi and no. I didn't want to start opening control panels and/or removing and inspecting the pump without a replacement. I know there's a slight chance I'll stumble across a fix, but would much rather stick a new pump on and forget all about it.