Not enough Heat

[Wagger]

We have recently had oil fired central heating installed.
All radiators have TRVs. We also have a system thermostat inthe hall, set at 25 degrees.
When the heating is first switched on all radiators becomehot or very hot but our rooms and the main thermostat reach only 19/21 degrees.After around 2 hours the radiators furthest from the boiler start to cool andwhile they warm up intermittently the rooms never get above 19/21. All TRVs areset at 5.
The system has been balanced and we are satisfied that thisis not a boiler problem. Our plumber is stumped. Any ideas?

 

[rpm]

Can`t help I`m afraid, but thanks for registering and welcome to the forum Wagger.

 

[stevetheplumber]

i would disconect the room stat and see if the rooms get hot then if they do its a romstat positioning problem if they dont its either rads pipework or boiler to small

 

[joni os]

If not the room stat. Is your boiler modulating correctly.

 

[ShaunCorbs]

if boiler is still fired and furthest rad is cold not the room stat

 

[snowhead]

Was the system designed (radiator sizes and boiler size) to work at 25 degrees?

Is 5 the maximum on the TRV?

Is the boiler cycling on and off when the temperature is 19 / 21 or is it running continuously?

 

[Wagger]

Thanks. It looks wired in and I don't know how to disconnect it. However, the stat has been replaced and made no difference. We also tried increasing the temp with a hair drier and were able to do so. Of course, it could be a problem with the connection as the stat is wired into a complicated box and I don't know what is happening in there.

 

[Wagger]

Thanks Snowhead. Answers : I don't know for certain but it should be OK . However, I suspect in some rooms the radiator may be too small although not in others where ther is the same problem.
Yes 5 is the max.
Boiler is cycling on and off when at 19/20

 

[Wagger]

Sorry Joni os, I'm not an expert I don't know what you mean by boiler modulating.

 

[Wagger]

Thanks ShaunCobs. I'll check that out.

 

[doitmyself]

We have recently had oil fired central heating installed.
All radiators have TRVs. We also have a system thermostat inthe hall, set at 25 degrees.
When the heating is first switched on all radiators becomehot or very hot but our rooms and the main thermostat reach only 19/21 degrees.After around 2 hours the radiators furthest from the boiler start to cool andwhile they warm up intermittently the rooms never get above 19/21. All TRVs are set at 5.
The system has been balanced and we are satisfied that this is not a boiler problem. Our plumber is stumped. Any ideas?

What was the design temperature of the system? 21C is the norm. If you don't know, ask the system designer/installer.

What is the outside temperature? Most systems are designed assuming it is -1C or -3C.

Which boiler do you have - make and exact model?

How do you know the system has been correctly balanced?

 

[AllyBongo]

Boiler make, model and size? How many rads? Boiler been commissioned properly?

 

[joni os]

Modulating. New super efficient boilers can recognise demand and adjust output accordingly. Previously humans brains did a similar but less complicated function by adjusting thermostatic control knob. As the brain of a boiler is zero the propensity to malfunction is now included by design.

 

[snowhead]

I don't know what you mean by boiler modulating.

Boiler stays on but the flame reduces so the heat output is lower

 

[Chalked]

Boiler stays on but the flame reduces so the heat output is lower

As its oil. I'm pretty sure modulating isn't an option! :chinese:

 

[joni os]

As its oil. I'm pretty sure modulating isn't an option! :chinese:

Sorry to say, even oil boilers have been infected.

 

[Chalked]

Sorry to say, even oil boilers have been infected.

I stand corrected.

Which ones? And how are they modulating a pressure jet?

Thanks ( sorry to hijack the thread)

 

[SimonG]

There's not many modulating oil boilers in the domestic market. Do the new blue flame ones modulate?

 

[joni os]

WB have a boiler that adjusts 12- 18 Kw. Literature says interactive. ie. does its own thing.

 

[SimonG]

WB have a boiler that adjusts 12- 18 Kw. Literature says interactive. ie. does its own thing.

Will have to have a look at that. Sounds like more sooty boilers when the system goes breasts up.

 

[SimonG]

To the OP. Has the boiler been commissioned and set up correctly? If it's not a modulating one then they run on a range of outputs. Different nozzles and settings will give you different outputs.

 

[Worcester]

Silly question... Do the radiators close to / in the same location as the room stats have TRV's on them?

 

[Worcester]

Aha !!!!

All radiators have TRVs.

 

[Nostrum]

Oil boilers don't modulate, you can only change the fixed output by changing nozzle sizes. Yes, they exist, but not in any great numbers here in the UK.

Even the blue flame technology is fixed output as far as I'm aware (Firebird have just launched one)

If the rads are at the right temperature and the room is cold, the rads are undersized or all the windows are open.

 

[Nostrum]

Actually, reading the post again; they may be sized accordingly, depending on what temperatures the rooms were designed for. Generally, 18 degrees is sufficient for bedrooms, 21 degrees for others. How hot do you find you need it to be to be comfortable?

25 degrees is pretty warm !

 

[Norcs]

Yes .. sounds like its working fine. The OP should invest in some wooly jumpers.
Modulating oil boilers. LoL.

 

[Wagger]

Thanks doitmyself. Answers. Will have to ask installer but when I said we wanted to get it up to 25c he didn't say that was not possible.
Temp outside been 5/8c not very cold.
Worcester Bosch Greenstar Danesmoor Ext 12/18
I saw the installer carry out the work when he came back to have a look at it but, of course, I don't know how well he did it.

 

[Wagger]

Greenstar Danesmoor ext 12/18.
9 rads - 1 v small.
Yes, has been commissioned separately

 

[Norcs]

he didn't say that was not possible

OOh dear. He shot himself in the foot there.
Was that before or after the installation was carried out?

Bigger rad needed probably.

 

[Wagger]

Yes they do but installer said that this was OK providing the TRVs were left o highest setting -5. What do you think?