right size boiler spec

[Timmy D]

Thanks for your thoughts.
I have plugged all draughts and holes to minimize heat losses from heated rooms including insulation on pipework and it has made a difference.
You are spot on using the thermal camera but there are hardly any heating engineers with thermal camera in my area, and honestly I cannot justify the cost of using it once.

Out of interest, where in London are you?

 

[Desktop987456]

Out of interest, where in London are you?

Sorry, I am not in UK, I live in Pakistan and have learned a lot about heating systems from forums and people such as yourselves. We installed a locally made heating system in 2013 during major house renovation. The system wasn't designed properly and they put two boilers in the property; one in front and one at the back, creating two zones. The front one was way oversized for my needs (35kw) and now after calculating my property needs I have connected all radiators to this boiler which is still way oversized for 13 radiators installed at our house. I have extended pipework creating heating zones and upgraded some undersized radiators to improve the system. At some point in time I need to change the boiler to a more efficient one.
There aren't many certified or registered heating engineers or plumbers in my country of residence. Winters here are not as cold as and not as long as in UK. It gets 5degC in January and winters lasts a couple of months. It was very cold in January but the chill in air is gone in February, I think because of short duration of winters we we don;t have many qualified people here. People either use gas or electric heaters for this short duration and very few people have central heating system.

 

[Timmy D]

Sorry, I am not in UK, I live in Pakistan and have learned a lot about heating systems from forums and people such as yourselves. We installed a locally made heating system in 2013 during major house renovation. The system wasn't designed properly and they put two boilers in the property; one in front and one at the back, creating two zones. The front one was way oversized for my needs (35kw) and now after calculating my property needs I have connected all radiators to this boiler which is still way oversized for 13 radiators installed at our house. I have extended pipework creating heating zones and upgraded some undersized radiators to improve the system. At some point in time I need to change the boiler to a more efficient one.
There aren't many certified or registered heating engineers or plumbers in my country of residence. Winters here are not as cold as and not as long as in UK. It gets 5degC in January and winters lasts a couple of months. It was very cold in January but the chill in air is gone in February, I think because of short duration of winters we we don;t have many qualified people here. People either use gas or electric heaters for this short duration and very few people have central heating system.

Thanks for the clarification. I asked as I notice your profile said London. Was going to pop round with my thermal camera if a bit closer than Pakistan!

 

[Desktop987456]

Thanks for the clarification. I asked as I notice your profile said London. Was going to pop round with my thermal camera if a bit closer than Pakistan!

Thanks.

 

[Desktop987456]

Thanks for the clarification. I asked as I notice your profile said London. Was going to pop round with my thermal camera if a bit closer than Pakistan!

Thanks Timmy D, I would have given you a red carpet welcome if you were!

 

[John.g]

Thanks, you have been very helpful and have answered my questions.
Apologies I did get the units wrong it is 1-2 bar and rads 7bar.
1. pipe sizes are 22mm from boiler and branches off 15mm just before or to rads;
2. The pump is coping up with these lengths so far in a non pressurised system but I have only tested it over 2-3 days how it performs during whole season, I don't know.
3. Boiler pipe layout involves pipes going upstairs twice; once from front (3m) and second from backside of the house after running 40ft horizontally on ground floor then 3m upstairs (all 22mm lengths). The farthest rad ~80 ft from boiler (upstairs on the back side of the house) gets hot too so this means pump is working fine, how will it perform in pressurised system I am not familiar with hence the question. How can I calculate pump requirement in a pressurised system?
4. Installers in my area aren't very helpful and knowledable and when it comes to central heating I am on my own mostly. A while ago I wanted to extend the pipework and he was insisting on PEX pipe which after consulting on forums like people such as yourself I was advised (rightly so) to go for copper which I did and I am happy that I made the right call. I don't want to spend money where I don't need to. I am making improvements in my system by bringing efficiency and reducing my gas usage that is why I wanted to buy an energy efficient boiler. My current boiler is not energy efficient and consumes 12m3/day for 15 hours of heating only (6am-9pm). Hot water arrangement consumes another 3m3/day. I am under the impression rightly or wrongly that a condensing or newer boiler will consume much less than this but I have no way of substantiating this theory or info.

12m3/day for a 15 hour heating day is 0.8m3/hr or ~ 8.8kw/hr boiler output, don't know what the efficiency of your boiler is but assuming 70% then your heating requirements are ~ 6.2kwh/hr, hardly outrageously excessive?. although you state elsewhere that the boiler consumption is 1.75m3/hr.

Your HW requirement of (gas) 3m3/day equates to a HW demand of 440LPD at 60C assuming the same 70% boiler efficiency, seems a very high HW demand?.

A condensing boiler might give a max of 20% greater efficiency IMO or less depending on the present boilers efficiency.

What is the make/model of your existing boiler(s)?.

 

[Desktop987456]

12m3/day for a 15 hour heating day is 0.8m3/hr or ~ 8.8kw/hr boiler output, don't know what the efficiency of your boiler is but assuming 70% then your heating requirements are ~ 6.2kwh/hr, hardly outrageously excessive?. although you state elsewhere that the boiler consumption is 1.75m3/hr.

Your HW requirement of (gas) 3m3/day equates to a HW demand of 440LPD at 60C assuming the same 70% boiler efficiency, seems a very high HW demand?.

A condensing boiler might give a max of 20% greater efficiency IMO or less depending on the present boilers efficiency.

What is the make/model of your existing boiler(s)?.

12m3/day is heating the essential rooms only (not the large fan coil unit which consumes 5-7kw). It is an old boiler and you I have seen its efficiency in the range of 65-70% range. 1.75 m3/hr that I stated in post is running the boiler on full load (sorry it this confuses you).

I have a separate DHW arrangement with cylinder's own burner (on gas) independent of boiler, its a 200 litres cylinder and it consumes in 2-3m3/day range.

The boiler and cylinder works independently, what would be the most efficient way for Central heating and DHW? Cylinder providing hot water to boiler or vice versa?

I have a non pressurized system and want to make it efficient if it doesn't cost an arm or a leg!

I also have 11kw PV system installed on the roof and cylinder is fitted with 2x1500 watts immersion heaters.

Thanks

 

[John.g]

You have a gas fired Hot water heater/cylinder supplemented with a PV diverter?, if so, then if you wanted to supply CH & HW from one gas fired source (the boiler) you will need a new cylinder + immersion heater(s). not sure what you mean by cylinder providing HW to the boiler.

 

[Desktop987456]

You have a gas fired Hot water heater/cylinder supplemented with a PV diverter?, if so, then if you wanted to supply CH & HW from one gas fired source (the boiler) you will need a new cylinder + immersion heater(s). not sure what you mean by cylinder providing HW to the boiler.

I don't have PV diverter installed in my system, I get credit from grid for selling excess power.
Since I have separate cylinder for heating (stored hot water), can it supply hot water to boiler and it can ciruclate hot water to radiators? Can it be done.

 

[John.g]

If I am interpreting you correctly in that you have a separate gas fired stored "DHW cylinder" then no or certainly not easily, you have plenty of spare capacity in your CH boiler to suppy a conventional DHW cylinder and can't see any efficiency gains the other way.