Ravenheat CSI85 - Stronger Earth???

[Slugbabydotcom]

Aaahhh - so the overheat cut out could kick in because of low flow pressure (or something along those lines)??? To test this, today I left all radiator thermostats on full and controlled room temperature by turning down the heat on the boiler instead.

Now we have something to go on heres my latest thoughts on the matter

Overheat stat cuts in because the water it is sensing is above the 'cut out' temperature.
You need to look into possible reasons why the water might be getting too hot.
Poor flow through the boiler is one reason and can be caused several things.
If theres a setting available on the pump this should be at Max [3]
Are the valves fully open underneath?
Is there a bypass fitted? There should be and it should be set to 3 if its a honeywell one, otherwise just enough for the pump to force it open should all the TRVs close off the rest of the circuit.
Did you get more TRVs fitted with your new boiler to conform to the Chess specification that came in during 2005 ?

Have the max and min pressures been set up on the gas valve as it says in the MI's? Too much gas can boil your water up before your system can circulate it.

Its the CH thermistor that controls the heat of the water in your boiler and although they usually fail on the safe side. Yours being a new boiler will be the clip on type and it could be that it has slipped off the thermal paste and is giving a delayed reading. Sometimes too much thermal paste can cause a problem according to one of my discussions with Ravenheat who say all that is required is a thin smear.
Running your boiler on a lower setting would compensate for this and could be a simple solution. It would also rule out the rare possibilty that your new and old overheat stats are oversensitive, perhaps from a faulty batch.

 

[D_Hailsham]

To test this, today I left all radiator thermostats on full and controlled room temperature by turning down the heat on the boiler instead.

So you do not have a room thermostat Wrong

TRVs on all rads Wrong

No automatic bypass? Wrong

 

[Agile]

when our house gets too warm, we turn down the radiator thermostats. Aaahhh - so the overheat cut out could kick in because of low flow pressure (or something along those lines)??? To test this, today I left all radiator thermostats on full and controlled room temperature by turning down the heat on the boiler instead.

If all the TRVs turn off and the boiler ius still on then there will be no flow as you dont have an auto bypass and that may well cause the boiler to overheat.

I recommend you leave ove TRV on maximum or even take off the head. this is usually most convenient in the bathroom.

Tony

 

[Woolf]

Hi all,

Thanks for your replies. A bypass was fitted at the time of installation - and it's been decided today that the bypass is the problem. It needs 2.38 galls per minute flow, and when the radiator thermostats are low it doesn't get this. So it's been opened fully. This seems like a fairly simple solution and as a layman I wonder why it's taken so many engineer visits and so much hassle to reach this conclusion.

Your messages do raise more interesting points though. We don't have thermostats on all radiators (I didn't say that - I said I left all radiator thermostats on full!) We don't have one on our hall radiator, which is a fairly small one! But we also discussed some of these issues with the engineer and direct with the manufacturer also.

The engineer gave us the impression that we were very much at fault for running our central heating 24/7. Now, (as a layman) I always thought that it was best to avoid switching the boiler on and off regularly. I thought that repeatedly firing the boiler up from cold was uneconomical, and that it was better to keep a nice gentle heat ticking over. I thought that I was economising by turning the radiator thermostats down. Because we are self-employed and working from home, (and we also have a household member who is severely arthritic and needs a gentle heat even in summer), constant heat is a good arrangement for us. I can think of lots of other circumstances where constant domestic heat may be needed: for instance, I think that some stroke victims tend to feel the cold, chemotherapy patients ditto, also the elderly or those who are not fully mobile.

However, the engineer suggested that we were wearing our boiler out by leaving the central heating on 24/7! He said it was like leaving a vacuum cleaner on all the time. (lolol) He may have a point but I wish he'd thought of a better example. At this stage, it just looked as though he was trying to abrogate responsibility for the fracas, and our own temperatures started to rise!!

We also learned about room thermostats. It may seem incredible to you guys, but we knew nothing about this! The engineer suggested that a room thermostat was a prerequisite for installation of this boiler, and that this information was given in the manufacturer's manual. As he left as I was speaking by phone to a technical person - who (according to engineer) was going to give me the page number of the manual where I could find this info. But tech guy said the opposite. He suggested that it is acceptable to leave the boiler on 24/7, and that there is no such instruction about room thermostat in the manual. But he did recommend that we get a room thermostat to make the boiler run efficiently, and we'll do that. No probs. Now that I know what it does, I think it's a great idea. It will save me worrying about the place getting too warm over night.

So - I think it's been an unnecessarily tortuous journey, but we hope that the problem has been solved. I am still a bit concerned about the apparent kitchen-heat cut-outs (although we attribute them to coincidence of problem above), and I'm very interested in your comments Slugbabydotcom, especially about the thermal paste and overheat stats. Thanks again for your replies and fingers crossed. It's freezing out tonight…

 

[Slugbabydotcom]

The engineer gave us the impression that we were very much at fault for running our central heating 24/7.

Confucius say

" A boiler that is turned off burns no gas"

" A room that is not overheated wastes no gas"

OK it was me and not Confucius, but if Confucius was still alive he would probably change the word gas for fuel, apply it globally then claim the fame for it.


Slugbabydotcom say: -

"The lower you set a [room or boiler] thermostat the cheaper your bills going to be and the longer your boiler will last"

Now having said all that, don't forget its your boiler and if you want to run it flat out 24/7 then there's no law against it ........ YET!

 

[D_Hailsham]

A bypass was fitted at the time of installation - and it's been decided today that the bypass is the problem. It needs 2.38 galls per minute flow, and when the radiator thermostats are low it doesn't get this. So it's been opened fully. This seems like a fairly simple solution and as a layman I wonder why it's taken so many engineer visits and so much hassle to reach this conclusion.

Apologies for suggesting there was no bypass.

You don't say, but I trust it is an automatic bypass and not just a gate valve or similar. The bypass should, of course have been adjusted by the installer at time of installation.

When boilers are replaced, they system is supposed to be brought into line with current building regulations, which includes fitting an autobypass. The Benchmark Log at the back of the Ravenheat book asks if an autobypass has been fitted.

We don't have thermostats on all radiators (I didn't say that - I said I left all radiator thermostats on full!) We don't have one on our hall radiator, which is a fairly small one!

My assumption, sorry

I always thought that it was best to avoid switching the boiler on and off regularly. I thought that repeatedly firing the boiler up from cold was uneconomical,

It's not like a car, which uses more fuel when it is cold (remember the choke) On a condensing boiler the gas rate is automatically adjusted to suit the demand

I thought that I was economising by turning the radiator thermostats down.

Not really, if the boiler was not being turned off (no room thermostat) it would continue running until the water in the system reached the temp set on the boiler. It would then cycle on and off to maintain the water at this temp, even if the rooms were up to temp.

The engineer suggested that a room thermostat was a prerequisite for installation of this boiler, and that this information was given in the manufacturer's manual.
But tech guy said the opposite. He suggested that it is acceptable to leave the boiler on 24/7, and that there is no such instruction about room thermostat in the manual. But he did recommend that we get a room thermostat to make the boiler run efficiently, and we'll do that.

Your engineer was quite correct. The Ravenheat installation manual does recommend a room thermostat. It is also a requirement under current Building Regs and is in the Benchmark Log.

What you really need is a programmable thermostat, such as the Honeywell CM907 or 927. This allows you to set up to six different temperatures over a 24 hour period. It also has an optimization feature which means that it knows when to turn the boiler on each morning to bring the house up to the required temperature when you get up. I've got one and it's brilliant. In the recent warmish weather the heating only comes on about 15 minutes before we get up and the house is always up to temp. My wife no longer complains about being cold as the temperature stays virtually constant throughout the day.

Have you had the radiators balanced? It's essential with TRVs, otherwise they do not work properly. You don't say what make TRVs you have but Drayton publish a good guide to balancing TRVs. You can find it at:

http://www.invensyscontrolseurope.c...F-5323-48E3-BD8B-B33ADB04A2E5/7139/D348v2.pdf

 

[JohnD]

... My wife no longer complains about being cold ...

I can't possibly believe that

 

[Woolf]

Hi Slugbabydotcom,

Many thanks for your reply. Confucius is very wise!

And he really did say 'he who will not economise will have to agonise'..

Unfortunately I was trying to economise in the wrong way. But I have always used the boiler control for heat output as well, and (up until the cut-outs with flashing warning light) it had never been set on more that '10 to the hour' (using clock-dial notation). The minimum boiler setting (which I used over our cold, wet summer to take the chill off the misery!) is at the bottom of the dial (or half past the hour). The capacity of this boiler is two thirds more than we've used normally (ie, the maximum heat setting is at twenty past the hour).

Now having said all that, don't forget its your boiler and if you want to run it flat out 24/7 then there's no law against it ........ YET!

And that's very true. I don't think anyone would dream of saying, for instance, that if you are foolhardy enough to use your new car a lot it will wear out and need repairs! I do feel that, at that point in the conversation with the engineer, he was trying to shift blame - as confirmed by my conversation with the tech person...

 

[Woolf]

Thanks for your reply D Hailsham. I take on board your points about the thermostat usage - thanks for explaining, and for the radiator link which I'm sure will come in useful in the future. Our radiators were balanced when we had full central heating system installed in 2004. When we had the new boiler installed in June this year we had all radiators checked by the installer. We bled the bathroom radiator (mentioned in earlier message) ourselves a few days ago and it's fine, so no problems with any radiators.

The only time we get uneven heating is when the thermostats are overridden by the hot water 'dumping' unused heat into the central heating system when the DHW tap is switched off. I know that this is an economy measure, but I don't like it. (This is a feature that the old boiler didn't have)!

The bypass is automatic as per Regs and it's indicated in the Installation Log as you suggest; thanks also for your thermostat suggestions. I've Googled a few and they look just the job.

Your engineer was quite correct. The Ravenheat installation manual does recommend a room thermostat. It is also a requirement under current Building Regs and is in the Benchmark Log.

Can you tell me where it says this, please? If you're looking at p.6, 2.3.5, I disagree with your interpretation. It says 'Interior space temperature is set by the room thermostat to be installed in the heating system.' Then it continues with details about connection and operation. The sentence quoted doesn't indicate that a thermostat must be installed. It certainly describes how internal space temperature is set, but, in my opinion, it doesn't make the thermostat a prerequisite. I'd be interested in reading the appropriate Building Reg if you've got a link.

With regards to the Benchmark Log, it says 'To Comply with Building Regulations, each section must have a tick in one or other of the boxes.' It doesn't say that the subjects of the tick boxes are enshrined in the Building Regs, just that one or other of the boxes must be ticked to comply. I'm not trying to teach my granny to suck eggs here - I'm just reading this carefully, and on the basis of that I disagree with what you've said. These are the types of fine detail that lawyers have a field day with!

However, in the tick box section we have 'Controls - Requirement' (1) Time and Temperature Control to Heating,' and 'Measures Provided' tick box choice of 'Room Stat & Programmer/Timer' or 'Programmable Room Stat.' The first box, 'Room Stat & Programmer/Timer' has been ticked. Could this mean anything else? The boiler itself has a programmer/timer. Or has my installer been telling porkies??

 

[D_Hailsham]

Your engineer was quite correct. The Ravenheat installation manual does recommend a room thermostat. It is also a requirement under current Building Regs and is in the Benchmark Log.

Can you tell me where it says this, please? If you're looking at p.6, 2.3.5, I disagree with your interpretation. It says 'Interior space temperature is set by the room thermostat to be installed in the heating system.' Then it continues with details about connection and operation. The sentence quoted doesn't indicate that a thermostat must be installed. It certainly describes how internal space temperature is set, but, in my opinion, it doesn't make the thermostat a prerequisite. I'd be interested in reading the appropriate Building Reg if you've got a link.

If you are not careful you will start a 'Regulations War' in this topic
Just do a search for Building Regulations on this site if you don't believe me

To put it at it's simplest. The Building Regs (aka Statutory Instrument 2006/652) which you can read here,
see para 19 Part L Conservation of fuel and power, only lays down very basic principles. The regulations also give the appropriate Government Minister the powers to issue "Approved Documents" giving information as to how the Regulations should be met. In the case of Part L, the Approved Document is here.

The problem that some have with the Approved Document is that it only says that something should be done, not that it must be done. The problem is made worse by the Domestic Heating Compliance Guide here

The argument goes: The Approved Documents and the Guide are not the Law because they have not been passed by Parliament, so we don't have to follow them. Also, the fact that it says should means that they are only recommendations and suggestions, nothing more.

Others argue that they are more than just suggestions and recommendations and that "should" in this context means "must".

With regards to the Benchmark Log, it says 'To Comply with Building Regulations, each section must have a tick in one or other of the boxes.' It doesn't say that the subjects of the tick boxes are enshrined in the Building Regs, just that one or other of the boxes must be ticked to comply.

One box is the minimum required to meet the regs, the other is best practice, i.e in excess of Regs

As I said above BRs do not lay down any details, only principles.

However, in the tick box section we have 'Controls - Requirement' (1) Time and Temperature Control to Heating,' and 'Measures Provided' tick box choice of 'Room Stat & Programmer/Timer' or 'Programmable Room Stat.' The first box, 'Room Stat & Programmer/Timer' has been ticked. Could this mean anything else? The boiler itself has a programmer/timer. Or has my installer been telling porkies??

If the installer has ticked this box, but not installed a room stat, he is indeed telling porkies. There are some boilers which have internal sensors which can tell when all the TRVs on the system have shut down and then shut down the boiler. But these are not very common and, in most boilers, the requirement to have an interlock can only be met by Room and Cylinder thermostats.

 

[JohnD]

Was it the same person who spoke of a "stronger earth"?

 

[Woolf]

No John, but the 'stronger earth' guy was the one who also suggested that running a boiler 24/7 was like leaving a vacuum cleaner on continuously. I think he currently gets my vote for taking the…biscuit!

 

[Woolf]

Thanks for your reply D Hailsham,

Well, it seems that you agree with me here - up to a point…

If I'm looking at the correct example (eg. p.16 Table 2 of the Guide, 'Minimum provisions for control of gas-fired central heating systems'), it does indeed say that things should be done, not that they must be done. And to go slightly off topic for a moment - there seems to be a common problem with a lot of Product Guides, Instructions and Manuals (and even the Tax Return) - they all appear to be written by experts in their field, and not experts in the English language! If they were edited by the latter, they would be easier to understand and unambiguous too.

As it is, the Regulations we are discussing seem to be interpretable. And remember, I haven't got a new system - I haven't got a replacement system - just a new boiler…! So basically, the only info on that table that applies to me (I believe) is that 'reasonable provision for a space heating system would be to control as one zone' Uummm..do my boiler heat control switch and timable programmer not do that?

I stand by what I said about the manufacturer's manual p.6, 2.3.5: it doesn't say that a room thermostat must be installed. However, this is an academic point since I am going to install one because it's been recommended, not only by yourself but by the manufacturer's tech guy (who confirmed to me that installation of a room thermostat is not a prerequisite of this boiler's installation, and also confirmed that no such information is given in the manual)!

If we can't agree, we'll have to agree to differ.

 

[mehran]

Putting your controls to one side for a moment

As long as you have an external by-pass that can pass the minimum flow the boiler/pump needs then even if you run the boiler 24/7 it should work. Your boiler should be able to shut down when it is up to temp and come back on when it cools down from it set temp with out over heating and locking out.

Now saying that your boiler will work better not blasting out heat!!!
You want warm rooms not red hot rads, the aim is to replace the heat that is lost from the house only

 

[D_Hailsham]

If I'm looking at the correct example (eg. p.16 Table 2 of the Guide, 'Minimum provisions for control of gas-fired central heating systems'), it does indeed say that things should be done, not that they must be done.

As it is, the Regulations we are discussing seem to be interpretable. And remember, I haven't got a new system - I haven't got a replacement system - just a new boiler…! So basically, the only info on that table that applies to me (I believe) is that 'reasonable provision for a space heating system would be to control as one zone' Uummm..do my boiler heat control switch and timable programmer not do that?

You have the correct table but there is more to it than that! If you look at page 10 Section 2.2, you will read:

The guidance in this section applies to the following situations:
(c) The specification of a replacement central heating system and/or component in existing dweelings where central heating is already installed - this situation is referred to in this section as a replacement system.

So, yes you new boiler is treated as a replacement system

Further down the page you will read:

In order to comply with the requirements of Part L, gas fired central heating systems which are provide as .. replacement systems .. should meet the following conditions:

This is followed by a number of conditions, of which para (f) is relevant in your case as it refers to boiler interlock, zoning etc as in Table 2.

So yes, you have the correct table, but it is the first section - boiler interlock - which is the relevant one. This says that there must be controls to turn off the pump and boiler when there is no demand for heating or hot water. The way this is achieved is through a Room Stat (and a HW cylinder stat and the associated motorized valves; but this is not relevant as you have a combi boiler).

I stand by what I said about the manufacturer's manual p.6, 2.3.5: it doesn't say that a room thermostat must be installed.

But 2.3.5 does say: The boiler continues to operate until it is stopped by the timer or one of the thermostats

And to go slightly off topic for a moment - there seems to be a common problem with a lot of Product Guides, Instructions and Manuals (and even the Tax Return) - they all appear to be written by experts in their field, and not experts in the English language! If they were edited by the latter, they would be easier to understand and unambiguous too.

I think the lawyers also have a hand in turning it into gobbledygook

If we can't agree, we'll have to agree to differ.

But you have agreed to fit a room thermostat, so who am I to argue?