Alde 2928 heating and hot water

[tangledfooted]

Recently bought a 40’’ by 12’’ broads cruiser with a rather dated interior. We move on to live aboard at the end of January. Yesterday I took out a kabola heater and single coil upright domestic hot water cylinder. Over the summer we hope to fit a wood burner cooker with back boiler ready for next winter. Right now I need to provide hot water and heating and have been offered a Alde Comfort 2928 with flow at a very reasonable price. If I can fit it now it can act as a back up to the wood burner later on. ( I realise there are all sorts of issues like thermosyphons and heat dumps – but Ill just have to worry about these later on)

Im trying to get my head around how to get the Alde to do both hot water and heat 3 maybe 4 rads. I understand the 2928 to be a fairly simple affair (thats good). The burner fires up when the temperature in the heat exchanger drops. It drops because cool water enters via the return because the circulation pump which is switched by a 12v room thermostat is on. All well and good the radiators get hot and we are toasty.

Now as far as the Alde is concerned the indirect coil of the hot water cylinder is just another radiator (heating a tiny room full of water).

My questions

1. Does the Alde 2928 have an internal circulation pump or am I going to have to source one?

2. In the summer I can isolate the room radiators and just heat the HWC and maybe a towel rad using strategically place manual values. All good, but now the room stat which controls the circulation pump has no relationship with the HWC. So may be a cylinder stat that I only connect in the summer? Or maybe connect permanently but in parallel to the room stat?

3. Im getting confused now. What if the cabins a nicely warm (its winter again) but we both need a shower. OK that’s just like summer - so manually close of the valves and unclose them after were both clean. That could work. But is there a more elegant solution? And anyway could the water get too hot – just don’t like having no control over the hot water situation

4. Do I have to use antifreeze? If Im not worried about anything freezing that is.

5. Are there any schematics diagrams etc that might help me?

 

Thanks in anticipation.

 

Sorry one more question. The Alde website wants me to plump the radiators inline rather than in parellel . I would prefer running two pipes round. Is there any reason I can't or shouldn't do this?

[dor]

!: The pump should be in the header tank at the top of the boiler.

2: Fit the calorifier in parallel with the radiators. Fit two 22mm full flow lever ball valves in each circuit so you can control them individually. You should also fit a towel rail or small radiator in the circuit so that neither ball valve will shut off the flow to it. That way you cannot cut off the load inadvertently by shutting both valves.

3: To use the boiler to just heat the calorifier, shut off the flow to the rads and turn the thermostat right up so that the boiler thinks it needs to heat the cabin.

4: Yes you must use antifreeze - same as the engine 25-33%. Mix it well with water and add it a bit at a time - if you are not careful then the concentration in the rads might be different and they won't get hot without a lot of effort forcing water through. They rely on a very slight density difference between hot and cold.

5: It's pretty straightforward. For the rads, run a pair of 22mm pipes along the boat and tee off in 15mm to each rad.

 

You can amend some of the above, e.g. by fitting tank stats or three-way valves, but the description above works and keeps it simple.

 

ETA: 3A: It can't get too hot - the Alde has a temperature dial and that will limit how hot the water in the system will get. If you leave it running just on calorifer it will just more or less shut down as the water in the boiler will be hot.

Edited December 29, 2012 by dor

[tangledfooted]

Thank you very much dor.

 

That was the missing link - an integral limiting thermostat in the boiler ! I should have thought of that- but I didn't.

 

All the rest make perfect sense (keep it simple) and I'll follow slavishly.

 

Thanks again

[dor]

You are welcome Tanglefooted.

 

Basically, what the room 'stat does is control the pump. If the boiler is running, i.e. the pilot is alight, the main burner will occasionally fire up even if the 'stat is off - but will shut down again when the contents of the boiler gets hots.

 

A couple of points with the 2928: If you find it difficult to light the pilot it will need cleaning. The pilot is a flat disk with two bits for a flame - one on the side of the spark ignighter the other on the other side which heats the flame sensor. If the pilot is dirty the second flame won't light. You can remove the whole burner assembly from the front by taking out about 16 screws. You can also send the whole burner assembly to Alde for a service which is worth doing every couple of years or so.

 

If you fit a switch to turn the pump on directly and get the calorifier hot from the engine you can get some heat to the rads by using the calorifier as a heat exchanger and getting the heat from the engine. This can be useful when travelling as it only takes about an hour to get the calorifier fully hot, after than you can use the excess heat to warm up the rads. They won't get as hot as when the boiler is running, but can give you some heat in the cabin; you may need to balance the flow a bit using the valves.

[rgreg]

!: The pump should be in the header tank at the top of the boiler.

2: Fit the calorifier in parallel with the radiators. Fit two 22mm full flow lever ball valves in each circuit so you can control them individually. You should also fit a towel rail or small radiator in the circuit so that neither ball valve will shut off the flow to it. That way you cannot cut off the load inadvertently by shutting both valves.

3: To use the boiler to just heat the calorifier, shut off the flow to the rads and turn the thermostat right up so that the boiler thinks it needs to heat the cabin.

4: Yes you must use antifreeze - same as the engine 25-33%. Mix it well with water and add it a bit at a time - if you are not careful then the concentration in the rads might be different and they won't get hot without a lot of effort forcing water through. They rely on a very slight density difference between hot and cold.

5: It's pretty straightforward. For the rads, run a pair of 22mm pipes along the boat and tee off in 15mm to each rad.

 

You can amend some of the above, e.g. by fitting tank stats or three-way valves, but the description above works and keeps it simple.

 

ETA: 3A: It can't get too hot - the Alde has a temperature dial and that will limit how hot the water in the system will get. If you leave it running just on calorifer it will just more or less shut down as the water in the boiler will be hot.

This is the arrangement that I have and it works a treat. The only thing I have considered adding to mine is a timer but rarely use it for central heating, mainly just water heating.

[Alf27]

I have replaced the room stat with a simple on/off switch, & use rad stats to control heat levels, as said earlier the boiler has internal stat to control water temp.