Convert C to S plan

Hi all,

I've been reading the group for a while now, and am just about to take the plunge with an upgrade to my existing heating/dhw system in a house that we bought last year.

The current system is C plan with gravity dhw. Boiler is an open flue Ideal Mexico CF80 in a cupboard (not to current regs I'm told, but ventilated externally nonetheless), but I'm not sure which burner is installed, so I'm not sure of the heat output. Is there any easy way to tell? I couldn't find a manual for it, but the CF445 etc on ideal's website appears to be very similar. Boiler is not going to be replaced as it is only 5 years old.

House is 4 bed, and I'm installing a power shower (possibly 2 if we go ahead with the ensuite). Current dhw tank appears to be a telford

1050x450 BS.

Recovery time on the gravity system is quite slow, especially when the CH is on (ie one bath per evening, second will be lukewarm).

I'm thinking of converting to S plan (as I already have a two-port Honeywell valve on the gravity HW), with a Telford Typhoon (probably their largest, which is 950x450) as this will fit nicely in the space that the old cylinder is in. I'm thinking of some of the suggestions made here, and given the power showers (one with bodyjets) I want fast recovery time on the DHW.

I think that I should run the dhw at 75 to 80 degrees, with a thermostatic mixer feeding the baths and shower pump, as this will provide more volume of bath/shower temperature water.

I also think that a dhw priority system could be used as the boiler output should be high enough to give a fairly fast recovery with the Typhoon, so the ch would not be off for long when dhw demand and ch demand are on.

I looked at DPS Pandora, but it looks expensive compared to going the Typhoon route, and also I'm not sure about my water pressure or flow rates, so I'd have to get that checked first.

All the existing ch dhw pipework is 28mm, so I'm going to do the new feed pipework in 28mm too.

According to the installation guide for the Ideal CF445, the boiler should be plumbed so that the header tank and expansion pipe are on one side of the boiler, and the system flow and return are on the other side of the boiler, with the distributor tube installed on the system (pumped) return. This is OK, but involves a fair bit of new pipework, about 4m from boiler to dhw cylinder and is rather fiddly, as some of the ch 15mm pipework is quite close after the pump.

Where would the two port control valves be best placed? After the pump near the boiler, or should the dhw valve be near the cylinder (which is where it is now).

What about any venting on the system flow/return? I think that I'll need a vent on the 28mm dhw circuit somewhere. What's best? An automatic vent, or a vent into the header tank? The ch circuit should be OK as any air in there can be vented from the radiator bleed valves. The heating system appears to work OK at the moment and I've not had to bleed any radiators so it looks like there aren't any air leaks in it.

I'm also going to fit an automatic bypass, so this will be near the boiler, just after the pump, as I'm going to fit TRVs to all radiators.

Any recommendations on controls? There is a Potterton EP2001 installed at the moment.

I'd really like to install the Honeywell CM zone system on the ch, but I've not found any prices yet. Anyone know where this can be obtained and any prices yet? Are there any equivalents?

Suggestions or comments appreciated!

Cheers,

Rick

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Richard Wood
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