Underfloor, condensing, thermal store and weather comp

[mysteryman]

Further to the separate thread on this topic:

The layout proposed by the thermal store manufacturer gives only very approximate control, and will not keep the boiler fully condensing whilst serving the central heating. It is much better to supply ufh direct from the boiler with variable flow temperature by direct burner control from weather compensation. The boiler will always be fully condensing when supplying the underfloor heating, modulating the gas rate to suit the current output. You do not then need a blending valve or second pump. The best boilers also have anti-short cycling control.

 

[highleigh]

Unfortunately too late for me but I do like this logic.

Why do you say the boiler will not be fully condensing whilst serving central heating? What conditions does a boiler fully condense or not. I guess we are now talking about a none modulating boiler?

 

[Dan Robinson]

How many threads does this need?



*edit* apologies....forgot this was the open forum....similar thread going in the CC.

 

[mickyg]

How many threads does this need?



*edit* apologies....forgot this was the open forum....similar thread going in the CC.

Not sure MM is quite happy he's advertised his employers enough so he decided to start a whole new thread. amazed that he's managed to avoid mentioning their name. I think anyone who works for a manufacturer and promotes their products should be made to be open about who they work for as their opinions will always be biased.

 

[highleigh]

I'm not in the cc so this may be my fault from a response In another public thread. Can't speak for mm motives but I'm happy to learn about different ways of powering ufh. I am renovating my house and genuinely interested in finding the different ways of doing everything.

I have already made my choice but it does highlight my need to ensure my return is significantly low enough to keep the boiler condensing, so I have learned something. There must be more than one way of doing this?

 

[Onetap]

The layout proposed by the thermal store manufacturer gives only very approximate control, and will not keep the boiler fully condensing whilst serving the central heating. It is much better to supply ufh direct from the boiler with variable flow temperature by direct burner control from weather compensation. The boiler will always be fully condensing when supplying the underfloor heating, modulating the gas rate to suit the current output. You do not then need a blending valve or second pump. The best boilers also have anti-short cycling control.

Twaddle.

If you're restricted to the boiler manufacturer's controls, they cater for the mass market with plug-and-play type controls which are inflexible for any non-standard application. If you are not restricted to boiler manufacturers' controllers. there is virtually no limit to what can be done.
Do not confuse 'our controllers cannot do that' with 'no controller can do that'.

Thermal stores, system reset, boiler reset and secondary mixing systems all have their appropriate applications.

Why is a thread about WC in the CC? Which part of the Gas Safe/ CORGI training syllabus covers mixing controls?

Don't worry the sheep.

 

[ALEC1]

the vast majority of plug and play controls are actually very flexible and allow you as many permutations as you like...granted the manufacturers tend to keep it to them selves and don't like to train us in the technology...

what is boiler reset and system reset? is that the american jargon for weather comp aka out door reset?

 

[Onetap]

what is boiler reset and system reset? is that the american jargon for weather comp aka out door reset?

Yes, but not because I have any fascination with Americanese, it's simply because most of the the texts are from America and I do not know of any corresponding UK terms, such as exists for weather compensation.

Outdoor reset (I don't use that term, I use WC) - Weather compensation
Boiler reset - Flow temperature reset by modulating the burner; no corresponding UK term

System reset - Flow temperature reset by modulating a mixing valve or pump set; no corresponding UK term

the vast majority of plug and play controls are actually very flexible and allow you as many permutations as you like...granted the manufacturers tend to keep it to them selves and don't like to train us in the technology...?

No they're not. They are intentionally made inaccessible, as are BMS systems.

 

[DeltaT2]

How many threads does this need?



*edit* apologies....forgot this was the open forum....similar thread going in the CC.

Not sure MM is quite happy he's advertised his employers enough so he decided to start a whole new thread. amazed that he's managed to avoid mentioning their name. I think anyone who works for a manufacturer and promotes their products should be made to be open about who they work for as their opinions will always be biased.

How does MM get away with it?? It's an open Public forum & he uses it as a spam dump. Is spam permitted on this forum & in the combustion chamber pot??? Can any boiler manufacturer sell their products via this forum??

I get banned for a minor misdemeanor, but spamming is freely permitted??!!!..............

 

[mysteryman]

You may question my motives if you wish, but they are to offer good sound advice.

 

[Agile]

I guess we are now talking about a none modulating boiler?

All domestic boilers now are both condensing AND modulating!

I wonder why MM does not sometimes recommend Intergas boilers if he is giving the best advice?

 

[mysteryman]

Unfortunately too late for me but I do like this logic.

Why do you say the boiler will not be fully condensing whilst serving central heating? What conditions does a boiler fully condense or not. I guess we are now talking about a none modulating boiler?

A boiler will be fully condensing when the flow temperature is below 55C. It will be partially condensing with the return below 55C.
If underfloor heating is connected directly with properly set weather compensation, the operating temperature will always be low enough for full condensation to occur. If you connect via a thermal store, you will need a blending valve and extra pump, and you can't be certain about how well the boiler is condensing. More kit, more complication, poor result!

 

[highleigh]

[/quote]A boiler will be fully condensing when the flow temperature is below 55C. It will be partially condensing with the return below 55C.

Thanks, I get this now. I didn't know this before.

If underfloor heating is connected directly with properly set weather compensation, the operating temperature will always be low enough for full condensation to occur.

Its not so this is now of no use to me. I think you have made your opinion on this very clear on this point.

If you connect via a thermal store, you will need a blending valve and extra pump, and you can't be certain about how well the boiler is condensing. More kit, more complication, poor result!

I've already got a blending valve and pump and this is completely seperate to how the boiler and thermal store work together. Why are you confusing the whole compensation/condensing argument with undefloor heating?

 

[mysteryman]

I'm trying to clear confusion for the benefit of others as well as your good self.
It is simply that the best way to connect and control underfloor heating to a condensing boiler is direct to the boiler, not via a thermal store and not via an external pump, blending valve, timer or thermostat.

 

[Onetap]

It is simply that the best way to connect and control underfloor heating to a condensing boiler is direct to the boiler, not via a thermal store and not via an external pump, blending valve, timer or thermostat.

No, it is not. That system is simplest and is perfectly adequate for most domestic systems. It is unsuitable for systems where there is a high demand for domestic hot water, or for systems with multiple zones with different heat loss/solar gain characteristics, or for systems with zones with a mixture of radiators and UFH.

Viessmann boilers can have a mixing valve set inside the boiler casing and which can deliver two different flow temperatures to UFH and DHW simultaneously. This has no advantages, and several disadvantages, over a separate external mixing valve set.

Thermal stores have some applications, strangely enough where there is a requirement to store heat. They also act as a 'thermal flywheel', the thermal capacity smoothing out temperature variations caused by on/off non-modulating heat sources connected to low mass distribution systems.

Horses for courses.