Vokera combi - very low pressure dhw

[Al-Glasgow]

A friend has this boiler.

When you first turn on a hot tap, the pressure is great, but within a few seconds it has died down to a trickle.

I have tried the valve that controls the hot pressure, this is fully open, when i close it the hot tap stops completely.

I think it can only be 2 things.
1) clogged hot pipe.
2) Diverter switch.

Could I run mains cold up the hop tap ?, do i need to observe pressure needle on the boiler, maybe not passingf 3 bar ?.

Any other suggestions very welcome.

thanks in advance.
Alan

 

[DP]

Better option is get someone in to fix the boiler.

I could suggest me, but that would be cheeky of me. I am in Glasgow (Baersden)

 

[Al-Glasgow]

Any comments from regular pro's please

Alan

 

[just-thinking]

there are a lot of vokera combi boilers.
all work in a different way,if one of my clients just said it was a vokera combi boiler and poor flow of hot water,i would charge them extra as they are stupid.
boiler name and model number are the very minimun info req,this is so i could look at makers instructions on way so i dont have to spend much of my time and clients money.
personally i would get vokera to repair it and service it if not serviced for 18 months.
decent boilers if looked after.

 

[kevplumb]

Any comments from regular pro's please

Alan

woddya think DP is

 

[DP]

Thanks Kev

 

[croydoncorgi]

You're virtually certain to find a Vokera pro somewhere in Glasgow - Vokera tech support is based there!

 

[Al-Glasgow]

I wasnt suggesting DP wasnt a pro.

He offered to come and repair, as he is in Glasgow. I am on level 2 city & Guilds 6129 (i think), and wish to learn myself.

If i wanted a repairman out i would lift yellow pages and call one out.

If you dont wish to help then dont, this is a DIY forum after all, I will get the model number bout doubt if anyone is actually intyerested in positive comments, that is off course unless i mention new baby in house lol.

Thanks again, but problem still exists.

Alan

 

[DP]

What better for you to watch while work is carried out on the boiler. This way the boiler is fixed and you get to learn (and repair) when you carry out hands on repairs.

Boiler repairing is a very specialised field. Not only do you need to be gas savy, you also need to know and understand electrics, electronics and mechincal components (and how they work). It is comendable that you are doing C&G but it will be sometime before you will have the magic to breath life into dead boilers. Before you ask, I have a good success rate but not 100%. Some boiler like to show you who the boss is.

By the way, changing parts does not make you a good service engineer.

To answer your query regards poor water flow. Why do you think the water flow rate is good to start with to become a tricle? What is happening inside the pipe when water is flowing? Have you checked the flow rate at the inlet to the boiler? If you had a 15mm pipe and you put a plug of steel wool in it, would you get constant flow rate at the end of the pipe? When checking gas rate at an appliance, why is the standing pressure 21 and working pressure a lot lower on undersized gas lines?

2) What does the diverter switch have to do with it? On the excel it is only there to start the pupm- nothing to do with what you get at the hot tap!

Why would you want to watch the pressure needle on the boiler? It has nothing to do with the water flow at the hot tap

If you are honest with yourself (and want to learn) you will come back with answers. You might think it is going to make you look silly, but you will go away kinowing a lot more about the excellent boiler.

Reading in between the lines, I suspect the boiler is a Vokera Linea

 

[Al-Glasgow]

Many thanks to DP with constructive posting.

I am still learning plenty about various boilers, and by no way would i say i was "competent" to fault find combi's in general. This is why i ask as to where the problems with low DHW would be associated eg. diverter valve.

I do NOT intend to open the boiler and start changing parts willy nilly, I do not know why the cold pressure seems very strong compared to the hot, I can only assume a restriction or faulty diaphramn, but this is why i request assistance im gaining more knowledge.

Your questions to me regarding standing/working pressure i couldnt answer this accurately i dont think, my gas experience is limited to tightness testing, let-by, burner pressure and calculating the heat input.

Why would i feel silly DP, I ask a question about a problem a friend has, I feel far from silly.

feel free to pass on advice.

ps - I guess my level 3 apprenticeship is out the window now.

Alan

 

[DP]

What model of Vokera?

Vokera diverters have varied over the years. In order to give a reasonable answer, boiler model would be required. It is very unlikely to be the diverter. It is almost certainly not going to be the HW HE as Glasgow water has pH of 7

A faulty diaphragm (if it is fitted to your boiler- might be a motor) would not effect delivery of water at the tap. Restriction could.

The example of standing and working pressure of gas can be compared to initial flow of water and reduction of flow rate.

 

[Al-Glasgow]

Thanks DP for reply.

I will return with model number shortly.

The flow of hot water from all the hot taps is the same at any time of day if that has a bearing on matters.

Once i get exact model ill look for parts diagram, then it might make more sense to me.

Regards
Alan

 

[pierrot]

8) may have a clogged up cold water inlet filter. cant r3emember whether this boiler has one or not. check manufacturers instructions.

 

[DP]

Some Vokeras do, others not. Some that have filter fitted, location can vary.

 

[Al-Glasgow]

DP

Model in question is a Vokera Compact 24, only 1.5 years old, 5 or 6 rads, installed in upstairs cupboard, all hot taps are on ground floor.

Regards
Alan