Gas combi boiler

moneytalks

Hi
My Baxi gas combi condensing boiler works well and heats the house. One thing I notice is, when boiler temp for rads is set to 60c after an hour the temp increases to 62c, then drops down to 58c, then increases again.
9 single rads and 4 double rads. TRV’s set 3 downstairs and 1-2 upstairs. Is it normal for the boiler to do this?

Rodders53

Yes. Normal.

Google < thermostat hysterisis >

NB your temp is possibly a tad on the high side and you may be more energy efficient (fully condensing) if you can go a bit lower.

moneytalks

Another niggle is after about 45 mins there is a high pitched sound coming from 2 of the TRV. This goes away if I turn the TRV slightly. I’m thinking the lock shield needs adjusted, am I on the right lines?

Thanks

ThisIsWeird

moneytalks said:

Another niggle is after about 45 mins there is a high pitched sound coming from 2 of the TRV. This goes away if I turn the TRV slightly. I’m thinking the lock shield needs adjusted, am I on the right lines?

Thanks

Possibly, if the affected rads are getting too much flow.
Do they heat up from cold noticeably faster than other rads? Are they closer to the boiler? And are the TRVs fitted on the flow pipes to the rads, the ones that heat up first?
If you do any adjustment of the ls, first mark the spindle, or tape a wee proper flag to it, so you can always return to the original point.
I think it's always useful to know just how far open it is to begin with, in case it's waaaay out. So, wee flag, and then turn it clockwise until it's fully off, counting the full and part turns this takes.
If you report back, we can probably I indicate if it's nuts.

moneytalks

In answer to your questions 
1. They do warm up slightly faster
2.Yes they are closer to the boiler
3. Yes, fitted to flow pipes

moneytalks

NB your temp is possibly a tad on the high side and you may be more energy efficient (fully condensing) if you can go a bit lower.

Will I try at 55-58?

ThisIsWeird

moneytalks said:

In answer to your questions 
1. They do warm up slightly faster
2.Yes they are closer to the boiler
3. Yes, fitted to flow pipes

Ok, they are fitted to the flow pipes, so it won't be a case that they are one-directional TRVs fitted incorrectly.

No harm in trying tweaks to the l/s, as long as you can always return them to the original setting if needed.

Let us know how 'open' they currently are, please.

ThisIsWeird

moneytalks said:

NB your temp is possibly a tad on the high side and you may be more energy efficient (fully condensing) if you can go a bit lower.

Will I try at 55-58?

Every bit helps, but you don't want the rads to be so cool that they struggle to heat the house. Now that the weather is improving, you can probably get away with ~55oC, but always be ready to turn it back up if a cold spell arrives, and your CH struggles.

How old is this Baxi? I wonder if it could handle Smart controls which could have features such as 'weather compensation' (ie, they'll turn the flow temp down as the weather warms up), and Opentherm (and other protocols) that will also adjust the flow temp to suit demand - ie, instead of hovering between 58 and 62oC, as the house approaches the chosen temp, it'll turn the output temp right down to try and approach the set temp gently, and then try and maintain the desired temp by backing off the flow temp, rather than just going 'click' when the set temp is reached.

moneytalks

ThisIsWeird said:

moneytalks said:

NB your temp is possibly a tad on the high side and you may be more energy efficient (fully condensing) if you can go a bit lower.

Will I try at 55-58?

Every bit helps, but you don't want the rads to be so cool that they struggle to heat the house. Now that the weather is improving, you can probably get away with ~55oC, but always be ready to turn it back up if a cold spell arrives, and your CH struggles.

How old is this Baxi? I wonder if it could handle Smart controls which could have features such as 'weather compensation' (ie, they'll turn the flow temp down as the weather warms up), and Opentherm (and other protocols) that will also adjust the flow temp to suit demand - ie, instead of hovering between 58 and 62oC, as the house approaches the chosen temp, it'll turn the output temp right down to try and approach the set temp gently, and then try and maintain the desired temp by backing off the flow temp, rather than just going 'click' when the set temp is reached.

It’s 4 years old

ThisIsWeird

moneytalks said:

ThisIsWeird said:

moneytalks said:

NB your temp is possibly a tad on the high side and you may be more energy efficient (fully condensing) if you can go a bit lower.

Will I try at 55-58?

Every bit helps, but you don't want the rads to be so cool that they struggle to heat the house. Now that the weather is improving, you can probably get away with ~55oC, but always be ready to turn it back up if a cold spell arrives, and your CH struggles.

How old is this Baxi? I wonder if it could handle Smart controls which could have features such as 'weather compensation' (ie, they'll turn the flow temp down as the weather warms up), and Opentherm (and other protocols) that will also adjust the flow temp to suit demand - ie, instead of hovering between 58 and 62oC, as the house approaches the chosen temp, it'll turn the output temp right down to try and approach the set temp gently, and then try and maintain the desired temp by backing off the flow temp, rather than just going 'click' when the set temp is reached.

It’s 4 years old

So surely should be Smartable if you wanted to.

Get the exact model, and ask Baxi what the best controls for it are. There will be lots of 3rd-party options out there too, of course.

What timer and room thermostat do you currently have?

FreeBear

moneytalks said: I’m thinking the lock shield needs adjusted, am I on the right lines?

It it just possible that the lockshield needs adjusting, but to do it properly requires a thermometer to be attached to the pipes either end of the radiator. With the system up to temperature and the TRVs open on all radiators, you then adjust the lockshield to get a nominal 20°C difference at a 70°C flow temperature. For lower flow temperatures, use the formula

ΔT = Flow Temp * 0.3

You may well need to turn the pump speed down if you find it difficult to get the required ΔT.

With fan assisted plinth heaters, a ΔT of 10°C or even 5°C is more appropriate regardless of flow temperature & pump speed.