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Andrew Smith
Andrew Smith, Construction Worker
Category: Plumbing
Satisfied Customers: 3629
Experience:  30 years experience in construction, City and Guilds qualified.
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We have a continuing problem with our Vokera 20/80 Flowmatic,

Customer Question

We have a continuing problem with our Vokera 20/80 Flowmatic, in that the pressure rises and we have to take water out of the rads to keep the pressure down. We have disconnected the filling loop, we have replaced the main expansion vessel and DHW heat exchanger - both new parts. Still the same problem, does anyone know why this is and what we can now look at ? Thank you
Submitted: 1 year ago.
Category: Plumbing
Expert:  Andrew Smith replied 1 year ago.
How long does it take to rise to 3 bar if you drop it back down to 1.5 bar?
Customer: replied 1 year ago.

We actually don't let it get to 3 bars. We normally keep it at say 1.2, then it will rise by .3 bar a day, we assume it will eventually reach 3 bars, but try to keep it at the lower level by taking water out of the rads

Expert:  Andrew Smith replied 1 year ago.
If the expansion vessel is not pressurised correctly or if you have a large system then system pressure can rise from cold to hot.
I would only worry if it rises over 0.5 bar during this cycle.
Customer: replied 1 year ago.

Sorry we don't really understand this, as if we left it - and did not take water out - it would keep rising by .3 each day. We feel that there is water getting in somehow. When there is nothing being used, overnight for example, this when we notice the presure rise. We are aware that it does rise when the hot water is being used but the new expansion vessel controls that. The rise is even when there is no heating or water being used.

Expert:  Andrew Smith replied 1 year ago.
ok.
Anywhere that has a link between the main cold water and the heating system will need checking;
1. The filling loop
2. The hot water plate heat exchanger
3. Heating Coil in pressurised cylinder
4. Additional underfloor heating fill points
Customer: replied 1 year ago.

Thank you, ***** ***** thing we have not checked is the coil, we'll have a look in the manual to find where that is.

Expert:  Andrew Smith replied 1 year ago.
Yes, but this is only if you have a pressurised cylinder also.
This will be the only place that mains cold water and heating water pass very close by and a pinhole in one of them will do this to your system