Heat only vs Combi boilers control- set flow temperature

Are you sure it only fires up once or twice per day?
Yep. According to my daily gas usage. See chart.

IMG_5142.pngIMG_5141.pngIMG_5140.png
 
Sponsored Links
Sponsored Links
Two of us in the house, gas hob for cooking, numerous hot water hand washing throughout the day, both of us have a shower every night, occasional baths. Hot water is on 24/7. When the heating is not used, we average 37p a day gas usage so personally, I CBA with switching the hot water on and off or even putting it on a timer. I might come home from work or the allotment in the middle of the day and want to jump straight in the shower so it’s nice to know I always have a cylinder full of hot water at any time of the day.

View attachment 307030
Your gas meter is probably passing unregistered gas.
 
1 kwh of gas boiler heated HW will give 15L if heated from 10C to 60C resulting in 25L of shower/bath water at 40C so easy to work out how much water is reheated once cost/kwh is known, this assumes a mains temp of 10C, at the now mains temp of 20C these numbers become 19L & 38L per kwh of gas consumption.
The vol of water used before reheat is largely determined by the positioning of the cylinder stat, the higher up on the cylinder, the greater the volume to reheat and the less the frequency but a longer reheat time obviously.
 
Hi,

Combi boilers have two knobs to set CH and HW temperatures. This way one can keep CH temp low to say 50C and condense for high efficiency, and HW temp higher say 60C.

Is there a way I can have two temp for heat only boilers activated by an external switch or openterm? I only start the boiler for HW before shower so I can increase supply temp to 65 to heat up the water cylinder and return to 50 for the rest of the day to supply the radiators.

I could not find any supplier that does manage openterm for heat only boiler switching CH/HW temp.

Many Thanks

Yes; is your boiler OpenTherm? If so use EPH controls and set for priority hot water reheat which it will do at high temp (set to whatever reheat temperature you want, say 75degrees) then when hot water is up to temperature supply space heating at a modulated flow temperature dependent on current demand.

If you set for simultaneous reheat of both the control will choose the highest but time the two reheats to be separate and it's the easiest and cheapest option for any OT boiler. If the boiler software permits (most don't) you can also introduce weather compensation. If you use the EPH Ember that offers remote control of system and boiler.
 
.. Hi.. I found out that I can achieve same result by fiddling with weather compensation thermistor. I just modify the thermistor resistance by external relay and can change the supply water temp.. much simpler than opentherm .. :)
 
.. Hi.. I found out that I can achieve same result by fiddling with weather compensation thermistor. I just modify the thermistor resistance by external relay and can change the supply water temp.. much simpler than opentherm .. :)

Yes, that's what we do on basic boilers, simpler but chalk and cheese. If it gets the job done however, go for it.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top