Problem with heating controls

[Chico]

I have a

problem with my central heating which my heating engineer is unable

to fix.

The

boiler itself works fine – the problem comes when the heating

circuit is switched on (to operate the pump and mixer valve). At any

time and without warning a loud buzzing noise comes from inside the

control unit and the heating system stops working. I can usually

reset this simply by switching off and switching back on again.

I avoid

problems overnight by switching it off. In the morning I switch it

on and all is well for a while, but sometimes when I switch it on

the buzzing starts immediately and I have to switch on and off until

it clears.

The

engineer says he cannot do anything as the heating is OK when he

arrives. My problem is that I will soon have to leave the house

vacant for several weeks during frosty weather.

I have

spoken to Viessmann in the UK and they cannot offer any help. I

cannot find any way of tracking down a Viessmann specialist in this

area (84). The engineer I am dealing with has known this boiler for

at least ten years and keeps promising to find a solution, but he

just goes into hiding until I ring him again. I am sure that if I

could point him in the right direction he would get something done.

My French is good enough to discuss technical matters with someone

who wants to communicate, but it is no match for someone who does'nt.

Any help

or suggestions would be appreciated.

Chico

Oil-fired Boiler:

Viessmann Vitola-biferal VE1 with mixing valve, manufactured

1985

Control

unit: Viessmann Tetramatik-FR-4

[Maricopa]

I found this manual for the control unit.

You will need to fill in the details here for the boiler manual.

[jondeau]

The usual procedure in the UK is to change the control box.........not cheap I know, but these things are full of electronic wizardry which no one ever seems able to repair.

25 years old is a pretty good lifespan for any heating control........

 

[Chico]

Maricopa,  Thanks a lot for this. The user instructions for the control unit are similar to the ones the previous owner left me - but more up to date.  I'm having trouble getting the system to accept my request for the boiler manual, but I shall persist as this could be vital info.

Chico

[Chico]

jondeau,  I was beginning to see this as a final option. Would the control box need to be a Viessmann to suit the boiler or are these units interchangeable?  It would be nice if I did not have to find a Viessman specialist - and probably cheaper.

Thanks for your input,  Chico

[jondeau]

You could change the control box to another make.........but you would have to be very certain that you had the right type, I am not familiar with this boiler but generally speaking the control box controls all the safety controls on the boiler as well as the selection of functions.

I assume that the boiler works ok when it is heating water ?

If so then the simplest and cheapest solution is to disconnect the heating pump from the control box and fit a seperate time switch to run the pump/heating system.

This may require some re-jigging of the other controls/wireing but this is a very simple method that I'm sure your heating engineer can manage quite easily.....

 

[BIG MAC]

Without further information on the boiler or system it's difficult to comment. Is it a combi?

Going on what has been said are you sure this isn't a case of  a mechical obstruction or defect in the diverter resulting in it faulting out as a consequence of not being able to swap ports in the valve? It may be that the buzzing you are hearing is the motrised head to the valve trying to do something that the mechanical side is having problems complying with. Sometimes occurs due to solids in the system ie Scale or solder etc It may be that the motorised head is itself shot. Neither are difficult things to fix (More of a pain than anything else really)    Most heating engineers would have checked this so its possible I have entirely the wrong end of the stick but without better information etc......

[Chico]

Thanks

for these replies.

On the

info front, the hot water production works perfectly and the problem

only arises when the pump circuit is switched on. It is not a combi

system. I have checked the pump myself and it turns very smoothly

without any friction at all. I have also checked the operation of

the mixing valve (more about this below) and it moves through its

full range very easily. I have located the source of the buzzing

sound in the control box and it is directly behind the set of three

thumbwheels which contol the heating curve which suggests that it is

something to do with the mixing valve.

I like

your suggestion, jonjeau, that I get an engineer to disconnect the

heating pump from the control box and fit a seperate time switch to

run the pump/heating system. But

what about the mixing valve? In his useful notes about French

plumbing funnies, Opel Fruit says

“For

some reason, the French insist on fitting something called a vanne

melangeuse [mixing valve] after the pump. This oddity is totally

unnecessary and is used to inefficiently control the radiator

temperature by allowing some of the boiler flow to immediately return

to the boiler as a kind of crude bypass. Never fit one.”

Well,

I've got one and as far as I can see it seems to be all about

adjusting the water temperature according to the outside temperature.

I would happily forgo this. The gate itself is in a cast iron

“manifold” and is controlled by a lever scaled from 0 (cold) to10

(hot). This lever is moved into position by a whacking great motor

which is controlled from the control box. The motor is held in place

by two nuts and I can easily remove it, which I did temporarily, and

that's how I know the lever moves through its full range without any

friction or grittiness.

Now the

big question. When I ask the engineer to fit a separate timer to the

heat pump, should I ask him to remove the motor to the mixing valve

and disconnect it from the control box? The lever controlling the

mixer valve is on full view and, without the motor on it it would be

easy to move it from open to shut according to need.

What do

you think?

Chico

[jondeau]

I must admit I never had read Opel Fruits posting..........(it looked a bit tooooo long)

But I wholeheartedly agree with his opinion on mixing valves. Total waste of time, so yes disconnect the mixing valve.

All you need is to do is re-wire the pump, and room stat if you have one, and that will solve the problem.

Do remember, that the control box controls all the boiler safety controls so do leave the rest of it as it is..