Adding UFH to a Worcester "Intelligent" solar syst

[scorky]

Hi, thought this would be simple but having real problems searching for the right solution so any help would be most appreciated.

In short i have upgraded my boiler as part of a house renovation/extension project adding solar panels and an unvented 300ltr twin coil tank. The system comprising worcester 30cdi system boiler fitted with optional diverter valve, worcester greenskies FKT solar panels & associated pump station, Inteligent ism1 module all essentially as per this link http://www.worcester-bosch.co.uk/cache/file/4/ism1-heating-system-diagram.pdf

All i want to do is add an UFH circuit (still to be bought) for the new extension and add this with the current radiator heating circuit of the original house. sounds simple but can anyone out there give me advice/direction please.

 

[Agile]

The UFH needs to be properly designed of course.

A common mistake is to not realise it has to be a seperate zone with different timing as the UHF takes 1-2 hours to get the rooms warm.

Its completely different to the thermal time constants of radiator heating.
Most ideally it needs intelligent controls including taking account of the external temperature when the start time is computed.

Tony

 

[Onetap]

Hi, thought this would be simple but having real problems searching for the right solution so any help would be most appreciated.

In short i have upgraded my boiler as part of a house renovation/extension project adding solar panels and an unvented 300ltr twin coil tank. The system comprising worcester 30cdi system boiler fitted with optional diverter valve, worcester greenskies FKT solar panels & associated pump station, Inteligent ism1 module all essentially as per this link http://www.worcester-bosch.co.uk/cache/file/4/ism1-heating-system-diagram.pdf

All i want to do is add an UFH circuit (still to be bought) for the new extension and add this with the current radiator heating circuit of the original house. sounds simple but can anyone out there give me advice/direction please.

Go and ask Worcester-Bosch, it is a standard request and they have, almost certainly, control devices to cater for it; all you need is their directions to the relevant section of their controls catalogue. The schematic appears (I'm not going to spend a lot of time reading the details) to show a weather compensation system for the heating, with the flow temperature controlled by modulating the boiler burner. On a demand from the cylinder, the heating will stop and the boiler will run at a higher temperature until the cylinder temperature set-point is reached. All standard stuff.

What you need is another heating zone which is supplied with a different (lower, usually) flow temperature through a mixing valve set. How you achieve that has to be dictated by the available Worcester-Bosch control package, otherwise you'll have a problem getting a separate control system to work with the W-B controllers that you've got.


PS They show an arrangement for 2 zones with the FW 100 weather compensator. You'd use one of the two zones for UFH, via a low loss header or a thermal store cylinder (to minimize the boiler cycling).

http://www.worcester-bosch.co.uk/ca...ng-fw100-weather-compensation-controller..pdf

The UFH would have it's own secondary pump and a mixing valve to give a reduced temperature (TMV or motorized 3-port valve).

I'm not greatly impressed, Vaillant do a much larger range of controls, albeit with their (intentionally) inaccessible bus system.

 

[scorky]

Have contacted Worcester Bosch as suggested and await their reply.
Nice find that the FW100 could be used to control two separate heating zones. I guess that the FW100 though only has two timing channels so would make the hot storage tank requiring its own single channel controller as I don’t believe it has 3xchannels?

For efficiency I am presuming that I would be better off leaving the ism1 as per the schematic previously shown in the link http://www.worcester-bosch.co.uk/cache/file/4/ism1-heating-system-diagram.pdf and add a separate timed controller for the UFH system. Obviously both heating systems would require separate 2xport zoned valves with a bypass fitted.

 

[Onetap]

Nice find that the FW100 could be used to control two separate heating zones. I guess that the FW100 though only has two timing channels so would make the hot storage tank requiring its own single channel controller as I don’t believe it has 3xchannels?

I didn't study it in detail, so I may have got it wrong, but the pipework schematic on your link shows an internal 3-port diverter (i.e., HWS OR CH) within the boiler. I assumed from this that the 2 external 2-port zone valves could be used for 2 CH zones.

PS I had misunderstood it. The FW100 only sets the boiler flow temperature.

There is a separate 2 zone time control operating the 2 zone valves; the micro-switches on both valves are wired so that a demand from either zone will start the boiler and heating pump. There's no reason why a 3 or more zones couldn't be added the same way.

 

[simond]

I will start by saying that although I'm an accredited Worcester installer, I havent fitted a zoned system with FW100.

It looks like you can delete the timer and use a programmable room stat in each zone, which would be simpler and easier to operate.

I don't think the FW100 when mounted in the boiler does CH and HW timings.

I imagine WB are going away to determine whether FW100 fitted inside the boiler and ISM1 will work properly.

If you are going for weather comp feeding into rads and UFH you may find the UFH doesn't get very warm at all on milder days, because the blending will still be taking place but at much lower boiler flow temperatures.

As Onetap says, the Vaillant controls are a bit cleverer in this respect.

 

[Onetap]

If you are going for weather comp feeding into rads and UFH you may find the UFH doesn't get very warm at all on milder days, because the blending will still be taking place but at much lower boiler flow temperatures.

I'd have thought the flow temperature required for the UFH would always be lower than that required for the radiators, given the difference in the size of the emitter surface areas. The UFH could also be controlled by a weather compensator device, but would have a heating curve (Tf v To) lower on the graph than that needed for the radiators.

You'd need a 3-port mixing valve capable of taking all of the secondary flow from the primary circuit, rather than an injection type device that could only handle, say, 30% of the flow from the primary.

 

[scorky]

Thanks Guys, I have had some contact this week with WB which started with "It can't be done", to "its possible if you remove the diverter valve + ism1 module and revert to an S-plan+ system" to "It Can be done with the components i have"!
Well that was just great but how? In the end they gave me a simple sketch which was pretty basic so i decided to draw up a full schematic on what i thought would do and ask them for their comments/opinion. In short i got a reply that said it should work ok!
Now as i'm not that familier with this site i would like to share my drawing with you but unsure on how to?
Thanks for the comments

Steve

 

[Onetap]

Scan image and save to a folder on your PC. Click on 'Upload New Images' button when posting a reply and upload the image to an album.

Or put the image on a picture sharing site (photobucket or similar) and post a link.

 

[scorky]

Thanks, don't know how this is going to look as its a scanned AutoCAD drg?
View media item 34800I've been told to have one mains isolation point for all rather than individually isolating the zone valves as shown. So take the field L & N as being fed from the boiler Ls & Ns.
Other than that the scheme should work but would welcome your comments especially around the heating supply loop to the Zn Valves. If the valves are not open should there be a bypass?
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[Onetap]

Other than that the scheme should work but would welcome your comments especially around the heating supply loop to the Zn Valves. If the valves are not open should there be a bypass?
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They haven't supplied you with any more information than you had in the previous schematics.

In both cases, the zone valves motor open when powered up, the microswitch closes when the valve is open and this puts a live onto the relevant terminal in the fascia-mounted FW100 (check which terminal, this schematic seems to show a different one to the FW100 schematic). Any zone valve will enable the boiler and pump. Control is by interrupting the live feed to the zone valve using a thermostat AND time-switch OR a programmable thermostat.

What they haven't shown you is how you simultaneoulsy achieve one flow temperature for the radiators and a lower flow temperature to the UFH. That was answered in this thread, so I won't repeat it.
http://www.screwfix.com/community/thread/82281

In the PMEngineer link, 'outdoor reset' means weather compensation. 'Boiler reset' is the WC system you have with boiler flow temperature being adjusted according to outside temperature. The relevant bit is Figure 5, which shows a WC system operating with a secondary mixing valve (system reset) system to give the lower flow temperature required by UFH.

You can use the Danfoss UFH controls which work by restricting the flow and don't provide a lower flow temperature; this is cheapest, but unsuitable for anything but a 1 room extension. I'd leave space to upgrade the system, if you should find it unsatisfactory.

You need to maintain the recommended minimum flow through the boiler. The UFH could be operating on it's own, taking a small amount of water from the boiler, so you need a by-pass OR a thermal store cylinder arrangement to maintain the minimum flow rate.