Do boilers only modulate with makers "own" controls

7 Feb 2006
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United Kingdom
Back in 2007 I had a Mk1 Glow Worm Ultracom installed. At that time the installer connected to the original simple Honeywell mechanical stat. The boiler did not modulate. I managed to pick up Glow Worm's own "intelligent control" from ebay and wired this to the original stat wiring. The boiler recognises this and now modulates.

My question is this - have things moved on? Do the latest boilers only go into modulation mode if they are connected to their own proprietary controls or can you fit generic makes of digital thermostat? For instance, does the Nest device allow boilers to modulate or are you back to simple on/off operation?
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All boilers modulate their output regardless of the controls, even your Ultracom. Most just take account of the difference between the current flow temperature, the target flow temperature, and the rate of change to effect this, and this is what your Ultracom was doing with the original Honeywell stat.

Some boilers will also take account of indoor and outdoor temperatures to alter the modulation rate to suit, and this may have been the effect you saw with adding GlowWorm's own control to your boiler. The new 3rd-Generation Nest is supposed to do this with OpenTherm-compatible boilers, although in reality they're still working on the software to make it work correctly so it actually doesn't operate as it should currently. Other OpenTherm controls will provide similar results to your GlowWorm control with OpenTherm compatible boilers, but both the controls and the boilers are a little rare as many manufacturers are now insisting that you use their own very expensive controls to generate maximum efficiency. If you're looking for a really good boiler that can use 3rd-party OpenTherm controls, look no further than Intergas
Normal controls are fine, Center brands Honeywell made wpr stat is a good cheap option at 51 squids. Nest is good quality and a blind man can fit both of these with ease. (As long as he's competent to remove the boiler case) Personally id spend any extra money you have on insulation that over priced controls.
There is a lot of development going on with smart controls at the moment.

Unless you have a particular need, my advice would be to wait for a couple of years until the market place is more developed.

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Thanks for all the replies. I don't have need to change anything at the moment. The question was just to keep abreast of developments with an eye to the future but it looks like the future is changing all the time!
The future isn't the future for very long. Some of it has become the past since you wrote that message. Blink and you'll miss it!

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