Condensing combi boiler high flow

[Hamedhbb]

Hi All

This is my first post here. Have been using this forum for a while but just joined. I have recently changed a radiator in toilet downstairs with a column type and it didn’t warm up properly. I thought I would balance the whole system to get it right. Searched the interweb a lot but many of things people talk about doesn’t work for me. I have studied mechanical engineer and understand some of it. This is the story:
The house is 3 years old in 3 stories. Combi boiler is ideal logic+ esp1 35. The boiler is downstairs, auto bypass valve and motorised zone valves are first floor. Zone one is ground floor and zone two is 1st and 2nd floor. Each zone has a standard danfus room thermostat. An outdoor sensors is wired to the boiler. There is no expansion vessel anywhere in the system other than the one inside boiler.

In an attempt to balance, I noticed:
1- auto bypass valve stuck open. Replaced it.
2- 5 out of 13 radiators has TRV on return. Swapped TRV and lock-shield valve on those.

I closed valves on 11 radiators and only left two radiators with double lock shield on. Although they are fully open, I have to set auto-bypass to 6 (around 0.6bar) to prevent any bypass. ABV is 1.5m higher than the pump.

Then I found the order of radiators in terms of distance to boiler and started balancing. I have to be extremely accurate with lockshield valves to get anything more than 5’C temperature difference(I use twin input thermometer). This applies to the radiators furthest from the boiler with two unrestricted flow on twin lockshield radiators.

even different between flow and return just below the boiler hardly goes above 8’C.

Even if I try to restrict the flow using flow or retun valves beneath the boiler the delta T will not go beyond 11’C. In fact boiler ramps up the flame and fan speed.

instruction manual does not mention how to adjust the pump speed. It is controlled by boiler and the only setting I could find was to set minimum pump power to 70%. It does mention temp drop over rads should be around 20’C.

The only reason I can think of is that the boiler is unnecessarily running pump at high flow and kicks the flame in to keep delta low.

All lockshield valves used to set fully open before I start and now I set them at absolute lowest flow which they will shut with slightest knock! Maybe 1/16 of a turn. Even if I could balance them, two rads with unrestricted flow will increase the return temp and boiler will not work at condensing point.

would you guys help me to understand what I am missing here?

thanks

 

[gasbanni]

One rad not warming up properly ....⁴.
Close all the rads ( just one lockshield and not both ) except the rad that's not heating up.
Put a demand on every circuit bleed the rad that's not heating up ...it should now heat up.

I didn't read all the thread its late and I'm tired, I'm assuming all your controls are working properly ....it you hear the sound of running water anywhere in the heating circuit you've gotvair in it so it needs bleeding..

The rad that's not heating properly should heat up now if it doesn't you got a problem and it isn't anything to do with balancing.

In decades in the game balancing has only caused problems a handful of times. Blockages or air locks that's different!

Once thevrads hot start at tge top of your house opening one rad at a timevand bleeding itvand work your way down. This should sort it out.

 

[DP]

In an attempt to balance, I noticed:
1- auto bypass valve stuck open. Replaced it.
2- 5 out of 13 radiators has TRV on return. Swapped TRV and lock-shield valve on those.

Close the bypass for the duration of the balancing process for the time being
TRV position makes no difference if these are bidirectional

Then I found the order of radiators in terms of distance to boiler and started balancing. I have to be extremely accurate with lockshield valves to get anything more than 5’C temperature difference(I use twin input thermometer). This applies to the radiators furthest from the boiler with two unrestricted flow on twin lockshield radiators.

Ensure all rads are on line as well as the cylinder. Greater Water flow will be through a loop with lower resistance. Furthest radiator will hence be deprived of adequate flow. So initially restrict shorter loops and open wide the long loop rads

Go for a walk. Come back when system has stabilised.
Now by feel and judgement, tweak each load to adjust for hot and not so hot flow and return pipes.
Go for another walk
Return and now get the pipe clamps out and adjust for 20 degree differential

ABF should open when the motorised valves have closed but the pump is running to dissipate residual boiler heat

radiators with double lock shield on.

What is a double lockshield

 

[ianmcd]

Post a pic of your new rad and valves

 

[Hamedhbb]

One rad not warming up properly ....⁴.
Close all the rads ( just one lockshield and not both ) except the rad that's not heating up.
Put a demand on every circuit bleed the rad that's not heating up ...it should now heat up.

I didn't read all the thread its late and I'm tired, I'm assuming all your controls are working properly ....it you hear the sound of running water anywhere in the heating circuit you've gotvair in it so it needs bleeding..

The rad that's not heating properly should heat up now if it doesn't you got a problem and it isn't anything to do with balancing.

In decades in the game balancing has only caused problems a handful of times. Blockages or air locks that's different!

Once thevrads hot start at tge top of your house opening one rad at a timevand bleeding itvand work your way down. This should sort it out.

Thank you. The column radiator was slow to warm up and it is sorted when I tried to balance. but still the difference between flow and return just next to combi boiler is small.

 

[Hamedhbb]

Close the bypass for the duration of the balancing process for the time being
TRV position makes no difference if these are bidirectional

They are bidirectional according to the arrows on the TRV. I switched them anyway only because it took ages for lockshield changes to take effect.

Ensure all rads are on line as well as the cylinder. Greater Water flow will be through a loop with lower resistance. Furthest radiator will hence be deprived of adequate flow. So initially restrict shorter loops and open wide the long loop rads

Go for a walk. Come back when system has stabilised.
Now by feel and judgement, tweak each load to adjust for hot and not so hot flow and return pipes.
Go for another walk
Return and now get the pipe clamps out and adjust for 20 degree differential

ABF should open when the motorised valves have closed but the pump is running to dissipate residual boiler hea

My problem is that there is too much flow. I can easily get the furthest radiator to 70'C by restricting the other one. my problem is to have them all have a 20C temperature drop across.

I did this:
1- shut all radiators except the two (one on each zone) which should have unrestricted flow (no TRV). set thermostat to call for heat. closed the ABV until I couldn't hear any flow through ABV. Then close motorised valves individually and fine-tunned the ABV. the setting is at its highest to get this going.
2- I opened the lockshield on all other rads by a quarter of a turn. let it run for 30mins. measured temp at the flow on each rad. based on temperature decided which one is getting more flow and started balancing from the rad with the highest temp to lowest.
3- Start to close the lockshield until the temperature drop is 20'C or as high as possible. Most of the rads had their valve open line 1/16 of a turn to achieve this.
4- Let it trun for an hour and recheck all rads and adjust if necessary.
During the whole above process, combi boiler flow was around 68'C and it was set to "e" that should control condensing automatically. ( I am not sure if the outside temperature can overwrite that?)

At this point, the radiator felt lukewarm but I achieved 20'C that is the figure mentioned in the balancing section of the instruction manual.

I closed the return valve on two unrestricted rads to the lowest possible position. these two can never achieve a temperature drop of more than 5'C.

5- I shut the whole system down overnight. In the morning, I set the thermostat to 24'C but the radiators got barely warm. checked the boiler, it turns the burner on for a few seconds, reached to 50'C at the boiler flow, switches the burner off and keep the pump running. I can hear the flow in rads but because the flow is low at the boiler, radiators don't get got.

So there is a contradiction between the minimum flow the boiler needs ( otherwise turns the temperature of the flow down), the mentioned temperature drop over rads according to the manual.
If I keep two rads without TRV open or set ABV low, there will be a quick return to the boiler, it increases the return temp, the boiler increases the flow temp, radiators get hot but a condensing boiler needs a larger delta T between flow and return to work efficiently (right?).
If I restrict those two rads without TRV, close ABV to force the flow through the radiators and set them to 20'C temp drop, the boiler return drops and boiler reduce the flow temp from 68'C to around 50'C. At this point, rads are effectively cold. The flow at rads reaches only 40 and the return of rads is only 20'C which was room temp at the time of my test!

I could not find any way to adjust the pump speed or set desired flow/head on the boiler. It only gives me the option of running at 100% "power" or automatically adjusting it between 70%-100% depending on the load.

What is a double lockshield

On each zone there is one rad that doesn't have a TRV. both sides are lockshield valves. one is fixed and the other one could be turned by hand.

 

[Hamedhbb]

Post a pic of your new rad and valves

I am not home now, this is the new rad:
https://www.bathroommountain.co.uk/...mirror-radiator-1800x260mm-31167?parent=V3081

this is the set on rads with TRV:
https://www.pegleryorkshire.co.uk/E...Mistral_II_TRV_Lockshield_Pack_with_drain_off

This is used instead of TRV on only two rads. one per zone:
https://www.pegleryorkshire.co.uk/E...es/product/M1PC_Mistral_manual_radiator_valve

Other rads are from various sizes, single or double of this type:
https://www.screwfix.com/p/kudox-pr...Vj4BQBh12xgDFEAYYASABEgJ2c_D_BwE&gclsrc=aw.ds

Boiler is :
https://www.travisperkins.co.uk/com...VW-vtCh1ylgDnEAQYAyABEgK1mfD_BwE&gclsrc=aw.ds

Is there any way to configure boiler settings other than service functions available? there is nothing in the user manual (link below).
https://idealheating.com/uploads/documents/logic-combi-esp1-installation-and-servicing.pdf

 

[Hamedhbb]

reading the balancing procedure for the boiler, it says to set the "programmer" to On for balancing and return it to "Normal". I assumed it is the room thermostat but reading it again, it is not. it doesn't mention in the manual what is the programmer. is it something connected through opentherm or another diagnosis device? or it's just a programmable room thermostat?
I have Danfoss TP5000Si, one per zone.

It seems the boiler has a service connector that is not mentioned in the manual but it has 4 pins and probably it uses a serial connection.

 

[BlueLoo]

Some amateur thoughts:

You don't need to have permanent lockshields on a non trv rad if you have a bypass. You are doubling up on the purpose. In your case, quadrupling up on the purpose. You now have 4 bypasses. 3xManual and 1 automatic.

Draw out your system (you're a ME, you know how to do that). Make sure your bypass is configured correctly (because clearly, the installer didn't do ut right) and then maybe put those three rads back onto normal trv valves. Read the manual on the bypass valve. It will tell you how to set it. It works off differential pressure.
Also, check the pump. Make sure its working in the correct mode if is variable speed. With an ABV, it has to be fixed speed. You could use variable speed but then you need to lock out the ABV and then open up those lockshield valves again.

Also, try to understand what balancing is vs what you think it is.

What you are actually doing is throttling flow to equalise flow rate in the system. If you have a modern manifold system, (check it) it's fairly pointless as a manifold is self balancing (within reason).

If you are deliberately throttling flow to adjust delta t over the radiator or circuit, thats something different.

Point is, don't get caught up "balancing" the system unnecessarily to find that you can't throttle (or not) for delta t at the boiler.

I'm still not sure how one throttles a complex CH system in a modern, well insulated house with low heat loss where the CH boiler is probably only operating at a percentage of its output and it hooked up to a modulating programmer with external and load compensation. So many variables.

Best of luck.

 

[Hamedhbb]

You don't need to have permanent lockshields on a non trv rad if you have a bypass. You are doubling up on the purpose. In your case, quadrupling up on the purpose. You now have 4 bypasses. 3xManual and 1 automatic.

That's right plus I am sure there is one auto bypass inside the boiler. the external one is just in case both zone valves are closed and to protect the internal one I guess.

Draw out your system (you're a ME, you know how to do that). Make sure your bypass is configured correctly (because clearly, the installer didn't do ut right) and then maybe put those three rads back onto normal trv valves. Read the manual on the bypass valve. It will tell you how to set it. It works off differential pressure.
Also, check the pump. Make sure its working in the correct mode if is variable speed. With an ABV, it has to be fixed speed. You could use variable speed but then you need to lock out the ABV and then open up those lockshield valves again.

The problem is user manual does not say anything special. not even pump head vs flow. I can see on utube a new version have all settings I am after on the display. mine doesn't have that. however, I found something interesting just a moment ago. mine has a weather compensations sensor and I am not sure how it is wired to my boiler but it seems when that is installed, pump flow is corrected based on the difference between thermostat setpoint and outdoor temperature. I had a room thermostat set to 27 and outside was around 2-3'C. my impression was my thermostat do not talk to the boiler. Opentherm port is not connected to anything. maybe flow was high due to cold weather and it didn't meant to achieve 20'C drop?

 

[BlueLoo]

That's right plus I am sure there is one auto bypass inside the boiler. the external one is just in case both zone valves are closed and to protect the internal one I guess.


The problem is user manual does not say anything special. not even pump head vs flow. I can see on utube a new version have all settings I am after on the display. mine doesn't have that. however, I found something interesting just a moment ago. mine has a weather compensations sensor and I am not sure how it is wired to my boiler but it seems when that is installed, pump flow is corrected based on the difference between thermostat setpoint and outdoor temperature. I had a room thermostat set to 27 and outside was around 2-3'C. my impression was my thermostat do not talk to the boiler. Opentherm port is not connected to anything. maybe flow was high due to cold weather and it didn't meant to achieve 20'C drop?

Don't assume that your new house is plumbed or wired correctly or competently.
Download the boiler OEM. Draw out your system, both electrically and hydraulically. download all the OEMs for all the kit you have.
Start from scratch. Make sure everything is connected properly.
I was in your position a few years ago. I ended up completely rewiring and replumbing the CH and HW system because it was all mostly installed badly.

Read the boiler manual it will be specific about bypass requirements.
I've argued with others on here about this so do your own research but imho, if the boiler doesn't need one as its managed internally, dont put another one in. Every additional bypass adds inefficiency to both the pump and the boiler.

Look to put Trvs on all rads. Read up about stat location and operations. Trvs can cause hysteresis errors if they are in the same room as the stat but having a trv body fitted means you can just remove the head if required or, eventually, update the system to smarts without further plumbing.

Also, whilst you are looking through that. If you are inquisitive, download the CBRE guide to domestic heating design. It's a great reference. It will tell you how a system should be designed and you can do some check calcs. I did this and using the pump OEM, set my pump curves accordingly. (Well, at least figured out what ball park it should be in).

 

[kidgreen61]

Some column rads have a baffle in them, and have to fed one side only

 

[Hamedhbb]

Don't assume that your new house is plumbed or wired correctly or competently.

That is very true! The system was not balanced properly when we moved in. all lockshield were fully open. the ABV was making a funny noise. we called the installer back and within 2 mins, he turned the ABV dial and left. which can have an impact on a balanced system. since then the heating became slow to warm the house up.
At the design level, it has a big problem that I could not get anywhere with the builder. The room thermostat that controls the zone valve for 1st and 2nd floor is located in the master bedroom, literally above the radiator only 20cm to the left and 80cm above) and that's the radiator which has two valves (i.e. always on!) If I shut the door at night or leave that radiator on, every other room would be cold. It doesn't need engineering knowledge to see this but builders insist that the system is designed by a qualified engineer and they use it on many houses each year! After getting it balanced, I have to fit a wireless thermostat that I can install somewhere in the hallway.

 

[Hamedhbb]

Some column rads have a baffle in them, and have to fed one side only

Yes, flow and return were labelled when arrived and I used them. the radiator temperature is fixed. it's just to get it working as a condenser boiler which is concerning me.

 

[BlueLoo]

That is very true! The system was not balanced properly when we moved in. all lockshield were fully open. the ABV was making a funny noise. we called the installer back and within 2 mins, he turned the ABV dial and left. which can have an impact on a balanced system. since then the heating became slow to warm the house up.
At the design level, it has a big problem that I could not get anywhere with the builder. The room thermostat that controls the zone valve for 1st and 2nd floor is located in the master bedroom, literally above the radiator only 20cm to the left and 80cm above) and that's the radiator which has two valves (i.e. always on!) If I shut the door at night or leave that radiator on, every other room would be cold. It doesn't need engineering knowledge to see this but builders insist that the system is designed by a qualified engineer and they use it on many houses each year! After getting it balanced, I have to fit a wireless thermostat that I can install somewhere in the hallway.

A cut n paste install by someone who doesn't give a ****.

Dreadful.

I keep seeing comment about the ABV being some sort of magic wonder knob that installers twiddle if called back. A basic understanding of it would tell you that is utter ******.

It's either set right or not, neither of which is likely with the valve at min or max.


As for thermostats, don't just install a new one somewhere else.

Go and look at the manufacturer's websites, read up on latest tech and see what can be done.

I got rid of the zones, zone valves and stats altogether. Probably a extreme but it works for me.

One of the reasons for me doing that was the bedrooms, having 5 users each wanting their own settings made having a gross zone control pointless. Having the zone stat in the main bedroom with two people warming it meant every one else were freezing.

If you put a zone stat in a hall, it needs to have a rad in that space. Otherwise, the stat will remain in a cold condition and heating will be on continually in the bedrooms, be that limited by trvs if fitted, and if so, putting the boiler in a state of constant bypass as it spends most of its time just heating up the zone circuit.

Take a step back and look at the logic of what you need vs what you have vs what you can get.

Forgot zoning. Use it if it suits but treat it as an option, not an absolute.

Best of luck.