Thermomatic were an Italian manufacturer of a number of products but with regards to the UK, mainly the Thermomatic RSM 20 and RSM 25 combination boilers.
And what is this RSM model?
This was before condesning boilers were anything more than a niche specialist product and was one of the few designs (in fact some might argue the most successfull) that stored an amount of water within the boiler for imediate use rather than waiting for the boiler to heat up before supplying hot water.
It managed this by acting like a small cylinder with the DHW in the coil and the “jacket” of water surrounding the coil supplying the radiators and so not wasting any heat. The “jacket” of water was kept at the desired temperature all the time the boiler was on so that this would transfer the heat into the coil and whenever a tap was opened the already warm water in the coil would leave the boiler and the mains water replacing this would heat as soon as it started its journey through the coil.
This design meant that for small amounts of DHW the boiler would not neddlessly fire and the store of water could be kept at temperature with a few short burst of heat throughout the day.
The design was in fact so efficient that it had to have a thermostat (called the anti-condensing stat) specificaly to stop it condensing.
If it is so good why is it still not around today?
The RSM model was a very simple piece of equipment with just a large heat exchanger/water jacket, gas valve, ignition PCB and a few thermostats. The only problem at that time was the weight and size. Although not large for its day, it was not small either and because of the size of the copper heat exchanger it was a two man lift (even when Health and Safety wasn’t so forceabley imposed).
Its real achilies heel was what set it apart from its competition. Most boilers had a basic heat exchanger (mostly low water content) which could be replaced with a condensing alternative (with a few other changes) whereas the large copper heat exchanger could not. So as soon as the laws in the UK changed the end of the RSM was in sight.
Within a few years Thermomatic stopped production as Europe followed with similar Condensing boiler laws and incentives. Although Thermomatic made a range of products and boilers, they have been facing many separate threats over the last five years and ultimately the family run business was let down by their banks and had to close the business in November 2010.
Why are you telling me this?
Whilst most of the industry have never heard of let alone seen or worked on a Thermomatic, there are a number of the thousands sold still out “in the wild” and because their design was so simple (not to be confused with basic) many of them are still going strong.
It is for this reason that as the sole importer of Thermomatic spares we bought any and all spares stock left for the models when Thermomatic went out of business.
We do not have everything for every model /version of the boilers as even the newest RSM 20 Mark 1 would be over 30 years old however we do have 90% of the parts and the technical knowledge to help if you are in trouble.
So if you see a Thermomatic in trouble, give it a bit of TLC, give us a call and before you know it you could have a working unit that should still go on for a few more years.
Paul and The Gas Boiler Parts Team.
Since this post was written we have had a number of requests for help from around the world. Since we can only help with the UK versions (which may or may not be the same as international versions) I have scanned and linked (below) copies of the manuals we still have for the mk3, mk4 and mk5 RSM 20FB (the 25FB was similar) so from these manuals you should be able to find some information to help.