Halstead Finest Gold - DHW problem

[paul993]

Hi, I have a halstead finest gold and have a DHW problem. It's cool, and gradually has got cooler.

The thing is I can fully open the hot tap, run around to the boiler, feel the pipe coming out of the heat exchanger and it's piping hot, but if I feel the DHW outlet leading off to the tap it's barely warm !?!

The plumber I had in to look at it last time (when the PCB went) didn't know what he was doing and replaced about 5 parts before deciding the pcb was up the creek.

I want to try and narrow this down to the exact part before I call him in... might save a few hundred quid if I can just say "Ahhh ... it's the DHW thermistor"

Any ideas what would cause this problem ? (is it the DHW thermistor ?)

Best Regards
Paul.

 

[Rob]

does the boiler stay alight all the time the tap is open. is any heat passing to the radiators?

 

[paul993]

That was the original problem, but the guy lowered the max burner pressure slightly and that seemed to cure that, (before it was making a modulating sound like WA-WA-WA-WA, now it doesn't, but now the DHW is even cooler).

I've had a good look at the pipe I was feeling that leaves the heat exchanger and it's on the CH circuit as it goes to the pressure release valve. This pipe has the overheat coil attached to it so I was wondering if it would cause the original problem.....i.e.... even though the hot water is only luke warm, if the CH pump isn't running the stationary water in the CH circuit gets so hot it just trips the overheat valve ?

Now, although the system runs OK, the CH is nice and hot, but the DHW is way too cool.

 

[scatmanjohn]

What rob884 meant was:

When you run the tap feel the ch flow pipe UNDER the boiler.

Does it get hot?

If so you have a diverter valve problem.


To answer your other question.

No.

The boiler won't run if the pump is not running.

 

[paul993]

Ignore that last entry from me........ I've just looked at the flow diagram of how the boiler works in DHW mode, and it uses the pipe with the pressure relief valve to send water into the heat exchanger, and then out of the DHW outlet....

So, how can the water going into the heat exchanger be so much hotter than the water coming out of it and going to the taps ?

 

[sime10]

AS above have already said turn the heating off, wait for heating pipes to cool then just run the hot water and see if the heating pipes get warm

 

[Rob]

Ignore that last entry from me........ I've just looked at the flow diagram of how the boiler works in DHW mode, and it uses the pipe with the pressure relief valve to send water into the heat exchanger, and then out of the DHW outlet....

no it doesnt. can you answer the original questions and as scatman has described.

 

[scatmanjohn]

Ignore that last entry from me........ I've just looked at the flow diagram of how the boiler works in DHW mode, and it uses the pipe with the pressure relief valve to send water into the heat exchanger, and then out of the DHW outlet....

So, how can the water going into the heat exchanger be so much hotter than the water coming out of it and going to the taps ?

I think you are getting yourself into a muddle here.

You have not answered the question about the ch flow pipe under the boiler getting hot during a hw demand.

 

[paul993]

OH.... I see...... If the CH flow pipe gets hot, then the water is running into there.

But surely my pressure gauge would go off the chart ???

I'll wait till the CH cools down a bit and try it.

 

[sime10]

But surely my pressure gauge would go off the chart ???

No

 

[scatmanjohn]

OH.... I see...... If the CH flow pipe gets hot, then the water is running into there.

But surely my pressure gauge would go off the chart ???

I'll wait till the CH cools down a bit and try it.

Why would the pressure gauge "go off the chart".?

 

[paul993]

S O R R Y CHAPS

There's just suddenly been a FLOOD of messages all at once and I got muddled.

When the boiler is in DHW mode it does use the pipe with the pressure relief valve on the end of it.... it justs gets diverted down into the heat exchanger plate.

http://www.meltland.50g.com/finest.html

Now.......the FACTS are :-

(a) The water in the pipe coming OUT of the heat exchanger plate to the taps is cool,
(b) The water going to the diverter valve is definetely scalding hot.
(c) The missus has had the CH on all day and I'm waiting for it to cool before doing the other test you wanted me to do.

But.... unless there is some other way to get cold water into the DHW outlet, it MUST be the diverter valve ?!?!????

(Is there another way )

 

[paul993]

I'm an arse

Can someone explain the plate heat exchanger to me.... there's me thinking it was just to warm the cold water a bit before going to the burner, but looking at the diagram it looks as though the cold water runs straight to the hot tap in my bath......passing through the heat exchanger as it goes ...... a little bit of the CH water is used in a small loop to heat up the heat exchanger......

EUREKA

I now understand it (I think) so if the diverter is kaput, the boiler will just run in sort of half CH mode, but as the heat exchanger isn't getting heated properly the water out of the taps isn't either..

(That was whu I said "Wouldn't the pressure guage go off the chart .... I thought the cold in -> heat exchanger -> burner -> heat exchanger -> taps.)

as I said ..... im an arse

(Please tell me I've got it right now)

 

[scatmanjohn]

as I said ..... im an a**e

Well i was going to say the same but i am too polite

You seem to have got the jist of it now.

 

[paul993]

errm.... new development now..... just discovered I can't perform the test described above as when the CH is off, the burner doesn't fire ... even with the tap on full pelt !!

the little DHW pressure switch is coming up and closing the relay. When I power it off and back on .... the pressure swich comes up, closes the relay for about 10 seconds.....no burner....then the switch goes back down ???