Calorifier performance

[tunafish]

So I installed a 20L marine calorifier in my VW Transporter van.
My van had a second heater in the rear, a paralel circuit with the cab heater.
I removed the rear heater and plumbed in the calorifier in this loop.

I am not satisfied with the performance of the calorifier.
The main problems are:

A. Volume
My target for a hot shower for 2 people was 20-30 liters.
My install is practically flowing 8L/min from the shower head (with a 14L/min pump)

from SureJust website:
* not the manufacture of my calorifier but just as a reference

The stored water within the boiler reaches the same temperature as the engine (generally 85°C). If the mixer valve is set at 65°C you will generally increase your available hot water supply by 25%.

calculating on this quote....
20L @ 85°C
25L @ 65°C (25% increase)
26L @ 45°C (30% increase)
28L @ 40°C (40% increase)

When I drive more than an hour, so the water should be around 85°C, my results are this:
! thermostat tempering valve set to 65°C, mixer tap full open to HOT
1L @ 46°C
10L @ 45°C
20L @ 28°C
30L @ 23°C
40L @ 20°C

> So why don’t I get 65°C to start with?
> Another concern that I have, if I consume 10L from my 20L calorifier taking a shower, those 10 liters will be replaced by 10 liters COLD water from the holding tank, since it’s a pressurised system - Right?
The hot water will be in the top and the new cold water pushed in the bottom.
But does it mix after all lowering the overall temperature in the calorifier?
> Was I expecting to much of a 20 liter model?

B. Heat Loss
When I drive more than an hour (85°C), park up for the night (lets say 10°C air temp overnight), the next morning the water is just barely warm!
Not even one shower… The manufacture from the calorifier says the temp drops 1°C/hour in 24h, but in reality it’s way more faster.

By now I insulated the pipework as best as I could and will also use two shut-off valves in the coolant loop to prevent heat creeping up vs the engine, but I doubt it will change a lot.
My van has an air heater (usually set to 18°C for the night) and I even routed the ducting just next to the calorifier with this in mind.
There is a definitely some heat radiation going on in the box where I installed the calorifier, even with the pipework insulated now.

> What else can I do to prevent heat loss?

 

[vyv_cox]

It seems to me that there is a problem with the supply from the engine to the calorifier. My boat calorifier is the same size, engine far smaller. It supplies plenty of hot water after about 15 minutes of running. Check for airlocks, correct route through the calorifier.

On my motorsailer I use a booster pump but the calorifier is 1.5 metres above the (big) engine.

 

[lw395]

Is it a diesel van?
A modern turbo diesel engine doesn't actually chuck out as much heat as most people think via the coolant, unless it's working quite hard.
You could start by fitting some thermocouples or other temperature sensors around the system. If the coolant inlet to the calorifier is not getting hot, either it needs more flow or the heat just isn't there.
Does your cab heater produce really hot air and lots of it?

A lot of car and van diesels have Webasto auxillary heaters. For good reason.

 

[duncan99210]

We have a 20 litre calorifier fitted, which happily supplies us with two/three showers plus warm water for washing up. That’s after running the engine for a minimum of about 20 minutes. The only time we’ve encountered problems I found that the coolant level had dropped (never sorted why.....), after topping it up all works fine.

I agree with Vyv and I’d check the hose routing, make sure that there’s no air locks and that the coolant is at the correct level.

 

[tunafish]

I did the calorifier install about 2 weeks ago.
My windsurf trip failed because of the performance, my wife was not happy with all the amount of time I invested in this gas-free shower project.

Airlock
When I had the calorifier just installed I indeed had some problems with the water not heating up at all.
So I drove the van uphill for about 15 minutes, than parked the front wheels even more uphill and opened the coolant expansion tank.
Finally the level dropped and I topped up about a liter and a half of coolant / distilled water mix until the marks.
I have never done the right bleeding procedure because A. I need to find out how to do it B. a tech guy who installed my hot air heater told me all the air would eventually expel by time.
Could it be that there is still a small air lock in the pipes that would affect the performance?

correct route through the calorifier
Yes I determined the flow direction when cutting the rear coolant loop and connected IN & OUT the correct way.

(booster) pump
My calorifier and connections sit well below engine block level.

fitting some thermocouples
Exactly what I installed today. I will attach some pics
Got 2 of them on Amazon for the incredible price of 5£
https://www.amazon.co.uk/SODIAL-Digital-Temperature-Controller-Electronic/dp/B076BC5F6W/
1. - left - inside the cavity of the electric heating element of the calorifier. I pushed and blocked the probe in with 2 plastic wedges, I hope they will not melt.
2. - right - on the brass elbow (feed) from my bypass valves, just in front of the calorifier
* unfortunately I don't have the engine temp gauge in my dashboard, ...VW cutting corners! I might get one of those OBD dongles.

Tonight I will do a test using the electric 220V element. I will connect it for 90 minutes.
Tomorrow morning, when the engine is cold, I will do a test with the engine driving around for a 40 minutes or so. Some people say you need to drive for 60+ minutes though.
I will post the results

Here some info from the calorifiers docs:
My model is BT2012 http://nautica.atimariani.it/eng/products/enamelled-range/enamelled-range/bt20.html

HEATING TIME (not clear if this is for the heat exchanger or electric)
15°C -> 55°C: 70min
15°C -> 35°C: 50min

ELECTRICAL HEATING
Adjustable thermostat, cutting off the power to the electrical heating element when the set temperature is reached (the temperature can be adjusted between 0 ° C and 65 ° C, according to the user’s needs).
Safety thermostat, cutting off the power to the electrical heating element when the temperature of the water reaches 90° C. A manual intervention is necessary to restart the appliance (manual reset)

HEAT LOSS
Made of polyurethane closed cell foam, it prevents unnecessary heat loss. In this way the
loss of heat by thermal inertia is reduced to 1 ° C per hour for a 24 hour period

HEAT EXCHANGER / COIL
heat exchanger/coil: thanks to its large surface can produce a large output of hot water

my scheme

some pics from the install

 

[vyv_cox]

Airlocks can certainly have the effect that you are experiencing. Try back-filling the hoses while holding them as high as possible.

 

[tunafish]

@vyv_cox. Yes I think I will try that, it's gonna be a mess but it should remove any doubts.

Today I did some driving around with the temp sensors.
Not a real performance test because the van is used for daily drives.

This morning the Air Temp was 3°C (the Webasto Thermo Top C automatically kicks in to help speed up cooling temperature)
BLU = calorifier sensor, inside the electric element cavity
RED = coolant feed sensor, at bypass valves in front of the calorifier

06.33: 21°C - 05°C
06.35: 20°C - 04°C
06.37: 21°C - 27°C
06.39: 20°C - 40°C
06.41: 21°C - 48°C

coffee stop

06.49: 23°C - 48°C
06.52: 24°C - 51°C
06.54: 25°C - 56°C
06.59: 28°C - 56°C

dog walk + other stuff (start & stop)
Air Temp 5°C

07.59: 38°C - 52°C
08.03: 39°C - 50°C

driving uphill and looking for coolant max

08.10: 40°C - 65°C
08.29: 57°C - 88°C (max high revs uphill)
08.43: 67°C - 78°C (low revs downhill)

stop for water temp test

08.56: 67°C - 69°C

closing bypass valves
calorifier reads 3.2 Bar pressure, tempering valve set to 65°C

COLD from mixer tap: 10°C
opening HOT all the way from mixer tap: 47°C (there was still some COLD inside)

discharging water from mixer tap (about 8Lpm)
05L: 50°C+ (my garden thermometer reads only until 50°C)
10L: 50°C+
15L: 33°C
20L: 26°C

Calorifier sensor reads 27°C now!
So it dropped from 67°C to 27°C discharging 20L in about 3 minutes!!
Is this normal??
How am I supposed to take 2 showers (20-30L) with this performance?

Looking at the massive temperature drop in the calorifier, that brings me back to my question:

> Another concern that I have, if I consume 10L from my 20L calorifier taking a shower, those 10 liters will be replaced by 10 liters COLD water from the holding tank, since it’s a pressurised system - Right?
The hot water will be in the top and the new cold water pushed in the bottom.
But does it mix after all lowering the overall temperature in the calorifier?

 

[lw395]

You have a Webasto Thermo Top?
That should be taking your calorifier to 80degC and reheating fast enough to have a 5 minute shower every 15 minutes?
You may need/want to change the plumbing so the Webasto prioritises the calorifier instead of heating the engine block. Or you may want it to heat the cabin heater/demister first.

 

[tunafish]

@w395
Yes I have a Thermo Top C factory installed to help speed up the coolant.
BUT, it's not a universal heater, it's modified by VW to work with the CANBUS system.
There is an upgrade kit available to "convert" to a parking heater, which let's you run the unit for 60 minutes to get some heat from the cab matrix to defrost the window and preheat the engine.
On top of that another kit is available to exclude the engine block with a 3-way solenoid valve.
Indeed I am thinking to install these upgrades, I will attach a scheme.
As you see the rear loop stands in parallel with the cab heater loop. I might modify them both in series, what do you think?
Mind you Nr 2) should be thermostatic valve, but I still need to check this.

Anyway, right now I want to concentrate on the performance of the calorifier, because I have serious doubts about it's design.
If I can proof with more tests that the calorifier does indeed not perform like it should on paper I might ditch it and install a 50 plate heat exchanger that runs off the Thermo Top on demand. That will give me endless hot water, or at least until my 45L tank runs out.

This afternoon I did a test using the 220V electric element, so without any air lock problems the cooling circuit might have...

Air Temp 10°C
Electric Element set to MAX (according to the docs between 0°C and 65°C)

12.14: 14°C, 2.0 Bar (pump pressure)
12.22: 19°C, 2.0 Bar
12.31: 30°C, 2.1 Bar (pressure going up heating electrically)
12.41: 39°C, 2.3 Bar
12.52: 51°C, 3.0 Bar
12.56: 55°C, 3.1 Bar

electric element switches off automatically!?
coolant sensor started rising!! hot water starts to exchange heat to cooling lines..

13.01: 57°C, 3 Bar

water temp test
tempering valve set to 42°C this time...

COLD from mixer tap: 13°C
opening HOT all the way from mixer tap: 32°C (there was still some COLD inside)
BLU = calorifier sensor, inside the electric element cavity

discharging water from mixer tap (about 8Lpm)
05L: 36°C
10L: 38°C, 42°C
15L: 37°C, 40°C
20L: 36°C, 35°C
25L: 26°C, 31°C
30L: 22°C, 27°C
35L: 20°C, 24°C

As you can see.... still not enough for my 20-30L target @ 42°C!!
What am I supposed to think?

Again, when showering COLD water is pushed in and drops the temperature for the second shower.
This 20L calorifier is just barely enough for a 20L shower.
What is it that I am missing here??

 

[tunafish]

Forgot the coolant loop scheme:

 

[duncan99210]

You’re using a lot of water for a shower..... in the summer when we use a solar shower, we use one bag of 20 litres for what we consider to be a generous shower for two people. Technique is to wet down, shower off, soap up, shower on and rinse down. Use the same technique when using the pumped water via the calorifier.

 

[lw395]

I struggle to understand that diagram in post 10..
I would be tempted to plumb the calorifier in series with the Webasto output, but there is some risk of boiling the domestic water if it's not isolated and you thrash the vehicle up a hill and then crawl in traffic.

 

[lw395]

You’re using a lot of water for a shower..... in the summer when we use a solar shower, we use one bag of 20 litres for what we consider to be a generous shower for two people. Technique is to wet down, shower off, soap up, shower on and rinse down. Use the same technique when using the pumped water via the calorifier.

+1.
It's OK to get clean, you will run out of water trying to get warm from the shower if you are seriously cold.
Cabin heater and hot drink for that.

 

[tunafish]

Heh yeah, I know it’s the price I have to pay for my beautiful wife :-D. She asked me only one thing to come with me on my van adventures: a real hot shower!

I think I overrated the 20L model. It is not enough, at least not in the winter. I think I will do the Thermo Top C upgrades with a plate heat exchanger for on demand water. I liked the idea to generate free water from the engine. Maybe I will do a combination of both calorifier and plate exchanger.

Thanks for the help.

 

[lw395]

My boat system would get the calorifier to about 70degC quite quickly.
Mixing that with water at say 10 degC for a shower at 40degC meant that your shower could use twice as much water as was in the calorifier. If the Eberspacher was running while we were showering, it would not keep the calorifier at 70, I assume this is because the coil in the calorifier wasn't big enough, but the shower would still deliver some water at 40, just a bit slower from the thermostatic mixer.
It's not like a power shower in a posh hotel, we simply did not carry enough cold water to be in that game.