Just for information

[jc_150]

Hi all,
I have a simple 6 radiator open vent system with 5 TRV's and 1 rad permanently open, on an Y plan. The boiler is a Worcester Bosch Greenstart 12 ri. with pump over run fitted in 2009. I have heat and hot water, so just wanted to ask 2 questions before BG do their annual check on 29th Dec. The manual states that the temperature dial is 35 C at one end and 82 C at the other. I have placed pipe guages on both the flow and return a few inches above the boiler. I often get the situation that the boiler has cut out before reaching the thermostat set temperature, and then switches on and off as the water temperature cools (I guess) I have at least 10 C difference between flow and return. The guage clipped on the flow pipe never reads more than about 62 C with the temp set to max. Is this normal as I do not know if the 82C is referring to pipe temp or some internal boiler temp. Would like to know, as I do not want to be bamboozled by the service engineer if I mention this. Also 1 other question if I may. What would be the best pump mode for this set up? I have Contant speed, Constant pressure or proportional pressure.
Thanks in advance for any answers.
John

 

[Ric2013]

Usually, PP for a radiator system is best, but the actual setting will be determined by which setting most accurately matches the required flow and pressure characteristics of your system and should have been selected by whoever installed the system.

Seeing as that will be a condensing boiler, there is no harm in having a greater than 10°C drop between the flow and return and it may even make the boiler run more efficiently. 62°C may well be ideal for heating your radiators, but you'd need to run your boiler hotter than that to get your cylinder up to temperature and it does sound odd that (as you describe it) the boiler appears to be regulating the maximum temperature at 62°C. In practice, the pipe temperature will be the same as the boiler internal temperature and shouldn't differ to any measurable extent.

 

[jc_150]

Thanks Ric for a speedy and informative reply. I just checked and set the thermostat to 24C and the boiler to max. The boiler stopped at 62 C and the temp on the thermostat was 21.5. The return temperature was 50C when the boiler stopped. I am treating this as a problem, and will print off your reply if you do not object, to show to the service engineer when he/she arrives on the 29th, as the boiler is on a service and repair contract.
John

 

[Ric2013]

Thanks Ric for a speedy and informative reply. I just checked and set the thermostat to 24C and the boiler to max. The boiler stopped at 62 C and the temp on the thermostat was 21.5. The return temperature was 50C when the boiler stopped. I am treating this as a problem, and will print off your reply if you do not object, to show to the service engineer when he/she arrives on the 29th, as the boiler is on a service and repair contract.
John

I don't object, but you might get a registered gas installer's back up if you quote a plumber against his higher qualifications. May be easier to ask if he could get the max up to 70 degrees as the temperature of your stored water in your cylinder isn't reaching 60 degrees and take it from there. Could be there is some kind of internal setting in that boiler that I'm not aware of.

 

[jc_150]

Hi again Ric,
Thanks for the advice, I will ask the BG service guy first if he/she thinks there is a problem, if he agrees then no need for me to go any further. If he/she says no it is ok, then I will quote the manufactureres guide, then if there is still a disagreement then I will show your replies, as I feel 62C is not enough for a boiler which says 82C max. Will post back after BG have been on the 29th

 

[Ric2013]

Yeah, well, if it were just heating, I'd say 62 flow may well be sufficient, but I can't see that a flow of 62 will get your hot water cylinder hot enough to be hygienic i.e. 60°C (the relevant law is in the so-called Water Regulations 1999). If you want it from somewhere official, have a chat with the Water Regulations Advisory Scheme Water Regs UK Limited Contacts - https://www.waterregsuk.co.uk/contacts/ who will give you free advice on UK water legislation.