posted on another thread when I should really have started a new one so here goes.
An ECO4 installer has fitted Honeywell (OpenTherm) controls to a Valliant Open Vent Boiler with remote Cylinder. Based on room size and radiator size calculators I believe the radiatiors have been specced to Delta 40 which gives a total CH heat demand of 12K. My finger in the air calculation for DHW demand - 67c into the cylinder to give 60c water is say 4k. The boiler fitted as a nominal rating of 18K. So it appears to me to be seriously over rated and needs to modulate down.
At present it gradually heats to just above the CH flow temperature then cycles between on and anti-recycle every 5 minutes or so
At present the CH flow temperature controls the HW cylinder reheat and if I put the boiler in summer mode (CH flow = 0c) the HW doesnt work. This installers recognise this as an issue and say there is a wiring error. I am not convinced.
My understanding, that the boiler will not modulate, load or weather balance with Honeywell Controls unless the non UK approved part VR33 is fitted. Secondly that the lack of seperate control over the HW temperature is also due to the incompatible OpenTherm controls - is this correct?
On the basis that my understanding is correct I am trying to get them to swap out the honeywell controls for Valliant eBUS and have come up with the following proposals
- Vaillant VRT350 wall mounted in the hall or VRT350F
- VR 66/2
replace the VRT350 with VRC700 to get weather compensation
Is there anything else that would be needed?
Boiler HW termperature display
The boiler appears to display CH flow temperature and HW actual temperature. I can understand, thanks to help on a thread i hijacked, that a smart boiler stat could send actual temperature settings back to the boiler and the boiler could adjust accordingly. BUT the cylinder stat is a Honeywell L641A looks to be a simple on/off stat which wouldnt send actual temperature readings back to the controller/boiler.
The manual appears to show, within the installer set up menus, flow temperature controls for HW 50-80c & CH45-80c.
I am guessing that there is a way to within the installer menu to set the HW flow temperature - I am told 67c is a good target?
ok so far so good ? but once the boiler is working as per the manual and there are seperate flow temperatures operating for the CH and HW does the CH temperature display/control on the front panel show/do with an on/off stat ?
many thanks in advance for any help support or input
An ECO4 installer has fitted Honeywell (OpenTherm) controls to a Valliant Open Vent Boiler with remote Cylinder. Based on room size and radiator size calculators I believe the radiatiors have been specced to Delta 40 which gives a total CH heat demand of 12K. My finger in the air calculation for DHW demand - 67c into the cylinder to give 60c water is say 4k. The boiler fitted as a nominal rating of 18K. So it appears to me to be seriously over rated and needs to modulate down.
At present it gradually heats to just above the CH flow temperature then cycles between on and anti-recycle every 5 minutes or so
At present the CH flow temperature controls the HW cylinder reheat and if I put the boiler in summer mode (CH flow = 0c) the HW doesnt work. This installers recognise this as an issue and say there is a wiring error. I am not convinced.
My understanding, that the boiler will not modulate, load or weather balance with Honeywell Controls unless the non UK approved part VR33 is fitted. Secondly that the lack of seperate control over the HW temperature is also due to the incompatible OpenTherm controls - is this correct?
On the basis that my understanding is correct I am trying to get them to swap out the honeywell controls for Valliant eBUS and have come up with the following proposals
- Vaillant VRT350 wall mounted in the hall or VRT350F
- VR 66/2
replace the VRT350 with VRC700 to get weather compensation
Is there anything else that would be needed?
Boiler HW termperature display
The boiler appears to display CH flow temperature and HW actual temperature. I can understand, thanks to help on a thread i hijacked, that a smart boiler stat could send actual temperature settings back to the boiler and the boiler could adjust accordingly. BUT the cylinder stat is a Honeywell L641A looks to be a simple on/off stat which wouldnt send actual temperature readings back to the controller/boiler.
The manual appears to show, within the installer set up menus, flow temperature controls for HW 50-80c & CH45-80c.
I am guessing that there is a way to within the installer menu to set the HW flow temperature - I am told 67c is a good target?
ok so far so good ? but once the boiler is working as per the manual and there are seperate flow temperatures operating for the CH and HW does the CH temperature display/control on the front panel show/do with an on/off stat ?
many thanks in advance for any help support or input
