Potterton System always on?

[collie666]

Hi,

First time caller, long time lurker

Just moved into a new rented apartement and the CH is playing up. Regardless of how the timer is set, the pump is always on and the boiler cycles up to the temp set on the stat on the boiler.

Boiler is a Potterton System (can't find exact model number). The controler is a Potterton Mini Minder.

I've had a poke around the cylinder and (from interpreting what you experts have been saying) there's a Myson Power Extra 3-port (it's in a white pvc case attached to 3 pieces of piping, a lever on the top with MAN / AUTO written on it & 2 LEDs with DHW & CH written). From the 3 port a cable goes to a non descript grey junction box of some kind, with only one other cable going from the junction box to the stat on the cylinder.

From all this it looks to me like the controller simply isn't connected to the 3 port.

Anyone care to offer any insights- I'm contacting the landlord tonight and would like to at least be able to convincingly argue my case!

Cheers!

 

[ArtfulBodger]

Does the 3PV respond to the cylinder stat? if it does it sounds like a programmer problem as you have pointed out on the CH side. Easy enough to check from the wiring centre that you've already located. Is there a room stat anywhere? if not then you're wasting gas and therefore money.

 

[collie666]

Hi Artful,

There's no room stat as far as I can see & I've been pretty much all over the place at this stage.

As for the 3PV responding to the cylinder stat - I'm not sure. As I mentioned the 3PV has two led's on, which (I assume) are off/on to indicate the position the valve is in. Funny thing is, I've never seen the led's anything other than both on. As for the manual / auto switch on the top of the 3PV, it always seems to be in the auto positon. From reading other posts this probably doesn't mean that much but should it offer any resistance if I try to move it? If I slide it across to manual, it offers no resistance until midway and then seems to resist a little bit. Moving across to manual has no effect on the leds on the top of the 3PV.

I've not messed with the temp control on the cylinder stat - it's set @ 60. I'll try reducing the cylinder stat tonight & see if there's any action from the 3PV.

As regards the gas wastage - I'm concerned about this too - assuming the issue with the programmer gets sorted, is it fair to assume that the system will still be wasteful during the timed on periods?

Thanks,
Colm.

 

[ArtfulBodger]

If you haven't got a room stat then all the boiler will do is cycle in response to its internal thermostat, 'cos that's the only thing regulating it. Fitting a room stat will save an absolute fortune.

 

[collie666]

Thanks for the reply,

That's what I thought regarding the room stat - unfortunately I'm in the land of rented accomodation so it's a question of badgering the landlord into getting one fitted. Nothing's in it for him so I imagine it wont get done & i'll end up contributing to the gradual depletion of our gas reserves while paying for the pleasure...

Just a couple other questions (simply out of curiosity)

1. Seeing as the cylinder stat is set at 60, does that mean the setting the boiler temp control above 60 is pointless - ie, once the cylinder hits 60, if the boiler is >60 then does the boiler end up cycling very quickly? And if so, is this detrimental to the boiler?

2. Is it possible there's a room stat hidden somewhere? In other places the room stat has been a small square box with a temp control. I assume that if there's one in the place it would be similar?

3. Am I correct in assuming that coz there's only two cables (one going to cylinder stat & other going to 3PV) in the junct. box that the timer isn't connected? Are the RC timers & if so shouldn't I be able to see a RC receiver for the timer control.

Thanks again for the helpful replies.

 

[collie666]

Spent a bit more time fiddling with things last night and it really does seem to me that something's not wired correctly...

The 3PV facia has two leds/neons which indicate that either CH, HW or both are being called for. It's also got arrows on the facia in the direction of the two "out" ports (CH & DW). The HW 3PV out does go to the cylinder loop & the CH 3PV out pipe disappears into the ceiling (and assumedly into the rads). So, my thinking is that that when the light for CH is on, the 3PV (if operating correctly) really is feeding the CH pipework & simlarly with the HW side of things - ie, the writing on the facia is correct & therefore if the 3PV neons say CH on, then there should be flow through the CH pipework.

But, with both HW and CH timers off & if I adjust the cylinder stat so that it's calling for heat, the 3PV neons indicate that the 3PV CH port is open! This doesn't seem right at all?

Operating the timer controls so that there's a call for both CH & HW does light both neons & I can hear the 3PV moving, so it looks like the 3PV is working (more or less correctly).

From all this, it appears to me that the HW output from the programmer is incorrectly wired & the only thing that's controlling the operation of the boiler is the CH microswitch being activated in the 3PV. Does that make sense or have I lost the plot completely?