Best settings for room thermostat, TRVs and boiler stat?

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RESULTS OF BALANCING

Before I started, the lockshield valves were all very different settings - a couple pretty much fully open (5 turns or so).

After 4 rounds, the rads felt pretty close in temperature. I was surprised that I did not have to open them far - the least was only set at the initial quarter turn open. The most at one full turn open.

OTHER THINGS I FOUND OUT

The boiler can easily heat all the rads really hot really quickly - so no problem there (ie with all stats set to max).

When they are all better balanced, it all seems to heat up quicker and more evenly than before. (success!)

The boiler stat seems to work. If I set it low, the rads are cooler than if set high. Next to the stat dial it lists flow temperatures - from 1 = 54 deg C to 6 = 82 deg C.

I borrowed a friend's infra-red surface temperature sensor and these are the rough average rad temps for each boiler setting I tried:

Setting 1 (flow 54C) rads at 49C
Setting 3 (flow 66C) rads at 56C
Setting 6 (flow 82C) rads at 69C

At 69C average, the individual rads were +/-7C from this.


QUESTIONS

1. Would you expect only to have the small openings of lockshield valves that I have?

2. Given the flow and rad temps I can get with the boiler, what would you set the boiler stat at?

3. Now I can measure temperatures of the rads, how close together in temp should I aim to get them (now +/-7C) if I re-balance?

4. One rad has a stuck (corroded) lock shield valve - it is the first in the flow - do I need to get this valve changed?

5. One rad seems to have the TRV on the outlet, not the inlet (found as a felt the first hot water circulate) is this a problem?

Thanks again.

 

[ajrobb]

Still speaking as a novice:

1. Would you expect only to have the small openings of lockshield valves that I have?

As you've got a couple open a full turn, you might be OK. There is not usually much difference between 1.5 turns and fully open.

2. Given the flow and rad temps I can get with the boiler, what would you set the boiler stat at?

I'd tackle the hot water next. You should set the RAVI to give you 60°C and make sure the boiler temperature is high enough so the RAVI closes within an hour (roughly).

3. Now I can measure temperatures of the rads, how close together in temp should I aim to get them (now +/-7C) if I re-balance?

Once the TRVs reach their set temperature, they change the radiator temperatures, so it is not vital they be the same with the TRVs open.

4. One rad has a stuck (corroded) lock shield valve - it is the first in the flow - do I need to get this valve changed?

All the radiators are getting hot quickly, so it doesn't seem to be causing major problems. Keep it on the list of things to do.

5. One rad seems to have the TRV on the outlet, not the inlet (found as a felt the first hot water circulate) is this a problem?

Modern TRVs can usually cope with flow in either direction.

You have two control systems, TRV and room thermostat, trying to control the through lounge temperature. Try setting the TRV to maximum on at least one radiator in the lounge so the radiator is controlled by the room thermostat. Otherwise you might waste more heat from poorly insulated pipes outside the 'heating envelope' (e.g. under a suspended ground floor). To cut down draughts, I choose to keep the radiator under the window at maximum.

 

[D_Hailsham]

1. Would you expect only to have the small openings of lockshield valves that I have?

Yes. The design of most L/S valves means that they are full open when about 1½ turns open. This means all adjustment must be made within that range. How much open the valve needs to be will be related to the size of radiator as you are really adjusting the flow rate, which is proportional to the rad output.

2. Given the flow and rad temps I can get with the boiler, what would you set the boiler stat at?

It needs to be at least 70°C to enable the HW cylinder to heat up to 60°C in a reasonable time.

3. Now I can measure temperatures of the rads, how close together in temp should I aim to get them (now +/-7C) if I re-balance?

It's not the surface temperature of the rad which you need to measure but the pipes entering and leaving the rad. See How to balance a CH system.

Don't expect perfection. Balance so you get the same drop across the radiators as across the boiler, even if it not 11°C.

4. One rad has a stuck (corroded) lock shield valve - it is the first in the flow - do I need to get this valve changed?

Might be a good idea as it may be wide open and really needs to be almost closed. You should be able to change it without draining down by bunging the feed and expansion tank. Get a Drayton Draineasy kit from B&Q etc. Make sure you protect the carpet.

5. One rad seems to have the TRV on the outlet, not the inlet (found as a felt the first hot water circulate) is this a problem?

Check the arrow(s) on the valve body. If two arrows at 90°, it does not matter which end it goes. But if there is only one arrow, it must point away from the rad.

 

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D_Hailsham - thanks again. I'll re-do this balancing.

Re-reading the balancing FAQ I see that some of my questions were answered there - so apologies for not spotting that.

The infra-red thermometer I have should allow me to do the inlet/outlet stuff and hopefully I am close to the right settings.