Grant vortex oil boiler thermostat temperature range

[james63]

I have a new Grant Vortex 15/26 oil boiler installed.
It has a boiler thermostat with no numerical information, just a wedge graphic and covers about 1/3 of a turn.
I wondered if anyone could give an indication of what the range of temperatures is likely to be (I don't want to set the boiler temperature lower than the hot water cylinder temperature). I can't find any indication in the manuals or online.

Thanks

 

[ShaunCorbs]

3/4 is 60dc

 

[james63]

3/4 is 60dc

Thanks! Do you know what the high and low limits are likely to be? (although I guess for hot water I shouldn't go lower than 3/4 on the dial then)

 

[ShaunCorbs]

Around low 40 and max 80 ish

 

[james63]

Having started up the heating again I'm looking into this again. I've got a dual K-type temperature sensor and with the boiler thermostat on max, the thermostat turns it off at a flow temp of around 72. In then drops to around 60 before starting up again. So my average flow temp is something around 65, on max setting. I have never been that happy with the performance of the system in terms of how long it takes to heat the house. The Grant manual recommends 70 degree flow, 50 degree return for radiators, but if thats average I would want the flow temp going up to 75 or closer to 80 before cutting out so the average over the cycle is above 70.

Is there anything I can do? I think I saw a post saying it is possible to remove and the dial and adjust to get a bit more range as it may not be calibrated accurately. but I can't find the post for this now.

 

[exedon2]

Running with a high return temperature will stop boiler condensing.
What controls do you have on your system?
If system takes a long time to get property up to temperature I would be doing heat loss calculations to make sure radiators are correctly sized.

 

[John.g]

If the rads are running with a average flow temp of 65C and assuming a return of 50C, (dT of 15C) and at a room temp of 20C then the rads will only emit 69% of their rated rating, to get their full rating you require flow/return temps of 75C/65C or else your rads at the above 69% output would have had to be oversized by a factor of almost 1.5 (1.45).

If the boiler gets the RAD temperatures up to 65C in say 25/35 minutes in the morning after a overnight shutdown then probably jetted OK, some oilfired boilers are supplied jetted to their lower output, in your case, 15kw.

 

[james63]

Thanks. At the moment when heating up I have 18-20C dT between flow and return on the heating, so I think I could get a bit hotter on the flow without worrying about going over 55. But actually I am not so worried about this because I have a PID thermostat on a 10 minute cycle and so through most of the day it is firing just on few minute cycles. Actually I'm more worried that the return temp is below 40 for much of the day because of the PID controller, but I'm hoping that's not a problem as it isn't burning for too long in those conditions. So that will keep the average flow temp to what they should be during the day.

Yes, exactly, I would like to get the average flow temp up to 70 (as recommended by Grant) but currently maxes out below that. Is it possible to remove the dial and rejig to get the dial to cover a slightly higher range? I think it's jetted OK, its on the middle nozzle and I think has more than enough capacity, would just like a slightly higher flow temp.

It is only out of condensing range when the hot water is on on its own, then the drop is 8-10degrees and flow is over 55. Not sure how this can be avoided though

Controls I have are a 2 channel programmable timer (hot water, single zone heating), standard cylinder stat, wireless danfoss room thermostat (PID, 10 minute cycle), TRVs on the rads (downstairs open, upstairs set to around 20).

 

[james63]

Actually most of the problems with slow heat up were when I was running with the thermostat at 2/3 to 3/4 of range which the installer recommended initially. But since I started measuring flow and return temp I can see this is far to low. With the thermostat on maximum it is heating up better, but it's not even that cold yet, so it feels like I would like a bit of extra range (ie max to correspond to thermostat cutting out at 80 or so which would still end up only 75 or so average flow temp).
I saw a post somewhere about shifting the range by removing the dial somehow, since they might not be calibrated properly from the factory, but can't now find the details of this.