Modena 80E - no DHW

[Robert Tyrrell]

This is the first one of these that I've come across so any help would be appreciated.
Customer complained of no DHW and drop in pressure at the gauge. I topped it up via the filling loop and re pressurised the expansion vessel, after which it was all fine.
Two days later and she's called to say that it's happened again but this time the last led is flashing (number 5 if I remember correctly).
I've got to go back but I'm thinking that the expansion vessel is shot - any comments or advice?

 

[ShaunCorbs]

This is the first one of these that I've come across so any help would be appreciated.
Customer complained of no DHW and drop in pressure at the gauge. I topped it up via the filling loop and re pressurised the expansion vessel, after which it was all fine.
Two days later and she's called to say that it's happened again but this time the last led is flashing (number 5 if I remember correctly).
I've got to go back but I'm thinking that the expansion vessel is shot - any comments or advice?

or heat exchanger

 

[wattsie1987]

These are prone to split internally and over pressurising. Could also be a blocked expansion vessel tube.

 

[jonnyswamp]

Check the basics before you go pulling it apart
PRV passing, causing pressure drop
Any visible leaks, rad tails, pipe work etc
Exp vessel needing recharge, don't know the specific pressure for a Modena, but 12 psi should be about right
Drain boiler before checking exp ves pressure, can get a false reading otherwise esp if hot
If the above is a case of "teaching your granny to suck eggs" just ignore me and delve deeper

 

[Robert Tyrrell]

Cheers for the advice guys, I'll go back in the morning a bit better prepared now.
Wattsie1987, what is it that actually splits?
jonnyswamp, your advice is very pertinent, and welcome, as I've been out of the industry for good while and combi boilers came around in the interim so I'm just learning about the intricacies of them really. It used to be all gas fires and back oilers when I started

 

[wattsie1987]

Cheers for the advice guys, I'll go back in the morning a bit better prepared now.
Wattsie1987, what is it that actually splits?
jonnyswamp, your advice is very pertinent, and welcome, as I've been out of the industry for good while and combi boilers came around in the interim so I'm just learning about the intricacies of them really. It used to be all gas fires and back oilers when I started ��

Sorry I assumed you would of checked all of the above first. As they are a duel hex they can split internally causing the mains pressure in the dhw part of the hex to push into the heating part of the hex causing the pressure to rise and a prv situation.

 

[Robert Tyrrell]

Sorry I assumed you would of checked all of the above first. As they are a duel hex they can split internally causing the mains pressure in the dhw part of the hex to push into the heating part of the hex causing the pressure to rise and a prv situation.

Would a split hex cause the prv to operate if the pressure was constantly dropping then?
She has been using it for a couple of days after I topped up the system pressure for her but it has still dropped from 1.5bar to 1bar over a couple of days.
I've now located a prv unit but it cost £80 so I hope that it's just the prv (Its the MF03 model so it's a manifold with everything already attached)

 

[Billy Bob Bob]

Would a split hex cause the prv to operate if the pressure was constantly dropping then?
She has been using it for a couple of days after I topped up the system pressure for her but it has still dropped from 1.5bar to 1bar over a couple of days.
I've now located a prv unit but it cost £80 so I hope that it's just the prv (Its the MF03 model so it's a manifold with everything already attached)

if its constantly dropping,its not a split hex,if it was over pressuring and the loop had been disconnected it could be the hex,there is either a leak there somewhere or the EV has failed causing the prv to open,if its Giannini head on the prv you can just change that ,ferroli used a mixture of different heads though

 

[Billy Bob Bob]

if the head looks like this,buy a factors giacomini 3 bar valve and swap heads over

 

[Robert Tyrrell]

gas man, that's the prv from the MF01 & 02 models. I already have one of those to take back to Plumbcenter
the part that I needed was the complete manifold with the prv and flow switch etc already attached. £72 inc vat.
Im going to fit it this morning - don't usually do weekends but they I did say that I'd fix it this week so it's my fault for saying

 

[Robert Tyrrell]

Update!
I had to cut the nut off the bottom of the prv manifold to get it out but it was definitely that causing the problem as nothing exiting via prv run off now.
I have a got another minor problem though - the union at the bottom of the prv manifold won't seal properly but I'm guessing that's because there's no washer in there to seal it. There wasn't a washer in the joint when I took it apart but there definitely should be one as it's just two metal faces mating against each other. Tried an O ring but that's no good and I'm all out of fibre washers at the moment so it'll have to wait until Monday now