Money Saving Boiler Challenge and Thermal Store systems

ourproject1

I hope somebody can help me.

MSE boiler challenge states that it is cost effective to set a combi system to 60 degrees.

I have a Thermal Store system - it is a Glendhill Boiler Mater A Class. Will this system also benefit from the 60 degrees challenge?

I ask, as everything I have read seems to suggest that the thermal store systems should be set to Maximum as that is the most cost-effective setting. It seems strange but apparently turning it lower means the boiler is always having to heat up the thermal store whereas on maximum, it heats it up quicker and is on for less time.

I am so confused and would really appreciate guidance here from someone who knows these thermal store systems well and can advise if they would benefit from being set from max to 60 degress (I am assuming is mid-way point on the dial shown in the photo)

I have attached pictures of my setup for ease of reference. 

Thanks!

RedFraggle

I wouldn't. The boiler should be at max to heat the thermal store. The store may have a winter and summer setting depending on age. 
Turn the immersion to the boiler mate off and let the gas boiler do its job. 

ourproject1

Thank you for your response. What do you mean by "Turn the immersion to the boiler mate off and let the gas boiler do its job" ?

Is there someone on in the pictures I attached that shouldn't be on? (could you indicate what as a lot of this goes over my head - thank you)

RedFraggle

So mine had a back up immersion with a switch for in case the gas boiler failed. It was separate to the actual unit itself. 
https://gledhill-repairs.forumotion.net/f5-boilermate
mike the boiler man (YouTube and website) and his forum will probably give you lots of info. 
https://boilermate-repairs.co.uk/background-to-boilermates.html

tacpot12

I understand why RedFraggle says to heat the store to its maximum temperature because this stores the most amount of energy in the therrmal store, and runs the boiler for the least time. But the boiler won't be condensing, so it will not be running at 80% efficiency rather than 88%+ it should run at when condensing.  

I think your system will be much more efficient with the flow temperature and cyclinder set for 60C. This should see the return from the cylinder somewhere below 55C, so condensing will occur. The boiler will running for longer compared to using a higher flow temperature of 70C and the boiler set for 70C, but at 70C you are creating a lot more thermal energy (which you may not need) and you are doing so inefficiently. Running the boiler efficiently to get the cylinder to 60C will use less energy for the same of energy put into the cylinder (but will take longer). The pump running for longer has a negligible effect - the efficiency of the boiler when condensing vs. non-condensing is much more important to the system efficiency. 

The cylinder will lose less heat at 60C than it will at, say, 70C. And 60C should still be sufficient for space heating and hot-water generation. I think you could go lower to improve efficiency further, say 55C. The time to stop reducing the cylinder temperature is when you aren't getting hot enough water at any of the taps. Unless your radiators are really small/old, the hot water production should be the limiting factor for efficiency.You always have the option to increase the temperatures if during very cold snaps, if the heating is struggling. 

RedFraggle

Is it a condensing boiler though? I don't think it is.

ourproject1

RedFraggle said:

Is it a condensing boiler though? I don't think it is.

I don’t know either. I have attached a picture of the setup. Do the pictures indicate if it is condensing or not ?

RonRamsgate

Thats an ideal icos 15kw very much a condensing gas boiler.. Its not a combi 

Iirc there is no user adjustment for hot water ,  hot water leaving the boilermate is regulated at around 53°C when running a hot water bath tap on full flow.
Your hot water at the taps may be lower than 53°C as your property may have thermostatic mixing valves which are set up on site but the bath hot water tap needs to be no more than 48°C  its to provide safe temperature bathing water.

if it aint broke......

ourproject1

Hi Ron,  being a complete noob; are you suggesting to leave at maximum per Red suggestion or move to 60 per TAC suggestion? Thanks 

tacpot12

I've also had a read of the BoilerMate manual, and it is clear that the DHW temperature can't be changed. They recommend the cylinder stat is set to 70C, in order to produce hot water at 55C. The small size of DHW heat exchanger is responsible for the large difference between these temperatures - it doesn't have enough surface area to covert hot water in the tank at, say, 60C to DHW at 55C. To be fair to Gledhill, a heat exchanger that would do this would be very expensive.

There is some potential to reduce the cylinder stat to perhaps 65C. This should produce hot water at around 48C, so hot enough for bathing, but with virtually no scalding risk. But the boiler can't be set below 70C if you want the cylinder to be at 65C, and at this temperature, it won't get into condensing mode unless there is also a substantial space heating demand, which there might be on cold winter mornings if the heating is on.

So I think the conclusion is that you can't go as low as 60C on the boiler flow, so you can't take part in the Challenge, but you can save money by turning you boiler and thermal store stat down a little. I would try turning them down by a couple of degrees and see if you can sense any difference in the heating and hot water production. If you can't, turn them down by a couple of degree more, and see if the result is still acceptable. That's probably as far as you can go, it will save money, but not as much as you should be able to do. It's one of the compromises of having mains-pressure hot water from a open vent cylinder. 

When Gledhill advise keeping the thermal store at its maximum "to maximise performance" they are talking about the performance to a) store energy and b) produce hot water. They are not talking about efficiency. 

RonRamsgate

Maximum will guarantee rapid reheating of the stored water inside the boilermate store, ready to deliver that water into the hot water taps (via a heat exchanger) or radiators.
Can try it at a lower temperature as in the photo and see how it goes, everyone every property is different. Try it and see if your hot water/heating experience is compromised.
The boiler burner may cycle on off on off  more often (not recommended) on a lower (photo) temperature as it tries to reach the expected store temperature or it may never reach store temperature when the heating is on. The radiators will  heat to a lower surface temperature but that may not effect room temperatures, 

Does your property have radiators in all rooms or underfloor heating ?

Tyy it and see.