Causes for no hot water from Potterton boiler.

[TonyR1]

My disabled daughter’s hot water has stopped working. It’s a relatively modern Potterton boiler with an indirect sealed hot water system and a Nest controller. I’m familiar with the old gravity and pumped hot water systems and the new direct systems but not with sealed systems.

Recently she had to have the motorised gate valve on the heating side changed and one possibility is the one on the hot water has now failed. I got them to manually open the hot water motorised valve but that didn’t work. But other than that what else should I look for? Do these systems have a separate pump or is it built into the boiler? There is a pump for the heating side but nothing obvious for the hot water.

The boiler itself is working and running the heating, just not the hot water. Manually overriding the Nest at the HeatLink also didn’t work Trying to do remote diagnosis for her as money is tight and the replacement of the heating gate valve was not cheap for her. Last time - plumber charged her £85 for just the motorised head part . Any thoughts or ideas appreciated.

 

[Gasmk1]

Opening manually won’t work as the motorised valve when working opens fully making a micro switch switch gives power to the boiler and pump. If the heating one works as a temporary measure put heating on and lock open the hot water valve you will get hot water but only till heating satisfie, is there not an immersion heater on the cylinder. Looks like the switch to the right on the wall may be the immersion heater switch.

 

[TonyR1]

Opening manually won’t work as the motorised valve when working opens fully making a micro switch switch gives power to the boiler and pump. If the heating one works as a temporary measure put heating on and lock open the hot water valve you will get hot water but only till heating satisfie, is there not an immersion heater on the cylinder. Looks like the switch to the right on the wall may be the immersion heater switch.

Thanks. I’ll get them to try that and it makes sense. If they just leave it locked open then the heating should naturally heat the hot water tank when it comes on during the day. Yes it is an immersion heater switch and she has that switched on for the moment. But you mention a pump. Is there likely to be a separate pump for the hot water circuit as there is only one pump in the cupboard (blue, bottom left). So same pump running both switched circuits? If its just one then we know the pump is working and no need to hunt for another.

Thanks for the advice. It will keep them going until I can get there and fix it for them.

 

[Ben-gee]

Yes, almost certainly yes one pump.

 

[Basher]

In relation to your mention of costs Tony, I see the normal Screwfix price for the motorised valve head is £72.98, currently on offer at £59.50. I'm not a professional plumber, but the part cost of £85 to get one on the premises, either through having one on the van already (£72.98?), or having to spend time and fuel to go and buy one locally, seems very fair to me

 

[TonyR1]

In relation to your mention of costs Tony, I see the normal Screwfix price for the motorised valve head is £72.98, currently on offer at £59.50. I'm not a professional plumber, but the part cost of £85 to get one on the premises, either through having one on the van already (£72.98?), or having to spend time and fuel to go and buy one locally, seems very fair to me

Yes, I saw them last night for £25-30 but realise those are likely Chinese copies. I’ll get her to get a Honeywell one off Screwfix or Amazon while they’re on offer.

 

[Basher]

Yes, I saw them last night for £25-30 but realise those are likely Chinese copies. I’ll get her to get a Honeywell one off Screwfix or Amazon while they’re on offer.

There is the vague possibility that the lack of hot water fault is due to the valve part becoming stiff, rather than the head not working. So maybe jumping the gun to get just the head? Sorry, I know that doesn't help, but just warning of the possibility!

 

[TonyR1]

There is the vague possibility that the lack of hot water fault is due to the valve part becoming stiff, rather than the head not working. So maybe jumping the gun to get just the head? Sorry, I know that doesn't help, but just warning of the possibility!

Yes, I’ve suggested they open the valve manually and see if the heating then heats the hot water tank. Which should show if there is a major problem with it. Can you buy the valve bit separately? Otherwise it will be a return and swap to Screwfix but that’s a much bigger job part draining the system if it is.

 

[Basher]

Can you buy the valve bit separately? Otherwise it will be a return and swap to Screwfix but that’s a much bigger job part draining the system if it is.

Turns out you can buy the valve body (at least online) on its own. Looks like one has to be careful with versions and part numbers, and it seems on more recent versions you can change just the plate with the shaft and rubber ball valve, thus not having to undo pipe connections, but you would still have to drain the system. Trusting that won't be needed!

 

[Timmy D]

I might have missed the info but when the hot water is turned on at the programmer, does the pump and boiler come on?

I ask, because looking at your pic, if they do, its likely air locked.

See if any air comes out of this bleed point.

 

[TonyR1]

I might have missed the info but when the hot water is turned on at the programmer, does the pump and boiler come on?

I ask, because looking at your pic, if they do, its likely air locked.

See if any air comes out of this bleed point.

View attachment 86911

Thanks for the thought but no neither come on with the hot water but they do with the heating thermostat.

 

[Timmy D]

Thanks for the thought but no neither come on with the hot water but they do with the heating thermostat.

Check your messages.

 

[ShaunCorbs]

At the moment when you move the hot water manually you can feel resistance

when you turn hot water on via the programmer and the cylinder isn’t upto temp eg cold does the port valve have the same resistance when you manually open it or is it loose ?