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paulgato · 03-11-2014, 08:52 PM

Interesting thread.

I installed a 2kw 240v coolant heater a week ago. It came with a little electric circulating pump and has a thermostat which switches off at 88 degrees C (190F) and on again at 78 C (172F).

It's certainly nice to start off with a fully warmed engine up at normal operating temperature, although as soon as I drive off the coolant temperature drops by 10 degrees C, presumably as the oil/coolant heat exchanger (aka 'oil cooler') does its job and equalises the temperature of the oil and the coolant.

However, from the point of view of fuel efficiency my feeling is that anything over 50 degrees C (120F) is good enough, and anything over 50 C uses far more electricity. At an ambient 10 degrees C it takes 20 minutes to rise 40 degrees up to 50 C and another 50 minutes to rise a further 38 degrees to 88 C. Even in the summer, startingthe engine at 50 C rather than 20 C should make a significant difference to fuel efficiency in the first few miles.

From the running cost point of view then the more powerful the heater the less it will cost to get to any given temperature (less cooling). I kind of wish now that my heater had an adjustable thermostat. The ideal I think would be a powerful heater with circulating pump and a 60 degree C thermostat. Such things are available, but I have what I have and I'm happy with it. I'm using it every day now and the fuel saving is noticeable. Can't give it a definite number as yet but it's in the order of a 15% saving over the first five miles. My drive into town is about five miles and I'm getting at least 15% better mpg on that run in the morning now. Much of that saving, I believe, is down to no longer having to manouver off my driveway with a stone cold engine, with all that reversing and so on.

My car is a 2002 VW Golf 1.9TDi.

I also installed an on-board battery charger and disconnected my alternator about a month ago, and that saves a clear 10% on fuel overall, and that is a far more cost-effective mod in my opinion. The coolant pre-heater I installed partly for improved mpg but also to save me time on cold mornings (scraping ice and de-misting windows). Also to reduce pollution. No more idling on the driveway, poisoning the neighbours' children. Also I believe it contributes to safety as I am never again going to drive off late for work with partially misted up windows.

The only problem with a more powerful heater is that it is easy to leave it on and forget it. If I am delayed in leaving the house for example. Once up to temperature the heater tends to only be on for 30 to 50% of the time though, so it's not too bad.

I've heard about this business of storing warm coolant, so the engine will heat up quicker after being stood in the cold during the day. It's a nice idea, but perhaps just as effective and easier to implement would be to simply insulate the oil sump (oil pan). The hot oil drops down there while parked up, so why not keep it hot a bit longer with some insulation? The oil is never going to overheat because it's cooled via the oil/coolant heat exchanger anyway.

03-11-2014, 08:52 PM	#10 (permalink)
paulgato EcoModding Apprentice Join Date: Sep 2013 Location: Oxford, UK Posts: 126 Black Beast - '02 VW Goff Estate S Thanks: 27 Thanked 51 Times in 31 Posts	2kw coolant heater with electric pump Interesting thread. I installed a 2kw 240v coolant heater a week ago. It came with a little electric circulating pump and has a thermostat which switches off at 88 degrees C (190F) and on again at 78 C (172F). It's certainly nice to start off with a fully warmed engine up at normal operating temperature, although as soon as I drive off the coolant temperature drops by 10 degrees C, presumably as the oil/coolant heat exchanger (aka 'oil cooler') does its job and equalises the temperature of the oil and the coolant. However, from the point of view of fuel efficiency my feeling is that anything over 50 degrees C (120F) is good enough, and anything over 50 C uses far more electricity. At an ambient 10 degrees C it takes 20 minutes to rise 40 degrees up to 50 C and another 50 minutes to rise a further 38 degrees to 88 C. Even in the summer, startingthe engine at 50 C rather than 20 C should make a significant difference to fuel efficiency in the first few miles. From the running cost point of view then the more powerful the heater the less it will cost to get to any given temperature (less cooling). I kind of wish now that my heater had an adjustable thermostat. The ideal I think would be a powerful heater with circulating pump and a 60 degree C thermostat. Such things are available, but I have what I have and I'm happy with it. I'm using it every day now and the fuel saving is noticeable. Can't give it a definite number as yet but it's in the order of a 15% saving over the first five miles. My drive into town is about five miles and I'm getting at least 15% better mpg on that run in the morning now. Much of that saving, I believe, is down to no longer having to manouver off my driveway with a stone cold engine, with all that reversing and so on. My car is a 2002 VW Golf 1.9TDi. I also installed an on-board battery charger and disconnected my alternator about a month ago, and that saves a clear 10% on fuel overall, and that is a far more cost-effective mod in my opinion. The coolant pre-heater I installed partly for improved mpg but also to save me time on cold mornings (scraping ice and de-misting windows). Also to reduce pollution. No more idling on the driveway, poisoning the neighbours' children. Also I believe it contributes to safety as I am never again going to drive off late for work with partially misted up windows. The only problem with a more powerful heater is that it is easy to leave it on and forget it. If I am delayed in leaving the house for example. Once up to temperature the heater tends to only be on for 30 to 50% of the time though, so it's not too bad. I've heard about this business of storing warm coolant, so the engine will heat up quicker after being stood in the cold during the day. It's a nice idea, but perhaps just as effective and easier to implement would be to simply insulate the oil sump (oil pan). The hot oil drops down there while parked up, so why not keep it hot a bit longer with some insulation? The oil is never going to overheat because it's cooled via the oil/coolant heat exchanger anyway.