Flow pipe hot, return cold - is this right
Discussion
pistonheadforum said:
They system seems to working at the moment but I feel at could all pack in at any moment!
I'm just trying to determine wha the best course of action is until the spring when I a look to get the system inspected and (most likely) the boiler swapped.
I don't want to adjust too much as the bills are managable but the rooms are a bit colder than most - currently 17c or so in the cold spell.
Have you got TRVs on every radiator? If so what's possibly happening is that the boiler runs until all the TRVs close off & then the boiler switches off as the return water temperature climbs. When you say "the rooms are cold" which rooms do you mean? If you mean the spare rooms then just turn the TRV up in those rooms. If you mean all the rooms then turn up the boiler water temperature.I'm just trying to determine wha the best course of action is until the spring when I a look to get the system inspected and (most likely) the boiler swapped.
I don't want to adjust too much as the bills are managable but the rooms are a bit colder than most - currently 17c or so in the cold spell.
A very common arrangement in older systems is a system boiler (as yours is called) that feeds a two way diverter valve that sends hot water either into the HW circuit and/or the CH circuit. There's a stat on the side of the HW tank which turns off the feed to the HW tank when the tank has heated up & a stat in one of the rooms which turns off the feed to the CH when the room is warm enough. It's possible that someone has fitted TRVs to all the radiators & disconnected the CH stat.
How hot is your HW? it should be at least 60°C to prevent Legionnaires bacteria growing so the boiler temp should not be set too low.
Try raising the boiler setting for a few days & see if the rooms are warmer.
pistonheadforum said:
They system seems to working at the moment but I feel at could all pack in at any moment!
I'm just trying to determine wha the best course of action is until the spring when I a look to get the system inspected and (most likely) the boiler swapped.
I don't want to adjust too much as the bills are managable but the rooms are a bit colder than most - currently 17c or so in the cold spell.
If your rooms are colder then you would like then yes your bills will increase if you turn the boiler up. I'm just trying to determine wha the best course of action is until the spring when I a look to get the system inspected and (most likely) the boiler swapped.
I don't want to adjust too much as the bills are managable but the rooms are a bit colder than most - currently 17c or so in the cold spell.
If they get to temperature and the TRV's operate, then you won't use more gas by turning the boiler up. The rooms will just get to temperature quicker.
pistonheadforum said:
98elise said:
Running it higher in winter shouldn't result in higher bills. The heat is still going into the house, just faster and more efficiently. If you run it lower your radiators effectively have a lower output.
Firstly, thanks to all for advice.This bit has confused me but then I probably don't fully understand I'm afraid.
The boiler is an old non-condensing boiler rated at 80,000BTU. I've converted this and think it's a 23kw rated boiler. It's not particular effeciant with the specs showing SAP of 65% efficiency. Actually that's a horrible effeciency rating.
The boiler is old and not great I get that! I'm trying to make do with the best I have. It has no smart controls.
The setting is currently at 1 and it goes all the way up to a max of 6.
I have 10 radiators in the house over 4 bedrooms with the TRV set low on unused rooms.
Is 1 a bit low?
What does this number relate to? Temp of water? Time boiler is on? How high the flame - is it like a gas cooker oven setting?
Would increasing the number not surely result in a massivly increased gas bill?
Thanks in advance for any light you can shed.
Radiators are rated in BTU based on a high flow temperature. If you use a lower flow temperature the BTU rating is lower. If it's still enought to heat the house them it's not an issue, your boiler will need to run for longer though to achieve the same room temperatures.
Think of it like this. If you halved the radiators output then it would need to run for twice as long to heat a the room. No more energy is being used, it's just being delivered over a longer period.
Mr Pointy said:
Have you got TRVs on every radiator? If so what's possibly happening is that the boiler runs until all the TRVs close off & then the boiler switches off as the return water temperature climbs. When you say "the rooms are cold" which rooms do you mean? If you mean the spare rooms then just turn the TRV up in those rooms. If you mean all the rooms then turn up the boiler water temperature.
A very common arrangement in older systems is a system boiler (as yours is called) that feeds a two way diverter valve that sends hot water either into the HW circuit and/or the CH circuit. There's a stat on the side of the HW tank which turns off the feed to the HW tank when the tank has heated up & a stat in one of the rooms which turns off the feed to the CH when the room is warm enough. It's possible that someone has fitted TRVs to all the radiators & disconnected the CH stat.
Try raising the boiler setting for a few days & see if the rooms are warmer.
Thanks - this is exaclty how it's been configured. It's a heat only boiler with a seperate pump and the CH and HW manifolds have been bypassed so that it's controlled entirely by the TRVs in the room. The hot water cylinder is always passing water as there is no TRV on this "radiator".I guess the boiler going off is because the system gets up to temp (from each room TRV setting), these then close and so the water is being returned to the boiler at enough of a temperature to mean it turns off.A very common arrangement in older systems is a system boiler (as yours is called) that feeds a two way diverter valve that sends hot water either into the HW circuit and/or the CH circuit. There's a stat on the side of the HW tank which turns off the feed to the HW tank when the tank has heated up & a stat in one of the rooms which turns off the feed to the CH when the room is warm enough. It's possible that someone has fitted TRVs to all the radiators & disconnected the CH stat.
Try raising the boiler setting for a few days & see if the rooms are warmer.
At least I think that's whats happening!
Edited by pistonheadforum on Monday 29th November 09:36
Sounds very reasonable to me. Making the best of an old system for minimum outlay.
Old boilers tend to be very reliable.
When you next have it serviced the tech should measure efficiency. See if it is as low as the 65% figure you've got.
If it really is that low then there is more of an incentive to replace.
You will need to update the control too - at the very least a diverter valve and tank stat. Although you could have that added anyway to the old system.
Old boilers tend to be very reliable.
When you next have it serviced the tech should measure efficiency. See if it is as low as the 65% figure you've got.
If it really is that low then there is more of an incentive to replace.
You will need to update the control too - at the very least a diverter valve and tank stat. Although you could have that added anyway to the old system.
jet_noise said:
Sounds very reasonable to me. Making the best of an old system for minimum outlay.
Old boilers tend to be very reliable.
When you next have it serviced the tech should measure efficiency. See if it is as low as the 65% figure you've got.
If it really is that low then there is more of an incentive to replace.
You will need to update the control too - at the very least a diverter valve and tank stat. Although you could have that added anyway to the old system.
Thanks. Looking at the system the pump is completly seperate from the boiler (heat only boiler) and is not controlled by the boiler in any way so it's continually running.Old boilers tend to be very reliable.
When you next have it serviced the tech should measure efficiency. See if it is as low as the 65% figure you've got.
If it really is that low then there is more of an incentive to replace.
You will need to update the control too - at the very least a diverter valve and tank stat. Although you could have that added anyway to the old system.
Is this likely to be a problem or will it actually put less stress on the system than contually starting/stopping the pump?
Will the pump continually running make any difference to keeping the pipes sludge free?
Thanks in advance.
pistonheadforum said:
Thanks. Looking at the system the pump is completly seperate from the boiler (heat only boiler) and is not controlled by the boiler in any way so it's continually running.
Is this likely to be a problem or will it actually put less stress on the system than contually starting/stopping the pump?
Will the pump continually running make any difference to keeping the pipes sludge free?
Thanks in advance.
Can't answer that, hopefully someone'll chip in.Is this likely to be a problem or will it actually put less stress on the system than contually starting/stopping the pump?
Will the pump continually running make any difference to keeping the pipes sludge free?
Thanks in advance.
IANAP (I am not a plumber
)pistonheadforum said:
jet_noise said:
Sounds very reasonable to me. Making the best of an old system for minimum outlay.
Old boilers tend to be very reliable.
When you next have it serviced the tech should measure efficiency. See if it is as low as the 65% figure you've got.
If it really is that low then there is more of an incentive to replace.
You will need to update the control too - at the very least a diverter valve and tank stat. Although you could have that added anyway to the old system.
Thanks. Looking at the system the pump is completly seperate from the boiler (heat only boiler) and is not controlled by the boiler in any way so it's continually running.Old boilers tend to be very reliable.
When you next have it serviced the tech should measure efficiency. See if it is as low as the 65% figure you've got.
If it really is that low then there is more of an incentive to replace.
You will need to update the control too - at the very least a diverter valve and tank stat. Although you could have that added anyway to the old system.
Is this likely to be a problem or will it actually put less stress on the system than contually starting/stopping the pump?
Will the pump continually running make any difference to keeping the pipes sludge free?
Thanks in advance.
Sludge will settle in low flow conditions, so when the pump is running you want a decent flow in the pipes/rads but it's not meant to be on all the time.
98elise said:
The pump should be running as long as there is a demand for heat in the house (ie the controls are calling for it). At other times it should be off.
Sludge will settle in low flow conditions, so when the pump is running you want a decent flow in the pipes/rads but it's not meant to be on all the time.
Agree. I'm not sure it should be diverting via the hot water cylinder though as per OP's earlier post - that could result in very hot water.Sludge will settle in low flow conditions, so when the pump is running you want a decent flow in the pipes/rads but it's not meant to be on all the time.
It sounds similar to my setup, but someone has chopped some wiring out on yours.
On mine there is an early 90's system boiler, a separate pump and a diverter to send water via the hot water cylinder OR via the radiators OR mid-way so both the hot water cylinder and radiator circuit get heat. I fitted a remote thermostat myself, and that is what turns the boiler on and off for the radiator circuit. The hot water circuit also demands heat and controls the diverter valve at certain times according to a timer. TRV's control room temperature but they cannot tell the boiler to stop heating.
All the magic seems to happen in the wiring box and 3 way diverter valve which has microswitches to control the valve position. I wonder if your 3 way valve died and someone hard wired your boiler for a cheap fix. Wonder if its manually set mid-way.
bmwmike said:
Agree. I'm not sure it should be diverting via the hot water cylinder though as per OP's earlier post - that could result in very hot water.
It sounds similar to my setup, but someone has chopped some wiring out on yours.
On mine there is an early 90's system boiler, a separate pump and a diverter to send water via the hot water cylinder OR via the radiators OR mid-way so both the hot water cylinder and radiator circuit get heat. I fitted a remote thermostat myself, and that is what turns the boiler on and off for the radiator circuit. The hot water circuit also demands heat and controls the diverter valve at certain times according to a timer. TRV's control room temperature but they cannot tell the boiler to stop heating.
All the magic seems to happen in the wiring box and 3 way diverter valve which has microswitches to control the valve position. I wonder if someone hard wired your boiler for a cheap fix. Wonder if its manually set mid-way.
Exactly this!It sounds similar to my setup, but someone has chopped some wiring out on yours.
On mine there is an early 90's system boiler, a separate pump and a diverter to send water via the hot water cylinder OR via the radiators OR mid-way so both the hot water cylinder and radiator circuit get heat. I fitted a remote thermostat myself, and that is what turns the boiler on and off for the radiator circuit. The hot water circuit also demands heat and controls the diverter valve at certain times according to a timer. TRV's control room temperature but they cannot tell the boiler to stop heating.
All the magic seems to happen in the wiring box and 3 way diverter valve which has microswitches to control the valve position. I wonder if someone hard wired your boiler for a cheap fix. Wonder if its manually set mid-way.
The divertor has been bypassed and the water continually goes to both the HWT and the radiators all the time. The TRVs control the heat in the rooms individually. The boiler turns itself off when the return water reaches a certain temp (ie TRVs are shut, water not flowing through radiators, HTW still has heat, in other words the water returning is now still hot as it has not needed to give up any heat).
The pump has been wired to be continually on (I'm guessing this is based on the fact that a pump starting and stopping continually will break faster than one that is just left running?) so the water is continually flowing round the system all the time.
I can't work out if it's pure genius with minimum things to go wrong, or if it needs looking at and modernised? Not broke, don't fix?
If the three way valve ( boiler > rads and tank) has been bypassed, the boiler will heat everything up until the TRVs all close, then it will heat the tank water up until the water returning from the tank to the boiler reaches the setting that the boiler switches off.
All this is great , but now the boiler is off and the pump is still running, the heat is slowly being sucked back out of the tank ( which is still open) as the pump is still running, you will be losing heat faster by running the water round the system than if it was just sat in the tank heating coil.
65% is poor, now might be a good time to change the boiler and reconfigure the system as the rising prices mean you will get your return on investment quicker. Certain areas have government schemes to replace your boiler for free. A friend has his done, as long as he had cavity wall insulation. Got the boiler fitted then they discovered he couldn't have cavity insulation
Our last place's boiler was recently replaced and the system was fitted with two on/off valves, rather than a three way valve.
All this is great , but now the boiler is off and the pump is still running, the heat is slowly being sucked back out of the tank ( which is still open) as the pump is still running, you will be losing heat faster by running the water round the system than if it was just sat in the tank heating coil.
65% is poor, now might be a good time to change the boiler and reconfigure the system as the rising prices mean you will get your return on investment quicker. Certain areas have government schemes to replace your boiler for free. A friend has his done, as long as he had cavity wall insulation. Got the boiler fitted then they discovered he couldn't have cavity insulation
Our last place's boiler was recently replaced and the system was fitted with two on/off valves, rather than a three way valve.
Agree 65% is poor on paper but during the really cold spell a few years ago mine kept chugging along whilst condensing boilers were freezing up. Also i dont use any more gas, oddly, than a 4/5 bed detached is supposed to use. Not saying OP shouldnt change it, but at the least should fix the rest of the system and will still see a benefit.
It sounds like, and others have arrived at this conclusion, your boiler setting is dictating your tap hot water temperature - i.e. it’s currently set at minimum 1 so as not to have scalding hot tap water. However you need a higher boiler setting for the radiators (say 5 or 6 for winter), but this would give you tap water of c.75-85c(?). IMHO you need a diverter valve plus a stat on the hot water tank so you can have independent control over the tap water and radiator water circuits. And the pump shouldn’t be running all the time.
If you’re worried about sludge I can highly recommend an IntaKlean 2 magnetic filter. I have an old radiator system running with a modern underfloor system - I had two fitted a couple of years ago, easily cleaned every 3 months or so and very satisfying to see the crap that comes out.
If you’re worried about sludge I can highly recommend an IntaKlean 2 magnetic filter. I have an old radiator system running with a modern underfloor system - I had two fitted a couple of years ago, easily cleaned every 3 months or so and very satisfying to see the crap that comes out.
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