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Discuss ESRTP4RF+ Opentherm in the Central Heating Forum area at PlumbersForums.net

mrrodge

Messages
10
Hi, new here.

I just had an Ideal Vogue Max 40 fitted and it has an ESI ESRTP4RF+ connected to it. I purposely asked for a cheap and cheerful control device so I could do my own research and choose a better control method in the near future. Plumbers were superb, clean, tidy and the job is great.

I didn't do enough research before getting the boiler so suspect I've pushed my installer into selling me a bigger boiler than I need - Going from a traditional boiler and cylinder to a combi I was worried about hot water flow rate but didn't think about the boiler being unable to modulate to lower temperatures. Here's hoping I'll still be able to get the most out of the new kit.

On reading the manuals I got with the boiler and controls I've noticed the ESRTP4RF+ supports Opentherm 'low load control'. My installer didn't really know about it and said he'd wired it for simple on/off control but was willing to connect the Opentherm if I wanted him to. I've since done a load of Googling and made some observations. My thinking is:

  • The boiler was left by my installer with a flow temperature set at 65C and the return hasn't been in the desired <55C range yet, it's just maintained 65C. Efficiency on it reports 0%, guessing because it hasn't been left on long enough to work it out but when it does, it won't be anywhere near as good as it can be.
  • I've turned off hot water preheat - can live without it.
  • If I connect my programmer via Opentherm, does the boiler's outside temperature feature become redundant? (It doesn't have a sensor connected now, I'm just wondering if my programmer can use this).
  • The ESRTP4RF+ manual says the Opentherm parameters need flow and return temperatures setting. Isn't that what the opentherm stat is supposed to work out itself? If so, what's the point in the settings?
I wasn't expecting my cheap programmer to feature anything that sophisticated and I had it in my head I'd end up buying a Hive, Tado, Nest etc - I'm not interested in any of the cloud features of the expensive ones though, I just want the boiler to run as efficiently as possible. Without outdoor temperature compensation, am I missing much if I just have my ESRTP4RF+ connected via Opentherm?

After having read the thread here I picked up on:

The slave (boiler) does not need to know how the master (thermostat) has calculated the control setpoint (flow temperature), e.g.whether it used room control or OTC, it only needs to control to the value. Likewise, the master does not need to know how the slave is controlling the supply.

So does that mean that my boiler is already modulating, keeping the flow at 65C without cycling? Then the Opentherm controller will change the flow temperature to suit heat demand and a more efficient return temperature? What will it do with the flow and return parameters that the installer sets on it? Is the flow temp the max the boiler can do, i.e. 80C, and the return temp the lowest, i.e. 30C, or should the return temp be something higher to prevent cycling?

Thanks and sorry for the lengthy post!
 

scott_d

Plumber
Gas Engineer
Messages
5,801
The ideal vogue can be wired for opentherm but I think the results seem to be mixed, some say it works well, other says the boiler cycles lots.
They have good modulation but you cannot set the heating output.

Would it be easy to wire an outdoor sensor for weather comp at your property?
 

mrrodge

Messages
10
The ideal vogue can be wired for opentherm but I think the results seem to be mixed, some say it works well, other says the boiler cycles lots.
They have good modulation but you cannot set the heating output.

Would it be easy to wire an outdoor sensor for weather comp at your property?

How do you mean you cannot set the heating output? Wouldn't that mean that opentherm is pointless? I thought the whole point was to reduce flow temperature so the return is always within condensing range?

Wouldn't be easy but prepared to do it if it's the only option. Boiler is in the middle of the house and even the vertical flue was a nightmare for the plumber, it had two elbows and went through two separate sections of roof.
 

scott_d

Plumber
Gas Engineer
Messages
5,801
How do you mean you cannot set the heating output? Wouldn't that mean that opentherm is pointless? I thought the whole point was to reduce flow temperature so the return is always within condensing range?

Wouldn't be easy but prepared to do it if it's the only option. Boiler is in the middle of the house and even the vertical flue was a nightmare for the plumber, it had two elbows and went through two separate sections of roof.
Some boilers allow you to set the heating output - eg10kw
On the Vogue it will go to maximum heating output then modulate down as the return temp increases. The boiler is just told on/off and doesnt know how much heat is needed so if the house is at 19 degrees and the room stat is calling for 20, it will fire at maximum then modulate down. In this instance it would only need minimum output and opentherm allows the boiler and thermostat to communicate with each other and work together.
 

mrrodge

Messages
10
Some boilers allow you to set the heating output - eg10kw
On the Vogue it will go to maximum heating output then modulate down as the return temp increases. The boiler is just told on/off and doesnt know how much heat is needed so if the house is at 19 degrees and the room stat is calling for 20, it will fire at maximum then modulate down. In this instance it would only need minimum output and opentherm allows the boiler and thermostat to communicate with each other and work together.
But isn't the dial on the boiler setting the output? I was under the impression that opentherm was able to adjust this on the boiler... Is that not the case with mine?
 

scott_d

Plumber
Gas Engineer
Messages
5,801
But isn't the dial on the boiler setting the output? I was under the impression that opentherm was able to adjust this on the boiler... Is that not the case with mine?
The dial sets the heating temperature.
I believe opentherm overrides this and reduces the temp depending on the demand.

You will probably get the best from the boiler by fitting ideals on controls
 

mrrodge

Messages
10
The dial sets the heating temperature.
I believe opentherm overrides this and reduces the temp depending on the demand.

You will probably get the best from the boiler by fitting ideals on controls

OK thanks, will take a look at those. Do you happen to know if they'll work with an external temp sensor connected to the boiler, or if they use an internet connection?
 

mrrodge

Messages
10
OK so had a look and no real detail - I'm not interested in the wifi version and the RF version uses Zigbee, which I already use for a home automation system so want to steer clear. I can see from the install manuals they install directly into the front of the boiler so don't use the OT terminals, so I'm guessing it's controlled using Ideal's proprietary protocol hence it'll have full control BUT nothing says anywhere if the outdoor temp sensor is ignored/still needed/used.

Then there's the Halo Lite - that one looks like it doesn't do anything different to the stat I have now, only it's wired as opposed to wireless. How do I find out if it speaks to the boiler any better than the Halo RF/Wifi, or if it uses the boiler outdoor temp sensor? If it can/does I'd be tempted by this as I can use wiring that's already in the walls. It does look like it can do the plain english fault codes so maybe it's better than generic Opentherm.
 
Last edited:

The Donut

Messages
5
Hi all , before I start I'm no plumber or expert and found this thread on my google travels looking for more opentherm knowledge and info on flow/return temps.
Just to get one thing out of the way , Hive isn't opentherm compatible , as I understand it , just a posh on/off switch. 🙂

To the matter in hand .
I have just had an Ideal Logic C24 + combi installed and pretty much all rads replaced too. About 2 weeks ago I learnt that my new Nest gizmo did this opentherm thing and so does the Logic boiler. Got my m8 to switch the wiring and away it went once OT was set on the Nest.

Firstly I have to say , what a difference in terms of the overall feel in the house , amazing imho. No more get to 19° , over run , cool down , turn on again on off on off on off.
Indeed the dial does get over ridden. I have it set at E (68°) but with the 'True radiant' enabled on Nest , the boiler just ticks over , occasionally lighting gas to sustain the desired room temp.
After the initial burst in the morning , the flow temp seems to settle around 43°- 45° and return temp then seems to be 4° - 5° below that. So AIUI that should mean the return is condensing a good part of the time🤷
I spoke to an Ideal tech guy the other day trying to find out about the 'Super efficiency level' on the display. As it happens this is not to do with the efficiency rating that the boilers are sold on , which I think is it's overall efficiency. If i understood correctly it's more about the condensing bit , loop scavenging?
When i told him i had 65% he said thats the highest he'd heard of. Now got it at 73% tho so happy with that , but hoping the Nests algorithms can get that higher.
My next task is to get a couple of temp sensors and see if i can tweak the lockshields to get a bit more of a drop across the rads. 10° - 15° seems to be the target but tbh I'm happy with way its working at mo so 🤷.
As regards a Weather compensator or OT , i think u can either on the Logic but not both , STBC on that tho. However the Nest pulls outside temp from local station/ Met office anyway and combines that with room temp / desired temp and it's algos to modulate the boiler , works for me 🙂👍
Anyway , not sure it's saving money , pretty sure it's costing no more though and the effect is great imho. Added a couple of pics for interest 1st is 23rd Nov prior to OT 2nd is 28th Nov after OT enabled. I've left off costs as weather was slighlty different. But you get the idea pictorially how OT tickles along.

Edit: Ignore green line , thats leccy 😁👍

Cheers

Donut 🙂👍
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Last edited:

The Donut

Messages
5
Just an update on using Opentherm.

(This is non scientific and doesn't account for outside temps)
Just had bill for Nov , and as bulbs app seems to apply prices historically , it would seem the cost of using Opentherm is almost certainly no more than using an on/off stat, when comparing to last year.

I will definitely stick with OT as the difference in overall feel is worth it imho.
With regards to Ideals 'Super efficiency level' , it's now up at 82% but that seems to be levelling out there , until I maybe have tweek with the lockshields.

For now though , it's definitely OT all the way for me. Just for interest I live in a small old stone house , and with Nest/OT am currently more than warm enough with a constant 18⁰C

Cheers

Donut 🙂👍
 

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