Is there a Honeywell V4043 2 zonevalve in 22mm with 6 wires?

Yes John, it was an emergency, hole in cylinder, had to get it working quickly, so straight replacement.
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The plumber that called said he has the same boiler and would never replace it.
I feel the same about my old mum's Potterton Profile. We added a 28mm valve and converted it to fully pumped a couple of years ago. Fitted a Magnaclean as well and captured a lot of old sediment out of the long horizontal 28mm pipes once the pump started.
Excellent John.

I dare say my system is full of iron oxide.

Magnaclean sounds like a good idea.

Cannot put any inhibitor in because of the primatic.
Right, further research on the Web indicates that no valves should be fitted to the flow or return to a primatic cylinder as it is also the f/e tank.

(So much for the plumber saying that it was OK to fit a valve there).

Apparently the solution to the problem of potentially scalding water when the boiler stat is set to high temperature, is to use a low pressure thermostatic mixing valve on the hot water draw-off. Sounds like a Plan.

Any comments?
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Yes John, but how about the Thermostatic mixing valve idea? Sounds easy enough to implement.
Replacing the cylinder and fully pumping is, I believe, the best option. It will save you money on the gas bill and will also be ready for when the boiler has to be changed - the one you've got won't last forever and all the new ones require fully pumping.
Yes, I hear you all - fully pumped, new cylinder...

However, I have been doing this in easy stages, first was to fit a room stat/ programmer, along with cylinder stat that limits the DHW temperature when only DHW is on (but not when CH is on).

The remaining problem with potentially scalding DHW in winter when CH is on for longer is my next priority. Hence the original idea of a valve to switch off the flow to the cylinder, but this is not advisable with a direct feed primatic cylinder. Now looking at regulating the HW coming out of the tank with a mixing valve.

Yes I could replace the cylinder again, but especially at this time of the year I don't want to start major plumbing works (and expense). Boiler is in very good nick as is the HWC, so reluctant to change either.

We don't use much hot water, as we have electric shower and the dishwasher and washing machine heat the cold water. So my hot water just sits in the tank warming the cupboard most of the time. I'm not worried by how long it takes to heat up after a bath.

Anyone any experience of Thermostatic mixing valves?
I wonder if it would help to turn down the boiler stat?

on gravity feed, over time, the cylinder creeps towards the temp of the primary flow from the boiler. So if your house is warm enough with rads at 55 ° or so, that might do

until you fit your new cylinder ;)
I read that it is more efficient to let the boiler heat up rather than limit it too much, but indeed before I had the room stat, I did keep the boiler stat at a reasonably low temperature (except when it was very cold weather and the system struggled to maintain the house at a comfortable temperature or took too long to heat up).

I'm actually enjoying the quick heat up afforded by the higher boiler temperature, combined with the Honeywell adaptive timing that makes sure the temperature is reached when I want it to be, even if there is a cold snap.

My radiators are of course ancient inefficient panel types, fed by micro-bore piping which is all under the floor which has a concrete raft a couple of inches below it, so absolutely no chance of getting access to the pipework in the future.

As I said, the only complaint we have is the danger of scalding from the hot water tap (we are careful, but visitors may not be).
Been doing more reading on TMVs:

Seems a good idea to have hot enough water to kill off bacteria, but still have protection at the taps for anti-scald. Need hot enough water available for some purposes like cleaning greasy items in the kitchen sink.

Looking at our problem , the main one is the bathroom sink hot tap which is not a mixer type, and of course is frequently used for hand washing.
The bath tap isn't a real problem as when we run a bath we have the cold running as well to fill it quickly, so not a danger, we don't have kids or elderly folks to worry about.

The kitchen tap is a mixer and usually used for dish washing where we need fairly hot water, actually the flow on that tap is very poor, wrong type of valve for the gravity feed I think.

So perhaps the interim solution is a TMV on the bathroom sink tap, that will prevent hand washing scalds to the unwary.
I bought myself a 22mm Honeywell valve for a C-Plan install and I too discovered that the valve had only a 5 wire flex....

Having dismantled the actuator I discovered that the microswitch is actually a SPDT item, ie. it does have the normally closed contact required for the white wire, but without the extra cable core in the flex.

I opened up the microswitch and found that the existing wires are held in the microswitch body by spring clips.

I've now added the extra cable core and saved a few quid.[/b]

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