Grant Vortex 36 KWh External dumping pressure 4am

[Rabbit1974]

Hi Guys,

Wet plumber 33 years experience here.

We have a Grant Vortex Pro 36Kwh external oil - sometimes I hear the boiler cycle when heatings off (after bed time) then next morning no pressure .

Seems if the heatings on all day , switch off 10pm - then sometimes next morning cold house. Go round to boiler room and boiler is sitting at zero.

Lights flashing low pressure etc.

Top up to 1.5 boiler kicks in and after 10/15 mins you have hot rads again .

If we do timed function 8-10 am & 4-9 pm it doesn’t seems to expel the pressure through the PRV .

But soon as we have a freezing temps and heatings been on all day we can get this problem.

The boiler is brilliant apart from this.

My question is - does the expansion vessel (24L internal grey one) - needing recharging - swapping ?
Or is it frost stat / combination of both ?


Grant Oil Vortex Pro 26 KWh 2018
Running 10 rads.

7 x 800/500 type 21s
1x towel rail
1 x 800/500 single
1 x 300/500 single

24L exp vessel.



Cheers.

 

[Johntheo5]

The grant PRV is set to 2.5bar vs 3.0bar for most boilers but you have a huge EV (expansion vessel) at 24L
With a precharge pressure of 0.7bar and a filling pressure of 1.3bar then that 24L EV will mean that the final pressure would still be less than 2.2bar even if the system contents are 180L, more than likely, they are ~ 100L.
Suggest just pressing it up to say 2.2 bar (cold), check that the PRV is not lifting/passing then press the EV schrader valve pin, if water comes out, new EV required, if air, EV OK, if so, depressurize system and remove the EV outlet pipe where connected to the EV and pump up the air end to 0.7bar, reconnect the pipe and then fill it (water end) to 1.3bar, keep a eye on it, note pressure when hot, wouldn't expect anything more than 1.8 to 2.0bar max.

 

[Rabbit1974]

Thanks Johntheo5 , sorry for delay in replying - very unwell. that is most helpful . I will try this when I’m better and see what the result is and I’ll update.

 

[Rabbit1974]

So I think it may be the expansion vessel - it’s a big grey 24L one , this shouldn’t be heavy as a concrete block should it?

I’ve pressed the valve in , and water cones out ?
Do I need to pop new one on.
Cheers

 

[Johntheo5]

If water comes out for more than say 10 secs and no air then definitely requires renewing.
You will have to drain down the system unless there is a isolation valve on the outlet from the EV, before installing the new EV reduce/ensure the precharge air pressure as measured at the schrader valve with a tyre gauge is 0.7bar to 0.8bar, connect the outlet pipe then refill the system until the pressure boiler side pressure is 1.3bar and not higher, boiler ready to go.

 

[Rabbit1974]

Am I right that the vessel shouldn’t be really heavy as in full of water heavy ?
We’ve been having the pressure building up and after 2/3 days sheds its pressure via the PRV as I put a sandwich bag over the pipe and it was full at same time the boiler was then not working and pressure at zero.

If I top boiler up we get another 2-3 days and same again.

I’ve ordered a replacement one £100 and I don’t think there’s an isolation on the EV hose but I have isolators in the top of the boiler - so take it I can switch the flow and return off and do as you recommended John ?

Cheers

 

[Johntheo5]

If the EV is connected in to the boiler directly and the boiler isolating valves are holding then yes, thats fine, you will soon know if they are holding when you remove the outlet from the (old) EV where it attaches to the boiler.

You can actually test the old one if you like by shutting those two valves, remove the EV outlet and pump up the air end to say 2.5bar, if the diaphragm is leaking you should feel air coming from the EV water end, hold your hand over it to see if pressure is building up.

 

[Exedon]

we install and maintain a fair number of Grant boilers,
We don't try using the isolation and pump valves to work on boiler, soon as they are a few years old they tend to leak for fun.
Stick a hose pipe on boiler drain off (easier if you drop burner out) drain till no water runs out.
Have a old towel or two to hand swap whatever you need to.
We change flexi pipe at same time as expansion vessel they have a habit of blocking up.

 

[Rabbit1974]

Hi exedon ,

The EV flexi pipe is brand new on this one, and the isolation valves I’m speaking of are in the top of boiler (brand new full bore butterfly valves sept 2024) - not the pump valves .

Also there’s full bore butterfly isolators internally - on pipe work before boiler - but that would involve taking plasterboard off wall . So not practical, unless we are changing boiler in future .

 

[Rabbit1974]

There’s another valve same as this on the flow pipe .

 

[DP]

Not read any previous messages-
Pressurise to 0.7 bar ( or what the manual says) while the pressure guage stays at 0 ( heating side drain valve open to ensure pressure stays at 0
Check short while later if pressure still holding at 0.7
Sometimes you can hear air leaking to water side when diaphragm is punctured
Some expansion vessels for some reason have some water on air side
One of the pictures above, is that a crack where the flexi pipe connects?

View attachment 378308Am I right that the vessel shouldn’t be really heavy as in full of water heavy ?