Honeywell Evohome with Worcester Bosch Greenstar System Boiler

[Mark8par]

I need a little help if possible as I am trying to check that my current system is running efficiently but not really sure how to check, sorry if this is a long one and I have tried to contact a Honeywell connected specialist but they dont seem interested unless installing a new system and the chap who installed ours has gone awol.

We currently have the following system
Worcester Green star 8000 Life System 35kw
Honeywell Evohome with hot water kit
All rads have HR92's installed
Megaflow cylinder
BDR91 x 2 - one controls CH and the other HW
2 x Motorised zone valve

I am seeing that the boiler seem to be firing quite alot and in short bursts, I have been checking my usage since we had a smart meter installed and considering we have alot of the rooms off most of the time the gas usage seems high and anywhere between 110kwh and 150kwh per day, to be honest the higher usage was when it was bloody cold though.

Anyway the system might be ok but I wanted to see if anyone has had any experience with this setup and has any advice.

thanks is advance and as I said I have tried to get professionals in but its just very difficult, hence I have resorted to a forum.

MH

 

[EvilDrPorkChop]

Would suggest checking the Minimum on time on the Evohome. The Worcesters seem to take a while to think about doing anything so by the time the Evohome has demanded and switched off the Worcester might only fire for 10/20secs.

 

[Mark8par]

Would suggest checking the Minimum on time on the Evohome. The Worcesters seem to take a while to think about doing anything so by the time the Evohome has demanded and switched off the Worcester might only fire for 10/20secs.

Thanks for the reply, would you be able to recommend a minimum on time?
Cheers

 

[EvilDrPorkChop]

Thanks for the reply, would you be able to recommend a minimum on time?
Cheers

With the Worcester i'd probably go 3 minutes, and 6 cycles per hour.

 

[EvilDrPorkChop]

Ideally, you'd of been better without the MV on the CH and you could then use the excess heat from the Pump overrun into the rads.

 

[Mark8par]

Ideally, you'd of been better without the MV on the CH and you could then use the excess heat from the Pump overrun into the rads.

Could I not then just leave the CH MV on permanent open?

 

[EvilDrPorkChop]

Could I not then just leave the CH MV on permanent open?

Not without any wiring mods, as it'll spring return on being powered.

Plus when they're manually open they're not open fully.

 

[Mark8par]

Could I not then just leave the CH MV on permanent open?

Cheers, I just wish I knew someone who can sort it out, the plumber I know does not install Evohome and never has. If I was to have the CH MV removed as far as I am aware the evohome will not do the boiler control with the Bosch so I can't use the evohome overrun unless you mean the Bosch will do it on its own.

 

[EvilDrPorkChop]

Cheers, I just wish I knew someone who can sort it out, the plumber I know does not install Evohome and never has. If I was to have the CH MV removed as far as I am aware the evohome will not do the boiler control with the Bosch so I can't use the evohome overrun unless you mean the Bosch will do it on its own.

In doing that you can then use the CH relay as a Boiler Relay instead. This will give you better control, and allow you to use the HW Overrun feature too.

Edit: The boiler will have it's own Pump overrun feature too. When a demand is switched off it'll overrun for so many minutes. You can use the excess heat for the radiators.

 

[Mark8par]

In doing that you can then use the CH relay as a Boiler Relay instead. This will give you better control, and allow you to use the HW Overrun feature too.

Edit: The boiler will have it's own Pump overrun feature too. When a demand is switched off it'll overrun for so many minutes. You can use the excess heat for the radiators.

Is it possible for the CH Relay (BDR91) to control the boiler, would it not require some re wiring? Also when you mention the over run can send excess to the radiators, if none of them are calling for heat would it not just circulate around the heating pipes or just sit in the (not sure what the term is) radiator in the hall that is open all the time.

 

[EvilDrPorkChop]

The boiler will ha

Is it possible for the CH Relay (BDR91) to control the boiler, would it not require some re wiring? Also when you mention the over run can send excess to the radiators, if none of them are calling for heat would it not just circulate around the heating pipes or just sit in the (not sure what the term is) radiator in the hall that is open all the time.

Yes you'd need to alter the wiring - I was just saying you wouldn't need to buy any more equipment.

Ideally the Hall Rad would need a HR92 on, as this would be heated whenever there is a demand. Regardless of that Rad, your system should have a Automatic or Manual Bypass in anyway for the pump overrun on the boiler when the Motorised Valves close.

 

[Mark8par]

The boiler will ha

Yes you'd need to alter the wiring - I was just saying you wouldn't need to buy any more equipment.

Ideally the Hall Rad would need a HR92 on, as this would be heated whenever there is a demand. Regardless of that Rad, your system should have a Automatic or Manual Bypass in anyway for the pump overrun on the boiler when the Motorised Valves close.

Thanks for all you help its really appreciated, especially on a Sunday lol. I have searched online for the wiring diagram for the Worcester Bosch 8000 Life System boiler to do what you suggest, any ideas? I wouldn't do the wiring myself but would be good to have for the electrician.

 

[EvilDrPorkChop]

Thanks for all you help its really appreciated, especially on a Sunday lol. I have searched online for the wiring diagram for the Worcester Bosch 8000 Life System boiler to do what you suggest, any ideas? I wouldn't do the wiring myself but would be good to have for the electrician.

Sorry really you need a Evohome Specialist to sort. It's fairly straight forward to wire but you really need a good idea of how the system works and a understanding of Evohome. Without doing them a discredit, most electricians struggle to wire a basic system from my experience!

 

[Mark8par]

Sorry really you need a Evohome Specialist to sort. It's fairly straight forward to wire but you really need a good idea of how the system works and a understanding of Evohome. Without doing them a discredit, most electricians struggle to wire a basic system from my experience!

Part of the problem is getting a Evohome Specialist to look at an existing system, they just aren't interested near me. Thanks for your help though, it's given me something to work with.

 

[John.g]

In doing that you can then use the CH relay as a Boiler Relay instead. This will give you better control, and allow you to use the HW Overrun feature too.

Edit: The boiler will have it's own Pump overrun feature too. When a demand is switched off it'll overrun for so many minutes. You can use the excess heat for the radiators.

Most oil fired boilers do not have pump overrun, should overrun be installed on boilers that dont have it if installing evohome?
I have a simple digital stat (no TPI) with the differential set to its minimum of 0.3C and it gives what I consider excellent control with only ~ 0.2C overshoot after initial heat up, my boiler has no overrun but I suppose Evohome will adapt if a oil fired boiler has overrun or not.