KW rating of boiler

[Steelmasons]

He has been given correct advice to which falls on deaf ears , 10 pages on other thread with some of the posters being vaillant gurus , maybe you have something to add that has sadly been overlooked.

I'll eat my hat if you have.

 

[Tipper]

I've recently fitted a LLH to supply 3 zones (2 x UFH each with 6 loops, 1 x rads circuit) fed from a Vaillant 937. This is the latest model and I suspect it starts at low fire then ramps up as needed.

Simple to install and works great!

I used the Worcester Bosch Greenstar LLH.

Separate thermostat and controls for each UFH loop and the rad circuit.

 

[dcawkwell]

Sounds like a pants boiler if it can't modulate down to heat a hot water cylinder.

My 35kW vokera has no problems doing it.

 

[Steelmasons]

Yes a LLH would be the way to go but then plenty ways to skin a cat bearing in mind what the OP has installed at the moment.

 

[JBPHS]

I've recently fitted a LLH to supply 3 zones (2 x UFH each with 6 loops, 1 x rads circuit) fed from a Vaillant 937. This is the latest model and I suspect it starts at low fire then ramps up as needed.

Simple to install and works great!

I used the Worcester Bosch Greenstar LLH.

Separate thermostat and controls for each UFH loop and the rad circuit.

What's the total heat load on your boiler?

James

 

[D_Hailsham]

Thanks. Just to expand on this a little - the flow rate of my system is determined by my pump, and therefore is fixed. (Please correct if wrong). Therefore, with the flow rate fixed, a 37KW boiler will heat the total volume of water far quicker (three times as quick even ?) than a 12KW boiler.

The flow rate is not fixed, it depends on the pump speed setting and the resistance of the circuit, which will vary as rads are opened/closed by TRVs. With fixed speed pumps there is always a compromise.

If you want to heat a house from -1C to 21C it will require twice as much heat as heating it from 10C to 21C.

 

[JBPHS]

He has been given correct advice to which falls on deaf ears , 10 pages on other thread with some of the posters being vaillant gurus , maybe you have something to add that has sadly been overlooked.

I'll eat my hat if you have.

So what are you suggesting? All I can say is that I love it when someone calls me to rectify their heating in situations similar to this, where 2, 3 or more heating engineers have been out to them beforehand with no success, after which I get all rads, UFH zones, etc working effectively. As I said in a previous post, you have to be experienced with these scenarios.

You don't need to be a Vaillant engineer to sort this out. If a WB engineer replaces a pump, primary heat exchanger, secondary heat exchanger, hydroblocks (including the diverter valve), etc (virtually a new boiler) without repairing the fault, does this mean that because a WB engineer cannot pin point the fault that there is no fault on the boiler? No is the answer, little old me had a look at the heating system, in half an hour found that it was clear, but found magnetite blocking one of the pipes inside the boiler above one of the isolation valves. Once cleared, it every rad started getting warm within minutes. So this little situation proves that you don't need to be trained on specific boilers to be able to fault find them.

I may not suggest something new, but you know what they say about a fresh set of eyes.

 

[Steelmasons]

I may not suggest something new, but you know what they say about a fresh set of eyes.

Well why don't you read the other 10'page thread and hopefully enlighten us as to what has been missed , then again considering you are part of the magic circle then i realise it may be difficult.


Regards the vaillant engineers it was suggested by others that the problems regarding the S53 issues are software related to which they are not in this case , the bunny boys (vaillant) confirmed this as did all other decent installers who fit these boilers , and before you comment most of these bunny boys don't work directly for vaillant so have nothing to gain.

Considering the extensive 10 page thread I was a tad amused that you feel you have something to offer but decide you don't wish to share your extended knowledge regarding the 438 issues.

 

[fezster]

The goal from the start has been as follows:

1) Each zone should be able to work independently.

2) Radiators should heat up as quickly as possible.

3) Hot water tank should heat up as quickly as possible (~ 30 mins recovery on the Megaflow 250L).

4) Gas usage should be as low as possible to achieve the above.


To achieve (4), I'd like to install a vaillant weather compensator and be able to independently control the hot water temperature on the Megaflow, which I understand can be done. Hot water is currently far too hot, but I believe the vaillant controls have an anti-legionella programme to allow you to heat the tank to a much lower temperature, and the programme takes care of legionella by occasionally heating to > 60 degrees. Any info on this would be appreciated.

As it stands, I think I may have achieved (1), (2) and (3), but as said, I'd need to run for a while yet to confirm all is ok. If it is running ok, I'd be interested to know what benefit a LLH would give me at this stage.

 

[fezster]

Regards the vaillant engineers it was suggested by others that the problems regarding the S53 issues are software related to which they are not in this case

I think the updated PCB may well give some advantage. I dont fully understand why, but as said in my second post above, I have seen the boiler get itself into a state where it constantly cycles. It's hard to monitor it constantly, but so far, having increased the rating to 26KW, the boiler is modulating down sufficiently to allow the cylinder stat to turn it off.

As an example (and Im not saying this is what happens, but this is something Ive observed) - if the downstairs heating is on full blast, the boilers been running for an hour, the flow temp is almost 70, and the return is 50. The upstairs zone asks for heat, and suddenly the return temp drops dramatically to 20 or 30. Boiler will hit S53. Maybe this is normal and a compromise which has to be accepted. As long as the boiler then recovers, that's fine. But if it goes into S53 permanently, then that is obviously not good.

 

[JBPHS]

steelmasons, you obviously have an issue with me. I may be able to please some people all of the time but I won't please everyone some of the time. I don't know about you, but I can find something better to do with my life than to trawl through 15 pages of suggestion after suggestion that so far has not been taken on board or worked.

Maybe you have a problem with me putting my money where my mouth is by suggesting to my customers if I can't fix it, I don't expect to be paid for any rectification work that doesn't improve performance. I may have a big head, but so I should if I've made systems work where others before me have failed. I'm sorry if it sounds too competitive for you, but that's how I operate!

Kind regards,

James

 

[Steelmasons]

, I'd be interested to know what benefit a LLH would give me at this stage.

Considering most of us have exhausted ourselves with regard to your issues then maybe JBPHS may want to give you the reasons why with an added bonus being size and specification with regard to the low loss header.

 

[Steelmasons]

I have no issues with you JPB , the issues I have are when members of this forum "talk the talk" with absolutely no back up regards facts and figures , so enlighten me what have we all.missed and to the point how are you going to solve fezsters issues given the facts so far?

 

[Steelmasons]

This is very easy to solve, a quote that my high school chemistry teacher used to say "It's like a page 3 model; seen one, seen them all." Anyway I digress, I'll provide information on how to change tap washers, etc. but for jobs like these, what I will tell you is that all of your problems (mentioned above) can be corrected, but you don't get a magician revealing his trick before he performs it, if you know what I'm saying?

Yes I will admit the above rattled my cage , no offence to you personally as I don't know you from Adam.

It comes across in such a way as to suggest we are missing something , I take into account you have read the other thread as you previously admitted.

 

[fezster]

, I'd be interested to know what benefit a LLH would give me at this stage.

Considering most of us have exhausted ourselves with regard to your issues then maybe JBPHS may want to give you the reasons why with an added bonus being size and specification with regard to the low loss header.

I appreciate any and all advice. But you have to see it from my point of view. A lot of suggestions are made, and (without being an expert) I have to try to decipher what they mean and whether or not they'll be beneficial. Having already experienced "experts" making suggestions and adding bits and pieces without solving the actual issue, whilst costing me money, I thought Id come on here and try to understand the problem Im trying to solve, before jumping head first into solutions I may not need. Im sorry it comes across as though sometimes suggestions are falling on deaf ears (!). I assure you they are not, but I have to take a measured approach to spending money on the advice of others, without knowing whether that advice is going to attain my goals.