Heating and cooling: Thermal Store and Radiators Temperature

31 to 60 of 80

- CommentAuthorBenm85
- CommentTimeJan 26th 2021
Posted By: philedgeHaving a pipe stat on the flow pipe that inhibits the pump when the boiler is cold, is Dunsleys recommended way of wiring things. Unless youve got problems with excess soot in the fire or flue then I woulnt worry about minimum stove temperatures, so long as the stat setting is correct!

Thank philedge.
- CommentAuthorBenm85
- CommentTimeJan 26th 2021 edited
Ok, this is my best go at a diagram. This is what it looks like (to me). The only difference is my solid fuel return is at the bottom of the tank, not half up as indicated on the diagram. Not sure if that makes any difference.
- CommentAuthorGreenPaddy
- CommentTimeJan 26th 2021
Philedge - when linked to a thermal store, unless you blend stove flow into the return, you will always be drawing cool water from the base of the TS, until the whole TS starts to get hot to the base, which for a 350 litre store like Ben's could take hours, all the while drawing the cool water into the stove. It may be recommended by some people, but as I said, it's not a way of controlling the temperature of feed water to the stove. That is something that is not good practice.

Also, as the stove starts to cool, having heated the TS to a temp above the fixed pump stat temp, there's a chance you could have a continuous run of the pump, as it pumps hot water from the TS, through the stove to the stat, self perpetuating. Also not clever.

Anyway, that's by the by. Ben your diagram is very helpful. All heat inputs and outputs are from the main body of TS water, so no issues with undersized coils. There is the issue with crud being able to get to all parts of the system, and choking flow rates. Your gas boiler at 30kW could charge your store from cold in about 30 mins. With full CH demand (16kW I think you said) it would take the boiler an hour.

So the heat is neither getting from the gas boiler to the TS, nor from the TS to the rads. That's either because the gas boiler is being told not to run, or because the flow rate is insufficient. Big coincidence that the flow rate could be insufficient in both the boiler AND CH circuits (ignoring the stove for the moment as it's less predictable). The only common link between gas boiler and the CH circuits should be the shared water (and any bits floating in it). You have all the right bits and pieces, they just are not being allowed to do their job.
- CommentAuthorBenm85
- CommentTimeJan 26th 2021 edited
Posted By: GreenPaddyP

Anyway, that's by the by. Ben your diagram is very helpful. All heat inputs and outputs are from the main body of TS water, so no issues with undersized coils. There is the issue with crud being able to get to all parts of the system, and choking flow rates. Your gas boiler at 30kW could charge your store from cold in about 30 mins. With full CH demand (16kW I think you said) it would take the boiler an hour.

So the heat is neither getting from the gas boiler to the TS, nor from the TS to the rads. That's either because the gas boiler is being told not to run, or because the flow rate is insufficient. Big coincidence that the flow rate could be insufficient in both the boiler AND CH circuits (ignoring the stove for the moment as it's less predictable). The only common link between gas boiler and the CH circuits should be the shared water (and any bits floating in it). You have all the right bits and pieces, they just are not being allowed to do their job.

Thanks GreenPaddy. I took some temp readings using a Salt food thermometer we have wedged between the copper pipe and insulation. Granted, probably not as accurate as a IR one, but thought I'd try. So the the flow from the boiler (at the boiler) was reading 65c. The flow from the boiler at the tank was also measure 65c. This is pretty odd as it is set to 85c. Don't think it coincidence that it struggles to get beyond 60c if it's only getting 65c from the boiler. Oddly, the boiler is knocking off as it gets to 65c, like it thinks the tank set to that temp. But the control stat is at 75c on the TS. You can audibly hear the click when you turn the dial of the thermostat to get a rough reading on tank temp, so it's working.

As it is a combi boiler being used as a system boiler, it has different setting for DHW temp and CH temp. Perhaps strangely, the DHW temp is set to 65c. The control panel is telling me the CH is running and thus should be pumping out 85c (or close to it). Probably just a coincidence! Need to order an IR thermo to be absolutely sure, but you can still hold the flow from the boiler, which I would be surprised you could if it was at 85c.
- CommentAuthorGreenPaddy
- CommentTimeJan 26th 2021
If you can hold the pipe, it's not much above 50oC.
- CommentAuthorBenm85
- CommentTimeJan 26th 2021
Posted By: GreenPaddyIf you can hold the pipe, it's not much above 50oC.

You can switch modes on the Intergas boiler, from combi, to heat only and to system. Theres a good video online, but really nervous about playing around with it. The temptation is to make sure it is in 'system mode' but no entirely sure how it works or it should be in some other type of mode.

Annoyingly, it was only serviced shortly before Christmas and nothing was picked up!
- CommentAuthorPile-o-Stone
- CommentTimeJan 26th 2021
We have a thermal store and its temperature plummets when the central heating is turned on, due to the hot water being pushed into the rads and pipework and the cold water coming from them. The thermal store heats up a bit once the radiators get hot, but the water is always losing heat (that's what radiators are for), so we never get a hot TS.

We also have an issue with the radiators not getting hot enough. Our plumber thinks we need a larger gas boiler as the house is quite large and over 3 levels. We have about 16 radiators and a 350l thermal store to heat and the boiler maybe isn't up to the job.
- CommentAuthorBenm85
- CommentTimeJan 26th 2021
Posted By: Pile-o-StoneWe have a thermal store and its temperature plummets when the central heating is turned on, due to the hot water being pushed into the rads and pipework and the cold water coming from them. The thermal store heats up a bit once the radiators get hot, but the water is always losing heat (that's what radiators are for), so we never get a hot TS.

We also have an issue with the radiators not getting hot enough. Our plumber thinks we need a larger gas boiler as the house is quite large and over 3 levels. We have about 16 radiators and a 350l thermal store to heat and the boiler maybe isn't up to the job.

If you have a read back of this thread, there is a bit of investigative work to do, such as working out the total heat output of your rads, the heat out put your boiler, temps of flow and returns, doing a diagram of your system etc. Hours of fun!
- CommentAuthorJeff B
- CommentTimeJan 26th 2021
Posted By: Pile-o-StoneWe have a thermal store and its temperature plummets when the central heating is turned on, due to the hot water being pushed into the rads and pipework and the cold water coming from them. The thermal store heats up a bit once the radiators get hot, but the water is always losing heat (that's what radiators are for), so we never get a hot TS.

We also have an issue with the radiators not getting hot enough. Our plumber thinks we need a larger gas boiler as the house is quite large and over 3 levels. We have about 16 radiators and a 350l thermal store to heat and the boiler maybe isn't up to the job.

See also: http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16819&page=1#Item_0

for a lengthy discussion along the same lines.(Don't be put off by the title of the thread, the discussion does deviate somewhat!).
- CommentAuthorBenm85
- CommentTimeJan 26th 2021
Definite issue with the boiler. The 65c temp on the boiler flow reading earlier (no CH on) then dropped to 58c when the CH had been on about 45 mins.

Canâ€™t really understand why flow temp would drop like that
- CommentAuthordjh
- CommentTimeJan 26th 2021
Posted By: Benm85Canâ€™t really understand why flow temp would drop like that

What's the return temperature to the boiler?

It sounds like as well as the plumbing diagram we really need to get a wiring diagram, showing what sensors there are and what they're connected to, plus various control settings.
- CommentAuthorBenm85
- CommentTimeJan 26th 2021
Flow is now at 55c at the TS and return is 42c. Both downstairs and upstairs heating on now, so the TS is struggling to maintain.

Iâ€™ll take a look at a wiring diagram later when the kids are in bed.

There are only two thermostats on the tank. One in the centre, connected to the boiler controls; and one at the top controlling the back boiler on the stove (the overheat, I think).

Just not sure why the flow temp would decrease, even ignoring the fact itâ€™s not coming out at the set 85c!

The temptation is the let the stove go out to ensure no input from that, and let the tank cool over night and fire the boiler in the morning to get a true test of what the boiler flow actually is. Not sure the wife will be happy with no heating whilst I run this experiment!
- CommentAuthorPeter_in_Hungary
- CommentTimeJan 26th 2021
Posted By: Benm85Definite issue with the boiler. The 65c temp on the boiler flow reading earlier (no CH on) then dropped to 58c when the CH had been on about 45 mins.

I think that you need to get a thermometer that gives an accurate reading of the pipes.

Posted By: Benm85You can audibly hear the click when you turn the dial of the thermostat to get a rough reading on tank temp, so it's working.

If the boiler out temp. is actually 65deg but the boiler is set 75deg then this would indicate a faulty thermostat. Hearing a click (usually) means that the thermostat is switching but the switch point temp. seen on the dial doesn't guarantee the actual switch temp. Whilst the boiler might have been recently serviced a thermostat misreading a temp. won't have been picked up.

Posted By: Benm85So the the flow from the boiler (at the boiler) was reading 65c. The flow from the boiler at the tank was also measure 65c. This is pretty odd as it is set to 85c. Don't think it coincidence that it struggles to get beyond 60c if it's only getting 65c from the boiler. Oddly, the boiler is knocking off as it gets to 65c, like it thinks the tank set to that temp. But the control stat is at 75c on the TS.

Is the boiler CH controlled by the internal boiler thermostat or the thermostat on the TS,it seems you are mentioning two thermostats, one at 75 and the other at 85.
I would also expect an over temp. thermostat on the boiler to cut it off if the temp. is too high - this is also a potential fault point cutting the boiler out at 65deg. regardless of the set temp.

Whilst the diagram of the TS is helpful it could be misleading. Your TS (having had a quick look online) has the optional extra of a coil for the boiler, do you know if this has been fitted?

Posted By: Benm85Definite issue with the boiler. The 65c temp on the boiler flow reading earlier (no CH on) then dropped to 58c when the CH had been on about 45 mins.

If there was a blockage in the boiler to TS pipework I would expect to see the boiler temp. at the set temp, but the return at TS return temp.. I would also expect to see the boiler short cycling.
- CommentAuthorphiledge
- CommentTimeJan 26th 2021
Posted By: GreenPaddyPhiledge - when linked to a thermal store, unless you blend stove flow into the return, you will always be drawing cool water from the base of the TS, until the whole TS starts to get hot to the base, which for a 350 litre store like Ben's could take hours, all the while drawing the cool water into the stove. It may be recommended by some people, but as I said, it's not a way of controlling the temperature of feed water to the stove. That is something that is not good practice.

Also, as the stove starts to cool, having heated the TS to a temp above the fixed pump stat temp, there's a chance you could have a continuous run of the pump, as it pumps hot water from the TS, through the stove to the stat, self perpetuating. Also not clever.

What you say may or may not be the case. Dunsley dont see the need for a TMV but maybe they didnt consider their stoves being hooked up to a TS! On Clearveiws advice at the time, we dont have a TMV on the back of our stove and use pipe stats to control water flow into the boiler. We dont have any problems with soot on the back boiler. I sweep the flue every 2-4 years and get half a bucket of of light grey ash out of the flue. Probably as clean a system as any out there, all without a TMV.

Whether stat controlled systems are classed as 'not clever' is open to debate. Youve already mentioned blocked strainers as a problem with TMVs. If a strainer gets blocked then the TMV gets defeated and the stove water temp control is lost. Id hazard a guess most users would notice a pump not running or running continuously long before they noticed a blocked strainer?

As said previously if the OP doesnt have a problem with soot, theres probably no need to be to concerned about the lack of TMV. Certainly not in terms of resolving the lack of heat in the house
- CommentAuthorphiledge
- CommentTimeJan 26th 2021
Posted By: Benm85

Iâ€™ll take a look at a wiring diagram later when the kids are in bed.

In the photo you posted there are 5 pipes showing in the cupboard next to the boiler which I assume are hooked up to the boiler. Could you update the pipework schematic to show where these are connected to save guessing. The stove pump also seems to be missing!
- CommentAuthorBenm85
- CommentTimeJan 26th 2021 edited
Posted By: Peter_in_HungaryI think that you need to get a thermometer that gives an accurate reading of the pipes.

Ordered one from ToolStation to pick up tomorrow, now.

Posted By: Peter_in_HungaryIs the boiler CH controlled by the internal boiler thermostat or the thermostat on the TS,it seems you are mentioning two thermostats, one at 75 and the other at 85.
I would also expect an over temp. thermostat on the boiler to cut it off if the temp. is too high - this is also a potential fault point cutting the boiler out at 65deg. regardless of the set temp.

Whilst the diagram of the TS is helpful it could be misleading. Your TS (having had a quick look online) has the optional extra of a coil for the boiler, do you know if this has been fitted?

Apologies, I should have been clearer on where the temps are set. The TS control thermostat is set at 75c. The boiler on it's control panel (i.e. on the front of the boiler) is set at 85c.

Posted By: Peter_in_HungaryIf there was a blockage in the boiler to TS pipework I would expect to see the boiler temp. at the set temp, but the return at TS return temp.. I would also expect to see the boiler short cycling.

When I was at the boiler, I noticed it does turn on and off, even though the TS is not at the 75c set on the control thermostat. Not sure if that is called short cycling, just an observation.
- CommentAuthorBenm85
- CommentTimeJan 26th 2021 edited
Posted By: philedgen the photo you posted there are 5 pipes showing in the cupboard next to the boiler which I assume are hooked up to the boiler. Could you update the pipework schematic to show where these are connected to save guessing. The stove pump also seems to be missing!

By way of clarification, that photo of the cupboard is actually next to the stove down stairs. Two pipes on the far left (i.e. one with the stat is stove flow and the pump is stove return) are related to the stove. The 5 pipes from left to right are Boiler Return, Boiler Flow, Cold, Ground Floor CH Flow and CH Return.

Apologies, having an issue with the diagram to show the stat and pump on the stove flow and return.
- CommentAuthorPeter_in_Hungary
- CommentTimeJan 26th 2021
Posted By: Benm85Apologies, I should have been clearer on where the temps are set. The TS control thermostat is set at 75c. The boiler on it's control panel (i.e. on the front of the boiler) is set at 85c.

So what does the 75c TS thermostat control and what does the 85c boiler thermostat control

Posted By: Benm85When I was at the boiler, I noticed it does turn on and off, even though the TS is not at the 75c set on the control thermostat. Not sure if that is called short cycling, just an observation.

Yes, frequent short run times is short cycling.
If the boiler is not up to the temp. you want but turns off anyway you need to find out what is turning the boiler off. If the boiler is turning itself off at 65deg regardless of what the thermostat is set to then this could be the whole problem
- CommentAuthorBenm85
- CommentTimeJan 26th 2021
Posted By: Peter_in_HungarySo what does the 75c TS thermostat control and what does the 85c boiler thermostat control

The TS control stat effectively dictates when the boiler should turn off when it has reached the set temperature (75c in this case). When it drop below that (and itâ€™s on the timer for when it should be running) it should then fire to bring it back up to temp. The boiler control temp is set on the boiler and should (Iâ€™m pretty sure) control what temperature the flow should be (in this case 80c).
- CommentAuthorPeter_in_Hungary
- CommentTimeJan 26th 2021 edited
I would suggest one of those is turning the boiler off at 65deg.

I presume you are also having problems with the hot water not being hot enough

Edit to ask - Where abouts on the TS is the thermostat located?
- CommentAuthorGreenPaddy
- CommentTimeJan 27th 2021
Ben, the boiler will not make 85oC water straight off.

- the output temp is dependent upon the incoming water. Your boiler is rated to lift the water temp by 25oC at a flow rate of 18 litre/min (that's DHW so CH will likely be less than that, but let's assume 25oC).

- the CH pump flow rate appears from the graph in the manual, to be something like that 20 litre/min flow rate, but depends what setting it is on. I'd start at a low setting and work up if needed. So unless the TS water temp returning to the gas boiler is 60oC, you won't get an output temp of 85oC. It will work it's way up to 85oC eventually, but likely will start outputting around 60oC (assume rads start cold, and that feeds back to the base of the TS).

- so why is the boiler shutting off at 65oC? You've described the TS stat appears to be functioning, and knocking off the gas boiler. The stat "shows" 75oC, but is that really 75oC. As a very simple test, turn the the TS which controls the boiler up as far as it will go. That should ensure the gas boiler continues running for longer. If that's the case, then the stat may be incorrectly set (maybe someone put the knob on the wrong position. Maybe it has an internal "off-set" that has been set incorrectly). That can be sorted. First is to confirm is that stat is really what is switching the boiler off/on.

- when you do get your thermometer, you can perhaps verify the temps you think you're seeing. Then we need to be clear about where the temp stats are positioned on the TS. That will clearly affect the temp values in the TS.

- is there definitely only one stat to control the gas boiler? Sometimes an upper stat and lower stat work as a pair, one to bring on the boiler, then the other switches it off. If one stat only, then it will have a set hysteresis, so it brings the boiler on AND off making the temp rise by that hysteresis value, maybe 10oC (eg 65oC to 75oC).

- has the gas boiler been set to "Heat Only" in the service set up parameters. One would assume it has been, but worth checking that (section 10.3 Parameters in the installation manual). Check the other settings whilst your about it, to see they are as per the manual.
- CommentAuthorBenM
- CommentTimeJan 27th 2021 edited
Posted By: Peter_in_HungaryI would suggest one of those is turning the boiler off at 65deg.

I presume you are also having problems with the hot water not being hot enough

Edit to ask - Where abouts on the TS is the thermostat located?

Hi Peter, we do have problems with the hot water if the stove hasn't been lit, i.e. just relying on the boiler to heat the TS.

The stat is located on the tank approximately in the middle (half way up and in the centre).
- CommentAuthorBenM
- CommentTimeJan 27th 2021
Thanks GreenPaddy. Picked up the thermometer this morning. Had a little play around to get used to it, even picked up the tip of using masking tape on the pipe to get a proper reading so it's not just reflecting off the pipe (thanks YouTube).

Posted By: GreenPaddy- has the gas boiler been set to "Heat Only" in the service set up parameters. One would assume it has been, but worth checking that (section 10.3 Parameters in the installation manual). Check the other settings whilst your about it, to see they are as per the manual.

I'll have a check of the manual to see how to do that. Just to check, should it be in 'Heat Only' or 'System' mode? Is there a difference? I thought I read somewhere that a TS would require it to be in 'System' boiler mode
- CommentAuthorGreenPaddy
- CommentTimeJan 27th 2021
A system boiler means it only gives one heat output (heat only), which you can then do with as you choose. Your manual shows the term "heat only".

https://www.intergasheating.co.uk/app/uploads/2018/04/Combi-Compact-HRE-Installation-manual-88287806.pdf

It likely will have been set up correctly, but just worth eliminating any doubt.
- CommentAuthorphiledge
- CommentTimeJan 27th 2021
Before you make any changes to the boiler config/settings I suggest you isolate the boiler from the TS controls to prove that the boiler is working properly, or not!

I could only find a manual for an HRE 36/30 so am assuming thats applicable to your boiler in terms of electrical connections. Look in chapter 13 and youll see a row of connectors labelled X4. Find terminals 6+7 in the boiler which are for connection of an external thermostat. If these have a cable going to the TS or one of the external thermostats, remove the cable and fit a wire link between terminal 6+7. This should stop the TS having any influence over when the boiler runs/shutsdown. Check that the boilers in built timer is set to run continuously and not timed.

The boiler should now run continuously until the boiler flow temperature reaches whatever youve got the max temp set to, 85deg C?? Youve got a modulating boiler so as the flow temp approaches the set temp, 85?, the boiler should start to reduce its power output. You should be able to hear the fan slow down and the burner intensity reduce. The boiler should only stop after its reduced its power and shouldnt suddenly stop while its running at full power.

If theres already a wire link in terminal X4 6+7, can you post a picture of the boiler wiring connections so we can try and work out how the boiler is connected to the TS/outside world.

Dont for get to switch off the power to the boiler while poking around!
- CommentAuthordjh
- CommentTimeJan 27th 2021
It might be worth noting that earlier Ben mentioned that the boiler has another stat - the DHW stat - that is set to 65Â°C but is supposedly not in use. It may be worth changing that setting of that in a separate experiment just to check that it really does make no difference to anything.
- CommentAuthorBenM
- CommentTimeJan 27th 2021 edited
Hi GreenPaddy,

Posted By: GreenPaddy- so why is the boiler shutting off at 65oC? You've described the TS stat appears to be functioning, and knocking off the gas boiler. The stat "shows" 75oC, but is that really 75oC. As a very simple test, turn the the TS which controls the boiler up as far as it will go. That should ensure the gas boiler continues running for longer. If that's the case, then the stat may be incorrectly set (maybe someone put the knob on the wrong position. Maybe it has an internal "off-set" that has been set incorrectly). That can be sorted. First is to confirm is that stat is really what is switching the boiler off/on.

- when you do get your thermometer, you can perhaps verify the temps you think you're seeing. Then we need to be clear about where the temp stats are positioned on the TS. That will clearly affect the temp values in the TS.

Set the timer to continuous to turn the boiler on, turned the thermostats up to maximum (90c on the dial), and went to the boiler check the temps on the flow. Just for context, the tank was at about 65c when I did this, as the boiler had been running for a bit and the CH had knocked off.

The boiler started (you could hear the fan/burner, seeing steam outside), the after about 5 minutes I was reading on the thermometer a temp of 68c on the flow and 60c on the return. After maybe 5 minutes of running, the boiler powered down with the fan/burner turning down and then it stopped burning (no steam out from the flue outside). Left it for another 5 minutes, the boiler didn't start up again. So something is turning the boiler off, potentially unrelated to the thermostats on the TS (unless they are faulty and knocking the boiler off).

Posted By: philedgeBefore you make any changes to the boiler config/settings I suggest you isolate the boiler from the TS controls to prove that the boiler is working properly, or not!

I think philedge makes a good point about isolating the boiler from the TS, to test if it is the TS knocking stats or the boiler itself knock it off. Very nervous about about playing about with wiring though, but accept it probably needs doing. Hopefully something to discuss with LustysDad next week!
- CommentAuthorphiledge
- CommentTimeJan 27th 2021
If youd happily fit a new doorbell, this is no different. Take a photo before you start. Switch the power off as a general safety precaution, not because the terminal are dangerous as the manual says they are only at 24volts.
- CommentAuthorPeter_in_Hungary
- CommentTimeJan 27th 2021 edited
Posted By: BenMThe stat is located on the tank approximately in the middle (half way up and in the centre).

Not withstanding the current problem - is TS thermostat moveable or fixed? Looking at the diagram above the return to the combie looks to be quite a bit below the middle. You will never get the TS hot (by the combi) beyond the position of the thermostat so if you can move the thermostat to just above the combie return you will get the TS hot down to that point i.e. more of a heat buffer.

You need to find out which thermostat is turning the boiler off. If you have a look at the TS thermostat to see how many wires there are, if there are only two then it is a simple single pole switch. (if there are more than two don't try the following!!) Thermostats usually make on low temp.and break on high temp. so with the power switched off if you connect the two wires in the thermostat together this says 'low heat, run the boiler' so when you switch on again the boiler should run continuously without switching off at 65deg. If it does continue running the TS thermostat is probably faulty, if it still stops at 65deg.then look somewhere else for the problem

I see that there is another thermostat set to 54deg.and the boiler switches off at 65deg. - that looks a bit suspicious but could just be a red herring.
- CommentAuthorBenM
- CommentTimeJan 27th 2021
Posted By: philedgeIf youd happily fit a new doorbell, this is no different. Take a photo before you start. Switch the power off as a general safety precaution, not because the terminal are dangerous as the manual says they are only at 24volts.

I probably wouldn't fit a door bell either....and we need a door bell! I'm just not confident with electrics (or plumbing by the looks!), which is confounded by colour blindness, so I tend to leave it alone.

It's a good point though, and I'll put it to the plumber.

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Heating and cooling: Thermal Store and Radiators Temperature