Combi boiler reduced hot water pressure

[roofman]

I have a 6 year old Viessmann 050-w with the above problem across all hot taps in the house...Heat exchanger plate clean or replace? when cleaned with the limescale acid does it bring it back 100% or am i better getting a new one...pump perfect and diverter valve perfect including very good pressure on cold side, also heating side working normal.

 

[gaz1]

a failed/failing diverter valve would cause your symtons but would also heat the nearest radiator as well

 

[roofman]

a failed/failing diverter valve would cause your symtons but would also heat the nearest radiator as well

When the heating is off then no rads at all get warm

 

[gaz1]

a failing diverter valve would still cause a rad to get warm as it sends the hot water through the central heating side of it

as its half open /closed can cause the issue your on about until pressure has built up in the rad system

low pressure on hot is also someone messing with the water mains between summer and winter it does change more so on pumped mains systems

im westyorkshire based and we should never see it fluctuate but yes i have over the last few years there is a pressure difference inbetween summer and winter

yours does have a flow limiter on it p59

https://viessmanndirect.co.uk/files//6675e654-7cbc-417c-88b2-a70d01685823/Vitodens%20050%20BPJD%20Install%20and%20Service%20Manual.pdf

if your going to do the heat exchanger make sure its a new one you cant normally clean them but your welcome to try

 

[addjunkie]

Is there an inlet filter on the water inlet, slight blockage would cause your symptoms.

 

[Kayos]

Those boilers are well known for the rubber hoses from the heat ex to the diverter and the plate heat ex filling with crud and going crispy, this in turn fill the plate heat ex with crud as well

Take the front off, carefully feel the rubber hoses, if they feel hard then that is your problem.

I have used a wetvac and a bucket of water to clean them in the past, best option is to clean the hoses and replace the plate heat ex

 

[Seadog]

Flush the heat exchanger with phosphoric acid, preferably warm. It will shift everything.

 

[roofman]

I am armed with this for the exchanger plate and hopefully check the hoses as Kayos has pointed out too after the holiday..

 

[the snooper]

a failed/failing diverter valve would cause your symtons but would also heat the nearest radiator as well

I don't see how a diverter valve would cause low pressure at the tap, the diverter valve diverts dirty water either to the rads or the domestic hot water heat exchanger, potable water doesn't enter the diverter valve

 

[gaz1]

I don't see how a diverter valve would cause low pressure at the tap, the diverter valve diverts dirty water either to the rads or the domestic hot water heat exchanger, potable water doesn't enter the diverter valve

water pressure is over 1 bar your rads are 1 bar pressure it can pressurise your central heating system rather well

when us plumbers are topping up the system we use mains pressure to do this which is really common scence

in poor areas you can use pumps to create pressure on the systems

nowadays in poor pressure areas we can use both pump and expension tanks to gain presssure on the system

 

[Seadog]

I am armed with this for the exchanger plate and hopefully check the hoses as Kayos has pointed out too after the holiday..

View attachment 344434

You'd better buy a new heat exchanger if you're using that

 

[roofman]

You'd better buy a new heat exchanger if you're using that

Why?

 

[Kayos]

I'd buy a new heat ex, but I've never really had the time to clean one out.

 

[Seadog]

Why?

Because hydrochloric acid and many stainless steels do not get along.

 

[knighty]

I thought white vinegar was the go-to stuff for removing limescale?

I bought 4 gallons of it ready to flush my water heaters at work.... :-o

 

[Wozzaaah]

I’ve always used brick acid on plate heat exchangers and have had zero issues, it cleans the magnetite out a treat.
I keep a spare one, when ours shows symptoms of partial blockage I swap it for the clean one then clean the dirty one at my leisure.
A partially blocked primary side doesn’t affect the water pressure though, and I can’t see how a faulty diverter valve can either, as, like Snooper says, it’s only diverting the primary side.

 

[Kayos]

On this boiler, other boilers are different, it is the rubber hoses and the plate heat ex causing the problems

I would recommend swapping the plate, based on experience but you can wet vac the hoses, once they are starting to clear I put one in a bucket of water (cover the back of the PCB) and wet vac through, then do it the other way

The hoses are the only thing that let an otherwise excellent boiler down, it's designed for German systems that use aluminium radiators and pipes

 

[500e]

Any mod then @Kayos

 

[Kayos]

Any mod then @Kayos

Sadly on the 050 you are stuck with the hoses, clean system and quality chemicals is the best you can do

I like viessman boilers but for a basic combi there are better choices, when you get into the specialist stuff like the 111 or the 222, nothing comes close

 

[roofman]

Sadly on the 050 you are stuck with the hoses, clean system and quality chemicals is the best you can do

I like viessman boilers but for a basic combi there are better choices, when you get into the specialist stuff like the 111 or the 222, nothing comes close

Thanks for your advice bud..will check the hoses when i take of the ex plate to clean, and i might take the advice from Wozzaaah too and have a spare for a fast change over.