Keeping boiler in condensing mode

weefarmer

yoshytoshy wrote: »

Diverter valve ? What your talking about is a bypass valve and the boiler would heat up even quicker with one

I mean a three way motorised valve and never thought it out fully whilst typing it, fitted on the return pipe and if the water is too hot to enter the boiler again it will send it into the circuit again via the flow pipe and back around until the temperature are right so the boiler can condense when runnning again, it was only a suggestion!

also i dont mean to undersize by much just a few kw or even have it as close to the kw the house requires because if oversized the house may heat up too quick and the return water temp would be too high and causing the boiler to be running and not condensing!

im my opinion this is the most straightforward way of getting max efficiency out of the boilers and the way it seems to work for me, other people have different ways and ideas and i'll not argue with them and any ideas i see here i'll take on board

weefarmer

weefarmer wrote: »

im my opinion this is the most straightforward way of getting max efficiency out of the boilers and the way it seems to work for me, other people have different ways and ideas and i'll not argue with them and any ideas i see here i'll take on board

It's not your opinion or mine that counts(i have been known to talk out of my backside), it's the manufactures of the boiler that decide if a boiler is suited to a particular purpose, if a installation fails and it's fitted outside of manufactures instructions/guidelines for the boiler then it puts the installer on the back foot, even at times if the design is not the issue that caused the problem, my advise to you would be to ring the technical department and get their view on your system design and their boiler, if you were to do this with a modern gas boiler it could effect it's ability to dissipate heat if it needed to, Gary.

oxygenman

weefarmer wrote: »

I mean a three way motorised valve and never thought it out fully whilst typing it, fitted on the return pipe and if the water is too hot to enter the boiler again it will send it into the circuit again via the flow pipe and back around until the temperature are right so the boiler can condense when runnning again, it was only a suggestion!

Hiya,

If the water is coming back in the return too hot, does this mean that the Flow has reached its Temp set point at the boiler and the boiler should have cut out by means of its Temp sensor in the boiler? If thats the cast is their a need to fit a diverter valve as the Return water will just pass through the boiler anyway and go back out the flow?

I've probably not asked that question properly so apologies if ye don't understand

heinbloed

oxygenman wrote: »

Hiya,
Hope you don't mind me asking but how can you set the temp of the return at the boiler? I always thought that the Temp control was only for the Flow pipe at the boiler panel?

The return temperature can be influenced with every boiler by setting the pump's speed. The longer the hot water stays in the circuit=radiator the less warm it will be when it returns to the boiler. Modern boiler not only modulate the flame/the heat they generated but the pump's speed as well. Simultaniously.

heinbloed

yoshytoshy wrote: »

People should keep in mind that radiators are sized with a temperature of around 60oC.

If you set your boiler below this temp ,your not going to be heating your home properly. You really need bigger radiators to compensate for the lower temperature.

The sizing of a radiator depends on the competence of the installer and his design (calculation of the energy demand).

One can heat his house or room with radiators who's rated output is given at a 70/50 or 60/40 or 50/30 degrees celsius. It simply doesn't matter. The question is how much thermal energy is needed to heat the place. And this has to be fullfilled.
A multitude of low output radiators would do the same job, even beter. Better distributed means faster heating, less primary energy demand.

heinbloed

oxygenman wrote: »

Hiya,

Would 50oC be hot enough though to heat your hot water cylinder?

"To heat" means what?

As long as your water is pressurised enough to hold it's chlorine there is no bacteriological/salmonella risk. If in doubt treat it afterwards, for example with UV light.

heinbloed

yoshytoshy wrote: »

I haven't got it or installed any yet myself:o

It's all still expensive though as far as I know ,even simple fittings seem to be overpriced. When things settle down a bit more ,I can see more people going for it.

Tank incl. collectors suitable to take an electric resistance heater(in case the sun doesn't shine) for €999.-. SUNSHORE. Check the web.

heinbloed

gary71 wrote: »

With some gas boilers the flows are split at the boiler sending 80c to the coil and what ever you want around the heating circuit.

ALL, virtually all combi -( condensing -) boilers have this feature. These are the A-rated combi boilers.

heinbloed

gary71 wrote: »

You can effect the warranty with a system design like that, if you were to do it with one of my boilers your on your own.

A house would have a heat requirement, that requirement would be found by doing a calculation, you can then fit normal sized rads to give that heat requirement or larger sized rads to give the same output and then you size the boiler to meet the need, to me under sizing is just as bad as over sizing, the boiler should match the required heat output anything else is a guess in my opinion.

This statement is wrong. A heating system comes on it's own. The installer's warranty covers the system, not the negligence of the architect/engineer/client, whoever wanted it to be as it is.
State the output, state the cunsumption and there won't be a discussion. A motorbike won't take a busload of passengers. If it is ordered it will be delivered.

heinbloed

oxygenman wrote: »

Hiya,

If the water is coming back in the return too hot, .....

I've probably not asked that question properly so apologies if ye don't understand

What means " to(o) hot"?

With radiators the standard setting is 20 Kelvin difference between flow and return. With surface heating it is around 6 Kelvin.....
These numbers could differ, depending on the envisaged reaction time and the thermal resistance of the emitting/transmitting surfaces.

oxygenman

heinbloed wrote: »

The return temperature can be influenced with every boiler by setting the pump's speed. The longer the hot water stays in the circuit=radiator the less warm it will be when it returns to the boiler. Modern boiler not only modulate the flame/the heat they generated but the pump's speed as well. Simultaniously.

Hiya,

Thanks for that, however, can you tell me how to get the boiler to modulate the pump so that it gives only 50oC at the point of re-entry to the boiler?
Thanks

oxygenman

heinbloed wrote: »

"To heat" means what?

As long as your water is pressurised enough to hold it's chlorine there is no bacteriological/salmonella risk. If in doubt treat it afterwards, for example with UV light.

Hiya,
To heat the water in the copper cylinder , If 50oc is going through the coil then surely the water in the cylinder won't heat up enough and there is a serious chance of Legioneers disease (probably spelt wrong), seems like an awful amount of work to treat the problem with UV light afterwards when all you had to do was up the Temp going through the coil in the cylinder so that it gives you 55oC and upwards in the cylinder. Prevention is better than trying to cure wouldn't you agree?

heinbloed

heinbloed wrote: »

This statement is wrong. A heating system comes on it's own. The installer's warranty covers the system, not the negligence of the architect/engineer/client, whoever wanted it to be as it is.
State the output, state the cunsumption and there won't be a discussion. A motorbike won't take a busload of passengers. If it is ordered it will be delivered.

Thanks for clearing up that point heinbloed.

As the fella who has to deal with people making buses out of bikes and warranty's i will now refer them to your post;).

heinbloed

heinbloed wrote: »

ALL, virtually all combi -( condensing -) boilers have this feature. These are the A-rated combi boilers.

Yep, i know what a combi does, but not every installation can have a combi and not all system boilers have a internal diverter valve with separate flows for heating and hot water with simplistic wiring allowing for low temperatures around the heating circuit and good hot water performance, i thought it was worth a mention.

yoshytoshy

oxygenman wrote: »

Hiya,
To heat the water in the copper cylinder , If 50oc is going through the coil then surely the water in the cylinder won't heat up enough and there is a serious chance of Legioneers disease (probably spelt wrong), seems like an awful amount of work to treat the problem with UV light afterwards when all you had to do was up the Temp going through the coil in the cylinder so that it gives you 55oC and upwards in the cylinder. Prevention is better than trying to cure wouldn't you agree?

It's very easy to overcome this with minimum cost.
You could have a timer on your electrical immersion and set it to come on for an hour every three days or so.

Thats just a suggestion though ,I think this thread is more about condensing and how to achieve it the best way possible.
You can't make an omlette without breaking eggs.

heinbloed

Oxigenman wrote:

Hiya,

Thanks for that, however, can you tell me how to get the boiler to modulate the pump so that it gives only 50oC at the point of re-entry to the boiler?
Thanks

A modern boiler does so on it's own. With older boilers one can usully change the pump's speed at the pump.
Most of the old pumps can be set in stages, I, II or III.
Try out what works best, i.e. how you get the longest firing sequences with the lowest return temperature.
The more heat is taken by the radiators (all valves 'open') the lower the return temperature will be. Unless a strong pump is connected to an oversized boiler this will be seen at the thermometer on the boiler. If no return thermometer is installed do it, they're very cheap. It should have been there from the beginning of the installation.

About the ligioneer's desease or other bacterial problems:
As said above as long as your hot/warm water is pressurised AND chlorinated there won't be a problem. This depends on the lay-out of the system.
There are small devices available for around € 200.- which contain a lamp producing UV light. These lights are used in the food industry, in hospitals and hotels and kill-off bacteria very efficiently.
Of course you can boil the water as well, the problem here is that the entire tank, from the bottom to the top plus the entire plumbing involved has to be done. This demands a.) a lot of energy and b.) someone who opens the taps, all taps, so infected water can get out and hot sterile water will take over it's position.
There are more than these two methods to make problematic water consumable, check this out with a real plumber.

oxygenman

Thanks, I am a plumber

tmcdlk

One of the best ways to make sure your boiler is in condensing mode is to use weather compensation control. With the weather compensation control the boiler will lower the flow temp (therefore the return temp will be lower too) as the temperature outside rises.
Outdoor temperatures will only be below 5ºc for a small part of the heating season. If a boiler is sized based on the total building heating and hot water load of the building then it will very rarely have to run a full capacity/highest flow temp. There is no need to make the sizes of the radiators larger. They should be sized for an 80ºc flow and 60ºc return (this might vary with certain boilers). Only in the middle of winter will the boiler be running at its designed load. Therefore the rest of the time the boiler will be running lower than the 80/60ºc and once the return flow temp gets to around 55º the boiler will be in condensing mode.
The problem of heating the DHW cylinder when in condensing mode can be can be solved by having a boiler with two stats. So if the sensor on the cylinder is calling for heat then the boiler will run at 80/60ºc until the cylinder is up to its designed storage temp (60-65ºc). The idea is to prioritise the hot water by using some zone valves. If the cylinder is calling for heat then the zone valve controlling the heating closes and the zone valve to the cylinder opens, and the boiler temp goes up to 80/60ºc. Once the hot water cylinder storage temp is reached the zones valves will go back to their original position and the boiler temp will go back to being controlled by the heating circuit. A storage cylinder with quick recovery should be used so that the heating circuit isn’t without heat for more than say 20min while the domestic hot water is being heated.

JohnnieK

tmcdlk wrote: »

One of the best ways to make sure your boiler is in condensing mode is to use weather compensation control. With the weather compensation control the boiler will lower the flow temp (therefore the return temp will be lower too) as the temperature outside rises.
Outdoor temperatures will only be below 5ºc for a small part of the heating season. If a boiler is sized based on the total building heating and hot water load of the building then it will very rarely have to run a full capacity/highest flow temp. There is no need to make the sizes of the radiators larger. They should be sized for an 80ºc flow and 60ºc return (this might vary with certain boilers). Only in the middle of winter will the boiler be running at its designed load. Therefore the rest of the time the boiler will be running lower than the 80/60ºc and once the return flow temp gets to around 55º the boiler will be in condensing mode.
The problem of heating the DHW cylinder when in condensing mode can be can be solved by having a boiler with two stats. So if the sensor on the cylinder is calling for heat then the boiler will run at 80/60ºc until the cylinder is up to its designed storage temp (60-65ºc). The idea is to prioritise the hot water by using some zone valves. If the cylinder is calling for heat then the zone valve controlling the heating closes and the zone valve to the cylinder opens, and the boiler temp goes up to 80/60ºc. Once the hot water cylinder storage temp is reached the zones valves will go back to their original position and the boiler temp will go back to being controlled by the heating circuit. A storage cylinder with quick recovery should be used so that the heating circuit isn’t without heat for more than say 20min while the domestic hot water is being heated.

I think this is a boiler house oil boiler he is talking about so as far as i know there wouold be no means of connecting an outside compensator to it. The ones I have used have been plug and play ones that conect to the pcb of gas boilers and the cylinder zone valve is wired to some kind of cylinder demand box connected to the boiler. The other way was through a type of building managment system which was very expensive as far as I can remember. The quickest way is through the speed of the pump.