Oil Central Heating working but no hot water

barrymurphy · 10 Jan 2021

Hi,

I have a two storey house with an oil boiler zoned heating system and two motorised valves. There is a horstmann H37XL control unit that has three buttons, one for downstairs and one for upstairs and one for hot water.

My first simple query is whether you should get hot water only when you hit the water button? would you not have hot water anyhow when the heating is on?
Or is this button for hot water without heating the rads?

Anyhow, both motorised valves work and the zoned heating works perfectly. But no hot water, whether I hit that water button or not.

I believe the system is a gravity feed system and we have a small header tank beside the main water tank.

Is there a valve somewhere that could be closed either on the pipes somewhere in the hot press.

Our immersion works fine.

Thanks

Barry

muggles · 10 Jan 2021

There will almost certainly be another motorised valve for your hot water. It's probably not making the contact properly to bring the boiler on. Hot water is timed just as your central heating is (assuming you have a fully pumped system)

Terrywookfit · 10 Jan 2021

A photo of pump etc would be handy. Which boiler do you have ?

barrymurphy · 13 Jan 2021

Hello, apologies for not replying before now. Here are pictures of the setup. I cannot think where a third motorised valve would be, cannot locate one. There is water in the header tank. Could the issue be one of these red valves in hot press?

muggles · 13 Jan 2021

Ah, third photo, there's a valve that looks a bit like a TRV with a sensor coming off it attached to your hot water cylinder. That's ye olde way of regulating cylinder temperature before fancy things like zone valves and cylinder thermostats came along. I expect that has failed and that's why you're not getting any hot water. As far as I'm aware they're obsolete and you'll need to upgrade to a zone valve & cylinder stat

polesapart · 13 Jan 2021

"valve that looks a bit like a TRV with a sensor" ="Cyltrol valve"

Still available but, as Muggles says, the concept is pretty old hat.

Might be worth unscrewing the thermostat head from the valve body and checking that there's movement on the steel pin.

Terrywookfit · 13 Jan 2021

Not like any Cytrol I have seen.
It looks like a Danfoss head with remote sensor A Tapstat !!

As above remove head and check pin .

ianmcd · 13 Jan 2021

muggles said:
Ah, third photo, there's a valve that looks a bit like a TRV with a sensor coming off it attached to your hot water cylinder. That's ye olde way of regulating cylinder temperature before fancy things like zone valves and cylinder thermostats came along. I expect that has failed and that's why you're not getting any hot water. As far as I'm aware they're obsolete and you'll need to upgrade to a zone valve & cylinder stat

well spotted @muggles I call them Ravi valves but other makes were available, just remove the sensor head and you will get hot water until you can get it sorted properly

barrymurphy · 13 Jan 2021

sorry, are you referring to the unit in cylinder 1 photo or cylinder 2 photo please?

polesapart · 13 Jan 2021

cylinder 2 photo

barrymurphy · 14 Jan 2021

Hello, I removed the stat head and the pin was a bit stiff but it does move up and down and was in the open position. The upper pipe at the point of entering the cylinder, i.e. after the stat valve is hot and the pipe coming out of the cylinder at the top is cold. The valve works as when I press it in the pipe coming down from the valve gets hot i.e. water is being diverted away from the cylinder. So there must be an airlock in the coil? and I suspect this has been there for a long time. Was going to use a hosepipe on the vent pipe in the attic and the other end on a tap to push the air out.

barrymurphy · 14 Jan 2021

Could be sludge also at the flow pipe entry or the return entry? I will try the air purge first but if it is sludge than I will have to drain the cylinder/system to fix this?

oilhead · 14 Jan 2021

Don't forget, if you have a cold cylinder, then the return will cool until the cylinder starts to warm. If it is cold after running for a while, then either you have an airlock or some other blockage. If an airlock, if you slacken off the top connection of the coil, this would release it. If you get water, then it is not an airlock.

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Oil Central Heating working but no hot water

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