Please help - the plumber's coming

[carrie1964]

We had a problem where the hot water would not come on unless the
central heating is on.

We are insured for boiler breakdown and the plumber duly visited.
I was advised that the problem was intermittent diverter failure due to the domestic hot water circuit being very restricted, due to scale.

They have advised that the dhw plate heat exchanger needs to be descaled and have recommended that the system be powerflushed to rectify the problem.

I hope you can advise as I am concerned that this may not be the correc t course of action. They have said that they will also manually descale the heat exchanger. By the way we have no probs with the central heating.

Had the same problem last year when a new diverter valve was fitted.

Any advice would be greatly appreciated, as the plumber is booked for next Monday

 

[Gasman1015]

Cannot see what your problem is.

 

[carrie1964]

Gasman,

I'm just concerned that powerflushing is not the solution to scale in the hot water circuit.

In my ignorance I don't know if powerflushing will descale my boiler for the domestic hot water problem?
Silly question - is this more for central heating problems?

 

[Slugbabydotcom]

Only thing I could add to that is to invest in some form of limescale protection

 

[Slugbabydotcom]

Gasman,

I'm just concerned that powerflushing is not the solution to scale in the hot water circuit.

In my ignorance I don't know if powerflushing will descale my boiler for the domestic hot water problem?
Silly question - is this more for central heating problems?

Powerflushing is not the solution to scale in your hot water circuit but it will save you another diverter valve. I agree that powerflushing is often oversold but seeing as you mentioned the DV it would imply that powerflushing is necessary. Without seeing the system myself I would consider it unfair to make any judgements on that point.

 

[carrie1964]

Thank you for your reply. It's just that I have read other posts where powerflushing seem to apply more to radiator problems than hot water probs.

Is powerflushing basically descaling? (sorry if this may be a stupid question to the experts!), but the insurance company want a piece of paper saying that the boiler has been descaled before continuing to cover it.

I would be very grateful if you could advise what the solution would be for scale in the hot water circuit.
Many thanks

 

[Gasman1015]

Maybe I have misunderstood you, from your post I concluded that the insurance company were paying to have the work specified done, is that not the case.

 

[carrie1964]

Gasman,

No-we have to pay for this: When the plumber visited on behalf of the insurance company, he adjusted the diverter valve as much as possible, but advised that it was a scale problem so this is not covered by our insurance and it has to be rectified by us, at our cost, before they will cover us for future problems.

So we have have booked to have the system powerflushed as advised by the heating company - but I am concerned this won't cure the scale in the dhw system? (perhaps i'm wrong as i'm no expert).

They are going to manually descale the heat exchanger in the boiler too?

My concern is: is powerflushing the best course of action?

Thanks

 

[Gasman1015]

Powerflushing alone will not cure your problem and will benefit the system, however as they are manually cleaning out the heat exchanger it really comes down to cost.

 

[ChrisR]

Descaling your tap water circuit can be done fairly easily via your washing machine taps assuming you have them ( h & c). A powerflushing machine can be used.
Powerflushing the CH system won't touch it. It will also not touch the primary (boiler) side of the tap water heat exchanger, unless the PF machine is connected inside the boiler and the HW tap is turned on.

Hence removal of the tap water h/ex is often best, though in severe cases scale in internal pipes etc remains a problem.

If this is hard to understand just highlight which bit and we'll expand...

 

[Agile]

Without examining your system its impossible to come to any accurate conclusion as to the problem. You have not quoted your boiler make or model.

The word "scale" is often wrongly used to describe oxide debris in the system. This can in the extreme block radiators but will first block a plate heat exchanger.

The diagnosis is quite possibly correct but I have twice been called to give a second opinion on these insurance company diagnosis. In one case it was air in the system and in the other a failed diverter valve!

In both cases the insurance companies refunded our diagnostic fees and in at least one case a "senior technician" visited and agreed their original diagnosis was wrong!

Tony Glazier

 

[meldrew's_mate]

As a mate of mine said, "I don't belieeeve the cheek of these insurance co.s".
Let's look at the symptoms again

We had a problem where the hot water would not come on unless the central heating is on.

Surely this suggests (subject to boiler make/model) that the hot water flow os not being detected. If it were a Puma the diagnosis may have been different.

We are insured for boiler breakdown and the plumber duly visited. I was advised that the problem was intermittent diverter failure due to the domestic hot water circuit being very restricted, due to scale.

I think we can conclude that this doesn't fit the symptom, because severe lack of DHW flow has not been mentioned.

They have advised that the dhw plate heat exchanger needs to be descaled and have recommended that the system be powerflushed to rectify the problem.

As most DVs do not directly "pull" the valve section (a spring moves it) the diaphragn should actuate the end switch(es) regardless of the sludge status of the main valve. Therefore a powerflush, though nice to have, is an irrelevance with respect to the primary fault.

They have said that they will also manually descale the heat exchanger. By the way we have no probs with the central heating.

As for powerflushing, though more relevant to this problem.

Had the same problem last year when a new diverter valve was fitted.

There are some cheap DVs about of, perhaps, questionable grade.
Could it be as simple as replacing a split/holed diaphragm?

So my advice is, solve the problem first (diaphragm?), then do the powerflush and descale at your own convenience. If the PF is a condition of further insurance cover then it is your call; the descale will help to increase DHW flow which will disguise (for a short time) the diaphragm problem. A bit long winded but I hope it helps.

 

[corgiman]

Just a thought chaps

If its a plated hot water heat exchanger then the ch water WILL flow through ergo sludge scale will build up quickly in the ch section of the heat exchanger, so I agree that a powerflush of the central heating is justified as sludge mucks about with plated heat exchangers terrible