Hi Flow 400

[pom001]

My hi flow 400 was fitted when my house was new, and is now 11 years old, in general it has been OK with no major issues
But i have had the same issue for a good few years now and that is noise when the hot water side kicks in from cold, ie morning start up, it has a sound best decribed as a 'creaking ship' and this happens for about 2-3 minutes, it makes a noise then goes quiet in cycles of about 30 seconds, the noise slowly reduces and then goes away.
system pressure is OK, Serviced quite regularly until my plumber went awol
Its had the pressure vessel replaced as it got water in the 'air side' , its had conditioner in the system from new.
It had a mysterious slow leak which turned out to be the washer /seal in the connector from the pump to the main heat exchanger.
But the noise is a personal thing now, as a mechanical engineer i am tyring to put some logic to it
If i was a betting man i would guess that either the hot water heat exchanger or the main one was clogging up and the noise i hear seems to be similar to a cavitation noise
as the more i increase the system pressure the less noisy it becomes, for a while and then starts again but i am getting towards two bar and its still noisy, anyone had the same .
Had a few plumbers look at it but they just changed things without any improvement , spoke to worcester bosh, they suggested the small bypass line blockage, checked that OK , and the water filter in the valve block , all Ok
any ideas

 

[Agile]

Some aspects of that would point me to air in the waterways.

Tony

 

[nickso]

sounds more like a blockage to me.

primary heat exchanger and DHW heat exchangers block/choke for fun on these. remove the pump and diverter and check the tube going back to the rear connection of the primary h/e. remove the servo pipe and check it, sounds like you are calling that the bypass pipe and have already removed it. i would use new diverter seals on refitting, one of them is very thin and prone to not going back on right.

while the diverter is out you could split it open and check its not choked too. there is a very small orifice in there that controls the movement of the diverter, if its choked i guess you could get slow switch over and possible noise in some circumstances.

if none of that works then its either the primary h/e is choked or the DHW one is, good luck getting the DHW one out.

pump is also a possiblilty i suppose.

 

[mickyg]

good luck getting the DHW one out.

Last time I did that I decided in my wisdom, as we gas peoples do, to ignore the instructions and try and manoeuvre it out the back..which I did and in the process sliced my hand open blood everywhere.. I hate these boilers

 

[nickso]

good luck getting the DHW one out.

Last time I did that I decided in my wisdom, as we gas peoples do, to ignore the instructions and try and manoeuvre it out the back..which I did and in the process sliced my hand open blood everywhere.. I hate these boilers

ive looked at that before and decided it was more hassle than good. what did you have to remove to do it that way? obviously i'd wear gloves

problem is most of them are fitted under kitchen units so getting to the back is no good.

 

[Agile]

I have been asked to go to one today with fan not turning.

Anyone know if they have a system flow switch?

Tony

 

[mickyg]

ive looked at that before and decided it was more hassle than good. what did you have to remove to do it that way? obviously i'd wear gloves

I can't remember tbh it was about 4yrs ago, I know it wasn't a quick job though, I think if I didn't split my hand open though it would have been better than following the instructions which basically tell you to remove everything. It slid downwards when it come out hence my misfortune.

 

[pom001]

Some aspects of that would point me to air in the waterways.

Tony

Agree, it does seem like an 'air noise' or caviataion, it only happens when the hot water curcuit kicks in from cold. I have changed endless auto bleed valves, manual bled the litte valve on the top of the pressure release valve also for ages, but nothing comes out ( air )

 

[pom001]

sounds more like a blockage to me.

primary heat exchanger and DHW heat exchangers block/choke for fun on these. remove the pump and diverter and check the tube going back to the rear connection of the primary h/e. remove the servo pipe and check it, sounds like you are calling that the bypass pipe and have already removed it. i would use new diverter seals on refitting, one of them is very thin and prone to not going back on right.

while the diverter is out you could split it open and check its not choked too. there is a very small orifice in there that controls the movement of the diverter, if its choked i guess you could get slow switch over and possible noise in some circumstances.

if none of that works then its either the primary h/e is choked or the DHW one is, good luck getting the DHW one out.

pump is also a possiblilty i suppose.

Thanks for that
the diverter was chaged a couple of years ago as it died over the summer break, it didnt make any difference to the noise.
Both the hot water and heating works well and heats quickly would this work OK if the HE were blocking ?
I must admit that there was a small leak on the main HE connection , and when i replaced the washer at the joint from the HE to pipe i could see inside the HE and it looked a bit slimey.
The unit is in a big cupbaord upstairs and about six inches space down each side , to get the hot water HE out looks to be a bit of a beggar, can it be done like this or should i just remove the boiler ?
I know i should chuck it out amd get a new one but have been quoted up to 6 .5 k £'s for a replacement
At least this ones reasonably simple

 

[Agile]

I know i should chuck it out amd get a new one but have been quoted up to 6 .5 k £'s for a replacement

At least this ones reasonably simple

Wow! I replaced one with a HiFlo 440 before christmas and did it for well under £3000 even including the FW100 weather Comp controller.

Tony

 

[pom001]

I know i should chuck it out amd get a new one but have been quoted up to 6 .5 k £'s for a replacement

At least this ones reasonably simple

Wow! I replaced one with a HiFlo 440 before christmas and did it for well under £3000 even including the FW100 weather Comp controller.

Tony

To be fair that was for a viesmann boiler of the same order , with an additional immersion type tank in the loft the hot water
Still bl**dy expensive
As a rule what are they like ?
To be fair i have has 11 years out of my WBosch and it still works OK

 

[nickso]

hiflow 400's are carp.

the 440's are a vast improvement and simpler too.

not seen the newer one yet, 550?

 

[pom001]

I know i should chuck it out amd get a new one but have been quoted up to 6 .5 k £'s for a replacement

At least this ones reasonably simple

Wow! I replaced one with a HiFlo 440 before christmas and did it for well under £3000 even including the FW100 weather Comp controller.

Tony

Maybe you could come and replace mine soon then with a 440