Modulation control in system boiler

Manninm

Hi all,

I am new to the Tado community, and just purchased a V3+ wireless smart thermostat starter kit as I have a dual hive setup (HW and CH) and am interested in having more control of the system, and hopefully lower energy bills as a result.

I have a Worcester bosch greenstar 4000 18kw system boiler with unvented hotwater cylinder.

Having done some reading, I was disappointed to find out the V3+ wireless starter kit doesn't have the ability to modulate the output of the boiler, something I am very keen to implement, and something the hive cannot do.

My question is, if I replace the included wireless receiver with the "old" receiver, part number EK01-TC-UK-03, will this allow me to control both the HW and CH, and be able to implement modulation control via either opentherm or EMS to the boiler?

Many thanks in advance for your assistance!

Regards,
Mark

johnnyp78

Generally speaking, if you have a system boiler you won’t be able to use modulation with it due to the need to provide hot water at 60c. If you’re willing to replumb to a priority domestic hot water system you might be able to get around this.

https://theintergasshop.co.uk/content/189-why-hot-water-priority-is-the-reason-s-and-y-plan-should-be-banned

Montage

Yes on the sensor location. I’d expect you’ll need to configure it on for the boiler to use it. You’ll gain control over the WC curve, for example.

I think I’d suggest having a chat with WB. If you can signal the boiler for DHW then you are sorted. Some boilers allow this, some not. It offers the potential for PDHW too, as Johnny suggests.

Regarding water storage/temp that’s a topic on its own. It’s common to store below 60 these days and do a weekly cycle to blast it higher. System/house/occupancy would all be factors.

I wouldn’t rule out a change of controller here. Tado might not suit best and the Bosch options are pretty compelling now.

Montage

How is your HW cylinder plumbed in? In other words, does your boiler have the optional integrated diverted valve?

Manninm

Thanks for your response, @Montage! The boiler doesn't have the optional WB integral diverter valve kit fitted as far as I can tell. I believe the system is a standard S plan and I can see two motorised valves present, presumably 1x for the CH and 1x for the HW.
I did take photos of my setup so i could upload here, but can't see an option to post them? I also note when I open the settings on the boiler, HW is set to "off" but I don't know of this is significant or not?

Thanks again for your help, I really do appreciate it!

Manninm

Ahh, thanks @johnnyp78! Appreciate the help!

Replumbing is probably not an option at this stage, so I may have to consider my options!

I was also considering the WB external sensor for weather compensation control as a plan b to try and bump up our savings, so can I assume that this option might also be off the cards given I don't have a priority DHW system?

If I am therefore limited to a timed, on/off approach (like I have with the Hive), is there still benefit/savings to be made switching to the Tado ecosystem (i have the SRT's as well) or will my gains be potentially less given the system I have?

Appreciate everyone's mileage will vary, so just trying to undetstand better the potential limitations upfront....

Thanks again!
Mark

Montage

As you can see ^ it’s a Tado limitation that they’ll only do modulation and won’t do relay switching at same time. I was hoping you’d have the diverter, which could potentially mean the boiler could control the HW.

PDHW is a good suggestion. I’d also look at weather compensation on that boiler. You’d get efficiency gains and wouldn’t miss the ebus, IMO.

Manninm

Thanks @Montage A few queries about WC on the Greenstar 4000 if that's OK please.

I believe sensor to be fitted in North facing side of house, and just a 2 wire cable back to boiler?

When wired in, is there additional configuration to made in the boiler, or will the boiler automatically switch to WC mode?

Can I assume with WC enabled, the boiler won't modulate the flow below a safe hot water cylinder temperature of circa 60-65, or is that set in config?

Thanks again!
Mark

gingertw

Hey Montage,

We're about to plumb in a Greenstar 4000 system boiler, with tank and immersion and want to use Tado. So I could specify the diverter you speak of. Can you give me a description of why I want modulation, and how that system would work and what the advantage is if possible? And why we need this diverter?

System in our property will be

A Wired Smart Thermostat for whole house, with wireless receiver and smart radiator valves.

A Wired Smart Thermostat for the underfloor

So kit is basically.
1. 1x Starter Kit - Wired Smart Thermostat (includes Smart Thermostat and Internet Bridge)
2. Wired Smart Thermostat. 3. 1x Add-on - Wireless Receiver 4. Add-on - Smart Radiator Thermostats for each room.

So i think and im no expert, we'd have 3 valves, one for CH, One for HW and one for the Underfloor downstairs in the kitchen. Currently Ive ran 2 x 5 core cables between the boiler location and the underfloor location probably overkill' but not exactly sure what we need.

Thanks

johnnyp78

If you’re set on using Tado you’ll save yourself a lot of bother if you just wire a multi zone system in on relay.

gingertw

Hey Jonny. Im not set on it, would you suggest doing something else? Not missing much by not having the modulation?

So a multi zone is just standard S-Plan. With a wired thermostat for whole house, with a wireless to control the smart radiator stats?

Then another wired thermostat for the underfloor?

johnnyp78

One wireless receiver for hw and one heating zone, one wired thermostat for the other uf heating zone in theory, though it depends on your wiring. In an ideal world true modulation would be better but tado simulates it with switched relay connections anyway, plus I don’t really think it’s an issue with ufh.

gingertw

Thanks for your time and help on this Jonny.

At the minute there is nothing in place so we can do anything we want, wiring wise, plumbing etc.

I was told by Tado on the chat today I'd need....

2 x wired thermostats
1 x Internet bridge
1 x wireless receiver
8 x trvs

But what you're saying is I get the Wireless Thermostat starter kit, then an additional wired thermostat, and a load of trvs.

I wonder why they thought I need another wired stat?

We currently have a combi boiler, and 1 heating circuit, with a thermostat at top of stairs which controls the whole house.

We're installing a Worcester Greenstar 4000 system boiler, with HW tank. Whole house will will be on 1 zone valve with TRVs. We'll have another zone valve for HW, and then another zone valve for UHF.

I just want the tado to control the lot. We were told by Tado we have to use the Relay system and it was unknown as to whether Tado could control Hot water.

Thanks
Keir