DIY & Ecodan Heating System

Possiblyretired

I've just moved into a house with an Ecodan Heating System, I know nothing about ASHP so this is quite a step learning curve.
It was installed by GreenGen in 2021 and I've booked a service and hope they can explain a bit to me then. Unfortunately the service is not until March and I wanted to remove a handbasin and radiator before then. 
When I've done that type of DIY before I've just turned the main stopcock off to work. 
Can anyone help me understand what's different and how I turn the water off for this system?

QrizB

Your domestic HW system will be normal, so you can deal with the handbasin like you normally would.

The CH system will be pressurised (like a combi boiler system often is) and may be filled with antifreeze, so you don't really want to drain the system if you can avoid it. If the radiator has working valves both sides you might be able to remove it without draining.

Possiblyretired

@QrizB thanks for that. I thought that might be the case but oddly the basin hot water didn't stop running after turning the stopcock off. It sort of threw me, guess there is another shutoff valve lurking somewhere 🤞

Netexporter

How long did you wait for the tap to stop? You need to wait until the pressure vessel has exhausted itself.

When I turn my hot taps on you get a rush, for a few seconds, until the higher pressure in the expansion vessel has equalised with the incoming mains pressure.

Possiblyretired

@Netexporter approx how long should I leave the tap on?

QrizB

Possiblyretired said:

@Netexporter approx how long should I leave the tap on?

It sound like you're used to combi boilers with on-demand hot water?

Your system will have a hot water storage tank. Depending on exactly what's what with your system, you might be able to leave the tank full and only relieve the stored pressure - this is what Netexporter is describing. I would guess this will take a couple of minutes (I've never had a pressurised HW system so I have no first-hand experience).

However, it's also possible that you'll have to drain the tank completely. This might take 10-20 minutes. If you do darin the tank, make sure you've switched off any direct electric heating (eg. an immersion heater) since, if that decides to switch on with the tank empty, there's a good chance it'll burn out.

I'm also assuming you don't have isolation valves in the tap risers below/behind the sink. If you do, closing these should be a much simpler option!

Possiblyretired

@QrizB thanks. Yes, combi, but really know very little about plumbing and have only changed a few things before. Whilst waiting for GreenGen to explain things in March, thought I'd crack on with removing bathroom bits so wall panels can be removed and all ready for plumber to refit.
I guess I just don't know enough to manage this.
Re isolation valves - yes they are there but rubbish ones that started spraying water as soon as they saw my screwdriver...

Netexporter

If you want to have one more go, turn off the mains supply and open all hot taps. That way the hot system will drain to its lowest point, quite quickly,  and then you won't get any nasty surprises later, if an air-lock breaks. If it doesn't stop flowing, you've got a problem with your stopcock.

QrizB

... and change the isolation valves while the system's dry!

Possiblyretired

Sorry, one more question. @Netexporter and ashp system should be OK right? @QrizB if I get that far I will!

Netexporter

The ASHP is isolated from the DHW, same as with any boiler.