Working out oil boiler daily operating time

Voodoomelon

Hey all.

I have an outdoor Grant oil boiler, which heats a 210 litre thermal store in the attic four stories up. I have underfloor heating in a limecrete slab on the ground floor and i'm trying to figure out a good method of determining how often my boiler is turning on with the current schedule I have set on my Honeywell controller (5 zone).

I'm not in the house long so still trying to find the sweet spot for the heating controls; currently the underfloor is running from 17:00 in the evening to 10:00 in the morning, so it's off for 7 hours during the day when the sun is potentially out and i'm usually at work. It's a very old house so insulation is non existent.

I find the ground floor doesn't really get up to set temperature and the boiler can be cycling on and off every 5-10 minutes for 2-4 minutes at a time in the evenings.

Of course many say the underfloor should run 24/7 but it doesn't do a bad job of maintaining 20 Celsius as is and pretty sure it's saving a good 7 hours of oil burning. That said, it has me wondering if i'd be better running it 24/7 and see if it's any more efficient.

As I tend to over complicate things, i'm thinking is there some way to wire in a relay to a Raspberry Pi and have it count the operating hours of the boiler in both scenarios for a week and compare results?

Or any other suggestions? Thanks!

antoinolachtnai

You can get gadgets like these.

https://ie.rs-online.com/web/c/automation-control-gear/timers-counters/hour-meters/

I have heard of them being used with oil boilers, but I have never used one myself.

I don't think your schedule makes that much sense. The floor in the ground floor will take hours to heat up. Ideally you would heat it several hours before you actually need the heat.

The timing when you pump water from the thermal store is also going to make a difference.

Are there radiators as well on the middle floors?

The temperature outside also matters a lot. The temperature in Ireland flies all over the place, unlike many other countries.

Voodoomelon

Thanks for that. Yes I was contemplating flipping the schedule on its head, have it go off for 5-6 hours over night, but that's also typically the coldest when most heat would be lost. But yes, the slab would then be fully heated for the evening time on return.

Yes there are cast iron rads on the upper floors, incredible things, they heat up in 20 minutes and get red hot, then stay hot for 2.5 hours after the heating goes off.

xl500

Voodoomelon wrote: »

Hey all.

I have an outdoor Grant oil boiler, which heats a 210 litre thermal store in the attic four stories up. I have underfloor heating in a limecrete slab on the ground floor and i'm trying to figure out a good method of determining how often my boiler is turning on with the current schedule I have set on my Honeywell controller (5 zone).

I'm not in the house long so still trying to find the sweet spot for the heating controls; currently the underfloor is running from 17:00 in the evening to 10:00 in the morning, so it's off for 7 hours during the day when the sun is potentially out and i'm usually at work. It's a very old house so insulation is non existent.

I find the ground floor doesn't really get up to set temperature and the boiler can be cycling on and off every 5-10 minutes for 2-4 minutes at a time in the evenings.

Of course many say the underfloor should run 24/7 but it doesn't do a bad job of maintaining 20 Celsius as is and pretty sure it's saving a good 7 hours of oil burning. That said, it has me wondering if i'd be better running it 24/7 and see if it's any more efficient.

As I tend to over complicate things, i'm thinking is there some way to wire in a relay to a Raspberry Pi and have it count the operating hours of the boiler in both scenarios for a week and compare results?

Or any other suggestions? Thanks!

If you simply want to see how long it runs each day just get a cheap electric clock and wire it in with burner then set clock at 12:00 and check later to see how many hrs it has clocked up

Irish Steve

I've had something like this for years, 2 radionics 240V mechanical hours counters, one counts when there is power being supplied to the boiler and pump, the other operates when the thermostat is providing power to the burner, and for me, the interesting figure is that overall, the burner is only operating 50% of the time the boiler is on. That's down to how much heat is being taken out of the water that's being circulated, and that of course varies with the timings, if the boiler's been off overnight, the burner is pretty much 100% on, but once the rads and hot water are up to temperature, then the heat being taken out of the circuit means that the burner is a lot less active.

At some stage, I may do some work with microprocessors to devise a time recording system that will give me the variations throughout the day, it's possible that with those sorts of results, there may be a case for a down size of the boiler, but without a clear pattern of the highest usage periods, that may be a false sentiment. At some stage, if we don't move to another location, there will be a case to be made for changing the boiler anyway, it's a non condensing oil burner, which if we are to believe some pundits is only one step removed from the devils spawn, but the costs of upgrading would be significant, and the saving may not actually mean much advantage.

And before I get jumped on, there's no point someone suggesting we go air to water or similar, or underfloor, as both would be very expensive to put in, the ground floor is tiled concrete, and changing the radiators to take advantage of a lower temperature system would be very hard to do, and either way, there would not be a lot of advantage in those routes before the house has been upgraded to deal with air tightness issues, 30 year old dormer bungalows are problematic draught wise, even more so if they were fitted with downlighters through the ceilings.

Voodoomelon

Interesting. With my system, the only thing calling for heat as far as i'm aware is the thermostat on the thermal store. Once it drops below 70 degrees, the boiler kicks on. The boilers only job is to keep the store up to temperature, the rads and underfloor pass through the store and use it as a heat exchanger, so i imagine if my boiler is kicking on for a few minutes every 10 minutes, it means the burner is active.

Presumably the boiler is only using fuel when the burner is active?

Wearb

Voodoomelon wrote: »

Interesting. With my system, the only thing calling for heat as far as i'm aware is the thermostat on the thermal store. Once it drops below 70 degrees, the boiler kicks on. The boilers only job is to keep the store up to temperature, the rads and underfloor pass through the store and use it as a heat exchanger, so i imagine if my boiler is kicking on for a few minutes every 10 minutes, it means the burner is active.

Presumably the boiler is only using fuel when the burner is active?

That's an awful lot of cycling from a boiler using a thermal store. I would be looking at the thermostat that's calling for heat from the store. There is something not right.

Voodoomelon

Well like I mentioned, the ground floor never gets to the set 22 degree temperature and hovers around the 20 degree mark. It's a 3 story 200 year old house with no insulation, so the store depleting by 10 degrees or so every 10 minutes with the heating running on all floors would seem reasonable to me?

antoinolachtnai

Voodoomelon wrote: »

Well like I mentioned, the ground floor never gets to the set 22 degree temperature and hovers around the 20 degree mark. It's a 3 story 200 year old house with no insulation, so the store depleting by 10 degrees or so every 10 minutes with the heating running on all floors would seem reasonable to me?

What temperature is the store?

What temperature is the flow and return to the ground floor UFH?

antoinolachtnai

Wearb wrote: »

That's an awful lot of cycling from a boiler using a thermal store. I would be looking at the thermostat that's calling for heat from the store. There is something not right.

Definitely.

It would be worth putting a light or something in series with the stat so you can tell if the cycling is happening because the store reaches its setpoint and stops calling for heat, or alternatively if the cycling is happening because the boiler has reached its setpoint.

Voodoomelon

antoinolachtnai wrote: »

What temperature is the store?

What temperature is the flow and return to the ground floor UFH?

The store is set to 80°C as per its spec.

The UFH flow temperature is 45°C and the return is 30°C, although at the start of last week I upped the flow to 50°C and the return is now 35°C as it was freezing over night and room temp was dropping to 19°C.

The UFH pump was set to speed 1, so I set it to speed 2 a few days ago and the room temperature has increased to 21°C.

Something that might be hindering the temperature on the ground floor is the fact that I have the UFH temperature in the utility room and small room beyond set to 17°C and both these rooms are kind of open plan, leading on to the hall and other downstairs rooms. Might make more sense to have the whole ground floor set to the same temperature.

Irish Steve

Voodoomelon wrote: »

Interesting. With my system, the only thing calling for heat as far as i'm aware is the thermostat on the thermal store. Once it drops below 70 degrees, the boiler kicks on. The boilers only job is to keep the store up to temperature, the rads and underfloor pass through the store and use it as a heat exchanger, so i imagine if my boiler is kicking on for a few minutes every 10 minutes, it means the burner is active.

Presumably the boiler is only using fuel when the burner is active?

It will depend on how the boiler is configured, and I don't have in depth knowledge of the heat store systems. If the heat store is asking for heat, then yes, the boiler is activated, along with the pump that moves the water between the boiler and the store, but that does not mean the burner is active all the time, if the boiler has an integral thermostat, that thermostat may be turning the burner off if the temperature of the circulation system between the boiler and the heat store exceeds the boiler thermostat temperature.

Depending on the size of the boiler, and the speed that the pump is running at, it may take a while for the heat store to absorb the heat it is being given, and at that point, the boiler stat will again activate the burner.

Voodoomelon

This is it, the run from the boiler to the store is actually incredibly long, about 12 metres under the back garden and then up another 12 metres or so into the attic, a good 24 metres. I'd imagine in a scenario like this, the burner would quite active.

0lddog

Voodoomelon wrote: »

.......
I find the ground floor doesn't really get up to set temperature and the boiler can be cycling on and off every 5-10 minutes for 2-4 minutes at a time in the evenings.........

Does the thermostat that controls this have adjustable hystersis ?

antoinolachtnai

0lddog wrote: »

Does the thermostat that controls this have adjustable hystersis ?

Very good point.

Another thing to consider is how the second pump, which drives water from the store to the UFH and radiators is controlled. For example, if it were to run while the store was cool, then it would serve to reduce the temperature of the concrete slab, not increase it.

A store of that size at that temperature should hold 10 to 15 kWh of energy by my calculations. That is a fair bit of heat. It would be interesting to observe what happens to the pump and the flow and return temperatures when the boiler is turned off.

If you really have the inclination to fiddle with a raspberry pi, I think the best thing to do could be to put temperature sensors on the flow and return from the boiler and from the UFH.

John.G

Irish Steve wrote: »

It will depend on how the boiler is configured, and I don't have in depth knowledge of the heat store systems. If the heat store is asking for heat, then yes, the boiler is activated, along with the pump that moves the water between the boiler and the store, but that does not mean the burner is active all the time, if the boiler has an integral thermostat, that thermostat may be turning the burner off if the temperature of the circulation system between the boiler and the heat store exceeds the boiler thermostat temperature.

Depending on the size of the boiler, and the speed that the pump is running at, it may take a while for the heat store to absorb the heat it is being given, and at that point, the boiler stat will again activate the burner.

The store has a hysteresis of 10C (80C/70C) so assuming every litre of this stored water is heated to 80C, it will emit 2.44 kwh in falling to 70C and will supply a 14.7 kw heating demand for 10 minutes before calling in the boiler, a 30 kw boiler should then replenish this store while also supplying the demand in ~ 9.5 mins. Don't know if the boiler is heating the store via a coil or is circulating the store's contents around the boiler but whether or which in order to maintain a deltaT of < 10C through the boiler would require a circulating flow rate of > 43 LPM, if not, then the boiler will cycle more frequently?.