No Central Heating only - fine on HW and CH or HW only

[Wildeman]

1. Yes
2. Also check that TRV pin can be pressed down and jumps up when released. Opening the LS valve will upset the balance so some rads may not get as hot as others.
3. Yes - as a starting point; it can be adjusted later.
4. Max is approx 82C; 75C should be all you need.
5. Worth checking all three options work.
6. Be careful using an IR thermometer on copper pipe as it may under-read by a considerable amount. It's best to wrap the pipe with black insulating tape and hold the thermometer right against the tape.

Let us know how you get on; we can discuss balancing later. You did remember to note the LS valve positions?!!

Thanks

In item 2 the balance is none existant but are you saying to NOT fully open all LSV's - if so what position should they be in?
In item 6 when you mention hold the thermometer right against the tape do you mean the infrared one as that is the only thermometer I have - or should I buy one and if so which type?

I have not commenced the testing yet but will when I get home and will note the LSV positions once you advise what they should be set to for this test.

 

[D_Hailsham]

2. Also check that TRV pin can be pressed down and jumps up when released. Opening the LS valve will upset the balance so some rads may not get as hot as others.6. Be careful using an IR thermometer on copper pipe as it may under-read by a considerable amount. It's best to wrap the pipe with black insulating tape and hold the thermometer right against the tape.

In item 2 the balance is none existant but are you saying to NOT fully open all LSV's - if so what position should they be in?
In item 6 when you mention hold the thermometer right against the tape do you mean the infrared one as that is the only thermometer I have - or should I buy one and if so which type?

I have not commenced the testing yet but will when I get home and will note the LSV positions once you advise what they should be set to for this test.

2. Fully open is fine for the test. I was just warning you that the rads further from the boiler may not get so hot as those nearer

6. I'm talking about the IR thermometer. They rely on the emissivity of the material being measured and are calibrated for a value of 0.95. Copper pipe can have an emissivity as low as 0.03. Plastic insulation tape will be about 0.9.

 

[Agile]

The correct type would be a contact thermocouple thermometer.

For comparative measurements an IR thermometer can be used because the inaccuracy cancels out when used for differential measurements like flow and return temperatures.

But IR types, whilst easy to use quickly, are not suitable for situations where an accurate measurement is needed.

Tony

 

[D_Hailsham]

Even a contact thermocouple thermometer will only measure the temperature to an accuracy specified by the manufacturer.

If IR thermometers are so inaccurate, why are they used so often in hospitals?

If you check out a table of emissivities you will see some materials where you do not need to use black insulating tape. For example: paint - 0.96 (no mention of colour); marble, white - 0.95; plaster - 0.98; water - 0.95 - 0.963.

So, providing the rad pipes have been painted there is no real need to use insulating tape - provided you hold the thermometer close enough to the pipe so it doesn't take into account the surrounding materials. Bare copper pipe is the real culprit as even when it is old and well oxidized the emissivity is about 0.78, so the thermometer will under-read by about 20%.

 

[Agile]

IR thermometers are accurate in the sense of giving accurate readings.

BUT their readings depend totally on the nature of the surface being measured.

They do seem to give a very accurate reading to measure body temperature inside the mouth.

Tony

 

[D_Hailsham]

IR thermometers are accurate in the sense of giving accurate readings.

BUT their readings depend totally on the nature of the surface being measured.

They do seem to give a very accurate reading to measure body temperature inside the mouth.

Tony

At least we are in agreement about the relevance of the surface so, provided the necessary precautions are taken, they are suitable for measuring pipe temperatures.

I have never seen one used to measure the temperature in the mouth; it's usually the ear.

 

[Agile]

Not sure where you have seen that.

I have just measured an ear and that was 32 C and the mouth was 36 C. ( The same live person before you ask )

Since the normal body temperature is meant to be around 36 C then I would suggest measuring in the mouth is far more accurate.

Tony

 

[D_Hailsham]

Let's agree to differ as in all my many visits to a hospital I have never seen or experienced using the mouth to measure temperature. It has always been the ear. Maybe the hospital thermometers are calibrated for the emissivity of a typical ear.

 

[dilalio]

What's wrong with the good old thermometer up the arris?

Or is that for core temp on dogs

 

[Agile]

Let's agree to differ as in all my many visits to a hospital I have never seen or experienced using the mouth to measure temperature. It has always been the ear.

I always try to stay away from Hospitals but certainly in Carry on Doctor film they used to use a mercury in glass thermometer in the mouth, under the tongue!

 

[Wildeman]

2. Also check that TRV pin can be pressed down and jumps up when released. Opening the LS valve will upset the balance so some rads may not get as hot as others.6. Be careful using an IR thermometer on copper pipe as it may under-read by a considerable amount. It's best to wrap the pipe with black insulating tape and hold the thermometer right against the tape.

In item 2 the balance is none existant but are you saying to NOT fully open all LSV's - if so what position should they be in?
In item 6 when you mention hold the thermometer right against the tape do you mean the infrared one as that is the only thermometer I have - or should I buy one and if so which type?

I have not commenced the testing yet but will when I get home and will note the LSV positions once you advise what they should be set to for this test.

2. Fully open is fine for the test. I was just warning you that the rads further from the boiler may not get so hot as those nearer

6. I'm talking about the IR thermometer. They rely on the emissivity of the material being measured and are calibrated for a value of 0.95. Copper pipe can have an emissivity as low as 0.03. Plastic insulation tape will be about 0.9.

S

Ok, this is the test plan I have put together for later - is this the best way to troubleshoot further?

1. Measure the gas usage at the meter with no other gas appliance running - only have a gas hob and fire in the lounge (pilot light out) to ascertain the setting of the boiler Min / Mid or Max.

2. Remove the TRV heads from ALL the rad's and fully open all of the LSV's to ensure there is a fully open path to and through ALL the rad's.

3. Set the Pump speed to MAX

4. Turn the boiler thermostat to MAX

5. Turn on the system in CH only mode on the programmer and see if the boiler fires and stays lit and if the rad's get hot.
Or would you first run the heating in CH and DHW mode with both stats turned right up to check ALL rad's get hot and measure the flow and return temps and then turn off the DHW at the programmer or turn down the Cylinder stat?

6. Whilst this is happening measure the flow and return pipe temps at the boiler using an infrared thermometer

If this works in CH only mode how would I then go about balancing the system to adjust the pump speed and LSV settings?

I have been away for a few days so only just getting back to this:

After measuring the gas usage at the meter the boiler appears to be on the Medium Settings which is 16.12kW

I have removed all the TRV heads and opened up all the LSV's and checked the TRV pins to be free, set the pump to max and the boiler thermostat to max

I have confirmed that the CH and works in CH and DHW together mode and the issue is still the same in CH heating only mode.

I am still unable to get the CH only to work - I did manage to get the boiler to fire once in this mode by messing about with the boiler thermometer but it just remained on for 1 min and then went out and no heat in the rad's. I am not having much luck with the measuring the boiler flow and return temps in CH only mode as all I seem to get is 27.8 flow and 27 degrees return. I am using a borrowed IR thermometer. When in CH and DHW the pipe temp to the pump is around 68 degrees and the flow from the boiler is about 68.9 with the return being 68.4

Not sure where to go from here but I have left all the TRV's at maximum and all the LSV's are fully opened - there is a lot of water rushing noise from the rad's and pipework!

 

[D_Hailsham]

I am not having much luck with the measuring the boiler flow and return temps in CH only mode as all I seem to get is 27.8 flow and 27 degrees return. I am using a borrowed IR thermometer. When in CH and DHW the pipe temp to the pump is around 68 degrees and the flow from the boiler is about 68.9 with the return being 68.4

If there's only a small difference between flow and return temperatures then not enough heat is being extracted by the radiators. This could be because the boiler is pumping out more heat than the rads can use, so it short cycles. It might be worthwhile getting the boiler turned down to minimum by a Gas Safe engineer.

Does the pump continue to run for a few minutes after the boiler goes out?

Does the boiler relight after a few minutes?

Have you checked the temperatures at the flow and return pipes of each rad?

Did you use black insulating tape when measuring the temperatures? It makes a considerable difference to the accuracy of reading.

 

[dilalio]

All TRVs and LSVs open and no heat in them in CH mode, but red hot in other modes!

It has to be the mid port valve!

Or if this has "always" been a problem, there is something very wrong with pipework design and layout!

Could the mid port have been replaced upside down? How would that affect the operation? Could it be simple as that? Again... Historical problem or mainly recent? Would it be better to change to an S Plan? I personally do not like Y Plan, but that's me!

 

[jackthom]

That's the crazy thing. If circulation is so terrible through the heating system how do the radiators ever get at all warm in Heating/DHW combined mode?

Why is the pump continuing to run, circulating cool water, yet the boiler doesn't appear to make any further attempts to fire after the first one?

 

[dilalio]

Electrician at fault?!