DIY fan coil unit

[news]

I'm trying to get a bit of blown hot air to the area around the vehicle lift at work, I have ample hot water from the buffer tank of the woodchip boiler. A 20kW device from Dunham-Bush costs around 700 quid new but I have the condenser from a 3ph mitsubishi air conditioner, it has a single 10mm coil laid serpentine like through the fins, so unlike a lorry radiator where the gill tubes are parallel. I'm told a vehicle radiator will not stand the 2 bar pressure and I cannot use aluminium in the circuit so oil coolers are out too.

Anyone care to venture a guess how much heat it may emit with 80 degree water pumped through it? and would a domestic central heating pump run sufficient water through at the likely back pressure of up to

6 metres of 10mm copper pipe?

AJH

[Andrew Gabriel]

I'm sure loads of fancoil units get chucked in office refits. The trick is to be there when it happens. Corroded/leaking drip trays is another reason they get replaced, which wouldn't effect you if you only want it for heating, so you might be able to get one from an aircon maintenance company.

Any idea what the heat pump capacity of the aircon unit was? At 80 degrees, I would hazard a guess at twice that figure. Might want to watch you don't overheat the fan motor.

Are you sure it's only one pipe run? Even my 3.5kW unit has a pair of pipe runs in parallel through the condenser, although there's only one feed and return, and they split on the edge.

[news]

Yes, we have a shopfitter on site and they cast off loads of stuff but nothing suitable yet.

Well it mentions 5kW of cooling on the face plate.

Yes there are 13 pairs plus the inlet and outlet about 0.7 metres height so around the 6 metre mark for length, trouble is the pipe doesn't seem to be standard 10mm, I'm hoping one of the aircon guys that do work for the shopfitter will pop in and have a look.

I need to decide on a pump, Grundfos UPS 15/60 looks like it will do, the wilo modulating ones on offer are cheaper but not suitable for this small bore.

AJH

[Andy Champ]

I imagine you'll get more than that owing to the bigger temperature difference. You may want to worry about safety though, with 80 degree pipes around the place.

Andy

[amcmaho]

On Monday, 15 October 2012 22:24:30 UTC+1, (unknown) wrote: =20

Probably enough, given the heating to air mean temperature difference men= tioned above. Heating coils are usually one or two row jobs; chilled water = coils very often had 6 or more rows to shift the heat into the water (usual= ly 6/12 f/r). The fins were usually a lot more closely spaced. I couldn't c= alculate it easily because the manufacturers did all the calculations. Prob= ably LMTD involved and I've forgotten that and I had little involvement wit= h DX coils.

The hydraulic resistance on the water side will be higher than ideal, pos= sibly too high. The fins on cooling coils are closely spaced and do act as = a filter. You should have an upstrean air filter. Is the 10mm tube one cont= inuous run?

Be aware that;

1) you need to safeguard the return temperature to ensure it doesn't fall l= ow enough to cause condensation in the boiler. 2) If there's any chance of freezing air, you need something like a hard-= wired manual-reset thermostat to stop the fans. The coils freeze and split = in seconds. Then again you could just chance it and bung a new coil in.

[news]

Yes

enough to cause condensation in the boiler.

No problem it will run from a 2000litre buffer and the boiler holds

600 litre

hard-wired manual-reset thermostat to stop the fans.

Fans and pump will run on a thermostat whenever the buffer tank is greater than 45C.

AJH