Adding a Bypass valve to combi installion

TedBk · 1 Apr 2020

I have almost finished my upgrade to my central heating. i.e. all new radiators, new pipes etc.

The combi boilers built in bypass is set to maximum at .35bar.

The existing system is a Valiant ecotec plus with 22mm used for about 1/4 the run and the rest are 15mm, 6 rads for 10KW.

I was going to fit a bypass valve in a accessible cupboard at the end of the 22mm run. Is it simply a matter of fitting it and setting it to say .3bar such that the combi boiler bypass stay closed? Or is the combi bypass meant to be disabled?

I was thinking of adding smart TRVs, as it currently stands if I close off the largest rads. The pump is either cavitating or there is some other noise that it is making, even with two small radiators acting as bypass but to set a low flow for balancing purposes.

durhamplumber · 1 Apr 2020

TedBk said:
I have almost finished my upgrade to my central heating. i.e. all new radiators, new pipes etc.

The combi boilers built in bypass is set to maximum at .35bar.

The existing system Valiant ecotec plus with 22mm pipes about 1/4 of the way around and the rest was 15mm, 6 rads for 10KW.

I was going to fit a bypass valve in a accessible cupboard at the end of the 22mm. Is it simply a matter of fitting it and set to say .3bar or such that the combi boiler bypass stay closed? Or is the combi bypass meant to be disabled?

I was thinking of adding smart TRV, as currently stands if a close of the largest rads. The pump is either cavitating of the there is some other noise that is making, even with two small radiators acting a bypass albeit lockshields restricting the flow for balancing purposes.

You lost me after the third paragraph!

TedBk · 1 Apr 2020

durhamplumber said:
You lost me after the third paragraph!

Ok shorter version.

I was going to fit a bypass valve at the end of the 22mm run, before it switches to 15mm. Is it simply a matter of fitting it and setting it to say .3bar or such that the combi boilers internal bypass stay closed? (Currently set to .35bar its maximum) Or is the combi bypass meant to be disabled?

Mottie · 1 Apr 2020

I thought combi's had everything built into them and that was all that was needed?

picasso · 1 Apr 2020

Try setting the kw rating in d0 to 10 and that should stop the noise in your rads and eliminate the need for a bypass.

TedBk · 1 Apr 2020

picasso said:
Try setting the kw rating in d0 to 10 and that should stop the noise in your rads and eliminate the need for a bypass.

The boiler has been upgraded to use opentherm, even when the controller demands 45deg and it is modulating to a very low setting the pump noise still happens, if a close off certain rads. Otherwise no noise.

picasso · 1 Apr 2020

Drop the kw rating to 10 in d0.

durhamplumber · 1 Apr 2020

Mottie said:
I thought combi's had everything built into them and that was all that was needed?

So did I

TedBk · 1 Apr 2020

picasso said:
Drop the kw rating to 10 in d0.

No difference, tried 7K as well. Using the opentherm interface means the boiler is often (at least now it wamer) just demanding 50degrees. But the problem is only when the big rads are turned off.

durhamplumber · 1 Apr 2020

picasso said:
Try setting the kw rating in d0 to 10

TedBk said:
The boiler has been upgraded to use opentherm, even when the controller demands 45deg and it is modulating to a very low setting

Why is that better than a room stat?

picasso · 1 Apr 2020

How did you access d0 ?

TedBk · 1 Apr 2020

durhamplumber said:
So did I

The only reason I thought I would benefit from a bypass is the main circuit is a mix of 22mm (closest to boiler) and 15mm where the circuit is expanded. Instead of being a 22mm circuit with 15mm branching off to the radiators.

durhamplumber · 1 Apr 2020

TedBk said:
The only reason I thought I would benefit from a bypass is the main circuit is a mix of 22mm (closest to boiler) and 15mm where the circuit is expanded. Instead of being a 22mm circuit with 15mm branching off to the radiators.

Many systems are combinations of 22/15/10 mm but do not need an additional bypass with a combi

TedBk · 1 Apr 2020

picasso said:
How did you access d0 ?

From the panels, two buttons to get to dianotoistic. I tried 10K and 7K settings.

durhamplumber said:
Why is that better than a room stat?

Instead of just on/off the boiler to heat to boiler set flow temp say 75 degree, it will ask the boiler to run at a lower temperature if can meet the demand by running longer. Simple upgrade, and the room is more comfortable. You can do the same thing manual by adjusting the boiler flow temperature. Supposedly more efficient.

picasso · 1 Apr 2020

The ecotec plus has a 2 speed pump, dropping the kw rating under 60% of full output keeps the pump in stage 1 which should stop the water noise, check the setting again and make sure its been saved at 10kws.

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Adding a Bypass valve to combi installion

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