Hot water priority !!

[nphil]

Hi My first post on this great site. My system is a

Vaillant ectoc plus 28
unistor
VR 65
VRT 360 f
Honeywell V4073A Mid Valve.
Main problem is when I have hot water and heating on system will only heat the HW, once HW is up to temp, CH will then heat up. The VR 65 is wired up as per manual. Boiler set up D 70 is set to 1, mid valve position. I contacted installer several times, tells me it is working fine. Same guy who told me the s53 code was my pipe work, But after checking this site found it was a setup problem. Any help or in fo the hot water problem would be great. Thanks

 

[Servotech]

Hi My first post on this great site. My system is a

Vaillant ectoc plus 28
unistor
VR 65
VRT 360 f
Honeywell V4073A Mid Valve.
Main problem is when I have hot water and heating on system will only heat the HW, once HW is up to temp, CH will then heat up. The VR 65 is wired up as per manual. Boiler set up D 70 is set to 1, mid valve position. I contacted installer several times, tells me it is working fine. Same guy who told me the s53 code was my pipe work, But after checking this site found it was a setup problem. Any help or in fo the hot water problem would be great. Thanks

It is the normal for hot water to be prioritised on central heating systems/boilers so your installer is correct this time.

 

[nphil]

The default setup is HW priority, but setup on the ectec boiler has been changed from "0" to "1" to enable parallel operation. Appears not to work.

 

[gaswizzard]

What boiler have you actually got? , the 28 is an ecotec pro 28 (combi boiler)

 

[nphil]

Sorry it is a Vaillant ecotec plus 428.

 

[gaswizzard]

Oh dear!

D70 doesn't apply to the 400 series boiler , what size pump has been installed? , these boilers require 2.4 metre head across the hex plus head loss through system pipework , a 15/50 won't cut it.

Too many threads regards the S53 , if the boiler has been installed correctly along with the correct size pump then S53 is rarely an issue , installed many of these 400s with NO issues whatsover , 99% of the time it is ue to UNDERSIZED circulators.

 

[dcawkwell]

I haven't checked the details but I assume you have a system boiler
and hot cylinder.

The installer hasn't put a valve in the line with the flow to the cylinder
so that the central heating and hot water can be balanced up.

As you have at the moment when both are calling for heat the pump
is just finding it so much easier to pump the water through the cylinder
coil hence the central heating doesn't get any until the valve switches
over to central heating only. This is quite common on 10mm pipe central
heating systems were there is quite a resistance in the central heating piping.

Having said that the cylinder should heat up from stone cold in approx 30minutes so simply set the boiler to heat hot water half an hour before you want the heating in the morning.

Incidently there SHOULD be 2 port valve before the flow to the cylinder
if there isn't the installation isn't correct. You cannot install an unvented cylinder with just a 3 port valve. There has to be the 2 port valve there to cut the source of heat off to the cylinder in case of a fault.

 

[nphil]

Thanks for the help, pump is a Grundfos 15/60, set at speed 3. Piped with 22mm then 15mm. There is no 2 way valve HW system. From pump to a 3 way valve, splits to CH and HW. I wasn't sure what was mean't by there was no d 70 in the 400 series as when I scroll through boiler menu there is a d70, default to "0", set now to "1" The unstor is unvent HW cylinder.

 

[gaswizzard]

Always thought D70 was for the 800 series? , possibly not.

 

[yodaveg]

[uncidently there SHOULD be 2 port valve before the flow to the cylinder
if there isn't the installation isn't correct. You cannot install an unvented cylinder with just a 3 port valve. There has to be the 2 port valve there to cut the source of heat off to the cylinder in case of a fault]

Very good point. All Pressurise cylinders come with a 2port valve for this reason. So you should ask which job he ended up fitting it on and if they would mind if you could have it back![/quote]

 

[matt1e]

The VR 65 is wired up as per manual. Boiler set up D 70 is set to 1, mid valve position.

The default setup is HW priority, but setup on the ectec boiler has been changed from "0" to "1" to enable parallel operation. Appears not to work.

If the valve is at the mid position then control wise it's working, you most likely have a balancing problem as dcawkell has pointed out

The installer hasn't put a valve in the line with the flow to the cylinder
so that the central heating and hot water can be balanced up.

Incidently there SHOULD be 2 port valve before the flow to the cylinder
if there isn't the installation isn't correct. You cannot install an unvented cylinder with just a 3 port valve. There has to be the 2 port valve there to cut the source of heat off to the cylinder in case of a fault.

agreed

 

[nphil]

The valve is not in mid position when both HW and CH is asked for.

 

[nphil]

Hi folks thanks for update. I don't put up much hope of installer coming back. I take it when you talk of balancing the HW,flow it would be by putting a gate valve in the flow to coil and reducing the flow. IF there should be 2 way valve in HW circuit, I take it the 3 way valve would be removed another 2 way valve is put CH flows.

 

[The831Bunny]

AFAIK mid position (D.70 = 1) is not possible when using the NTC sensor. Mid position is only possible if using a standard cylinder thermostat wired to the 'cyl' terminals.

Obviously the best operation for efficient hot water and heating (if the boiler is set correctly to the system) is for (D.70 =0) Hot water priority. Your cylinder should reheat in around 30minutes, so theres little impact on heating of the house in that time.

In fact if mid position is enabled and the cylinder temp is 10C below target, and the heating comes on from cold at the same time dhw is being heated, heat can be taken out of the cylinder for 15minutes or so due to cool water circulating through the cylinder coil.

BTW Three port valves are approved to use with a VR65, an ecoTEC boiler and a UniSTOR UV cylinder.

 

[Dan Robinson]

[uncidently there SHOULD be 2 port valve before the flow to the cylinder
if there isn't the installation isn't correct. You cannot install an unvented cylinder with just a 3 port valve. There has to be the 2 port valve there to cut the source of heat off to the cylinder in case of a fault]

Very good point. All Pressurise cylinders come with a 2port valve for this reason. So you should ask which job he ended up fitting it on and if they would mind if you could have it back!

Not true.