DHW heat exchanger - Unica 32HE

[ntl142]

Has anyone got any tips for removing the DHW heat exchanger from the Unica 32HE boiler? It's held in with two screws which are accessible, just, from the front of the boiler past all the pump and other pipe work. There is about 4cm behind the HE.

Can I remove those two screws, push the HE backwards 4cm to disconnect from the CH and DHW pipes, and then wiggle it out the side?

The installation manual doesn't actually cover removing the heat exchanger.

Thanks.

 

[ianmcd]

very easy to remove

 

[ntl142]

very easy to remove

Thanks a lot. By the method I mentioned? Does anything else need to be removed first?

Is it worth getting new seals while it's out or will the existing seals usually be ok to reuse?

 

[ianmcd]

Thanks a lot. By the method I mentioned? Does anything else need to be removed first?

Is it worth getting new seals while it's out or will the existing seals usually be ok to reuse?

I usually use silicon grease and the lip seals are fine, but if you want new ones here is a link, why are you removing it ?
https://www.ebay.co.uk/itm/Vokera-U...48b4a8b278e2754c95fc|ampid:PL_CLK|clp:2334524

 

[ntl142]

Thanks for the link.

Getting intermittent loud noises that sound like what I imagine kettling sounds like (never heard it before), the hot water temp fluctuates more and more to the point where the boiler can't modulate enough so sometimes just turns off the flame then back on again, and is worse when the CH has recently been on.

Do I need to remove anything else to get the HE out or does it come out like I suggested above?

 

[ianmcd]

no nothing else needs removing just undo the 2 screws, when was your boiler last properly seviced, lots of companies do a flue gas analyser check and call it a service, your Boiler Must be properly serviced every year , not just poke and go, the internal coil in the heat exchanger has to be properly cleaned and flushed

 

[ntl142]

Yeah that's kind of why I'm asking. It was 'serviced' about a month ago and I was hoping it was going to be a bit better after. I wasn't in when it was done but I'm sure it was the bare minimum. The service two years ago was by a Vokera engineer and was a bit more in depth.

Are you talking about the main heat exchanger or the DHW one? Maybe both! Either way I'm hoping to give this a clean out and see if the boiler DHW problem improves.

Thanks for your help.

Edit Am I right in thinking I'm not allowed to get into the main heat exchanger or is that ok for non-gas safe?

 

[ianmcd]

No you cant do the main heat exchanger, but nothing stopping you doing the Plate heat exchanger (DHW) some really cheap new ones on ebay about £30 and come withe the lip seal washers, if you want to just clean out the existing that is fine too,just be carefull with your choice of chemicals some use brick acid,just be carefull the plate will become very hot and make sure you completely flush it before re-fitting,

 

[ntl142]

Had the boiler cover off the last few days to try to listen to where this noise is coming from. It's not the plate heat exchanger, but is clearly from inside the metal box above that that houses the main heat exchanger and fan. Can hear and feel it on the cover of that box, like a loud droning vibration. It sounds like a combustion noise, much clearer with the outer cover off. When it stops (tap turned off) it finishes with a sort of whooshing noise which makes me think gas/exhaust rather than water. Might be imagining it, but a faint smell of gas too when it makes that noise but no smell when it's running normally. I can recreate it by having had the heating on recently, and then open the hot tap just a small amount. The flame comes on, modulates down low, then lower, then lower, then vvvvrrrrmmmmmm this noise happens and continues until the tap is turned off. Trying to get a recording of it but it's intermittent.

 

[ntl142]

Got a video at last! Been trying for weeks. Tap was on low. Turned up to medium then back low. Can hear the boiler modulate and then the noise is clear at the end. What is it? When I talk to someone on the phone what can I tell them is going on/how can I describe it?

Video: https://streamable.com/c14r5g

 

[ianmcd]

Got a video at last! Been trying for weeks. Tap was on low. Turned up to medium then back low. Can hear the boiler modulate and then the noise is clear at the end. What is it? When I talk to someone on the phone what can I tell them is going on/how can I describe it?

Video: https://streamable.com/c14r5g

The boiler is resonating, the gas ?air ratio is wrong , the main heat exchanger will need properly cleaned and the gas valve settings will need set up, not something you can do yourself, have a look at Vokera fixed price repair or servicing, they are good boilers but very few Gas Engineers properly service them and the likes of BG and others will definately not service it they just stick in a flue gas analyser and tell you that you need a new boiler

 

[ntl142]

Thanks very much, I'll give them a call on Monday and at least now I can tell them a bit about what's going on, rather than just "it's making a noise when the hot tap is on" which might mislead them. Thanks again.

 

[ntl142]

Well they only just managed to turn up to have a look. Paid for the 1 year boiler cover from the manufacturer in Dec. The appointment before Xmas was cancelled by them due to vehicle problems, fair enough. They've been this morning and turned the boiler off as it was unsafe apparently. Say the gas pipe from the meter is too small (15 instead of 22mm I think) and won't work on it until that's replaced. So now no heating or hot water and a baby in the house. Great! Just glad the appointment a few days before Xmas was cancelled...
Frustrating because it was serviced by a third party 6 months ago. It was serviced by the manufacturer themselves (same as today) in 2015 when we moved in. Nothing mentioned on those visits. And how unsafe can it be if it's been like that for the 4 years we've lived there and the 5 years before that when the boiler was fitted? Not a great start to the day.

Anyway, would the small gas pipe be a likely cause of the resonating noise? Bearing in mind the noise has been getting more frequent over the last year.

 

[ianmcd]

Was it a direct employee from Vokera or sub contractor that visited ?

 

[ntl142]

Today, a direct employee. He implied that the person who came a few years ago wasn't a direct employee, even though sent by Vokera.

Trying to find someone to fit a copper pipe in a hurry isn't easy!