Makes sense to me.

Everything else is, as they they, just theory. Enjoy!

That's a fantastic device. I was not aware that such a boiler control existed.

My only problem with using it is that I have to maintain a floor temperature of 150°F. for domestic hot water. This negates some of the benefit of full regulation by such a control. Most of the year (excluding January and February), the control simply maintains 150°F. I need to raise it if we hit a cold spell when the ambients drop below 20°F. and remain there.

If I had any greater demand for hot water and installed a separate hot water heater, this device would be perfect.

Thanks for the link. I'll be keeping it in mind for the future. I've got to believe that Honeywell also makes a similar unit??

Ain't Google wonderful?

I found a Honeywell AQ475 Johnstone Supply online. Link

There may be others. Your local heating/cooling supply could be helpful.

Aha! A 'tankless' in-line point-of-use water heater might be just the ticket here! I will have to do some research to see how they are rated for higher ilet temperature.

When your heating water was turned back to 130F, you only need a 20F-30F 'boost' so the you might be able to raise the temp of more gpm for the same BTU/kW rating, or use a smaller unit.

Thanks for the link.

A single "tankless" unit that would boost the water from about 100°F. to 165°F. would be perfect. However, that's a lot of climb and I'd need decent volume for the washing machine (maybe six gallons per minute or so).

Remember that the output temperature from the tankless coil is usually 30°-40° below the boiler temperature.

I also have a boiler floor temperature of 130°F. due to condensation issues. Below this temperature, there can be condensation inside the boiler which is undesirable for durability.

What you need is something like a 'booster' heater used for commercial dishwashers.

Hubbell Model J Booster

From a brief read, you set the desired output (32F - 194F) and the controller gives you that temp up to the maximum flow rate. You have to figure out the kW required given your maximum temperature rise and flow rates, but for edited: 130F-160F, or a 30F rise, at 6 gpm for the washer you need a 30kW heater. The electric service would be the equivalent of a house, 125A or so at 240V! Maybe a smaller 3gpm unit and let the washer fill slower?

I can't say I have heard of a system such as yours, but it looks technically feasible. Price of such a booster, though, might be steep, as it is commercial duty. It would probably out-last your house, though.

Stefano's biggest problem is that is heat pump is trying to deliver heat from the roof. Great place for an AC, worst possible place for a forced air heater.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Same old problem. To get sufficient flow rate a huge amount of power is required. Unfortunately, a proper tank seems impossible to avoid if the boiler is to operate at cooler temps.

The best solution would probably be a gas fired 40 gallon water heater that's fed by the tankless coil on the boiler. But, I don't think the savings of running cooler boiler water would offset the losses of maintaining 40 gallons at 150°F. 24/7.