Grant Vortex external combi 21

[Beboers]

Hi,

I have just installed a grant external combi 21 and upon firing up and commissioning everything is as it should be. I have run a bath with it for the first time today and it initially ran nice and hot and then it went like warm and only slowing it down by Alot it went hot again? Can't be heat exchanger as brand new? Why does the water come out red hot to start with??

What's wrong with it???i am oftec registered btw

 

[lame plumber]

stored water combi with too big a flow rate would be my first thought, you sure your oftec?

 

[Beboers]

Yes Thankyou, that is what I thought but the tap is having to be turned down to a vet poor flow of which I am sure the boiler can do better than that!

 

[WHPES]

Boiler thermostat set high enough?

Pump speed?

Pump valves fully open?

 

[Roger Welton]

Smallest combi they make, I'd bet you are exhausting the store. I think they are rated at 15lpm for the 1st 100ltr dont recall the temp rise though.

Personally never fit the 21 only 26 and even then when cust is adamant they don't want a cylinder. Oil combis imho aren't great.

 

[Beboers]

Would the boiler thermostat affect the temp of the hot water?i think the hot water pump is set to 2 does it need to be on three then? I think I remember turning it down when installing it! Doh!

 

[lame plumber]

Smallest combi they make, I'd bet you are exhausting the store. I think they are rated at 15lpm for the 1st 100ltr dont recall the temp rise though.

Personally never fit the 21 only 26 and even then when cust is adamant they don't want a cylinder. Oil combis imho aren't great.

50 degree rise, just looked, also check your combustion settings, nozzle size,and fuel filter for fuel flow.

 

[Beboers]

It is such a small one bed garage conversion that I just didn't want to go bigger than the 21 but maybe I should of upped it. 15 LPm is a good flow tho for running a bath so I think there must be something else?

 

[lame plumber]

check the flow rate on the bath tap for starters.

 

[SimonG]

Nothing wrong with the boiler. It will be doing exactly what is required of it. Its a combi after all. Valve on hot to bath to restrict flow.

 

[heliotrope]

Check out the blending valve.

This may have been tampered with, wrongly set or developed
a fault.

 

[kimbo]

Pump speed should be on 3 and blending valve should be on about 4. I have never had a problem with these they normally perform very well., give grant a ring they will send someone out to fix it, if you look over his shoulder you might learn a thing or two about the boiler
Check to make sure that the thermistors are in the right place. Their is a separate stat for the hot water. Also on the incoming mains in the check valve I think is a flow restrictor hope you havent taken it out.
The boiler is under guarantee anyway.

 

[MarkOil]

Same as Kimbo, if it's installed correctly by a competent person then the fault will be on the boiler and Grant will sort it.
If it's user error or wrongly installed, you will probably get a fair old bill from Grant.

 

[gbheatingtech]

Id check flow rates on the bath taps first then maybe try a flow restrictor or similar to see if that improves things before calling up grant and having the potential of a big bill and looking like a prat!

 

[kimbo]

This boiler has a flow restrictor fitted to it internally. If you have to fit a second flow restrictor then the fault lies within the boiler.
the restrictor in the boiler may have been forgotten to have been put in, doubtfull but possible.
you need to increase the internal pump speed on the hot water pump to 3 before you do anything else, this has the effect of putting hot water from the store through the heat exchanger quicker. If the pump is set too low you will get the symptom that you describe. It may of course be something else but the basics have to be right first before you investigate further.

 

[WHPES]

Please post the outcome for everyone's benefit

Thanks