Viessmann 100-W WB1B 26kw open vent `S`Plan Control Wiring

[simond]

We generally dont advocate changing from a legacy OV set up to a sealed system, unless there are other reasons making it necessary.

So many issues arise from the increased system pressure, no point in making problems. Surely you dont advise all your customers to change from OV?

 

[Agile]

Whilst an OV system in good condition and correctly installed will work well, converting to a sealed system will prevent many problems and is more efficient.

If a new boiler is being fitted and the OV system is in good condition then I would recommend that converting to a sealed system would be an advantage.

Most of my customers would take my advice because I am only there because they want me to be working for them.

Unlike you I am not in a competitive tendering situation where doing the minimum to be done secures the job.

Tony

 

[simond]

Unlike you I am not in a competitive tendering situation where doing the minimum to be done secures the job.

I wasn't hitherto aware that I was in a 'competitive tendering situation'. It seems you understand my business better than I do.

Most of my customers would take my advice because I am only there because they want me to be working for them.

Are you suggesting that my customers don't want me working for them? I just come round, uninvited and unwanted, and start work?

 

[Kellymont]

It seems you would have been happier with a Viessmann 200 series!

I have contacted Viessmann and they say i need to fit their cylinder demand box for the 2 channel timer to operate correctly, i am still not sure this will give me what i want, and i may install the old programmer.

Regarding the pump over run on this boiler what would be the best solution considering i already have the two zone valves for a `S.` plan, if i fit a mid-position valve (go`Y`plan instead of `S` plan) there will always be an open circuit for the hot water to pump into, and i will not have to make a return loop to the boiler, is this correct?

I am happy with the 26kw compak it`s just what i wanted to fit into my existing open vent syatem.
Thanks.

 

[Agile]

I think you will quickly realise that having a a three port valve which is always open to something makes not the slightest difference to pump over run if the pump is not controlled by the boiler!

Connecting the pump to the boiler and thus enabling pump over run reduces thermal stress/cycling and can only be beneficial to the boiler life. For the sake of a few metres of cable and 30m to connect it I dont see why so many installers dont bother.

Edit: If you have a permanent live to the boiler and it powers the pump then the integral frost protection circuits are enabled.

Tony

 

[Kellymont]

I think you will quickly realise that having a a three port valve which is always open to something makes not the slightest difference to pump over run if the pump is not controlled by the boiler!

Connecting the pump to the boiler and thus enabling pump over run reduces thermal stress/cycling and can only be beneficial to the boiler life. For the sake of a few metres of cable and 30m to connect it I dont see why so many installers dont bother.

Tony

The pump Will be connected to the boiler whatever it takes in cable and time, this i assume will give the pump over run but a three port valve always has a path open for the over run hot water to pump to, zone valves close both the paths on a `S` plan and require a return loop with a bypass valve?

 

[Agile]

Yes, thats correct in theory.

EXCEPT at the house I went to today where the tenant had ALL the TRVs closed.

people who do that during the summer usually find they have STUCK closed when winter starts thus adding to my autumn work overload.

At least tonight at 2030 there was a BG van arriving at a house opposite my customer. I did not say hello to him in case there was a stream of abuse hurled at me.

 

[mysteryman]

There should, of course, be one rad on lockshield valves.

 

[Agile]

I think the tenant is very careful with her money.

That might explain why she did not reply when I texted her about coming last Friday so that I could get on with the OV boiler installation.

It could also explain why she never makes me any coffee ! Totally contrary to well established arab hospitality! She does like it when I speak to her in Arabic but still no coffee!

But she can still manage to fly back to the Middle East for holidays.

 

[Kellymont]

Kellymont,

I'm not familiar with the Viessmann plug in digi programmer, we do not use Viessmann controls with the WB1B.

If you want you can wire your new boiler similar to the old one, using the previous programmer. If not, ring Viessmann technical tomorrow, they are very helpful.

Let us know how you get on, the Compact is a great little boiler.[/quote

yes i like the boiler and i brought it to fit into my existing open vent system.
Should i stay with the `S` plan and make a bypass loop for the pump over run, or make it a `Y`plan with a mid position valve?

 

[mysteryman]

Y Plan.

 

[simond]

I would disagree with the former post.

If you already have an S plan it is usually a simple matter to incorporate a bypass (such as a Honeywell DU144) between the pump and the return.

More importantly, if you have a 26kW boiler a 3 port is a bit restrictive, you would need to bush up to a 28mm version and even then it would be borderline.

From recollection (I'm sure someone can Google it) Honeywell suggest around 86,000BTu is the max they recommend through a 3 port. For this reason we do not specify them for boilers over 18kw.

 

[Kellymont]

I would disagree with the former post.

If you already have an S plan it is usually a simple matter to incorporate a bypass (such as a Honeywell DU144) between the pump and the return.

More importantly, if you have a 26kW boiler a 3 port is a bit restrictive, you would need to bush up to a 28mm version and even then it would be borderline.

From recollection (I'm sure someone can Google it) Honeywell suggest around 86,000BTu is the max they recommend through a 3 port. For this reason we do not specify them for boilers over 18kw.

Hi, sorry for the late reply, i have been away.

I have to confess, when i said the original was an `S` plan it was a kind of hi-bred plan!
The oil boiler that had been running for 20+ years was installed by an old school plumber, HW gravity and the CH pumped. (four pipes to the boiler 2x28mm HW gravity, and 2x 22mm CH pumped) all this worked kind`a ok but some of rads got warm in summer, not ideal, and i know is an old problem with gravity systems.
So, 8 years ago my more modern plummer mate while fitting a new Cylinder said we should fit a 22mm valve on the CH flow circuit to stop gravitation to the rads, and also fitted a 28mm valve on the HW return (system vented on the flow just before cylinder) to try and get the best from an antiquated system with least disturbance.

Now has come the time to fit the new Viessmann compak 26Kw open vent.

I would like to make it into a proper `S` plan as i like the idea of two seperate water flow paths (also taking advice on the more powerful boiler retricted with a `Y` plan) and fit a bypass valve and return loop.

Now the questions,
1)Pump into or away from the boiler?
2) Ok to let the boiler vent backwards through the coil of the cylinder as the flow path will be valved?

Any Suggestions Please

 

[Agile]

Er.... no!

The vent must rise directly from the boiler flow to the header tank.

For the last 30 years it has been normal to put the pump on the flow immediately after the vent, then the motor valves.

 

[Kellymont]

That link is not for a WB1B compact model.

I know, the op hasn't mentioned having the compact model and also

The wiring connection page 14 etc

connection details are on page 13 of the compact model
but seeing how he mentioned the stats listed on 42 where as they're on 41 you could well be right,

you wire them the same way anyway!

Hi all, sorry for the very late reply.
You may remember that i had problems fitting the 2x channel digital timer to my 26kw open vent Viessmann Compak WB1B as i could not find the switched timed outputs!
After contacting Viessmann for a second time and talking to another engineer he told me that the digital 2x channel Viessmann timer does Not in fact fit to the compact open vent and you cannot fit the timer to this model.
I told the engineer that the timer is listed as an accessery by Viessmann and the box is ticked for it to be fitted to the Compak, this is a Viessmann error in their listings and explains my problems fitting the timer.
However, as the timer fitted perfectley into the boilers front panel and plugs into the pc board where it picks up 24vdc i decided to use it by fitting 2x 24vdc relays (one for each channel) into a small ABS box and use the contacts of the relays to switch the 240vac to run the boiler, i know that this may be outside some fitters technical capabillities but if anyone wants to use this timer be aware that it switches the `0` volts lines from the timer Not the +24vdc line, i nearly gave it up until i found how the signals were being switched.
Thanks all, boiler working fine, i may need to do a plumbing modification as i think the hot water is shorting around the bypass loop and telling the boiler to shut down? i have tightend the bypass valve right down (.5 bar) and have balanced the rads to get the best results but they are not as hot as the old oil boiler got them and it was only half the power of the Viessmann.
Could i fit an electriclly operated shutoff valve in place of the bypass? it would need to be normally open and when either motorised valve opens it would close!
Thanks for any replies, and lets have a happy warm New Year
Kind Regards