35mm 3 port zone valve with spring return?

Hi,

Can anyone tell me whether it's possible to get a 3 port zone valve with spring return that will connect to 35mm copper? (or maybe even the next size up). My googling has thusfar failed me. I did speak to one supplier until it turned out that theirs wasn't spring return; the supplier said that some of their competitors made such an item but he wasn't allowed to name them.

It seems that the bigger sizes are listed in inches, so for 35mm copper I need a 1.25 inch one (or 1.5 inch for the next size beyond that).

What it's for ...

We have an Aga that heats the hot water via 28mm copper using gravity feed. It has no thermostatic control. Before we can have a new boiler, I need to fix this as the supplier is saying they won't fit the boiler otherwise because it won't be Part L compliant.

The Aga is already sharing the heat between the hot water cylinder and a large radiator in the bathroom, so my plan is to fit a zone valve that when off, diverts all water to the radiator and allows none in to the water cylinder coil. When the tank thermostat demands heat, it powers the valve which sends water to the heating coil. That's the plan, anyway.

A 28mm zone valve would be an obvious and easy fit, but because the internal ports are narrower than the bore of the pipe I'm concerned that this could restrict flow too much, given that there's very little pressure with gravity feed. If the flow is reduced too much, I'm worried that the water might overheat in the Aga's heating coils and then boil in the pipe.

My thought was therefore to go up a size or two on the zone valve and then use converters to convert back to 28mm pipe. However, finding a zone valve big enough seems to be quite a challenge.

The reason for wanting spring return is that the thing is supposed to fail safe. In a power cut the Aga will continue to run, so it's essential that the spring can close off the feed to the hot water tank if this happens.

Failing that, I could get maybe a couple of 28mm ones and wire+plumb them in parallel, but that seems like an untidy solution.

Any suggestions?

Cheers,
Kingsley.

This is the existing and proposed layout:



The zone valve actuator will be fed from a thermostat strapped to the side of the water tank.

Cheers,
Kingsley.

Whats the aga running on ?

Oil.

Have a thermostat fitted to the aga.

I don't see how that would help as I can't see how the temperature of the Aga would necessarily correspond to the temperature of the water, and it could muck up the temperature of the ovens.

Besides, the assessor said he wanted to see a thermostat on the hot water tank that could cause the water supply from the Aga to be shut off if the water in the tank became too hot.

Not a recommended setup but,:

https://www.jtmplumbing.co.uk/centr...40v-actuator-powered-open-spring-close-p21843

Could work out cheaper in the long run to have the boiler removed from the aga and have it recalibrated to use less oil.

simb82 said:

Not a recommended setup but,:

https://www.jtmplumbing.co.uk/centr...40v-actuator-powered-open-spring-close-p21843

Click to expand...

In what respect "not a recommended setup" ?

picasso said:

Could work out cheaper in the long run to have the boiler removed from the aga and have it recalibrated to use less oil.

Click to expand...

The boiler isn't connected to the Aga anyway. There are two heating coils in the tank and two expansion tanks in the loft.

The Aga already runs below the ideal temperature - it's own thermometer says it's cooler than it should be and the ovens aren't as hot as they ought to be.

As it happens the Aga doesn't get the water particularly hot, so in reality it's not a problem at all. However, we've been offered a grant for a new boiler but the installer says they can't install the new boiler without a thermostatic cutout valve for the Aga hot water heating, despite the fact that it probably never gets above 40C on the Aga heating alone, muttering about the installation wouldn't be Part L compliant.

So, regardless of the temperature of the Aga, we've got to put a stat on the tank and have that control a valve that shuts off the heat from the Aga if it gets too hot, which I'm sure it never will. Rules, rules, rules and red tape.

Esbe do a 1.1/4 3 port divertor

https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.co.uk/ulk/itm/253622480061

There is a boiler attached (ie inside) the aga which can be removed (if I have the right aga)

There is no need to remove the boiler, just disconnect from water and drain down. Fill the boiler with sand to maintain some insulation but leave pipework open.
Of all the oil Agas I've serviced, if they don't perform as you wish, it is usually the opposite to yours; too hot!! If you did have an isolation valve fitted to the Aga to isolate the cylinder, I think this will contravene the M.I's unless the radiator is big enough to sink the heat from the Aga. As you have a twin coil and separate header to the boiler, I'm not sure I agree with the surveyor. By all means fit a cylinder stat, but let this control the boiler supply. This would satisfy Part L. as it would stop the boiler firing unnecessarily

picasso said:

There is a boiler attached (ie inside) the aga which can be removed (if I have the right aga)

Click to expand...

Above the burner assembly inside there's a pipe coil - is that what you meant?

oilhead said:

There is no need to remove the boiler, just disconnect from water and drain down. Fill the boiler with sand to maintain some insulation but leave pipework open.
Of all the oil Agas I've serviced, if they don't perform as you wish, it is usually the opposite to yours; too hot!! If you did have an isolation valve fitted to the Aga to isolate the cylinder, I think this will contravene the M.I's unless the radiator is big enough to sink the heat from the Aga. As you have a twin coil and separate header to the boiler, I'm not sure I agree with the surveyor. By all means fit a cylinder stat, but let this control the boiler supply. This would satisfy Part L. as it would stop the boiler firing unnecessarily

Click to expand...

I've not been able to figure out why it doesn't run to temp. I've checked the oil depth in the burner tray - about 5.5mm. I'm told this is about right. I tried fitting new wicks, no difference. It used to get hot enough, but now the mercury only gets within about 5mm of the "normal" line and won't get any closer. I've checked the thermostat thing is getting power, which it is. It's a bit baffling really.

I'm assuming the engineers would fit a cylinder stat for the boiler in addition to any I add for the Aga.

This is the bathroom rad - a chunky aluminium thing: