Danfoss RAS-C2 TRV's radiator value adjustment

[mogget]

Why not just take the simple option and turn the 'duff' trv down a bit.

In my experience trv calibration can vary from new.

 

[PJ-DIY]

Why not just take the simple option and turn the 'duff' trv down a bit.

In my experience trv calibration can vary from new.

You will like this mogget...

Because the cats sleep in that room and the wife doesn't want the temperature to drop under 16-17 degrees at night

At present the heating is usually around 18.8 when we get up but cold nights have not arrived yet.

I have put rad TRV on 2 this morning instead of 2.5 (heating off until 7pm). I will sit by the radiator from 6:45pm and check temperatures and radiator has timer actives. Subject to what happens tonight, I guess the radiator will definitely come on by 7.05pm regardless of room temperature, tomorrow I may wind it up to '3' and do the same, if only to test if the rad comes on at 7pm when timer clicks in.

I have also turned the TRV off and back to full a few times up and down before putting it at 2. I have done this previously and it made no difference.

Heating was installed from new two years ago, when we retired, at first we thought maybe it would level itself out! Full new installation including gas supply from the road.

 

[D_Hailsham]

RAS-C2 Instructions

It might be worth checking that the flow control is correctly set. Also that the head is correctly fitted - make sure it is set to maximum when fitting.

If no joy, try swapping heads.

If still no luck, the rad is probably way out of balance (have you checked this?), so the pressure across the valve is too high and it is being kept open.

 

[PJ-DIY]

The heat loss from a room is determined by its dimensions and construction, and by its surroundings - adjacent rooms etc. Just because one room has a heat loss of 2kW and another 4kW does not mean that the temperature in the 4kW room will drop twice as fast as the 2kW room.

The room is a conservatory, it was only built February this year. It extends just over 4m although 55% of this are existing walls to rear of bungalow and kitchen that extends part way. The roof is also glass. The Glass in the roof retains 70-75% of the heat, the glass in the sides retain approx 45-50% of the heat. Prior to fitting the radiator the plumber calculated the rad size, I did the same using a calculator on the internet. Taking into consideration all these factors the plumbers rad size (output) was slightly less than my calculation, we discussed it at the time and increased the rad output size by an extra 50% so we have a double convector radiator certainly capable of sufficient output as required.

The rad size is therefore not an issue but the workings of the TRV certainly do appear to be a problem. I considered general convection may be an issue due to the type of room but this doesn't add up either. I expected maybe the temperature near the TRV must be much lower then in the middle of the room that was not the case either.

Note: the special glass in the conservatory is not just effective against heat loss but also for heat gain. It was definitely worth the money, we can sit there in the sunniest of days and not suffer from over heating from the sun outside. Heating in the conservatory is balanced but naturally heat loss, though small, is faster than the rest of the bungalow which has cavity and extra thickness loft insulation, more so when we have sub zero temperatures naturally.

So although the thermal efficiency of the bungalow is good, including the conservatory, naturally heat loss in the conservatory is greater than the rest of the bungalow. This brings me to the second concern (the first being the TRV on the conservatory rad), if the hall warms up and knocks off the temperature via the room stat, the system switches off. The heat in the bungalow will reduce slowly, the heat in the conservatory will reduce quicker. Therefore the conservatory will be demanding the heat to raise but cannot do so as the temperature near the room stat isn't low enough to trigger the heating to come back on again.

I hope all that makes sense.

 

[Agile]

I k that you are failing to understand that you cannot expect a thermostat in the house to effectively control a conservatory with higher heat losses.


The real fault is that building regulations require a conservatory to be equipped as a separate heating zone so that you don't have the problems that you are experiencing.

The plumber does not seem to have been helpful as he should have know about all these issues.

Or perhaps he correctly advised you and you refused to pay for the separate heating zone to be installed?

Tony

 

[PJ-DIY]

I k that you are failing to understand that you cannot expect a thermostat in the house to effectively control a conservatory with higher heat losses.


The real fault is that building regulations require a conservatory to be equipped as a separate heating zone so that you don't have the problems that you are experiencing.

The plumber does not seem to have been helpful as he should have know about all these issues.

Or perhaps he correctly advised you and you refused to pay for the separate heating zone to be installed?

Tony

Hi Tony

We were not informed of any items you have stated, the plumber just took it as another radiator in another room. I requested the increased size radiator so that it was man enough for the job.

I hadn't mentioned conservatory up to this stage so that it didn't influence the reply to the issues. But having now done so, I have confirmed the efficiency of the glass, we paid to get the most efficient, considering both heat loss and heat gain, but naturally compared to the thermally efficient bungalow the conservatory is naturally not as efficient.

So as I see it there are two issues still to find a way round or find the reason for what appears to be a fault.


1 - is the radiator valve

2 - is the room stat issue vs the conservatory heat loss.

Item 2 - I do wonder if the room stat would be better in the conservatory as that would then dictate he heating requests and the TRV's in other rooms would only come on if needed. But I also do not know if a room stat would still work wired to the conservatory a distance of probably 7 to 8m allowing for rise and fall of wiring not just distance as the crow flies.

 

[PJ-DIY]

RAS-C2 Instructions

It might be worth checking that the flow control is correctly set. Also that the head is correctly fitted - make sure it is set to maximum when fitting.

If no joy, try swapping heads.

If still no luck, the rad is probably way out of balance (have you checked this?), so the pressure across the valve is too high and it is being kept open.

Hi

I did say to my wife earlier this morning maybe we should check which end of the radiator pipes get warm first when the heating comes on so as to be certain the flow and return are correctly installed. Thank you.

Now this brings me to the next issue, I need to find out what is wrong before I involve a plumber/heating engineer. Unfortunately due to my disability I cannot get down to do any of these checks, I have to get my wife to do the basic low level items, anything from plugging in a mains plug, etc, but cannot expect her to start looking at or playing with the valves.

I could ask the original plumber who was very meticulous, but as it now seems didn't know about Building Regulation requirements for heating in a conservatory or I could ask the one our neighbour has used and being happy with for years. We did ask him to price the job initially but he didn't want any involvement with the trench for the new gas supply.

I thank everyone for your help, I just need to be clear of why we have the faults and how we can get round them before I involve a plumber.

 

[D_Hailsham]

Apart from Building Regs requiring a separate circuit, with separate controls, if an extra radiator has been added to the system and the installer hasn't bothered to re-balance the system, no wonder you are having problem.

I can understand now why you have not checked the balance.

The conservatory will cool down faster than the rest of the property because it has a smaller heat capacity. This is one of the reasons why Building Regs require "external standard" walls and doors between the conservatory and the rest of the house and a separate circuit with separate controls.

See Approved Document L1B paras 3.15, 4.8 and 4.9.

 

[PJ-DIY]

With your help guys, we appear to be getting a better picture of 'all' the issues with the radiator/TRV in the conservatory.

Results of tests when heating came on at 7pm tonight ~ Room temperature 23.1 C

• radiator TRV on #2, heating 'didn't come on' (interesting)
• waited 15 minutes then raised TRV to #2.5 - within 5 minutes the heating started to come through (as it did last night)
• got my wife to check which pipe to valve got warm/hot first - result the wrong end! (not TRV valve end)

1. This seems to me that the valve may not be installed correctly or possibly it is not working at the right/expected temperature?
2. Can a radiator work correctly with the hot water coming in from the wrong end first???

I am looking at the diagrams on the link provided earlier when I ask question 2 above.
http://heating.danfoss.com/PCMPDF/013R9355_RAS_C2_Keymark_VISXM302_.pdf

 

[mogget]

1 it would seem that the valve is working correctly but has maybe drifted somewhat out of adjustment.

2 yes but the trv needs to be bi-directional, I think yours are but having never used that model am unsure (Danfoss not Drayton)

 

[PJ-DIY]

Apart from Building Regs requiring a separate circuit, with separate controls, if an extra radiator has been added to the system and the installer hasn't bothered to re-balance the system, no wonder you are having problem.

I can understand now why you have not checked the balance.

The conservatory will cool down faster than the rest of the property because it has a smaller heat capacity. This is one of the reasons why Building Regs require "external standard" walls and doors between the conservatory and the rest of the house and a separate circuit with separate controls.

See Approved Document L1B paras 3.15, 4.8 and 4.9.

Interesting thanks

 

[PJ-DIY]

1 it would seem that the valve is working correctly but has maybe drifted somewhat out of adjustment.

2 yes but the trv needs to be bi-directional, I think yours are but having never used that model am unsure (Danfoss not Drayton)

This would now appear to make more sense why the heating appears to be switching on when the TRV is set at a low temperature, yet the room temperature is much higher. Especially as the temperature the following morning appears reasonable.

So we have worked out the valve is working, (just on lower number settings than expected), and as the heating in the room appears to be around 19 C the following morning it must be set for bi-directional flow. (and may be balanced???)

I will wait for replies from you guys before going back to other issues. Best sort this first, although it appears to me subject to what you guys think we now understand what is happening and why things seemed the way they did.

Thanks everyone for your help, it is appreciated.

 

[Agile]

Putting your room stat in the conservatory would overcome most of your problems.

A wired stat can operate at over 100m so distance is not going to be a big problem.

Alternately you could use a wireless stat.

Or you could use a wireless programmable stat wired in parallel with the existing hall one.

Then you could set it at more appropriate times so that its not heated when heat is not required.

I never can understand why some people want to heat a conservatory all year round. I don't really believe that many people occupy them after dark when they look like fish in a goldfish bowl !

 

[D_Hailsham]

1. This seems to me that the valve may not be installed correctly or possibly it is not working at the right/expected temperature?2. Can a radiator work correctly with the hot water coming in from the wrong end first???

I am looking at the diagrams on the link provided earlier when I ask question 2 above.
http://heating.danfoss.com/PCMPDF/013R9355_RAS_C2_Keymark_VISXM302_.pdf

1. If it is the Danfoss RAS-C2, then yes it is can go on either end - as shown in the link's diagrams. Setting the flow adjuster may help.
2. There is no right and wrong end on a typical radiator (there are exceptions, e.g some vertical designer rads). All the TRV does is control the flow through the radiator.

Have you tried swapping the TRV head for another one?

 

[PJ-DIY]

Putting your room stat in the conservatory would overcome most of your problems.

A wired stat can operate at over 100m so distance is not going to be a big problem.

Alternately you could use a wireless stat.

Or you could use a wireless programmable stat wired in parallel with the existing hall one.

Then you could set it at more appropriate times so that its not heated when heat is not required.

I never can understand why some people want to heat a conservatory all year round. I don't really believe that many people occupy them after dark when they look like fish in a goldfish bowl !

I never sleep well and so often end up lying in bed for hours with a wondering mind, last night was another of them nights, I suddenly thought what about a wireless room-stat? Bingo this morning you are there with the suggestion.

I am not sure about having both in parallel but can see many advantages of a wireless room stat. One obvious one is the stat can be tried in so many different positions to ensure to best position is found. Being a conservatory, even though it has energy efficient glazing does have an increase in temperature from the sun. But after pondering this in my mind in the small hours of the night I do not see that as an issue.

Regarding your last comment, I understand what you are saying, maybe it is the sit in front of the fire situation we are all used to but, the conservatory is carpeted, has blinds, a table and two chairs, a welsh dresser and a wine rack. Nearly forgot two Lazboy chairs, a recline for the wife and an electric chair (as my wife calls it) for me. The walls take up 50% ass the conservatory is built off the rear wall, between the kitchen that extends and the neighbours wall so the there is on 50% glass. The roof however is all glass, thermally efficient and tinted blue. It is a roof to the bungalow not a conservatory built out on its own.

Due to the fact we both have long term illnesses and I am disabled, I cannot walk far, I cannot stand for long, ten minutes max. the room, overlooking the garden, is nice all year round. There is always nature to watch winter and summer, it is a peace and quiet room, ideal for reading and relaxing in. That is what the cats told me

I will have a look for a wireless room stat I think, it seems a good ideal. I will just need to make sure it is capable of working through an insulated cavity wall.

Thank you