Engine Thermostats

Trundlebug

Trundlebug

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I have a Profile 33 with twin VP MD31A's.

A couple of years ago I fitted a Webasto Madera 8kw heater matrix supplied by the starboard engine (port engine heats the calorifier) to provide "free heat" when under way. It's been fairly successful and after about 45 minutes the inside of the boat reaches around 20 degrees, when outside it's around 5.

However the air coming from the heater never really feels as warm as the outlet from a car heater, just a bit warm really and certainly not hot. That's with the fan on slowest speed setting, and the engines working hard too. The engine temperature gauge shows normal, around 82, and it warms up quickly enough so I don't think there's any kind of a problem with the thermostats function.

What I'm wondering is whether to employ a trick I've used to great effect on cars in the past, i.e. to fit a warmer ("Winter") thermostat to the starboard engine, to boost the heater output. Upon reading the VP manual, it appears the standard t/stat starts to open at 81deg, (fully open at 94deg). Usually a car summer t/stat is 82deg, and winter 88deg.

Has anyone else tried this? Would I be able to successfully transplant a couple of spare 88 t/stats originally from a Mini engine, or are they a completely different size and fitting? I am a bit mindful of the high temp engine alarm set at 93deg but don't think it'll be a problem.

I'm just trying to plan ahead, aged parents coming on board over Christmas break who feel the cold, therefore roasting temperatures required quite quickly if we are to avoid the moans and groans!

Any thoughts from the forum much appreciated, even if it's "leave well alone"..!
 
Trundlebug said:
I have a Profile 33 with twin VP MD31A's.

A couple of years ago I fitted a Webasto Madera 8kw heater matrix supplied by the starboard engine (port engine heats the calorifier) to provide "free heat" when under way. It's been fairly successful and after about 45 minutes the inside of the boat reaches around 20 degrees, when outside it's around 5.

However the air coming from the heater never really feels as warm as the outlet from a car heater, just a bit warm really and certainly not hot. That's with the fan on slowest speed setting, and the engines working hard too. The engine temperature gauge shows normal, around 82, and it warms up quickly enough so I don't think there's any kind of a problem with the thermostats function.

What I'm wondering is whether to employ a trick I've used to great effect on cars in the past, i.e. to fit a warmer ("Winter") thermostat to the starboard engine, to boost the heater output. Upon reading the VP manual, it appears the standard t/stat starts to open at 81deg, (fully open at 94deg). Usually a car summer t/stat is 82deg, and winter 88deg.

Has anyone else tried this? Would I be able to successfully transplant a couple of spare 88 t/stats originally from a Mini engine, or are they a completely different size and fitting? I am a bit mindful of the high temp engine alarm set at 93deg but don't think it'll be a problem.

I'm just trying to plan ahead, aged parents coming on board over Christmas break who feel the cold, therefore roasting temperatures required quite quickly if we are to avoid the moans and groans!

Any thoughts from the forum much appreciated, even if it's "leave well alone"..!
Click to expand...


If the engine thermostat is working to spec and the heater is not producing very warm air I would look elsewhere for an issue first.
It sounds like either the pipes are loosing too much heat on the way to the heater and need insulation, or the water flow is restricted/poor.
What it the pipe temperature like at the Input/Output sides of the heater matrix?
I can't see a few extra degrees in the engine temperature making much difference.
 
If the engine is running around 82 degrees then I would have thought that would be hot enough. I would look into how much flow of water there is around the cabin heating system. Maybe a boost pump is needed to improve the flow.

Is the feed pipe much hotter than the return pipe? (indicating poor flow)

How long is the pipe run? (feed and return)

What size of pipe has been used?

Any tight corners?

Have the correct the feed and return pipes been connected to the correct ports on the engine?

Hope this helps.
 
Trundlebug said:
I have a Profile 33 with twin VP MD31A's.

A couple of years ago I fitted a Webasto Madera 8kw heater matrix supplied by the starboard engine (port engine heats the calorifier) to provide "free heat" when under way. It's been fairly successful and after about 45 minutes the inside of the boat reaches around 20 degrees, when outside it's around 5.

However the air coming from the heater never really feels as warm as the outlet from a car heater, just a bit warm really and certainly not hot. That's with the fan on slowest speed setting, and the engines working hard too. The engine temperature gauge shows normal, around 82, and it warms up quickly enough so I don't think there's any kind of a problem with the thermostats function.

What I'm wondering is whether to employ a trick I've used to great effect on cars in the past, i.e. to fit a warmer ("Winter") thermostat to the starboard engine, to boost the heater output. Upon reading the VP manual, it appears the standard t/stat starts to open at 81deg, (fully open at 94deg). Usually a car summer t/stat is 82deg, and winter 88deg.

Has anyone else tried this? Would I be able to successfully transplant a couple of spare 88 t/stats originally from a Mini engine, or are they a completely different size and fitting? I am a bit mindful of the high temp engine alarm set at 93deg but don't think it'll be a problem.

I'm just trying to plan ahead, aged parents coming on board over Christmas break who feel the cold, therefore roasting temperatures required quite quickly if we are to avoid the moans and groans!

Any thoughts from the forum much appreciated, even if it's "leave well alone"..!
Click to expand...

I would suggest that f1rst of all you do a bit of tactile testing. You have water at 80 plus in the engine block however is any of this making the trip around the heater matrix. You might get an idea of this by feeling the pipes between the heater and the engine. The pipe to the heater and the pipe from the heater should not be at to great a difference if there is a good flow of water. The flow can be affecter by airlocks. sludge or closed control valves in the water circuit.

Airlocks are frequent where the matrix is higher than the engine as that is where air goes naturally after the system has been drained and refilled and can only be removed by slackening of the highest hose clips after a run while the engine is hot and pressurised. TAKE CARE! Might have to do this more than once. If there has been sludge in the system then the heater may have to come out for cleaning but not likely in a well maintained system where there have not been head gasket problems. Control valves can produce a multitude of problems. depends on what valves are fitted.
 
Ah, some interesting thoughts there, thank you.

I have used standard size heater hose the same as is used on the port engine for the calorifier, which has very long pipe runs and after a lot of initial bleeding works fine.

The pipe runs for the heater are much shorter as the heater sits about 500mm below engine height, i.e. where the outlets / stabbings are, and about 300mm in front of it.

The hoses run in nice gentle sweeps, and I fitted a solenoid operated / spring return valve in the feed line to enable me to turn the hot water on and off. The intention was for it to be able to blow cold in the summer, (but it doesn't quite work like that because the fan ends up drawing warm air from the engine bay via the bilges...although they are thankfully clean and odour free!)

I've used the same outlets as used on the starboard engine for the calorifier, I used them as the guide for which plugs to remove, so I'm confident they're the right ones. As regards the heater matrix I figured it didn't really matter but I conneceted them so as the system would self bleed, i.e. feed at the bottom and return at the top.

I must confess though that I don't remember feeling the hoses for temperature difference - an elementary step I seem to have missed somehow! I'll have a check again this w/e. I am fairly confident there aren't any air locks though.

I'm beginning to wonder, do you think the solenoid valve is offering too great a resistance to the flow? it was an expensive fitment, and I was rather proud of the ability to switch on the hot water flow at the touch of a button... much more civilised than a lever operated ball valve I thought. Interested in your comments about a host of related possible problems...?

Thanks again for the ideas
 
Heater matrix

Hi Trundlebug,
I have a motor sailer yacht with a Volvo MD22 (actually a Perkins Prima, painted with very expensive green paint). Last winter I fitted a heater matrix, out of a Ford Transit, and all I did was to tee into the feed to the calorifier, so that the hot water from the engine passes through the matrix on its way to the calorifier. Instead of fitting a separate fan, I used the "cold blow" facility of the Eberspacher, by connecting its ducting through the matrix. It works perfectly, and doesn't even seem to reduce the water temperature coming from the calorifier.

If you are interested, it was written up in Novembers (?) PBO.

There must be something stopping the water flow. Maybe, as you suggest, the solenoid valve, but as others have said, feeling by hand should tell you if there is proper circulation. It's definitely worth persevering with. Good luck.
 
Update

Well we went out on the boat yesterday for a short run up the river, to get the oil flowing and the engines hot. It was a lovely day, still and sunny and very pleasant - until we got back to the marina when it went black and tipped down!

I took the opportunity to check out the pipes to the heater, and can confirm that everything does indeed seem to be working perfectly. Good flow of water, very hot to the touch on the feed side, the return being cooler though still quite hot.

I'm beginning to think that the reason the heater takes a while to warm up the inside of the boat is because of the large air volume it has to heat up, simply that.

However, I still can't help thinking the heater would be more efficient, and effective if the engine was running just a bit hotter. As I said originally, just those few degrees can make a significant difference in a car heater, so I can't see why it shouldn't be the same in the boat. The engine was running at 81 degrees yesterday, i.e. at just thermostat opening temp.

So, my question stands, are the thermostats the same size and fitting as automotive ones?
 
I don't know about the size of thermostats, but remember that the airspace in the car is allot smaller than your boat.

I really wouldn't be inclined to swap out teh thermostats for an extra 2 degree's of engine heat, I can't think it will make any difference at all.

I know your pipe temps are okay at each end, but may be worth temp swapping out your solenoid valve to see if teh extra flow does make any difference...?

A couple of well placed 12v low draw PC fans may also help distribute the heat more effectively?
 
Trundlebug said:
I took the opportunity to check out the pipes to the heater, and can confirm that everything does indeed seem to be working perfectly. Good flow of water, very hot to the touch on the feed side, the return being cooler though still quite hot.
Click to expand...

If the return pipe is still quite hot it would seem the heater matrix is not very efficient. - Could it be scaled up (the scale acting as an insulator)?
If the heat cannot get out of the water as it is, I am not sure hotter water will be any more effective at transferring it's heat.
 
BGW said:
If the return pipe is still quite hot it would seem the heater matrix is not very efficient. - Could it be scaled up (the scale acting as an insulator)?
If the heat cannot get out of the water as it is, I am not sure hotter water will be any more effective at transferring it's heat.
Click to expand...

There's no way it's scaled up, as the whole thing is brand new. It is quite efficient at transferring the heat, as there is a noticeable temp difference between flow and return, and the flow is quite fast.

As I said, I know from practical experience it can make all the difference, despite what may appear to be just a few degrees. It's all about temperature difference, (or Delta T as they called it in Thermodynamics); many moons ago it made a long midwinter trip to Germany in a 1977 Mini 1000 very warm, as opposed to barely comfortable before - when it had only been blowing warm. The weather was minus 8 outside too, and very icy!
We wondered why the car had been handling a bit strangely after driving for hours on deserted country roads in the pitch black, and wondered if we had a puncture. We stopped for a break, and to check the tyres, got out of the car and all fell over it was so slippery!
Sheet black ice was the problem..

Anyway, I digress. The blower on the heater is very powerful, that may be part of the problem, on fast speed there's so much air going through it doesn't get time to heat up past the matrix! On slower speed it is warmer but still not HOT like comes out of your car heater.

Fitting a full bore ball valve may help a bit, I admit, but still not sure it'll make any noticeable difference as the flow is good already.
 
Are your engines fresh or raw water cooled?

on mine I have one of each. Fresh is on the engine suppying the calorifier as the raw water cooled engine never gets hot enough.

Remember water only circulates when the stat is open and then the winter water will quickly cool the engine and close the stat again
 
The engines are fresh water cooled, i.e. with antifreeze in and a separate system & heat exchanger for the raw water. As in cars, the heater circuit taps off the engine circuit, such that it always gets the warmest water, regardless of state of opening of the thermostat.

I measured the flow by feeling the return pipe temperature. SWMBO turned on the switch to open the heater valve, and I counted how long until the return pipe felt hot. It took less than 5 seconds, about 2-3 seconds, which I considered quite OK.
 
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