Real world testing example of Condensing Boiler in older home

[SJB060685]

That’s the problem with fixed rate burners without modulation. When the boiler output and system load are equal the boiler should reach design flow temperature and never cycle on or off, just run constantly. However when the loads don’t match which is probably 90% of the year then you are always going to get cycling, especially if the system is micro zoned. I love oil burners, have worked on them since about 11 years old but most domestic oil boilers are still primitive compared to their gas cousins. There is now a fully modulating oil boiler on the market which is a step in the right direction.

 

[JC22024]

That’s the problem with fixed rate burners without modulation. When the boiler output and system load are equal the boiler should reach design flow temperature and never cycle on or off, just run constantly. However when the loads don’t match which is probably 90% of the year then you are always going to get cycling, especially if the system is micro zoned. I love oil burners, have worked on them since about 11 years old but most domestic oil boilers are still primitive compared to their gas cousins. There is now a fully modulating oil boiler on the market which is a step in the right direction.

Very interesting to hear there are new modulating oil boilers coming out! It appears liquid fueled boilers definitely got left behind in boiler controls over the last decade. I looked up the new modulating oil boilers there, they look good but I'll probably wait a numenr of years until they have the maintenance issues ironed out!

Yes the boiler has to be oversized most of year so it can provide the heat in the few coldest days of the year it is required. Which is where the modulation ratio would be key.

But - reading up on boiler cycling issues on the interwebs there are hundreds of theads like this one which touch on balancing rads, checking for faulty bypass valves, old un finned radiators etc etc but little to zero mention of Boiler Energy Managers in all of them. It seems there is little knowledge or uptake in BEMs for current Oil Boilers. It does make a difference for sure and adds a "Brain" to the antiquated £10 controls still coming on new £1400 Condensing Oil Boilers!

I think it is farly easy to understand how a BEM like this can function. A one size fits all alithogram would be / is very effective. Especially one that goes between the stat and burner. It is getting the raw burner function and works off of that. With the major limitation being open loop control - not having delta sensors. (Needs to power off between zones / heating cycles but not a problem for me as I programme my heating as such)

I think it works just like this but could be wrong - just my opinion:

It lets the boiler first run to temp. Then slight delay of a few secs and let it run again until up to temp. This conintues on and each time the BEM is monitoring the run time and stat call times to see how much it can pare back the burn time VS stat calling again. Until it finds the equilibrium / Sweet spot whereby it knows that over a given time frame the stat call time is increasing so it knows this is the heating demand / duty and keeps it there.

I may not be explaining that very well but in my head this is pretty much perfect control for an imperfect boiler. It loses power and re-sets each time a heating zone is fired up. Therefore real time monitoring and pairing back of the duty cycle each time. So if it was really cold outside and the house was needing more burn time the BEM will be offseted to match whilst still pulling back as much time as it can. With stat still meeting 70c call each time.

Disclaimer - I am not a heating engineer and have no interest in anyone buying BEMs whatsoever. I am a Design Manager by trade. I found the Vector one new really cheap on ebay and tried it out as a part of this project and it worked. (I think they are prohibitively expensive otherwise) Just thinking its odd that probably only 0.01% of homes with Oil Fired Oil Boilers in the UK would have a BEM fitted and could be saving 15 - 25% in oil consumption if what I am seeing so far is correct.

 

[SJB060685]

Well said. Yes the BEM controller certainly has its advantages. The EOGB SAPPHIRE boiler is the one particular modulating burner I was referring to. Outputs up to 32kw if I remember correctly and with a turndown ration of 6-1. Although that’s not particularly anything to boast about it’s still a step in the right direction.

 

[JC22024]

Haven't had time to tinker much with my heating system since. Just been running it as normal. Racked up 60 hours boiler thermostat call time on the BEM and it's showing an overall saving of 17.5%.



This is the average saving it does better on the upstairs than downstairs zone. Perhaps because running the upstairs the boiler is definitely oversized whereas it's just about right on the ground floor.

Still interested to carry out balancing when I get time. And to see if this new condensing boiler with BEM will get me through spring on 900L which would more than halve my regular winters oil bill!

 

[JC22024]

Update- checked oil tank level today pretty much another month on and I am amazed at how little consumption is happening!

Mind you I am running downstairs room heat multi fuel stove each evening and weekend so its only upstairs zone powered for a few hours every day. But this is how I always ran the house this number of years and the oil consumption is about half of what it used to be.

 

[SJB060685]

So you can clearly see how fuel is being saved by the frequent cycling at the burner . Being fixed rate the burner is constantly burning a set amount of fuel, even when the load is reduced. This has a drastic affect on fuel consumption, level of condensing and overall combustion efficiency. As I said above some time ago, if you now replaced your boiler with an EOGB Sapphire you would see even greater levels of fuel consumption, system performance and overall comfort.

 

[John.g]

Makes one wonder why people arn't seeing big increases in their energy bills when they install Evohome who constantly cycle oil/gas boilers as often as 1 minute every 5 minutes even when the (gas) boiler is perfectly capable of continuous running once the heating demand is > 4 or 5kw.

 

[SJB060685]

Makes one wonder why people arn't seeing big increases in their energy bills when they install Evohome who constantly cycle oil/gas boilers as often as 1 minute every 5 minutes even when the (gas) boiler is perfectly capable of continuous running once the heating demand is > 4 or 5kw.

A lot of variables to consider there mate. Gas modulating boilers are better suited to such a control strategy as a posed to fixed rate pressure jets. Take the new Viessmann 200 with a turndown ratio of 19-1. Their boilers have the best modulation available on their high end boilers but even they would cycle at certain times.

 

[JC22024]

So you can clearly see how fuel is being saved by the frequent cycling at the burner . Being fixed rate the burner is constantly burning a set amount of fuel, even when the load is reduced. This has a drastic affect on fuel consumption, level of condensing and overall combustion efficiency. As I said above some time ago, if you now replaced your boiler with an EOGB Sapphire you would see even greater levels of fuel consumption, system performance and overall comfort.

Thanks for that- just as a refresher , I made the following changes to my heating system this winter:

Old non condensing boiler with 0.85gph jet removed.
Firebird Condensing boiler installed and jetted at 0.65gph.
New circulator pump as heating system was never right before.
Adding the BEM.

So there have been a number of upgrades there the most substantial being the boiler itself.

But I never would have guessed the oil consumption could HALVE in the house or would have upgraded the old boiler sooner.

When I say old boiler it wasn't that old in the grand scheme of things- it was a Worchester Bosch Dansmoor 36kw and the servicing guy always said it was a great boiler and don't replace it until it died, which it did this winter by rusting out the water jacket

 

[SJB060685]

Condensing is paramount to maximising efficiency. All oil boilers on the market today are condensing but for most oil boilers the similarities to their gas cousins stops there. The dew point for kerosene flue gases is a lot lower than mains gas. At ~ 47°c return temperature condensing will start but you are then relying on the secondary heat exchanger efficiency to make sure the water then returning to and through the primary heat exchanger is above dew point else you will get back end rot. There is ways to prevent this but it’s added parts, added cost and a bit of maths to make sure everything runs properly.
Gas boilers have higher dew point temperature but more importantly have the heat exchanger constructed of materials able to withstand lower water temperatures and not rot. The lower the return temperature can be the greater the level of condensing and therefore efficiency. Also gas modulating boilers are even more efficient at part load, whereas with oil you have to meet certain criteria on most boilers.
I know I’ve banged on about it a lot and I do apologise but the Sapphire boiler is an absolutely huge advancement in the oil world. Fully modulating, so can closely match the ever changing load with minimal cycling, excess fuel consumption and burner wear and tear.
For maximum efficiency you want good modulation and low flow temperatures. If a fixed rate burner like most oil burners I would consider a different system design approach to the common S and Y plans.

 

[John.g]

Oil also contains more sulphur than gas which used to have little or none, may have changed now, also I think the minimum flow temperature selectable on grant condensing boilers is either 60 or 65c, gas boilers go as low as 35C??.

 

[SJB060685]

I can’t comment on the gas boiler as I’m not a gas engineer but you are correct about the oil stats.

 

[JC22024]

Oil also contains more sulphur than gas which used to have little or none, may have changed now, also I think the minimum flow temperature selectable on grant condensing boilers is either 60 or 65c, gas boilers go as low as 35C??.

Of limited use in an older property with radiators as we know. Need rhe higher temps unlike modern houses with UFH etc.

 

[JC22024]

Condensing is paramount to maximising efficiency. All oil boilers on the market today are condensing but for most oil boilers the similarities to their gas cousins stops there. The dew point for kerosene flue gases is a lot lower than mains gas. At ~ 47°c return temperature condensing will start but you are then relying on the secondary heat exchanger efficiency to make sure the water then returning to and through the primary heat exchanger is above dew point else you will get back end rot. There is ways to prevent this but it’s added parts, added cost and a bit of maths to make sure everything runs properly.
Gas boilers have higher dew point temperature but more importantly have the heat exchanger constructed of materials able to withstand lower water temperatures and not rot. The lower the return temperature can be the greater the level of condensing and therefore efficiency. Also gas modulating boilers are even more efficient at part load, whereas with oil you have to meet certain criteria on most boilers.
I know I’ve banged on about it a lot and I do apologise but the Sapphire boiler is an absolutely huge advancement in the oil world. Fully modulating, so can closely match the ever changing load with minimal cycling, excess fuel consumption and burner wear and tear.
For maximum efficiency you want good modulation and low flow temperatures. If a fixed rate burner like most oil burners I would consider a different system design approach to the common S and Y plans.

Yes I understand and the Sapphire modulating oil boiler is definitely the way to go!

When my old boiler burst I needed one quick, fast and in a hurry.

Perchance the Firebird was available good used locally and only 6 months old.




It was being pulled out for gas conversion. (Bet they somewhat regret that now with the way gas prices are rocketing!)

So I got a pretty much new boiler for £500 cash. It was correctly serviced and set up none the less of course.

So I'll get a couple years out of this boiler then look at a new modulating one for sure.

 

[SJB060685]

Firebird boilers are good boilers, we installed many over the years and yours has the Elco burner which is a very good burner. I’m not slating fixed rate burners at all. When designed and run properly they can be very efficient, the problem is 99% of the systems these units supply energy to are not optimal for a fixed rate burner. With Part L of the building regulations changing again this year we will see all new builds with wet central heating systems having a flow temperature of no more than 55°c. Careful consideration is needed when designing these systems on oil boilers.

 

[JC22024]

For anyone remotely interested , these are the 2no mutil fuel stoves I have:

A new Stanley Oisin 6kw room heat only, this is lit every evening as soon as we get home from work and heats open plan living room to 22c odd:



(It just replaced a 4kw Hunter stove in same fireplace since 2010)

Then I have another beast (at the time it was biggest in range at 32kw ish IIRC) boiler stove by Yeoman - stove group.



I seldom light this stove but it is a backup in the event the oil goes kaput. I have a full winters worth of firewood to burn if I could be bothered bringing it in and running this one! I really should light this one more.

 

[SJB060685]

Both nice fires. How old is your property? Looks like could be several hundred ?

 

[JC22024]

Both nice fires. How old is your property? Looks like could be several hundred ?

The house was built in 1974, then substantially renovated and extended in the late 80s by my Dad.

So I know the small stove fireplace looks antique but it was all done in Chinese slate in the 80s. I used to hate it but quite like it now if you get the room colour scheme to gell with it.

The other fireplace was just a Plain chimney breast before serving an aga on the kitchen on other side. I done away with the aga then cut open the chimney breast on dining room side. And got an oak beam, chainsawed the back out and rendered it myself internally to look cottagey I suppose. But the rest of the house is modern enough, in the snapshots may look old!

I also like having the ability to heat house with solid fuel. Say oil prices rocket and I'm running out I can switch to wood etc for a few weeks.

 

[JC22024]

For anyone who doesn't have one, I highly, highly recommend a quality efficient multi fuel stove. Even small room heat ones. They belt out heat and make room very comfortable and very easy to run. I found a local supplier who sells top quality coal doubles which produce almost no ash in the stove. Half a dozen bags in boot of car does me 4+ weeks running stove every night without fail and Saturday/ Sundays all day when very cold out.

 

[SJB060685]

I’d love a wood fire in my living room. The problem is due to my disability I live in a ground floor council flat. I would need permission for a wood fire from them and the external flue would look ugly even if they did agree, which is highly unlikely seeing as I have an ASHP . Electric fire would fo but at the price per KWH of electric I’d rather put more clothes on.

 

[JC22024]

I’d love a wood fire in my living room. The problem is due to my disability I live in a ground floor council flat. I would need permission for a wood fire from them and the external flue would look ugly even if they did agree, which is highly unlikely seeing as I have an ASHP . Electric fire would fo but at the price per KWH of electric I’d rather put more clothes on.

Yes the wood Fire is nice to look at also! How do you find the ASHP? I havent heard much good about them here mainly due to very high electricity bills in the dead of winter. (In new houses too) Did you see the recent Skill Builer you tube video on ASHPs?

It powers your underfloor heating? Is there a thermal store or any other heat inputs?

Don't get me wrong I'm sure they are great when set up correctly in a new property. I also did the plans for houses that has other renewables which worked very well. One for example had a ground source heat pump with piping buried in a fieled and a solar grid array down the garden out of sight powering it. Would have cost a furtone to install but basically runs itself

 

[SJB060685]

First off if the Skill Builder video series is who I think it is then do not pay attention to them. Heat Geek have a lot of videos on their website etc that are far more realistic.
My heat pump works don’t get me wrong but my electricity bill in the winter months is astronomical. It’s worth noting my installation was not done by me and to be honest not the best job but it does work. Unfortunately though because of the electricity it uses I would of preferred a mains gas boiler but that isn’t into my block of flats.
I’m 36 and have had chronic rheumatoid arthritis since birth. I’m now at the point where I walk with a walking stick and can’t imagine a wheelchair is too far away. I need warmth in my home and if I didn’t get my warm home discount this winter I would of froze to death.
Heat pumps do work but the system need careful design.

 

[JC22024]

First off if the Skill Builder video series is who I think it is then do not pay attention to them. Heat Geek have a lot of videos on their website etc that are far more realistic.
My heat pump works don’t get me wrong but my electricity bill in the winter months is astronomical. It’s worth noting my installation was not done by me and to be honest not the best job but it does work. Unfortunately though because of the electricity it uses I would of preferred a mains gas boiler but that isn’t into my block of flats.
I’m 36 and have had chronic rheumatoid arthritis since birth. I’m now at the point where I walk with a walking stick and can’t imagine a wheelchair is too far away. I need warmth in my home and if I didn’t get my warm home discount this winter I would of froze to death.
Heat pumps do work but the system need careful design.

Maybe they could add a central LPG tank and meter the flats separately?

Can you get an economy 7 type electricity tariff? I have that on my house. Nowadays its just how the meter charges the rates not actually separate circuits or anything as you likely know anyway.

So I have my hot water immersion auto timed every morning and also delay time my appliances like washing machine tumble dryer and dishwasher.

You might save some by having the ASHP run all night on the 3rd price electricity(?)

Sorry to hear of your arthritis I am 35 and kudos to you getting on and having a passion in your work

 

[SJB060685]

I had a smart meter installed a month ago and I’m under the impression I’m not entitled to any off peak special tariffs.
I had a play with my smart meter hub after writing my last comment. At the time my tv, fridge freezer and living room light were pulling 283 watts of power per second. I turned my room stat up to 23°c to bring on the heat pump. After the minute it takes to bring on the heat pump I checked the power my house was pulling. It had gone from 283 watts to 1.64 kw per second. I’m not sure of the COP of my unit at this outside temperature of 7°c in Taunton. Let’s say it’s 2.1. The unit was pulling an additional ~ 1.3 kw, therefore it would produce roughly 2.6 kw to every 1.3 of electricity drawn. It’s still free energy but that COP reduces as the outside temperature decreases.
These options I’ve found on the smart meter hub will allow me to run some tests in the near future.

 

[JC22024]

I had a smart meter installed a month ago and I’m under the impression I’m not entitled to any off peak special tariffs.
I had a play with my smart meter hub after writing my last comment. At the time my tv, fridge freezer and living room light were pulling 283 watts of power per second. I turned my room stat up to 23°c to bring on the heat pump. After the minute it takes to bring on the heat pump I checked the power my house was pulling. It had gone from 283 watts to 1.64 kw per second. I’m not sure of the COP of my unit at this outside temperature of 7°c in Taunton. Let’s say it’s 2.1. The unit was pulling an additional ~ 1.3 kw, therefore it would produce roughly 2.6 kw to every 1.3 of electricity drawn. It’s still free energy but that COP reduces as the outside temperature decreases.
These options I’ve found on the smart meter hub will allow me to run some tests in the near future.

Well it would be worth checking if your electricity provider if they offer am off peak tarrif.

Have you got LED lighting in your home also? I have been slow on the uptake myself. I had older energy saving lamps in my kitchen then upgraded to LED about a year ago. Only because I work full time and have a part time Architectural practice at home I did a tax return in Jan and noticed I saved £100 in electricity this year from the kitchen LED lights went In.

So a couple weeks back I raided the local electrical wholsaler of LED bulbs and upgraded the whole house.

 

[SJB060685]

No I don’t have LED lighting in my flat. Should definitely make the transition.

 

[John.g]

Haven't had time to tinker much with my heating system since. Just been running it as normal. Racked up 60 hours boiler thermostat call time on the BEM and it's showing an overall saving of 17.5%.

View attachment 73715

This is the average saving it does better on the upstairs than downstairs zone. Perhaps because running the upstairs the boiler is definitely oversized whereas it's just about right on the ground floor.

Still interested to carry out balancing when I get time. And to see if this new condensing boiler with BEM will get me through spring on 900L which would more than halve my regular winters oil bill!

Condensing is paramount to maximising efficiency. All oil boilers on the market today are condensing but for most oil boilers the similarities to their gas cousins stops there. The dew point for kerosene flue gases is a lot lower than mains gas. At ~ 47°c return temperature condensing will start but you are then relying on the secondary heat exchanger efficiency to make sure the water then returning to and through the primary heat exchanger is above dew point else you will get back end rot. There is ways to prevent this but it’s added parts, added cost and a bit of maths to make sure everything runs properly.
Gas boilers have higher dew point temperature but more importantly have the heat exchanger constructed of materials able to withstand lower water temperatures and not rot. The lower the return temperature can be the greater the level of condensing and therefore efficiency. Also gas modulating boilers are even more efficient at part load, whereas with oil you have to meet certain criteria on most boilers.
I know I’ve banged on about it a lot and I do apologise but the Sapphire boiler is an absolutely huge advancement in the oil world. Fully modulating, so can closely match the ever changing load with minimal cycling, excess fuel consumption and burner wear and tear.
For maximum efficiency you want good modulation and low flow temperatures. If a fixed rate burner like most oil burners I would consider a different system design approach to the common S and Y plans.

Worth a read.

Boiler Modulation: What is Boiler Modulation & Boiler Cycling

Discover the benefits of boiler modulation! Learn how boiler modulation optimises energy usage, increases efficiency, and reduces operating costs.

www.heatgeek.com

This trend (from the above) doesn't make a lot of sense though as it doesn't give the total cycle time(s)

 

[JC22024]

No I don’t have LED lighting in my flat. Should definitely make the transition.

I ended up going with warm white LED lights throughout the interior of my house. There are multiple studies out there indicating white LEDs may be detrimental to your health

Light Pollution - Human Health Impacts from LEDs

Light Pollution - Human Health Impacts from LEDs - Designing Buildings - Share your construction industry knowledge. A groundbreaking report released by the American Medical Association (AMA) Council on Science and Public Health affirms known and suspected impacts to human health and the...

www.designingbuildings.co.uk

In any case I also simply prefer warm lights anyway so it was an easy decision. And LEDs give out alot more light typically.

 

[SJB060685]

I ended up going with warm white LED lights throughout the interior of my house. There are multiple studies out there indicating white LEDs may be detrimental to your health

Light Pollution - Human Health Impacts from LEDs

Light Pollution - Human Health Impacts from LEDs - Designing Buildings - Share your construction industry knowledge. A groundbreaking report released by the American Medical Association (AMA) Council on Science and Public Health affirms known and suspected impacts to human health and the...

www.designingbuildings.co.uk

In any case I also simply prefer warm lights anyway so it was an easy decision. And LEDs give out alot more light typically.

So avoid white LED’s?

 

[SJB060685]

Worth a read.

Boiler Modulation: What is Boiler Modulation & Boiler Cycling

Discover the benefits of boiler modulation! Learn how boiler modulation optimises energy usage, increases efficiency, and reduces operating costs.

www.heatgeek.com

This trend (from the above) doesn't make a lot of sense though as it doesn't give the total cycle time(s)
View attachment 74117

Several of us on this forum have done the Hest Geek course . A subject discussed on their website quite a lot.

 

[JC22024]

So avoid white LED’s?

Yes I think for a dwelling it is best to avoid white LEDs personally. For Offices and Commercial uses White are great however.

2700 - 3000k is what I aim for.

I do have a pre payment type Electricity Meter in my house. Electricity prices went up here in Jan. But before they did I topped up £300. For only two of us in the house we tend to go through alot of electricity..... depite using delay settings on washing machines at night etc too on the cheaper economy 7 rate.

I had about 50% of my house on LED lights until recently. Then I updated the remaining bulbs to all LED warm white. Some rooms like the hallway had alot of bulbs so the 90% savings multiplied by over 10 bulbs would add up.

And certainly knowing how much we normally consume and checking the meter reading since (Which is just a £ remaing figure in a small display in the Kitchen) it appears swapping the remaining bulbs and probably the ones that get the most use has made a marked imrovement in savings. More than I would have thought I mean. Will know better after a few months and when doing Tax return (Which makes me go through utility bills) but could be saving 50p per day.

 

[Chuck]

I ended up going with warm white LED lights throughout the interior of my house.

About four or five years ago, after some experimenting with types and makes I went for Philips 2700K LEDs throughout and they're great. In a couple of places I have the dimable ones and these reduce the colour temperature as you dim them (getting a touch more orange at lower levels), which is a nice touch. The whole exercise paid for itself in about 12-18 months.

I'd strongly recommend you only choose between traditional brands (Philips, Osram, etc.) because the cheaper 'own brand', eBay, etc. samples proved to have a bad colour spectrum, be unreliable and, in one case, dangerous.

 

[JC22024]

I just purchased one of these smart Oil level monitors. It can determine the estimated run out date and chart oil Consumption trends. Will install it Saturday evening and see how it does over the next while. Much more reliable than depending on myself to look into the tank!

 

[JC22024]

The sensit is up and running, pretty good the way it can record and chart data and try to anticipate run out date. Weekly email reports can be generated etc detailing the exact litres in the tank for records.

 

[Ric2013]

Hi @JC22024 again. I've been reading through a printed-out copy of this thread and regarding post #92, I feel a need to correct your misunderstanding of how smart pumps generally work. A proportional pressure pump (including Grundfos Autoadapt) seeks to keep the pressure drop constant across the radiators. It very slightly drops the pressure as TRVs close to try to compensate for the decreased pressure losses across the boiler primaries (so there is some truth in your understanding) but one TRV shutting should not cause other radiators to fall dead. It does not drop the pressure very much. Conversely, a 'dumb' pump cannot help but increase its pressure as TRVs throttle down, thus forcing more flow through any TRVs that remain partially open, sometime resulting in whistling. They (smart pumps) aren't without issues, particularly as the conventional automatic bypass valves often fitted to heating systems rely on an increase in pressure to open up as TRVs are shutting down.

Constant pressure will keep the pressure constant across the boiler (but not compensate for the primaries: that's the difference, plus CP is usually a much higher pressure setting).

The way most smart pumps do this is by monitoring power consumption to get an idea of how much drag is being created and then varying the speed of the impeller. Unlike the older pumps which ran at a fixed speed.

I've balanced my own house before and after replacing a pump. The new pump has proportional pressure and I thought I'd give it a go. It actually made balancing MUCH easier as, when I throttled back one radiator, that didn't then result in an increase in pressure and hence flow to the remaining radiators. So instead of going around the house several times tweaking as I went, I only really needed a couple of passes.

Re post #152, I wonder if you could help me follow your explanation better? Please let me know if I follow your understanding correctly or not... you say you think the Vector BEM works by allowing the boiler to first run to temp [i.e. until the boiler cuts out on its internal thermostat?] and then, [when the boiler decides to re-fire?] slightly delays [the next firing up of the boiler?] and then continues doing this while also monitoring the run time and stat call time? Which stat are we discussing? Room stat, I assume?

Are you saying that your understanding is that the BEM is monitoring the boiler duty cycle and delaying the boiler from firing for progressively longer times until it notices that this is reducing the system's ability to get the room temperature up to the required temperature? I'm struggling to get my head around how this works, but it would be interesting to be able to do so.

Thank you.

 

[JC22024]

Hi @JC22024 again. I've been reading through a printed-out copy of this thread and regarding post #92, I feel a need to correct your misunderstanding of how smart pumps generally work. A proportional pressure pump (including Grundfos Autoadapt) seeks to keep the pressure drop constant across the radiators. It very slightly drops the pressure as TRVs close to try to compensate for the decreased pressure losses across the boiler primaries (so there is some truth in your understanding) but one TRV shutting should not cause other radiators to fall dead. It does not drop the pressure very much. Conversely, a 'dumb' pump cannot help but increase its pressure as TRVs throttle down, thus forcing more flow through any TRVs that remain partially open, sometime resulting in whistling. They (smart pumps) aren't without issues, particularly as the conventional automatic bypass valves often fitted to heating systems rely on an increase in pressure to open up as TRVs are shutting down.

Constant pressure will keep the pressure constant across the boiler (but not compensate for the primaries: that's the difference, plus CP is usually a much higher pressure setting).

The way most smart pumps do this is by monitoring power consumption to get an idea of how much drag is being created and then varying the speed of the impeller. Unlike the older pumps which ran at a fixed speed.

I've balanced my own house before and after replacing a pump. The new pump has proportional pressure and I thought I'd give it a go. It actually made balancing MUCH easier as, when I throttled back one radiator, that didn't then result in an increase in pressure and hence flow to the remaining radiators. So instead of going around the house several times tweaking as I went, I only really needed a couple of passes.

Re post #152, I wonder if you could help me follow your explanation better? Please let me know if I follow your understanding correctly or not... you say you think the Vector BEM works by allowing the boiler to first run to temp [i.e. until the boiler cuts out on its internal thermostat?] and then, [when the boiler decides to re-fire?] slightly delays [the next firing up of the boiler?] and then continues doing this while also monitoring the run time and stat call time? Which stat are we discussing? Room stat, I assume?

Are you saying that your understanding is that the BEM is monitoring the boiler duty cycle and delaying the boiler from firing for progressively longer times until it notices that this is reducing the system's ability to get the room temperature up to the required temperature? I'm struggling to get my head around how this works, but it would be interesting to be able to do so.

Thank you.

Thanks for that, yes I would agree I don't fully understand the Smart Pumps! Its quite likely my Grundfoss one was faulty too. The regular type pump has been fantastic so far so I don't need to test the pumps any further but no doubt smart pumps have advantages yes.

Ref the BEM, it only has 2no inputs.

1st input is a live feed which is the boiler call signal. Aka the live feed from the room stats which powers the boiler and pump in my conventional system.

2nd input Is from the call side of the boiler thermostat.

That's it. It has no other sensors or data from indoor or outdoor temperatures.

First time the boiler fires up for the day the BEM gets its power feed and starts and also sees how the boiler is firing until the boiler thermostat is satisfied and shuts off. BEM is still live and monitoring from the boiler call feed. Then the boiler stat begins to call again and the BEM delays the burner from firing for a short time then let's it fire until the boiler stat is fully satisfied once more. Watch the video below to see this cycle:


The BEM continues to monitor and log the boiler firing cycles and delaying them more and more until it is effectively matching the system demand over time. (At least this is my understanding of it) Then once the room thermostat / heating call signal stops the BEM and boiler stops and will start from scratch again the next time heating is fired up.

What I like about this particular one is it always let's the boiler thermostat fully satisfy and turn off before it then delays it firing up again. Therefore the comfort inside the house is unaffected as the water temperature does reach full stat just that it will be dropping lower in between boiler firing cycles.

What I will say thinking about this more in recent weeks is the clocks it is showing are accurate in that it is recording boiler stat call time and the boiler burner time (which it reduces) but it's not really accurate to say this is a xx% saving in oil.

Its more of a meter showing how much it has delayed the burner. So the % of oil saved is lower than what the clocks state but it is definitely reducing the boiler cycling as much as practical so this is its main purpose and advantage.

 

[SJB060685]

@Ric2013 your comments about PP and CP are bang on, so no need to elaborate further there.

With regards to the controller it does exactly how you picture it and is actually quite an intelligent and sophisticated unit.
The heat source in question is an oil boiler and as I’m sure you are aware 99% of domestic oil boilers currently installed are fixed rate output (there are now a couple boilers on the market that one fully modulates and the other is a two stage burner).
The problem with fixed rate burners is unless the outdoor temperature is at design temperature (say -2°c, depends on location) then a fixed rate burner will always cycle and the warmer it is outside the greater this cycling is. This particular unit will monitor and I assume learn these cycle rates and prevent unnecessary firing cycles. Let’s say it’s a 20 kw load at -2°c and a target room temperature of 20°c but the outside temperature is 11°c. You now only require half the output and you would find the burner will run for say 5 minutes and off for 5 minutes while maintaining your internal temperature. The problem is though during that burner off period the flow sensor will notice a drop in temperature and bring the burner on while the rooms are at temperature and try’s closed. This then only circulated water through a bypass or heat sink, the water doesn’t displace any energy and in turn the boiler cycles more. Constant stop starts for any heat source are not good and I know you know why. This unit can minimise this cycling, not only saving fuel but also extending the life of burner components.