run heat pump and boiler hot water coil together

Rich_d

Could there be any issues with running both the heat pump and the back up boiler hot water loop together? IE.. over heating the fan. Would it be efficiant to do this if heat pump is not keeping up of should I just run the back up heat?

Thanks, Rich

Rich_d

The unico air handler has a ecm fan.

Ironman

If the hot water coil is upstream of the refrigerant coil, then DEFINITELY NOT! You'll overload the compressor and kill it real quick. The system should be setup with a fossil fuel kit or dual fuel thermostat to prevent this from happening.

If the hot water coil is DOWNSTREAM of the refrigerant coil, then yes, it can be done; but I see no benefit in doing it other than some minuscule fuel savings that would be far outweighed by unnecessary wear on the heat pump.

You're better off letting it be "either or" but not "both" at the same time.

njtommy

I guess it depends where the fan in relation to the coils.
If the blower is after the coils yes it is a concern.

Rich_d

> If the hot water coil is upstream of the refrigerant coil, then DEFINITELY NOT! You'll overload the compressor and kill it real quick. The system should be setup with a fossil fuel kit or dual fuel thermostat to prevent this from happening.

ok, the hot water coil is upstream. The T-stat has the option to either so I was just curios if it would be a good idea. I will be going with the "DEFINITELY NOT"

>
> If the hot water coil is DOWNSTREAM of the refrigerant coil, then yes, it can be done; but I see no benefit in doing it other than some minuscule fuel savings that would be far outweighed by unnecessary wear on the heat pump.
>
> You're better off letting it be "either or" but not "both" at the same time.

ok, Thanks for the great advice..

Rich_d

> @njtommy said:
> I guess it depends where the fan in relation to the coils.
> If the blower is after the coils yes it is a concern.

Yes, the blower is after the coils. I will not be going with the run together option for resons above , However would you know at what temp the ecm motor could be affected? With just the boiler coil running I am getting 160 deg as a discharge temp.

njtommy

160 supply air temp?

That's very hot. I would turn the boiler supply water temp down a bit. What type of boiler do you have?

Rich_d

> @njtommy said:
> 160 supply air temp?


If by supply temp you mean the discharge temp (just after the blower reported from my delta T sensors) then yes.

>
> That's very hot. I would turn the boiler supply water temp down a bit. What type of boiler do you have?

buderus g115 temp set to 180 no economy setting set. I would like to keep it at 180 if possible becouse the garage has a modine heater. When the economy setting had the max temp set to 150 it took a long time to get the garage up to temp.

The air hanndler only has approx 15' of pipe to the boiler ( very close)

Techman

You are lucky if you do not have a blower motor problem from all that heat going into/across the motor. Find out from the HP Mfrg about the air temp going into the blower motor.

Rich_d

> @Techman said:
> You are lucky if you do not have a blower motor problem from all that heat going into/across the motor. Find out from the HP Mfrg about the air temp going into the blower motor.

You are corrrect. I finally found the correct manual and it does specify a recomened air temp of 130 with a max of 150. According to the manual the blower will shut down if overheated but continued operation in the 140 to 150 range will decrease the life of the motor.

Thanks for the Info..

Rich_d

Could you kind folks post some recommendations on the most efficient way of cooling 1 zone of the boiler. I have 2 other air handler located far enough from the boiler that they run at the correct air temp with boiler at 180 and as mentioned above my modine works best at 180.

Thanks, Rich

njtommy

@Rich_d you maybe be able to add a mixing valve on the supply water side of that zone to bring the water temp down to 150 or possibly even lower if need be. It depends on how it's piped and also if your boiler can handle sending 130f return water back to it or not.
Pictures of your current piping would help us out a bit or even a drawing.

Rich_d

Do you think I could just put a small strip of baseboard heat on the zone? That way I would at least throw some heat in the basement. I turned the boiler down to 160 and now the 2 distant air handlers are running at 120 and the basement air handler is at 140. so I need to cool approx 20 deg give or take.

Rich_d

Our sun room (3 outside wall) ended up not getting enough heat in the current system. It is on the same heat pump/ zone, So it would be nice to put some extra heat in there with pehaps a very small panel radiator but I fear that would take too manty btu's from the loop.

GW

You could get funky and add a simple strap on aqaustat to open the burner or TT call for that zone


http://www.supplyhouse.com/Honeywell-L6006C1018-High-or-Low-Limit-Circulator-Strap-On-Aquastat-65-200F-range-5-30F-Adj-Differential-1738000-p?gclid=Cj0KEQiAwMLDBRDCh_r9sMvQ_88BEiQA6zuAQ4xacs8EI9WLik2estEEUZj2fNBy_3JyemhR5_ufzXgaAoNE8P8HAQ

Rich_d

> You could get funky and add a simple strap on aqaustat to open the burner or TT call for that zone
Thanks for the reply..
Where would I put the aqausat? Any location I can think of would eithier giv no heat to the zone or really short cycle that zone.

Rich_d

Any thoughts/ conserns on just adding a small section finned pipe to the loop? After all to truly ballence the 3 zones I would just run the same diameter pipe ( the other 2 zones go into a smaller rolled insulated pipe) the same distance, So why not just put a srtip of heat into zone that is too hot?

Techman

The "type" of boiler that you have may not be able to take 120* water temp. Flame quenching, flue gas condensing,depending,thermal shocking the boiler.

Rich_d

It is just a standard buderus g115. I am just talking about getting all 3 of my air handler hot water coils getting the same inlet temp water. If My boiler has a issue with low return temps then I am already in trouble becouse 2 of the three already have a below 120 return temp.

Rich_d

> @Ironman said:
> If the hot water coil is upstream of the refrigerant coil, then DEFINITELY NOT! You'll overload the compressor and kill it real quick. The system should be setup with a fossil fuel kit or dual fuel thermostat to prevent this from happening.
>
> If the hot water coil is DOWNSTREAM of the refrigerant coil, then yes, it can be done; but I see no benefit in doing it other than some minuscule fuel savings that would be far outweighed by unnecessary wear on the heat pump.
>
> You're better off letting it be "either or" but not "both" at the same time.

As stated above My hot water coil is upstream of the refrigerant coil. However after several calls to the unico reps It seems that thier air handler / heat pump (I seies) will not allow the boiler heat to run without the heat pump running if the outside temp is above the boiler change over set point (32 deg). I live in new england so the winter temps are often around 32 deg. At 32 deg it can take the heat pump over 1 hr to bring the temp up 2-3 deg, this is not a issue during the day when no one is home and we have lowered the temp to 64 deg. But when we come home we want to bring the house up to 66-68 deg. We do the same for sleeping at night and in the morning​ do not want to wait for the heat pump, we would prefer to bring the temp up faster with the boiler.

1. Has any one else run into this issue with the unico air handlers, If so did you find a solution?

2. Is this common or do other brands of air handlers allow you to run the boiler heat 'or' heat pump when outside temp is above the boiler change over set point ?

Thanks for any information or comments.

Techman

Check into the "allowable" T'stat setback temps w/ a HP.

Rich_d

> @Techman said:
> Check into the "allowable" T'stat setback temps w/ a HP.

Thanks for the reply..

I did some reading on this subject and there does not seem to be too much argument that a heat pump with electric back up should be very limited on any type of set back. Where as a with just conventional oil fired boiler a large set back can be more efficient. I live in a area with fairly high electric rates and the wife works for the family oil company so we get a discount on oil. So with these factors and the fact we have very unpredictable schedules IE programmable thermostats or smart recovery would not work well, I feel using an aggressive set back would be beneficial and coincide with the way would like to heat our home. So even if I am off the mark and it may cost me more money in the end should that not be my choice. Should I not be able to run my boiler any time I feel the heat pump is not giving me as much heat as I would like? The folks at Unico seem to think they know best how I should Heat my home. So I was simply wondering if anyone else has had this issue with the unico I series and if other manufacturers allow the system to be set up to allow this.

Techman

Can you wire in a separate relay for the boiler off of W2 on the T'stat? After the setback when the T'stat is manually set from 60*F up to 72*F ,W2 is now "calling" for heat, utilizing the boiler.

Rich_d

> @Techman said:
> Can you wire in a separate relay for the boiler off of W2 on the T'stat? After the setback when the T'stat is manually set from 60*F up to 72*F ,W2 is now "calling" for heat, utilizing the boiler.


Yes, I have a prestige T-stat so there are many options available on that end. The issue is I can not control the Unico AH fan. The only option available is to power the 'fan' terminal on the AH and this will run the fan on low. The only way to get the fan to med or high is to call for heat at y1 or y2 of the AH and if the outside air temp is above 32 deg-f then the heat pump will run. If it below 32-f then the Unico AH has a option to run the aux heat and it will shut off the heat pump and run the fan at the med or high (y1 or y2).

So currently if I want boiler heat when outside air temp is above 32-f I can only run the fan on low( with no call for heat to AH). Which is still better then waiting for the heat pump to bring temp up but does not seem very efficient and not the way it should be working in my opinion.