Pump switches off during heating

[Norfolkboy]

Hi, i have posted this question in a different thread i had started, but have a few more details about the ongoing issue.

Whenever there is a change in demand from a zone(s) and therefor the Opentherm bridge is requesting a different flow temp to the boiler, the boiler will shut down and switch off the pump for 40 seconds. after this it starts up fine and will carry on untill the next event.

its almost as if the Viesmann boiler doesnt what to do when i new flow temp is requested and therefore stuts down and starts again.

Thanks

[paulockenden]

Really? That sounds a bit rubbish!

[Norfolkboy]

Yep, I know its a bit infuriating! Doesn’t make the system very smooth

[paulockenden]

Have you spoken to Viesmann about it?

P.

[HenGus]

Oh no. I have got an installer coming to see me later today to give me a quote for a 100 boiler with an Opentherm connection to Evohome. He wasn't at all convinced about Opentherm when I talked to him about it on the phone, so it will be interesting to hear what he has to say.

[HenGus]

Have you spoken to Viesmann about it?

P.

If my experience is anything to go by it is as follows:

1. It takes tech support time to find the guy who can spell Opentherm.

2. The standard response is 'that a man from Honeywell has visited and tested the Evohome/Opentherm connection' - and 'PS - it doesn't work with the 200 series'

I got a similar response from Intergas who made no mention of the fact, until I pressed them, that their boilers appear not to play nicely with Evohome's multi-zones.

I think that they see compatibility with their boilers as sitting firmly within the control manufacturers' baliwick.

[paulockenden]

Perhaps we need a new thread where people who have Evohome/Opentherm working PROPERLY with their boiler can post the exact model details.

It seems to me like too many combinations are compromised.

P.

[HenGus]

Perhaps we need a new thread where people who have Evohome/Opentherm working PROPERLY with their boiler can post the exact model details.

It seems to me like too many combinations are compromised.

P.

Agreed - along with system configuration. The one quote that I have had for an ATag boiler proposed a modification to my 'S' plan configuration which removed the heating zone valve and replaced it with a motorised on/Off valve. When HW was required the motorised HW valve would open and the 2-port valve on the CH system would close giving HW priority. It would also trigger to the boiler to provide max output.

We have also got reports of the Viessmann 100 working on Opentherm with and without the HW junction box. No wonder my old mind is becoming increasingly confused.

[paulockenden]

or maybe a google spreadsheet that anyone can edit?

P.

[Norfolkboy]

Viessmans response was Opentherm is like putting a BWM gearbox in a Mercedes! Very helpfull. its a niggle which i can live with, but agree with Hengus that no one supports Opentherm fully and both sides blaming the other party

[paulockenden]

Viessmans response was Opentherm is like putting a BWM gearbox in a Mercedes!

What a stupid analogy. Opentherm is (supposed to be) manufacturer independent.

So it's like putting a Bosch 12V battery in your Mercedes. You'd expect it to just work.

P.

[DBMandrake]

What a stupid analogy. Opentherm is (supposed to be) manufacturer independent.

So it's like putting a Bosch 12V battery in your Mercedes. You'd expect it to just work.

P.

What I also find ironic, is that at least one of the boiler manufacturers seems to blame Honeywell for any compatibility issues - completely overlooking the fact that OpenTherm is a protocol that Honeywell developed ?! So if anyone was going to get OpenTherm right, I would have thought it would be Honeywell's flagship product, and that it was the boiler that had less than ideal adherence to the protocol....