honeywell sundial rf2 pk2

[treecott]

Hi. I enquired in November as to whether i could use a honeywell sundial rf2 pk2 with a Vailant Ecotec 624 system boiler and unvented cylinder. Thank you for your replies. I have now had this installed, but am having a problem with my hot water, and wonder if anyone could give any help or advice please.

When the Honeywell programmer is active, and the hot water is "on", there is no flame on the hotwater side to say its working, but when the heating is "on",there is a flame on the heating side showing it is working. My question is on the ST9420c should it show a flame on both the heating and the hot water sides showing they are on?, when I have a system boiler and unvented cylinder or not.

I had a problem when I tried to instal this programmer myself before christmas, as the diagram that came with it was different to how the boiler and unvented cylinder was wired up. I had taken off the ST699 programmer I had previously been using, and my heating engineer came and got me up and away over christmas temporarily until he could arrange for an electriian to come and wire it up on his behalf. He has rewired all the boiler, unvented cylinder, and programmer following the Y plan diagram in the Vailant manual, but I am not sure whether it has been wired up correctly.

Dont get me wrong, it is working ok and we have hot water, and heating, but the hot water is not getting as hot as it should, nor is it showing a flame sign to show it is heating the hot water. I have tried to get my installer back, but he is so busy, with the bad weather, that it could be a while, and I thought I would ask this question on here in the hope someone could either help, or reassure me it is correct - whichever way.

Any help would be much appreciated.

 

[D_Hailsham]

When the Honeywell programmer is active, and the hot water is "on", there is no flame on the hotwater side to say its working, but when the heating is "on",there is a flame on the heating side showing it is working. My question is on the ST9420c should it show a flame on both the heating and the hot water sides showing they are on?, when I have a system boiler and unvented cylinder or not.

Are you getting muddled? There is a flame on the heating thermostat, but the programmer only has two lights (between the "extra hour" and "override" buttons) to show that CH or HW is in an ON period.

 

[simond]

An unvented cylinder should not be wrired as a Y plan.

 

[D_Hailsham]

An unvented cylinder should not be wired as a Y plan.

Surely it's OK if you have a zone valve in the HW line to act as a safety device? Albion have a wiring diagram for Y plan showing this.

Or are you talking specifically about Vaillant boilers and cylinders?

 

[treecott]

Hi, and thank you for your quick replies.

in reply to D Hailsham, thank you, dont think I am getting muddled. I know there is a flame on the thermostat, but it is the programmer I am having trouble understanding. On the programmer, there are two green lights, one for hot water, and one for heating, in between the extra hour and the override buttons I agree, however, on the actual blue display screen, above the words "auto" "once" "cont" "off", when the heating is on it shows a "radiator" symbol, and there is also a flame symbol showing inbetween the "radiator" symbol and the words.
I am not sure whether the same should apply to the hot water side.

When the dhw is on, above the words "auto" etc, there is a tap symbol, but no flame symbol, the flame symbol is on the heating side of the display. This is what is confusing me.

I am not sure whether this is because off the way it has been wired up, i.e. yplan, or if it has not been wired in correctly. When I have both heating and hot water on, the water does not get as hot as it does when it is on as dhw only. Incidentally, there are two motorised valves attached to the system, one on the hot water supply, so I think that one of them is the safety device you mention in connection with the unvented cylinder.

I know this is difficult to explain, hence the above ramblings, but it is the only way, as a woman I can explain it. I hope you can understand what I am trying to get at. Thanks.

 

[warmadmax]

two motorised valves suggests S plan,
Y plan uses a mid position valve.

Safety device on the HW cylinder should be a T&PRV, you'll figure out which one this is by looking near the top of the cylinder for knob + pipe that should run outside.

When your asking the boiler to heat the central heating and hot water, it won't get as hot initially as it should due to the fact it's having to split its workload between the heating and hot water.

as the radiators constantly dump heat, the extra you'd normally have for hot water isn't there, just a fact of life.

What should happen is as soon as the room stat is satified, the zone valve for the radiators should shut, putting all the flow through to the hot water.
This will happen till the room stat calls for more heat or your HW tank stat is satisfied and turn the pump and boiler off.

 

[D_Hailsham]

Your equipment must be very new as the programmer flame is not shown in the online literature for your model, but it is for other models.

The flame is a "status indicator" and should be shown when the boiler is on, for both heating and hot water. There are not separate flames for CH and HW.

 

[treecott]

Hi everyone, and thank you yet again for your help.

Firstly, it is new, I only purchased it within the last 2 weeks, so perhaps that is why I cannot find any info about the "flame symbol" on the net. Thank you for clarifying the "flame symbol" for me D. Hailsham.

To warmadmax, thank you for your help as well. I had to wait till my husband came home to ask about the T/prv. as I did not know what that was. I have been advised that it is a tundish, and a pressure relief valve, which apparently is on the cylinder. I presume he is right !!!!. My husband has also had a look at the two motorised valves, and one is a Honeywell motorised valve, and the other one is a Orkil microswitch - I hope that means something to you! as it means nothing to us!!!!!!. I understand about the hot water not getting so hot when the heating is on, and perhaps I am expecting too much, sorry. The system does work well, but when the new programmer and thermostat was installed, that is what has made me a bit unsure, especially with the "flame symbol" on the programmer, but it seems D. Hailsham has answered that one for me.

I think you all have answered my question, and I am very grateful to you both, and to this site, which has been so very useful to us. Thanks very much.