Worcester 30CDI - Boiler Operating Temperature & More...

[nh001]

Recently had a 30CDI fitted and had a few problems. The installer has been back a couple of times but getting there. A couple of questions if anybody can help.

1 - Can anybody tell me what the boiler temperate should show if set on 5 or 6? I tend to get between late 60 degrees to early 70s but that seems to take a long time to heat the house.

2 - Also - the rads are hot but every so often a couple of them cool (TRVs are fitted) and these are nearest to the boiler - could this be balancing issue?

3 - Finally, I note that I have a TRV fitted in the room where room temp controller is and this is one than goes cool. Hence very rarely gets to room temp so boiler always working. I guess I need to get TVR replaced with open value?

Any help appreciated.

 

[D_Hailsham]

1 - Can anybody tell me what the boiler temperate should show if set on 5 or 6? I tend to get between late 60 degrees to early 70s but that seems to take a long time to heat the house.

1 is 40°C and Max is 90°C. Assuming the control is linear, 5 should be about 73°C and 6 about 81°C.

Has the boiler been range-rated, i.e. the max output reduced for heating?

2 - Also - the rads are hot but every so often a couple of them cool (TRVs are fitted) and these are nearest to the boiler - could this be balancing issue?

Quite possibly. Some installers have the mistaken idea that rads with TRVs do not need balancing.

3 - Finally, I note that I have a TRV fitted in the room where room temp controller is and this is one than goes cool. Hence very rarely gets to room temp so boiler always working. I guess I need to get TRV replaced with open valve?

That's the best solution. You could, however, just remove the TRV head or set it to MAX.

 

[nh001]

Thanks for reply.

I spoke to Worcester this am and they say at Max (7) it should be around 88C that makes sense. They suggested getting installer back or to get one of their guys out. On 5 I am getting about 64 and 6 about 70.

Not sure on the range testing - when I complained it was cold he came back and turned up boiler (from 5 to Max) and changed the pump from setting 2 to 3.

After spending quite a lot on this would like to get this right.

 

[D_Hailsham]

On 5 I am getting about 64 and 6 about 70.

Is the boiler continually going on and off? If so this could be the problem - it is never able to get up to temperature. This could be because the boiler is producing more heat than the radiators can use.

You can estimate your total rad output by using the info in Stelrad Elite Catalogue

Not sure on the range testing - when I complained it was cold he came back and turned up boiler (from 5 to Max) and changed the pump from setting 2 to 3.

Did that improve things or make it worse?

 

[nh001]

No boiler is always on (green light to show burner running) as the room with room stat (and TVR) never reaches 21 degrees where it is set to. Normally gets to 19 degrees before radiator shuts down.

When boiler and pump turned up this did help but was still relatively warm outside - I am feeling it now colder!

 

[D_Hailsham]

No boiler is always on (green light to show burner running) as the room with room stat (and TVR) never reaches 21 degrees where it is set to. Normally gets to 19 degrees before radiator shuts down.

Where is the room stat in relation to the radiator?

Remove the TRV head so it is fully open. Then report what effect this has, if any.

Check out your rad output - link given earlier.

Another thing to check is the actual heating requirement of your house. Use the EST online boiler calculator

Post the results of both rad output and boiler size checks.

 

[nh001]

Radiator is opposite side of room from room stat that I know won't help.

Radiator output is 1691 watts / 5769 Btu/Hr.

TVR is off but looks like pin maybe stuck down so need to loosen but will advise.

Very quickly done the boiler check and comes out at 27Kw that seems about right.

 

[D_Hailsham]

Radiator is opposite side of room from room stat that I know won't help.

At least the rad is not underneath the room stat.

Radiator output is 1691 watts / 5769 Btu/Hr.

I was actually suggesting that you find out the total output of all your rads and compare this with that provided by the boiler calculator.

TVR is off but looks like pin maybe stuck down so need to loosen but will advise.

If the pin is stuck down the local rad would be off, so the room stat would take longer to reach temperature and possibly never turn off

Very quickly done the boiler check and comes out at 27Kw that seems about right.

You must have a very large house.

 

[nh001]

Very quickly done the boiler check and comes out at 27Kw that seems about right.

You must have a very large house.

Yes - 4 floor victorian!

I have some rooms with no rads and underfloor heating so gets complicated. I think I will get TVR removed and boiler checked as seems to be low heat output.

 

[D_Hailsham]

Yes - 4 floor victorian!

Ah, solid walls - so no cavity insulation, single glazed sash windows with half inch gaps to let the heat out. You might have a warmer house if you relit all the open fires and threw £50 notes on them

 

[nh001]

Not far off - double glazed but single walls. The kitchen is always warm when the fire is lit but normally go for coal!

 

[nh001]

OK - head off TVR and have set room stat to 25 (not that would ever run it that high ongoing). Boiler is set high (6) and room has got to 20 without much effort so will see if gets higher. I am guessing around 21 is where I want it in winter.

I've also done some running of the boiler at different settings and just had a reply from Worcester from an earlier email.

As a summary (but know all approx. estimates):

For setting 5 Worcester say 67 and Dh said 73. Boiler is getting to 65 so not far off.

For setting 6 Worcester say 75 and Dh said 81. Boiler is getting to 71 so a bit further away.

For setting Max Worcester say 88 (that seems a big jump to me) and boiler is getting to 74. Big difference here.

I think I read somewhere that optimum temp is 80 for efficiency so probably do need to get the boiler looked at. However, I may just be a bit impatient at the time takes to heat the rooms.

 

[D_Hailsham]

Try setting the pump back to 2. If the pump is going too fast the water does not have time to heat up before it is whisked away, so to speak.

One factor to consider is the effect of the temperature difference between flow and return. Older boilers were designed for a temperature difference of 11°C, modern one, like your WB work with a 20°C difference. The problem the is that the radiators do not give off so much heat, approx 15% less. This means that, if you rads were sized for an 11°C boiler and you now install a 20°C boiler, your rads will not be producing as much heat.

A second consideration is whether the system has been properly balanced.

 

[nh001]

Quick update and think about there.

Had the TVR replaced in room with stat and that has made a huge difference. Also reduced pump setting back to 2 and rooms are getting much warmer.

Finally, I noticed that if you turn the boiler up you need to give is an extra bit of a turn to get it onto the max setting (you should hear a click). This gets the temp to 84 which is near enough to the 88 I was told so happy with this.

Thanks for all help.

PS. I am assuming ideal pressure is around 1.2 bar and does anybody know the temp boiler should operate at to be most efficient?

 

[D_Hailsham]

Also reduced pump setting back to 2 and rooms are getting much warmer.

Thought it might help

does anybody know the temp boiler should operate at to be most efficient?

A temperature of 75°C or less will be the most efficient, provided you can maintain a comfortable house. This will ensure that the return temperature is below 55°C, which is necessary if the boiler is going to condense.