What happens when you give an expansion vessel a name and let installers across the UK talk to it?
More than 100 conversations, as it turns out – covering everything from specifying the right vessel and diagnosing system faults to checking whether you’re on the right track. We’re talking, of course, about Cal, Zilmet’s AI assistant, introduced at the start of the summer to give installers instant access to technical and product information around the clock. It can get you straight to datasheets, sizing guidance and product detail, without the search or the wait.
Since then, you’ve been putting it to work on-site, in the van and at home. We’ve looked at what keeps coming up and pulled together the 10 questions installers ask Cal most:
1) Which Zilmet vessel is right for this job?
Start with the application. CAL-PRO is designed for closed heating systems, while Zilmet’s potable water ranges include HYDRO-PLUS E, ULTRA-PRO, ULTRA INOX-PRO and Trade-Tec Potable. Working on solar thermal? You’ll need a vessel designed for the higher temperatures involved.
Once you’ve identified the right range, check that the vessel size and technical limits suit the system.
2) How do I identify an old Zilmet vessel from the label or product code?
Take a clear photograph of the label and make a note of anything that is still readable. The product code, serial number, capacity, pressure rating and pre-charge can all help.
If the label is damaged, the vessel dimensions and connection size may also help identify it.
Still stuck? Send the information to Cal or Zilmet UK. If you’re looking for a replacement, it will still need to be checked against the requirements of the system.
3) What are the dimensions, weight and connection details for this vessel?
Start with the exact vessel you’re looking at. Dimensions and connection sizes vary by model, capacity and orientation, so give Cal the product name, capacity or product code and it can pull up the relevant specification.
Cal can provide the available dimensions and connection details from the product information. Vessel weights aren’t listed in the available specifications, so if you need one confirmed, contact Zilmet UK on 01889 272185 or email sales@zilmet.co.uk.
4) Is this vessel available, what does it cost and how quickly can I get it?
Cal can help you identify the right product and answer technical questions, but it doesn’t have access to live pricing, stock levels or lead times.
For current prices, stock and lead times, contact Zilmet UK or your usual merchant.
5) Can I fit an expansion vessel horizontally, upside down or at an angle?
Where possible, keep the water connection pointing downwards. That’s the position Zilmet recommends, and installation guidance will usually show the vessel upright above the pipe, with the connection at the bottom and the air valve at the top.
Need to install it differently? Some Zilmet ranges include vessels designed specifically for horizontal installation, so check the product description and installation manual before fitting one in another position.
6) Where can I find the datasheet or installation instructions for this vessel?
The best place to start is the Zilmet Technical Support Hub. You’ll find technical datasheets, installation and maintenance manuals, downloads and the Expansion Vessel Calculator all in one place.
7) What warranty, certification or test paperwork comes with this vessel?
It depends on the vessel and the range. Warranty cover, approvals and technical documentation can vary, so check the information for the exact product you’re working with.
Depending on the range, this can include factory testing, Pressure Equipment Directive certification, WRAS approval, technical datasheets, drawings and installation manuals.
If you need paperwork for a particular vessel, check the relevant product information or contact Zilmet UK. For a warranty claim, contact the original supplier or email sales@zilmet.co.uk.
8) What size vessel do I actually need?
Size the vessel for the system you have in front of you, not simply the vessel that was there before. Systems can change over time, and an existing vessel may not have been correctly sized in the first place.
Zilmet’s Expansion Vessel Calculator can help you work out the required capacity using details such as system volume, pre-charge pressure and maximum operating temperature.
If the result is close to the limit of a vessel’s capacity, or the installation has unusual operating conditions, get it checked by a qualified person before ordering.
9) Can I get a replacement membrane, bracket or other spare for this vessel?
It depends on the vessel and the range. ULTRA-PRO vessels have a removable membrane, while ULTRA INOX-PRO and Trade-Tec Potable also include models with interchangeable membranes.
Other ranges use a fixed membrane, so check the product code before ordering a membrane, flange or bracket. Spare parts are specific to particular ranges and vessel sizes.
10) How do I check, recharge or replace an expansion vessel?
Start by taking the system pressure off the water side of the vessel. It needs to be at atmospheric pressure before you check the air pressure.
Isolate the vessel where possible and depressurise the system, then measure the pressure at the air valve using a suitable gauge. If it needs recharging, bring it back to the specified pressure and follow the product instructions when putting the system back into operation.
If the vessel won’t hold the correct pressure, keeps losing its charge or shows visible damage, it needs further investigation. Some Zilmet ranges have a replaceable membrane, while others use a fixed membrane and are replaced as a complete vessel.
Still have a question?
If your question didn’t make the top 10, Cal is still there to help with vessel selection, sizing, installation and pressure problems.
For manuals, datasheets and the Expansion Vessel Calculator, head to the Zilmet Technical Support Hub.
And if you need project-specific advice, help identifying an older product or technical sign-off, contact Zilmet UK directly on 01889 272185 or email sales@zilmet.co.uk.
