Biasi 28S no hot water, CH OK.

[Ianmenai]

Strange as it may seem this is a brand new combi! I purchased it ages ago (2002) for my retirement project in France and FINALLY I have got as far as installing the boiler! It has stayed in a dry place in its box since then! Suffice to say my project got waylaid by the pleasant French way of life and possibly too much wine!!
Big problem is that there is no hot water, the CH works perfectly. When turning on the hot tap only cold coomes out. I suspect the DHV as when the pump comes on in central heating mode the plunger at the front of the DHV comes out and the micro switch makes and the boiler fires up. When the hot water tap is turned on the plunger at the side does not come out and the micro switch is not made.
Removing the micro switches the plunger at the front is easy to pull out, but the one at the side is very difficult to pull out. It isn't seized and can be pulled out with a pair of pliers with difficulty as there appears to be a strong spring inside.
In the 'summer' mode i.e. hot water only, the boiler does not fire up but also the pump does not start up when the hot tap is turned on. Should the pump start?
So is it the DHV faulty or is it something else?
Rather than buy a new DHV unnecessarily I would love to hear your views.
As I said the boiler is unused though quite a few years old and well out of any warranty, so no recourse with Biasi!
Thanks
Ian

 

[Agile]

I am assuming it is the real 28S with THREE knobs.

When dealing with warranty issues we initially look at installation issues as they are more common than actual boiler faults.

I am assuming that you fitted it yourself!

The warranty only is supported in the country of purchase.

So the first thing to check is that the DHW flow through the boiler is correct.

It must enter from the fourth pipe and leave from the second pipe.

You must check that somehow.

Where the blue tap is fitted is irrelevant as it can be wrongly fitted too.

So a normal simple check would be to turn off the blue tap on pipe four and turn on house hot tap and then loosen pipe two on the boiler and see if you get wet!

What Departement are you in?

Tony

Untitled

• Agile
• 4 Apr 2009
• 29

 

[Ianmenai]

I am assuming it is the real 28S with THREE knobs.

When dealing with warranty issues we initially look at installation issues as they are more common than actual boiler faults.

I am assuming that you fitted it yourself!

The warranty only is supported in the country of purchase.

So the first thing to check is that the DHW flow through the boiler is correct.

It must enter from the fourth pipe and leave from the second pipe.

You must check that somehow.

Where the blue tap is fitted is irrelevant as it can be wrongly fitted too.

So a normal simple check would be to turn off the blue tap on pipe four and turn on house hot tap and then loosen pipe two on the boiler and see if you get wet!

What Departement are you in?

Tony

Untitled

• Agile
• 4 Apr 2009
• 29

Hi Agile
First off nice R4, Charente registered? I'm in 24 but right on the border of 19 and 87, you'll know where I am referring to!

Now to the boiler.
Biasi 28S combi and yes it has three knobs!
Bought from Screwfix, driven to France by me so definitely no recourse from Biasi, and I wouldn't expect any.

The water flow through the boiler is fine. In through (31) and out of the pipe between (30 Gas and 28) Trust me when I say it is plumbed in correctly as per the installation manual!

I've installed plenty of boilers, and do know what I am doing!
To reiterate, the CH side is working fine, just no hot water out of the hot tap either when the CH is on or when it isn't.
As I said the pump doesn't work when the hot tap is opened in either summer or winter setting.

What I would expect is when the hot tap is opened the pump starts and sends water through the heat exchanger which then heats the hot water side and I 'should' get hot water from the hot tap. Sadly NOTHING happens in the boiler when the hot tap is opened. Surely the request to the pump comes from the DHV actuating the micro switch for the pump. I've checked this micro switch and it does start the pump and the boiler starts, unfortunately I can't keep the shaft pulled out AND press the micro switch!
So my thinking says it is the DHV not pushing the shaft out. Maybe the diaphragm has perished in the intervening time, well it is 14 years old! Would this stop the shaft being pushed out to actuate the micro switch?

Thanks for your help and anything else you or anybody can suggest would be gratefully received.
Ian

 

[Agile]

Be aware that some so called professional installers have sworn blind the water flow through the boiler is correct when it was not!

You can carefully undo the two square headed screws that hold the diaphragm unit in place and pull it slightly to the left.

Then see if the pin comes out when hot water is run.

If it does then see how hard it pushes. Should be too strong to hold in with thumb.

If that works properly then use something about 10-15 mm diameter to depress the pin in the socket and push it to the right and see if that starts up the pump.

But regardless of how certain you are of the water flow, my advice would still be to check it first to be sure!

Tony

 

[Ianmenai]

Hi Tony

I am certain that it is plumbed in correctly, 1) because I've double checked with the installation manual and the pictures and 2) where the cold feed comes in the pump valve block, there are two small pipes taking the incoming cold feed pressure to the diaphragm body you referred to.
Turning on a hot tap does not move the shaft. If I manually do it the pump starts followed by the boiler firing up.
So it must be that diverter valve! I'm returning to the UK next week so will pick up a new/refurbished valve.
I think a new valve rather than a refurb kit would be in order, just to make sure it will be reliable.
A bit of a disappointment considering the boiler is unused but that's life!
Thanks for your help.
Ian

 

[Agile]

I am very surprised that you don't want to do the simple test that I have explained for you.

I am not totally sure that you have done the other test properly either.

It would be unusual for the diaphragm unit not to work.

But even if it did not, then it would only be the pin slightly seized in the gland.

But for the diaphragm unit to work the venture needs to be operating correctly. But its rare for that to fail.

But it can all be dismantled and examined.

So much easier to do the basic test first though!

Tony

 

[Dan Robinson]

So a mechanical item sat on a box for 14 years and you expect it to be tip top?

And a Biasi to boot?


Christ.


Tony will come for £84 plus the bus fare and get it up and running before you can warn up the brie.

 

[Agile]

Hi Tony

I am certain that it is plumbed in correctly, 1) because I've double checked with the installation manual and the pictures

Thanks for your help.
Ian

One idiot installer piped it wrongly because he followed a picture in the book of the boiler taken from the rear!

 

[Ianmenai]

Hi Tony,
Hopefully a picture of the connections is attached to this post.
This will prove to you that it is plumbed correctly!
I totally understand your frustration, but I did what you said in a different way which I thought I had explained.
Rather than dismantle the diaphragm end of the diverter valve I simply released the micro switch from the other end of the shaft!
I could then feel and see the shaft which doesn't come out when the hot water tap is turned on. By simulating the shaft coming out, by pressing the thin screwdriver into the micro switch I can fire up the boiler.
I am now convinced it is the diaphragm actuator that isn't working, i.e. forcing the shaft in the valve to change the flow from the pump to the heat exchanger.
So today I WILL release the diaphragm unit and check that.
From what you say there is enough play on those small pipes to give the required room, because if I release them I will have to drain the DHW circuit and won't be able to check if the diaphragm is actuating.
Dan is quite correct in that a boiler sitting around for 14 years can be prone to problems, though I didn't know the trade despised Biasi that much!
The worst thing that happens with no use is in the electronic circuits, the capacitors dry out and swell, thankfully the Biasi is made with better components.
Ian

 

[DP]

Ian the boiler has two manifolds with micro switches. One has four screws- it's function is to check pump run and water in system. When pump run, circulating water will cause the plunger to operate the switch. If there is no power to boiler, obviously this microswitch will not operate.


Second manifold has two micro pipes connected to it and is the one you find is difficult to operate. The section with two small pipes on the left and microswitch to the right of the brass section, is hot water demand manifold/ hot water diverter valve
Two bundy pipes to the brass section have equal pressure in them when there is no hot water demand. When you run hot water, pipe on the right goes low pressure causing the heavily sprung diverter to move to the right operating the microswitch

Suggest you isoate cold water to boiler, check no water now flows from hot tap, loosen two small screws on the brass section that clamps the large brass manifold (with two pipes going to it), separate the two so now have 6 screw manifold with two pipes attached to it sale rated from the brass housing

Make sure water is isolated at the mains else you will get wet if hot and cold pipes under the boiler are reversed

Remove 'U' clips that hold the bundy pipes in place in their sockets. Identify left and right pipe as connections are polarised. Remove six screws and check condition of diaphragm within. If ok, reassemble and reconnect bundy pipes to manifold, but this time fit the manifold the wrong way ie, the spindle to the left. Run a hot tap and see if the spindle in the six screw manifold pushes out. If it does, then hot and cold pipes reversed. If spindle weak to push out with manifold fitted correctly or reversed, Venturi in the brass section where the pump is, is goosed

By the way, hot water manifold will function even with boiler power supply isolated, ie plunger pushes out operating the microswitch

Good luch

 

[Ianmenai]

Well a result!
First I disconnected the diaphragm unit and carefully checked that there was water going to one side, there was. That confirmed the pump manifold body was OK.
Next I took the diaphragm unit completely out of the boiler and undid the screws to have a look at the diaphragm. All seemed OK until I tried to blow into the orifice which actuates the diaphragm, and no matter how hard I blew no movement in the diaphragm. So I CAREFULLY pushed a blunt rod down the pipe until it touched the diaphragm and then suddenly the diaphragm released itself from the back out the housing! Because it hadn't been used it had stuck to the housing!
Now when I blew the diaphragm ballooned. So I reassembled the diaphragm housing and blew into the hole again and this time the little rod came out!
Put everything back in the boiler and did a water test, no leaks and I could hear the micro switch at the end of the shaft being actuated.
Fired up the boiler and everything now works. Hot water comes out of the hot tap, well after the boiler has fired up for a bit.
My Baxi combi in Cardiff keeps a small reservoir of warm/hot water to give hot water fairly quickly, but the Baxi combi is 14 years newer in design technology!
The Biasi is fine for France where it will be used for winter use, a hot water cylinder suffices for the summer months. Gas is far more expensive than Electricity in France for water heating!
I'm going to buy a new diaphragm when I come back to Cardiff and replace it when I next come out.
So thanks to all.
Ian

 

[Agile]

Your expectation that the photo of your boiler will indicate anything, shows that you have not understood what I have been trying to get you to check.

However had you done what I asked initially then you would have identified that the diaphragm unit was not operating.

Little point in replacing the diaphragm if its working now, just keep a spare on hand.

Tony

 

[DP]

Well done Ian