Excessive OpenTherm heating demand

[JIBYC]

I've recently fitted a Wiser system to my OpenTherm boiler where it has replaced a Weather Compensation on/off system.

I'm finding the Wiser system is demanding a very high initial temperature leaving the boiler unable to operate in condensing more as the return temperature is too high.

Is there a way to set a limit the maximum OpenTherm temperature, and get a slower more efficient heating demand?

[PhilHornby]

Perhaps it is still in a "learning phase" and applying full power, until it learns how quickly each room warms up?

[aslater3]

Yep I have the same issue

coming from Nest im not sure the OpenTherm implementation is any good

also can’t regulate the DHW via OpenTherm like I could with Nest

[JIBYC]

I am confident that the Wiser+OpenTherm system is using more gas than Nest+On/Off which is very disappointing.

As a minimum I would expect the ability to set an upper temperature for Child safety alone.

Ideally the upper temperature should be set based on the outside temperature, emulating the boiler's weather compensation.

[aslater3]

I was actually using OpenTherm with Nest. That has the ability to set the maximum flow temp which to me is critical. 

When I set the max on the boiler it is overridden by the Wiser to 90 degrees via OpenTherm. Previously I would use a max of 50-60 for a longer more efficient burn!

Extremeley frustrating I think I will be asking for a refund 

[DaveP]

That's interesting, as my Baxi 830 combi boiler is Opentherm compatible, and I have recently installed the Drayton Wiser single channel hub, room stat and 6 radiator thermostats, I also ran the Opentherm cable BUT wanted to get the system running well first; it's just as well as we had that really cold spell and I had to up the boiler temperature and the condensate pipe froze..... and I believe with the Opentherm it disables the manual boiler control. Based on what I'm reading here I may give it a miss.
I am assuming it is the hub responsible for calculating the temperature and not the boiler?
That aside, I think it's a great system at a great price, and I got that bundle in the Black Friday sale for £274!
I looked at the Honeywell EvoHome system, but as well as being way more expensive, it's unclear what you get with their deals. What I did pick up ion is that you have to decide whether you want a receiver for the boiler at £85 or the OpenTherm bridge at £115; the Drayton hub includes the OpenTherm. The TRVs are over £100, and I know they have a display, but I don't want a display and I imagine it will use the batteries up quicker?

[andyblac]

Is this still an issue ??, just ordered Drayton Wiser and wonder if I have made a mistake ?

[DaveP]

The only possible issue is how well Opentherm works, so I haven't enabled it. The system as a whole is running brilliantly, can't fault it

[JIBYC]

I had to set an upper temperature limit on the boiler to stop it commanding high temperatures.

[DaveP]

What boiler is it, and how do you do that, as I don't think I can on my Baxi 830 as Opentherm overrides it?
Do you think the Opentherm is better than not using it?

[andyblac]

yeah, I have Baxi 800 series as well, ATM I have Tado˚, In there, they have an Installer web page that allows you to set the MAX Flow Rate. How well does the throttling work, most of the time my boiler in tado˚ sittings around 25-40˚c, it only ever hit the MAX Flow when it really cold outside (-5˚c). But getting sick of tado˚ lack of support.

[aslater3]

The only way I could control this was with the OTGW. I had to inject the max flow temperature that way. Seems crazy they didn’t offer this natively. It must be easy to do!

the throttling I’m not sure is as good as Nest / others 

[robertwigley]

FWIW Drayton have publicly stated that they are working on improving the OpenTherm implementation this year. Without explicitly saying it’s not quite up to scratch, they have sort of acknowledged that it isn’t as good an implementation as they would like it to be.

[PhilHornby]

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@aslater3 wrote:

The only way I could control this was with the OTGW.

OTGW❓ Please put me out of my misery and tell me what that stands for 😀

[andyblac]

OpenTherm GateWay