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Engine Preheater on 2.25 diesel

Thanks for the link to the speed controller, I'll get one and experiment. Re airlocks - when I fitted the rear heater I put in a bleed fitting soldered into an elbow. Waste of time, it was as likely to let air in as out. The Webasto pump seems able to shift enough water to get the air out, a few miles drive once the stat is open also seems to work. Today I got the £20 heater and set it up on a test rig (bucket and two hoses) and ran some measurments. I was impressed. 17.5 ltrs of cold water and temp outside of 10C, claimed 2000w:
Rise across the unit was 4c inlet to outlet.
15 mins to 35c
20 mins to 45c
30 mins to 65c
it started to regulate at 70c and stabilised at 75c.
It had a simple job as it was only warming a bucket of water not an engine block but the flow was better than I expected from such a small pump. I use the same bucket for testing Webastos so it was interesting. I would say the flow was about half, but the heating rate was about 80% which is surpising as the Webasto is claimed at 5kw. The issues I found were:
1 the pump is water luburicated and seems sensitive to orientation and bleeding
2 the pump runs when the heater runs as it is on the internal thermostat, this means the pump stops when hit hits temp, really the pump should run all the time there is power and only the element cut in and out. Easy job to get it apart and change the wiring (I hope..)
3 The internal thermosat has no hysteresis so it cuts out at 75c and back in at 74c, not a huge problem but it will spend a lot of time switching if its used as a night heater. Another reason to rewire the pump to bypass the thermostat.
Re the water going where it wants, yes, I have the Webasto tee'd so it goes to both the engine and heater and this works, I can shut the engine valve to get all the flow to the heater (but still expansion back through the engine / rad). I think the front heater flow is reversed when the Webasto runs, I never run it and the engine together. I think the electric heater will go in series with the rear heater as that's what I want to heat, I don't want to heat the engine as that's wasted heat when camping. My new dilemma is how to regulate it on air temp, I have a thermostat on 12v controlling the Webasto but I don't want any 12v and 240v wires anywhere near each other. The 240v system is to be sealed and separate as a double insulated system with no earths to chassis. The 240v earth issue is a minefield and I got my current set up looked at by a pt17 expert. His advice was to treat it like running an exstension lead into the back and plugging into that with no elecrtical connections to the vehicle. The alternative is to treat it like a mobile home and run earths and an earth stake / conductive tyres, this is ok in a fibreglass body but very risky in a metal one where you touch the metal. If someone damages the hook up lead and links live to earth it must not make the body live. My mains lead is in conduit from the side locker where it comes in to a sealed camping socket with earth trip and circuit breaker.
 
Highly advanced test rig....
 

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You could use a solid state relay for switching it as these are great for controlling 240v with a low voltage mainly because they are fairly large which provides enough separation between 240 and something like 12v.


Lots of electronic kit thermostats are designed for refrigeration so just watch what you pick. Some do provide good hysteresis though and you can adjust your turn on and turn off temperatures individually. Using the air temperature to control the on/off cycles may cause overshoot. Could be better to control the fans and pump from the air temperature and just keep the water system within limits. If you set the upper and lower limits far apart it should keep you warm enough without too may restarts. Just make sure the pump turns on when the heater is on but the pump can run by itself without the heater.
 
robwlondon said:
......................
The 240v earth issue is a minefield and I got my current set up looked at by a pt17 expert. His advice was to treat it like running an exstension lead into the back and plugging into that with no elecrtical connections to the vehicle. The alternative is to treat it like a mobile home and run earths and an earth stake / conductive tyres, this is ok in a fibreglass body but very risky in a metal one where you touch the metal. If someone damages the hook up lead and links live to earth it must not make the body live. My mains lead is in conduit from the side locker where it comes in to a sealed camping socket with earth trip and circuit breaker.
Click to expand...
I decided the extension lead method was best both for simplicity and safety.
However (as an old sparks who began work back in the early 1960s) I would never use an electric engine preheater without a 2-pole RCD (Residual-current device) in the mains supply.
The likelihood of receiving a serious electrical shock from the LR bodytwork is very high if anything goes wrong and an RCD will protect you by switching off the circuit before you start to fry.
 
Agreed, I have an rcd in line in the lead at the plug end and again in a "proper" camping unit inside. My fears were damage to the lead or a live /earth fault in the supply as you are very dependent on someone else's outdoor sockets and some look a bit neglected. I've just found these on e-bay:
I'll order the thermostat and try it. It solves the 240v wiring issue as there is none and it claims to be OK in greenhouses (humid/damp like the series...) but there no mention of any IP rating. A search under "plug in thermostat" also throws up some with remote sensors so it would be possible to put that on the top hose and control the engine heater. We have a CO alarm but no smoke detector so I think I'll get one of those too, better safe than sorry.
 
I think I might have a go at this while I'm messing about with mine. I'll try the thermostat module and relay combination and see how it goes and report back.

There are other types of heater out there so may try one of the pot types - https://www.ebay.co.uk/itm/CAR-ENGI...sh=item1cc4999ab7:g:1AsAAOSwEVtbztZ8:rk:20🇵🇫0

If you have yours apart to access the pump I would like to see a photo of the insides and any problems re-sealing it. I am hoping the pot type is just an O ring with wiring accessible from the base.
Also check if yours has any thermal protection, as it could be possible for all the coolant to leak out of it and the heater set on a thermostat to come on and possibly catch fire. The original Hotstart had a button type thermostat switch in it for safety and is not unusual to have two or a thermal fuse as well.
 
Here's the pictures of the electrical insides. The second one shows the pump motor wired across the elment which is how they come, first one shows it after I have rewired it so the pump runs all the time its live. It makes no sense to turn the pump off when it hits temp as the element will just get even hotter due to heat soak with no flow. Aslo if you are goinf to control it with an engine mounted sensor you want it to keep flowing. Next step is to install it, probably under the rear tub in the rear heater pipes, I have a side locker to get access.141696141697
 
Progress report. Its installed in series with the rear heater under the bulkhead. I've had to lag it otherwise it looses a lot of heat from the heater circuit when its not in use, just passing hot water. Tested yesterday outside temp around 5c and it got the interior up to a modest warm - enough for sleeping in around 45 mins and was still getting warmer. Its quiet but I have to run the inlet with a bend so I fear air locks, may need to put a bleed point in. As Richie says, the big problem is the blower current. I used the mains hook up with a 3.5 A charger. The idea is for the 240v to power the heater and to trickle charge the lesiure battery at the same time with the blower running of the lesuire batt. problem is even on "low" the blower draws 4A so theres a slow voltage drop. I could up the charger size but the blower is noisy so I'd rather drop the blower speed right down - less air but hotter. I've ordered that speed controller and a 1 ohm 100W restistor, one should work. (for anyone interested a 1 ohm 100w resistor is about £3.50 off e-bay and the right size for a diy 2 speed blower Med is abound 1/2 ohm and slow around 1ohm, the 100w rating means it will run forever, its about 3" long and finned.)
 
I suppose you could use a zener diode In place of the resistor, not for the normal use of stabilising voltage but in series with the motor to act as a voltage drop?
 
I have just changed mine . removed the one with the noisy pump that got hot but did not pump for a new one this one pumps but not heat . time to make one good one from the two . any hints or tips
 
If they are both the same model then swapping the pump may be easier than the heating element which is usually sealed a bit better.

Re the zener idea. It would work I think with a fairly beefy npn pass transistor and the zener on the base with a small bias resistor. The new series voltage regulators are this design and handle 6A+ but switching regulators are cheap if you don't mind radiated noise.
 
Richie_asg1 said:
If they are both the same model then swapping the pump may be easier than the heating element which is usually sealed a bit better.
Click to expand...
I have taken apart the heater with the non working pump and removed the heater and what looks like a thermostat switch . they look as if they are sealed with some sort of silicone . I will use instant gasket to seal it
 
Update with pics on the other design. Arrived in post today, so took it apart naturally. :)
141848
Made in China, Instructions in Russian. This is the small pot type - https://www.ebay.co.uk/itm/273584857493 Around £17.

I will modify the pump the same as yours to run constantly, just waiting on the thermostat module on mine to get it working.
Out of the two designs I think I prefer yours because it must have a larger heating element and they tend to last longer.
I will make the mounting more heat resistant and leave room for lagging of some type as you say it needs it, and must get pretty hot with 2Kw going into it.
Think I will add a thermal fuse to the heating element too. 2000W at 230v should draw 8.7A (Watts/ Amps calculator) and 10A thermal fuses are only a pound for 5 - https://www.ebay.co.uk/itm/5pcs-SF2...ash=item25fb81098b:g:l7gAAOSwLilak9oU:rk:4🇵🇫0
I'll post you a couple when they arrive if you want just PM your address.
Those thermal bi-metallic switches can fail, and the results could be a fire. The 216°C ones should give enough leeway for normal operation to fit and forget. Needs to be insulated in high temperature silicone and glass sleeving, and connections crimped, then attached somewhere close to the heating element connections.
 
just fitted a new one . do they run constantly or do they get to a set temp then stop cool a bit then start again ? that's what mine is doing . it looks the same as the one robwlondon fitted
 
They get up to temp then stop becuse the motor is wired into the thermostat, that's why I took mine apart and wired it to the supply so the motor runs all the time.
 
Mine runs all the time until it reaches temperature, then it switches off and on to keep it at temperature.
At first the switching on and off is quite fast as the hot and cold coolant continues to circulate by convection and the after effects of the pump.
Eventually almost all the coolant in and around the engine is hot and it switches off for a much longer period.

Are you sure you have got all the air out of the system?
If you haven't the heater may be reaching temperature because the coolant isn't circulating very well.
 
I am going to have another go at bleeding it tomorrow. as the engine wont run till I have finished playing with the winch wiring . old cars are great fun .
 
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