Heating system issues

mkshadows1

We bought our first house in 2021, and I don't think the previous owners only did the bare minimum on the heating/water system, shortly after we got the keys we had to have the 3 way valve replaced and then once moved in had the boiler circuit board replaced, new fan, new heating pump and pipes in the airing cupboard reconfigured as the boiler was cutting out on thermal overload and hive installed as the property had no thermostat.

We're still having issues heating the house, it's a 3 bed detached built around 1997 and we're struggling on some days when it's around 8 - 10 degrees outside to heat the property above 16 degrees, even with the heating on for prolonged periods of time, We really felt this in the cold snap, where we struggled to get the temperature above 14.5 degrees even after having the heating on all day. I believe the boiler is the original that was installed when the house was built; it's an ideal classic FF240, we've got 9 radiators in the house, hot water cylinder in the airing cupboard in the main bedroom and tanks in the loft, radiator pipes appear to be microbore pipes.

I've noticed a couple issues that could be causing this.. One is that when the hot water is on; the hot water seems to get priority and doesn't feed the radiators, even if the heating is on first the hot water will always appear to stop feeding the radiators. I've checked the 3 way valve and this is in the correct position to feed both the heating and hot water systems.

Another is that when it is just the heating switched on; the downstairs radiators take a very long time to warm up - around 20 minutes or so; the upstairs radiators can be at full temperature before the downstairs are lukewarm.

Also I'm not sure if this is when it's just heating only or when both are switched on; but the boiler seems to switch off even if the heating system is still calling for heat, this might be linked to the first issue.

Our plumber can't get out to us until early feb when they come out to service the boiler; just wondering if there is anything that I can check / change to try and keep the heating working?

benson1980

Do you have a separate central heating pump? First things I would check is pump speed (as it possibly sounds like it can't cope with dual demand presently), and I'd balance the radiators. There was a really simple method (from another forum) that I used which is essentially as follows:
- open all TRVs fully
- close all lockshields 1/8 turn from closed
- turn on heating. Leave radiators that heat up. Those that don't, turn another 1/8th.
- repeat until all rads warm.

The method did include doing the above whilst adjusting flow temperature from 40, to 50, then 60 and 70. I didn't really understand the science behind that bit (I am sure there is a good reason), but just did it at 50 I think and then 57 which is where I've left our flow temp.

There is a mode on our boiler where it can shut off temporarily if the pump speed is insufficient, so yes it might tie in with that.

grumbler

mkshadows1 said:

We bought our first house in 2021, and I don't think the previous owners only did the bare minimum on the heating/water system,

Think or don't think?

shortly after we got the keys we had to have the 3 way valve replaced and then once moved in had the boiler circuit board replaced, new fan, new heating pump and pipes in the airing cupboard reconfigured as the boiler was cutting out on thermal overload and hive installed as the property had no thermostat.

The only real issue I see is lack of thermostat. You knew this when buying the house. However, it's hard to believe that 1997's house has no thermostat. Who built it? I think it's very easy to add a thermostat nowadays when wireless thermostats are available.

We're still having issues heating the house, it's a 3 bed detached built around 1997 and we're struggling on some days when it's around 8 - 10 degrees outside to heat the property above 16 degrees, even with the heating on for prolonged periods of time, We really felt this in the cold snap, where we struggled to get the temperature above 14.5 degrees even after having the heating on all day. I believe the boiler is the original that was installed when the house was built; it's an ideal classic FF240, we've got 9 radiators in the house, hot water cylinder in the airing cupboard in the main bedroom and tanks in the loft, radiator pipes appear to be microbore pipes.

Nothing wrong with microbore pipes for connecting each radiator to the main CH pipes that, most likely, are at least 15mm. If the house is draughty and poorly insulated, then the boiler power can be insufficient for heating it to the temperature you want.

I've noticed a couple issues that could be causing this.. One is that when the hot water is on; the hot water seems to get priority and doesn't feed the radiators, even if the heating is on first the hot water will always appear to stop feeding the radiators. I've checked the 3 way valve and this is in the correct position to feed both the heating and hot water systems.

If the valve isn't faulty and is in the correct position, then hot water from the boiler has to flow in both directions  - touch the corresponding pipes to feel this. However, if the boiler isn't powerful enough to heat the house, it's even less capable of doing two tasks simultaneously.

Another is that when it is just the heating switched on; the downstairs radiators take a very long time to warm up - around 20 minutes or so; the upstairs radiators can be at full temperature before the downstairs are lukewarm.

Did you try playing with the radiators' valves?

Also I'm not sure if this is when it's just heating only or when both are switched on; but the boiler seems to switch off even if the heating system is still calling for heat, this might be linked to the first issue.

The boiler has its own thermostat for water it heats. It heats it faster than this water heats the house. You can try increasing the water temperature - this will help with heating both the house and the HW cylinder.

mkshadows1

Do you have a separate central heating pump? First things I would check is pump speed (as it possibly sounds like it can't cope with dual demand presently), and I'd balance the radiators. There was a really simple method (from another forum) that I used which is essentially as follows:
- open all TRVs fully
- close all lockshields 1/8 turn from closed
- turn on heating. Leave radiators that heat up. Those that don't, turn another 1/8th.
- repeat until all rads warm.

We have TVRs on all the radiators bar one; I haven't touched any of the lockshields - so the system could be out of balance - will have a look at that. All radiators do get hot eventually, just the downstairs ones take a lot longer than most. Yep it's a separate heating pump, will check and maybe increase the pump speed - I think the plumber set it to 2 when he installed it.

The method did include doing the above whilst adjusting flow temperature from 40, to 50, then 60 and 70. I didn't really understand the science behind that bit (I am sure there is a good reason), but just did it at 50 I think and then 57 which is where I've left our flow temp.

I'm not sure on what the flow temp from the boiler is; the temperature adjustment knob just has 1 - 6 on it, it's currently set to 5 as this was the only way I could keep the heating on mostly during the cold snap.

Think or don't think?

Apologies I think they only did the bare minimum of maintenance on the system.

The only real issue I see is lack of thermostat. You knew this when buying the house. However, it's hard to believe that 1997's house has no thermostat. Who built it? I think it's very easy to add a thermostat nowadays when wireless thermostats are available.

I'm not sure on the builder; but it wasn't something I really noticed when we looked around - it's only when we started the process that the EPC stated no thermostat and when we got the keys, we had a hive wireless system installed when the heating controls failed..

If the valve isn't faulty and is in the correct position, then hot water from the boiler has to flow in both directions  - touch the corresponding pipes to feel this. However, if the boiler isn't powerful enough to heat the house, it's even less capable of doing two tasks simultaneously.

I'm hoping the valve isn't faulty as it's newly installed; I'm assuming the boiler should be powerful enough, max output is 11kw - it doesn't look like the radiators have changed either; none have been added so the boiler should of been rightsize when installed?

I'll try checking the radiator balance as above; just in case it's been messed with over time and isn't balanced anymore. The boiler is already set to 5 it can go to 6, but I'm not sure I should set it to its maximum.

The issue is more noticeable in the morning and early evening, when the heating and hotwater are both running at the same time.

Thank you for your replies, I'll try the above and see if it improves the situation.

FreeBear

benson1980 said:

Do you have a separate central heating pump? First things I would check is pump speed (as it possibly sounds like it can't cope with dual demand presently), and I'd balance the radiators. There was a really simple method (from another forum) that I used which is essentially as follows:
- open all TRVs fully
- close all lockshields 1/8 turn from closed
- turn on heating. Leave radiators that heat up. Those that don't, turn another 1/8th.
- repeat until all rads warm.

Slightly more nuanced method of balancing radiators here - https://forums.moneysavingexpert.com/discussion/comment/79741493#Comment_79741493
As for pump speed, assuming it is a basic "dumb" pump, turn it down to the lowest speed. Increase the speed by one click if the radiators still don't get hot after balancing them. With a modern "smart" pump, it will often have a slow speed, and then an adaptive setting that changes speed as TRVs shut off radiators.

Apodemus

Just to pick up on one point:   Your plumber reconfigured the pipes because the boiler was going to thermal overload...and now unless you turn the boiler flow thermostat up to 5, it is still going to thermal overload?  Does this not suggest that the pipework is insufficient to deliver the heat produced and that the dump radiator (the always-on one without the TRV) is failing to dump the extra heat? 

I wonder if there is a build up of sludge in the system and some of the rads or microbore pipes are not flowing well.  You don't mention if you've had the system flushed or a magnetic filter added?   While I personally would baulk at the cost of a powerflush, I would think it might be worth adding a good magnetic filter, putting in a cleaning additive and doing a number of cleaning washes on the new filter (possibly also turning the pump up to III, while going through this regime). 

mkshadows1

Just to pick up on one point:   Your plumber reconfigured the pipes because the boiler was going to thermal overload...and now unless you turn the boiler flow thermostat up to 5, it is still going to thermal overload?  Does this not suggest that the pipework is insufficient to deliver the heat produced and that the dump radiator (the always-on one without the TRV) is failing to dump the extra heat? 

I wonder if there is a build up of sludge in the system and some of the rads or microbore pipes are not flowing well.  You don't mention if you've had the system flushed or a magnetic filter added?   While I personally would baulk at the cost of a powerflush, I would think it might be worth adding a good magnetic filter, putting in a cleaning additive and doing a number of cleaning washes on the new filter (possibly also turning the pump up to III, while going through this regime). 

The boiler is no longer going into thermal overload; essentially they replaced a small section of pipes in the airing cupboard when the pump was replaced; as these pipes had build ups in them, I believe by turning up the boiler to 5 - it kept it running longer as it hadn't reached temperature yet.

There is no magnetic filter; and we haven't had anything powerflushed and based on what I've seen so far; I highly doubt it's ever been powerflushed.

Slightly more nuanced method of balancing radiators here - https://forums.moneysavingexpert.com/discussion/comment/79741493#Comment_79741493
As for pump speed, assuming it is a basic "dumb" pump, turn it down to the lowest speed. Increase the speed by one click if the radiators still don't get hot after balancing them. With a modern "smart" pump, it will often have a slow speed, and then an adaptive setting that changes speed as TRVs shut off radiators.

The pump is a Grundfos UPS3, which has 3 speeds and then two extra functions that I'm not sure of. And is set on speed 1 - I might try turning that up to see if that helps things circulate quicker

benson1980

mkshadows1 said:

Just to pick up on one point:   Your plumber reconfigured the pipes because the boiler was going to thermal overload...and now unless you turn the boiler flow thermostat up to 5, it is still going to thermal overload?  Does this not suggest that the pipework is insufficient to deliver the heat produced and that the dump radiator (the always-on one without the TRV) is failing to dump the extra heat? 

I wonder if there is a build up of sludge in the system and some of the rads or microbore pipes are not flowing well.  You don't mention if you've had the system flushed or a magnetic filter added?   While I personally would baulk at the cost of a powerflush, I would think it might be worth adding a good magnetic filter, putting in a cleaning additive and doing a number of cleaning washes on the new filter (possibly also turning the pump up to III, while going through this regime). 

The boiler is no longer going into thermal overload; essentially they replaced a small section of pipes in the airing cupboard when the pump was replaced; as these pipes had build ups in them, I believe by turning up the boiler to 5 - it kept it running longer as it hadn't reached temperature yet.

There is no magnetic filter; and we haven't had anything powerflushed and based on what I've seen so far; I highly doubt it's ever been powerflushed.

Slightly more nuanced method of balancing radiators here - https://forums.moneysavingexpert.com/discussion/comment/79741493#Comment_79741493
As for pump speed, assuming it is a basic "dumb" pump, turn it down to the lowest speed. Increase the speed by one click if the radiators still don't get hot after balancing them. With a modern "smart" pump, it will often have a slow speed, and then an adaptive setting that changes speed as TRVs shut off radiators.

The pump is a Grundfos UPS3, which has 3 speeds and then two extra functions that I'm not sure of. And is set on speed 1 - I might try turning that up to see if that helps things circulate quicker

I would imagine having it on setting one will be causing at least some of your issues.

our plumber turned our old grundfos pump down to 2 last summer, without really explaining the consequences (or perhaps he didn't realise, which is a little concerning but perhaps that's because they aren't heating engineers as such). What happened was our radiators didn’t heat up properly, and our house was cold.

Setting 3 was really noisy so I ended up installing a new pump but I think you will be fine with your one turning up the speed a bit (our one was around 29 years old!)

FreeBear

mkshadows1 said:

Slightly more nuanced method of balancing radiators here - https://forums.moneysavingexpert.com/discussion/comment/79741493#Comment_79741493
As for pump speed, assuming it is a basic "dumb" pump, turn it down to the lowest speed. Increase the speed by one click if the radiators still don't get hot after balancing them. With a modern "smart" pump, it will often have a slow speed, and then an adaptive setting that changes speed as TRVs shut off radiators.

The pump is a Grundfos UPS3, which has 3 speeds and then two extra functions that I'm not sure of. And is set on speed 1 - I might try turning that up to see if that helps things circulate quicker

Installation & operating instructions - https://api.grundfos.com/literature/Grundfosliterature-6014815.pdf
Your pump is one of the smarter ones that have a choice of constant speed or constant/proportional  pressure - Select the mode appropriate for your system and go from there. You probably don't want to use the constant/proportional pressure modes, so don't set the "menu" for flashing LEDs.

ThisIsWeird

5 out of 6 will be 'hot', so I'd guess around 75oC; your boiler will probably go up to around 80oC. The radiators that do heat up, how hot do they feel? Is it 'ouch', and you can't keep your hands on them?

And do the downstairs rads heat up much more quickly if the upstairs ones are turned off, or do they still take quite a while?

11kW output isn't a lot, but presumably was chosen to be enough. It might struggle when outdoor temps are very low, but 8oC is not at all 'cold', so it shouldn't be struggling with this.

A few things we can say, I think:

1) Your radiator system is not properly balanced. All the rads, downstairs and up, near and far, should be heating up at roughly the same time (provided their TRVs are 'open').

2) Your CH/DHW balance also appears to be out. The DHW will be a much easier path for the boiler water than the CH's especially since the latter has microbore, but it still shouldn't be pinching that much away from the CH - it should be nicely shared. Not sure how this is best done in practice). It's a shame that the pipework mods didn't include swapping the faulty diverter valve for two 2-port types, so that the CH and DHW could be fully independent.

3) The slow-to-heat downstairs rads could be due to two reasons - the upstairs ones are 'open' too far, or the downstairs ones are 'closed' too far. By that I mean their lockshields. (Of course, there could be pipe restrictions too).

Q's:
1) when you try and heat your house, do you mean the whole house, or just the 'living' areas?  I mean, during the day and eves, are the bedroom rads off, or way down at 1 or 2? If not, they should be, or else that's a waste.

2) the section of pipe that was removed because of 'build ups', what were these? Was the stuff black? Did the plumber make any comments on this? If a larger copper pipe was sludged, then microbore pipes would be more vulnerable. 

It's impossible to tell from here what the issue is, but hopefully your plumber will go through it all systematically. Meanwhile, can you time your DHW to come on at an earlier time so you have a hot cylinder, and is then off before your CH comes on in the morning? And any rads that do not need to be on, turn them to 'frost'. 

ThisIsWeird

Your Grundfos pump is a capable fellow. It has the three fixed speeds you mention, but also another two settings, one of which is likely to be a lot better, and which could also sort the dominant DHW issue you are having, if done with another tweak.

The first of the other weird symbols is 'proportional pressure' (or flow). This means it will adjust the pump speed to match actual demand. For example, as TRVs on some rads begin to close and the flow becomes more restrictive, the pump will back down in order to match this. When all rads demand flow, the pump will speed up to max. Far more efficient, and far more effective.

Better still, it will change to match the DHW demand. At the moment, it seems as tho' your hot cylinder is getting far too much flow because its path is too open. However, if you fitted a gate valve in the circuit in order to reduce this (and therefore give more flow to the rads), the pump on the current fixed speed would just try and push against this. With Prop pressure, tho', the pump would back off to suit; when only the DHW is required, the pump would be running nice and slow. When the rads are also needed, the pump would automatically speed up to suit. 

NB: that is my understanding! It might be more complex than that.

What I would do in your situation is:
a) time the DHW to come on  to heat the cylinder before the CH is needed in the morning, so the CH doesn't have to share.
b) try the pump on 'prop pressure' for a few days and see how it compares. It can always be returned to a fixed speed afterwards. Hopefully the pump will now fire up faster when the rads are crying for heat, and will back right down as rads begin to turn off.
Look up the instructions for it. Don't worry about trying to understand it all - I certainly don't. But just look at how to change the setting, and which LEDs need to light up